Category 6™

Leonardo DiCaprio’s Before the Flood: A Movie Review

By: Jeff Masters , 3:09 PM GMT on October 31, 2016

“Before the Flood” is Academy Award-winning actor and environmental activist Leonardo DiCaprio’s worthy 96-minute documentary on climate change that will be streamed for free all week on Facebook, Youtube, Hulu, Playstation, and can be viewed on demand on Apple iTunes, Amazon, and GooglePlay. DiCaprio spent three years traveling the globe to meet with key political leaders, climate scientists and environmental leaders to understand and document the changes and challenges of climate change. While the movie does not cover much new ground compared to other climate change documentaries like An Inconvenient Truth, it is entertaining to see DiCaprio’s personal journey of understanding, which started with a meeting with Al Gore in 2000, when DiCaprio had “no clue” on the issue of climate change. The movie is worth watching just to see DiCaprio’s remarkable star power—which allows him to interview President Obama, Pope Francis, U.N. Secretary General Ban Ki-Moon, Tesla Motors founder Elon Musk and U.S. Secretary of State John Kerry.


Figure 1. Leonardo DiCaprio visits the NASA Goddard Space Flight Centre to discuss Earth science with former astronaut Dr. Piers Sellers. Image credit: NASA/GSFC.

Highlights
The movie gets its name from a scene in Hieronymus Bosch’s painting "The Garden of Earthly Delights", which hung over DiCaprio’s bed as a child. He gives a rather compelling personal narrative on how the painting influenced him, and how the painting’s final panel, showing a “paradise that’s been degraded and destroyed”, acts as a warning to humanity on what awaits if we fail to act on climate change.

Another excellent scene occurs when DiCaprio visits with former astronaut Dr. Piers Sellers. Accompanied by spectacular time-lapse video from the International Space Station, Sellers describes how the experience of looking down on Earth from space made him immensely more fond of the planet and its people. In a dark room illuminated by full-wall graphics of Earth, he then describes how a stage-four cancer diagnosis inspired him to create visualizations of the Earth to help educate and draw attention to climate change and its impacts.

The movie ends with a speech DiCaprio gave in April 2016 to the general assembly of the United Nations in his role as a U.N. Messenger of Peace with special focus on climate change. “No more talk, no more excuses, no more 10-year studies,” DiCaprio says in the speech. “This is the body that can do what is needed, all of you sitting in this very hall. The world is now watching. You will either be lauded by future generations or vilified by them.” As he delivers his words, the movie cuts between video of him speaking and images of a planet in peril, in a way I found very moving.

Overall: three stars out of four
While the movie documents many gloomy and depressing aspects of climate change—like pollution in China, sea level rise in Florida and on low-lying Pacific islands, the climate denial industry in the U.S. and the failure of the U.S. to lead on the climate change issue—the movie shows there is a lot of optimism that we can avoid a fate like depicted in “The Garden of Earthly Delights”. One of the more hopeful moments comes during DiCaprio’s interview with Tesla founder Elon Musk, who is building the world’s second largest building—a lithium-ion battery “Gigafactory” near Reno, Nevada. Musk estimates that 100 such factories would be enough to power the entire world. DiCaprio, who admits to a profound pessimism about climate change several times during the movie, brightens, as he and Musk use the word “manageable!” to describe the issue of powering the world with renewable energy.

DiCaprio gets the science of climate change right in “Before the Flood”, and addresses pretty much all the key issues—an impressive feat for a non-scientist. The only major dings I give against the movie—it is, after all, a documentary—is that it has no real plot, not much action, and runs a little long at 96 minutes. Nevertheless, I highly recommend checking out “Before the Flood”, and give it three stars out of four. I also recommend the companion website, beforetheflood.com, which has nearly 50 articles by leading climate change communicators and climate scientists.

Links to my other reviews of climate change documentaries

The 2013 six-part Tipping Points series that aired on the Weather Channel.

James Cameron’s 8-part series on climate change, Years of Living Dangerously, which aired on Showtime.

Al Gore’s 2006 movie, An Inconvenient Truth.

The 2013 documentary, Greedy Lying Bastards.


Video 1. The YouTube trailer for Leonardo DiCaprio's 96-minute climate change documentary, Before the Flood.

Jeff Masters

Book and Movie Reviews

Scary Warm: Welcome to the Halloween Heat Wave of 2016

By: Bob Henson , 3:55 PM GMT on October 28, 2016

Trick-or-treaters and adult partygoers will be doing their best to keep their cool over the next several days. It’s been seasonally chilly and even snowy across parts of the Northeast, but Phoenix saw its latest-in-any-year 100°F reading on Thursday. Over much of the central and eastern U.S., temperatures will soar to unusually warm heights as we roll through All Hallows’ Eve and into the first several days of November. Temperatures on Halloween (Monday, October 31) are projected to reach the 70s from South Dakota to West Virginia and the 80s from Kansas to the Carolinas. As a very strong Pacific jet continues to pump mild air into the nation, we could see a few all-time monthly records for November threatened later next week, especially across the U.S. South. Here’s a day-by-day guide from weather.com on the warmth next week could bring.

Even more noteworthy than the degree of warmth is the lack of widespread autumn chill. For example, Minneapolis has yet to dip below 36°F as of Friday, October 28. That doesn’t look likely to happen before at least next weekend (November 5 - 6). In records going back to 1873, the latest Minneapolis has ever gone before seeing its first 35°F of the autumn is November 1, way back in 1931. The city’s latest first freeze was on Nov. 7, 1900.

The contiguous U.S. might still eke out some frigid weather later in November or December, especially if an emerging early-season split in the Northern Hemisphere’s stratospheric polar vortex works its way to lower levels over the next several weeks. The Weather Company’s latest seasonal outlook for North American industry clients, produced by Dr. Todd Crawford and colleagues, stated: “Recent evidence (expectation for blocking and enhanced Siberian high in November) is beginning to suggest that high-latitude blocking may be more likely than we originally thought, so colder risks beginning in December are now a concern.” For the time being, though, it looks like 2016 will maintain its current pace as the second-warmest year in U.S. history, giving 2012 a run for its money. And based on one index in particular--one that’s gotten little attention so far--this year is leaving all of its predecessors far behind.


Figure 1. Projected departures from average temperature (degrees C) on Thursday evening, November 3, 2016, based on output from the 00Z Friday run of the GFS model. Image credit: tropicaltidbits.com.

What happened to our record lows?
Because the contiguous U.S. is packed with so many long-term reporting stations, almost every year will produce thousands of record highs as well as record lows. The torrid year of 2012 produced more than 50,000 daily record highs, including 12,000 in just one month (March 2012, which gave us a historic and memorable “summer in March”). Yet 2012 also produced more than 10,000 daily record lows. Because the numbers on either side of this equation are always quite large, it’s the ratio of daily record highs to lows that points out most vividly where our nation’s climate has been heading in a world warmed by ever-increasing amounts of human-produced greenhouse gases.

Parallel with NOAA’s National Centers for Environmental Information, meteorologist Guy Walton has been compiling data on daily records for more than a decade. In 2009, Walton teamed up with Gerald Meehl and Claudia Tebaldi (National Center for Atmospheric Research) and several other colleagues to show that the ratio of highs to lows has been increasing decade by decade. In larger cities, the urban heat island effect is no doubt having an influence, but these relentless trends extend throughout rural and urban America. In the 1970s, the U.S. saw roughly 5 daily record lows for every 4 daily record highs. That ratio flipped in the 1980s, which produced about 6 highs for every 5 lows. By the 2000s, we were getting nearly twice as many daily record highs as lows (350,181 to 187,323). For the 2010s thus far, the ratio has climbed even higher: we’ve had about 2.2 times as many record highs as record lows. This is especially remarkable given that the years 2013 and 2014 both managed to buck the trend, scoring more daily record lows than highs. This year through October 25, the ratio is more than 5 to 1. That’s higher than in any full year on record.

Hiding in plain sight in the 2016 data is something even more astounding. Walton’s and NCEI’s numbers through October 25 show that this year has produced 20,847 U.S. daily record highs but a mere 3920 record lows. The latter may sound like a lot, but it’s a phenomenally low number. Since the mid-1920s, when the bulk of U.S. weather stations had accumulated a meaningful 30-year history, the nation has notched at least 9000 daily record lows by the end of October in every single year. This year, we’re not even halfway to that point!


Figure 2. Number of daily record lows for the Jan-Oct. period, 1980 - 2016. Data for 2016 are through October 25. The number of record lows for 2016 thus far (3920) is less than half of the next-lowest number of 9107 record lows that occurred from January to October 2012. Data courtesy Guy Walton and NOAA/NCEI.


Things could change dramatically between now and New Year’s Eve. It’s entirely possible for a single month to generate more than 10,000 daily record highs (as did November 1999) or lows (as did November 1991). Still, the take-home message is that 2016 so far is most impressive not for the number of its record-setting warm days but for its extreme lack of record-setting cold nights. This goes hand in hand with the high levels of atmospheric moisture that have kept many nights unusually warm in many areas, especially during the summer.

Seymour has come and gone
It never affected land, but Hurricane Seymour made a splash in East Pacific annals. Seymour both intensified and weakened with uncommon speed, going from a tropical storm to a Category 4 hurricane in 36 hours on Monday and Tuesday and then weakening from a Cat 4 to a tropical storm in just 30 hours on Wednesday and Thursday. The National Hurricane Center declared Seymour a post-tropical cyclone early Friday. Moisture from Seymour’s remnants will feed into a Pacific storm that will drench parts of central California this weekend.

There are no named tropical cyclones on Earth as of Friday morning, and none are expected through the weekend. A tropical wave parked in the northwest Caribbean is continuing to spawn showers and thunderstorms, but NHC gives it a near-zero chance of development over the next five days in its Friday morning Tropical Weather Outlook.

We’ll be back Monday with a new post. In the meantime, have a safe and fun Halloween weekend--and if you happen to be near Chicago’s Wrigley Field during the World Series game on Friday night, watch for wind-assisted baseballs flying out of the stadium!

Bob Henson



Heat Extreme Weather

Sea Ice Extent Is Near Record Lows--South as Well as North

By: Bob Henson , 4:03 PM GMT on October 26, 2016

It’s been a banner year for global sea ice, and not in a good way. After a record-smashing mild winter, the Arctic’s summer sea-ice melt culminated in a tie with 2007 for the second-lowest extent since satellite measurements began in 1979. The drama intensified this month, with Arctic sea ice extent now at a clear record low for late October as calculated by the National Snow and Ice Data Center (see Figure 1 below). This behavior isn’t really such a shock, given that Arctic sea ice has been declining for decades in the midst of sharp high-latitude warming. What’s more startling is the huge extent loss this year in the Antarctic, where sea ice extent had actually been increasing in recent years. This year’s Antarctic extent peaked very early, on August 31, and it’s now at its second-lowest value on record for late October, beaten only by 1986 (see Figure 2 below).

Together, these simultaneous drops have sent global sea ice extent--Arctic plus Antarctic--to its lowest level by far for this time of year since regular satellite monitoring began in 1979. The global extent as of October 25 was more than 1 million square kilometers below this date in 2011, the previous record-holder. In fact, it appears that the last few days are the first time we’ve seen a global departure from average in sea ice extent of more than 3 million sq km—which is more than four times the area occupied by Texas.

We shouldn’t pin too much on this record, because global sea ice extent is a much-abused and somewhat artificial metric. The Arctic and Antarctic have vastly different climate regimes, and what happens at one pole is far more important to its own regional climate than what’s occurring at the other pole. Still, the dramatic dip in global ice extent is worth noting if only because climate-change skeptics and deniers have pointed to global sea ice for years, and especially the Antarctic’s unexpected evolution, in an attempt to discount other evidence of a planet being warmed by increasing amounts of human-produced greenhouse gases. As Jeff Masters put it in this blog in 2010: “Diminishing the importance of Arctic sea ice loss by calling attention to Antarctic sea ice gain is like telling someone to ignore the fire smoldering in their attic, and instead go appreciate the coolness of the basement, because there is no fire there.”


Figure 1. The extent of Arctic sea ice has moved into record-low territory this month compared to all other Octobers since satellite monitoring of the Arctic began in 1979. This year surpassed its nearest rival, 2007, in mid-October. Image credit: National Snow and Ice Data Center.


Figure 2. The extent of Antarctic sea ice decreased rapidly in October 2016 compared to all other Octobers since satellite monitoring of the Antarctic began in 1979. The only year with a lower Antarctic extent as of October 24 was 1986 (gold line). Image credit: National Snow and Ice Data Center.

The big north-vs-south difference in sea ice
The stark difference between yearly patterns of sea ice in the Arctic versus the Antarctic is mainly a function of where the land sits. Northern sea ice melts and freezes within the Arctic Ocean, which surrounds and includes the North Pole. Southern ice melts and freezes in a ring around the continent of Antarctica, which keeps it well away from the South Pole and at lower latitudes than Arctic sea ice. As a result, southern sea ice covers a larger area than northern sea ice each winter, yet more than 80% of it disappears each summer. From winter max to summer min, a typical yearly drop in sea-ice extent in recent years would be from around 15 to 5 million sq km in the Arctic and from around 19 to 3 million sq km in the Antarctic.

Unfortunately, the longer-term, year-round decline in Arctic sea ice extent over the last couple of decades makes all too much sense. Temperatures at high northern latitudes have been soaring, this year in particular. (One example: the statewide temperature average in Alaska for the first nine months of 2016 is nearly 3°F warmer than for any Jan-Sep period since records began in 1925.) The Arctic is still more than cold enough each winter to re-cover the Arctic Ocean with sea ice, but the quality and thickness of that return ice has been declining, and the amount that survives as multiyear ice has plummeted.

Scientists long expected the Antarctic’s sea ice to decline as well. Instead, it’s actually expanded to record-high extents at times over the last few years. Even top computer models have been flummoxed by this trend. Among the simulations of Antarctic climate carried out in support of the most recent IPCC report, a majority predicted that ice should have declined between 1979 and 2013. In a review paper published in Nature Climate Change in September, a group of Antarctic experts surveyed what we know about high-latitude southern climate. It appears that a set of interlocking, difficult-to-model factors over the last few years has fostered the increasing trend in Antarctic sea ice, especially in the Ross Sea area. These include:

--A strengthening of the midlatitude westerlies that encircle Antarctica. These have fostered upwelling of cold subsurface waters across the Southern Ocean, which allows sea ice to expand more readily.

--Increased meltwater flowing from Antarctica into the Southern Ocean. This reduces the salinity of waters near the coast, thus allowing the surface to freeze at a warmer temperature.

--Strengthening of a prevailing low in the Amundsen Sea off West Antarctica. The flow around the Amundsen Sea Low pulls cold air off the continent and into the Ross Sea. The resulting increase in sea ice over that region has made up for ice reductions in the Amundsen-Bellingshausen region, where the circulation around the prevailing low tends to bring relatively mild air onshore.

The same study also noted unmistakable signs of climate change in the Antarctic, including warming of the subsurface ocean, thinning of ice shelves, and the acceleration of outlet glaciers that ring the ice sheet. According to an essay in The Conversation by three of the study’s authors, the cooling of surface waters around Antarctica has been masking “a much more ominous change deeper down in the ocean, particularly near the West Antarctic Ice Sheet and the Totten glacier in East Antarctica. In these regions, worrying rates of subsurface ocean warming have been detected up against the base of ice sheets. There are real fears that subsurface melting could destabilise ice sheets, accelerating future global sea level rise.”


Figure 3. Maximum extent of Antarctic sea ice in 2013 (left) and 1979 (right) as observed by satellite. October is typically the global maximum for sea ice, largely because of the vast extent of Antarctic ice at that time. Image credit: Jesse Allen and Joshua Stevens/NASA Earth Observatory.

What the tropics tell us about the future of Antarctic sea ice
I asked David Schneider (National Center for Atmospheric Research), a coauthor on the paper above, for his thoughts on recent changes in the Antarctic and what they might portend. Schneider has carried out extensive research on the intriguing links between tropical and Antarctic climate. “The Amundsen Sea Low [ASL] is strongly influenced by tropical variability, and in particular it is deeper during La Niña years,” he told me. As it turns out, La Niña events were more frequent than El Niño events from 1999 to 2014, in sync with a negative phase of the Pacific Decadal Oscillation (PDO). “Around the end of 2014, the PDO transitioned to its positive phase, and then the 2015-16 El Nino event occurred,” Schneider noted. “I would hypothesize that this transition of tropical climate is important for Antarctic sea ice and probably marks the end of the record high Antarctic ice extents that were observed through 2014.” Schneider added a word of caution: “The ASL exhibits the largest large-scale variability of any atmospheric circulation system on Earth, and it can vary independently of La Nina and El Nino. Thus, anomalously deep ASL years and relatively large Antarctic ice extents, particularly in the Ross Sea, are still possible.”

It should also be emphasized that the globe’s overall sea-ice budget has been in the red for quite some time. In 2015, NASA’s Claire Parkinson showed that the losses in Arctic ice were already outweighing the lesser increases in Antarctic ice. “I think that the expectation is that, if anything, in the long term the Antarctic sea ice growth is more likely to slow down or even reverse,” Parkinson said.


Figure 4. Monthly departures from average sea ice extent for the entire planet (bottom) are driven mainly by losses in the Arctic (top) rather than smaller gains in the Antarctic (middle). Image credit: Jesse Allen and Joshua Stevens/NASA Earth Observatory.


Figure 5. Temperatures across parts of the Arctic ran more than 30°F above average during the first two weeks of October 2016, based on an NCEP/NCAR reanalysis technique that involves observations across the region. Image credit: University of Maine and NOAA/ESRL/PSD.

The Arctic this autumn: Warm air, warm water, thin ice
The Arctic sea ice entered record-low territory this month after a faster-than-usual refreeze in late September and early October. “The thinned and broken ice across the central Arctic basin was able to refreeze rapidly as temperatures cooled after the sea ice minimum,” noted Zachary Labe (University of California, Irvine), a doctoral student recently profiled by Climate Central. Labe thinks the slower-than-usual growth of sea ice over the last few days is in large part due to very warm sea surface temperatures (SSTs) for the time of year. The record-warm air temperatures currently slathering the Arctic are not only associated with an atmospheric blocking pattern, but also related to the warm oceans themselves, Labe noted. “The air-ocean heat exchange from the open water is helping to modify the cold air near the surface, in addition to the release of latent heat as sea ice refreezes. The warm SSTs are really acting to prevent the sea ice to expand, especially into the Beaufort, Chukchi, and East Siberian Seas.”

Labe is even more impressed by the very low ice thickness and volume, as estimated by computer models that reproduce the ice in three dimensions. “I think this will become a bigger story,” he said. “The Arctic ice is looking incredibly thin, which is to be expected from such warmth in both the air and ocean.”


Figure 6. The Barrow Sea Ice Webcam, operated by the University of Alaska Geophysical Institute, showed ice-free conditions on the Arctic Ocean coast on October 25, 2016. Barrow’s average temperature for the period October 1 - 25, 2016, was 30.6°F, which is 11.5°F above average for the period. In records going back to 1922, Barrow’s warmest October was in 2012, which averaged 27.5°F. Forecasts through the end of the month indicate that Barrow is very likely to break that October record. Image credit: Barrow Sea Ice Webcam.

Antarctic ice claims a polar researcher
Dr. Gordon Hamilton, a glaciologist based at the University of Maine’s Climate Change Institute, died on Saturday, October 22, in an accident about 25 miles from Antarctica’s McMurdo Station. Hamilton was killed when his snow machine plunged some 100 feet into a crevasse located in an area known as the Shear Zone. He and colleagues affiliated with the U.S. Antarctic Program, managed by the National Science Foundation, had been working to identify and remediate crevasses that had appeared in the past year. “The death of one of our colleagues is a tragic reminder of the risks we all face--no matter how hard we work at mitigating those risks--in field research,” said Kelly Falkner (NSF Division of Polar Programs) in a statement on Facebook.

Figure 7. Gordon Hamilton. Image credit: University of Maine.

Hamilton’s research focused on mass balance and other aspects of polar ice sheets, including the stability of ice shelves in Antarctica, one of the most crucial uncertainties in the future of global sea level rise.

Justin Gillis (New York Times) wrote in a tribute to Hamilton: “He died doing a job whose urgency and importance, whose implications for the fate of all humanity, he understood as well as anyone. Yet he had carried out his work with a sense of wonder. Can you believe, he said to me in one of our conversations, that some of us get to spend our lives exploring places like Greenland and Antarctica?”

The four-minute film below, produced by the UM Climate Change Institute features Gordon Hamilton discussing his work. “I can’t think of another job I’d rather be doing,” Hamilton says.

We’ll be back with a new post by Friday. In the tropics, amazing Hurricane Seymour peaked on Tuesday night in the East Pacific with Category 4 sustained winds of 150 mph. Seymour was located more than 700 miles southwest of Mexico’s Baja Peninsula. As of 11 am EDT Wednesday, Seymour’s peak winds were down to 140 mph. Seymour should weaken at an increasingly rapid pace Wednesday through Thursday, remaining no threat to land.

Bob Henson



Arctic Antarctic Sea Ice

Small Yet Mighty, Hurricane Seymour Quickly Strengthens

By: Bob Henson , 4:17 PM GMT on October 25, 2016

On Sunday night, the National Hurricane Center (NHC) correctly pegged a small tropical cyclone off the coast of Mexico as being a candidate for rapid intensification, and rapidly intensify it has. Just a minimal tropical storm as of 11 am EDT Sunday, and a minimal hurricane at 11 am Monday, Hurricane Seymour was a strong Category 3 storm as of 11 am EDT Tuesday, with top sustained winds now at 125 mph. Located about 600 miles southwest of Cabo San Lucas, Mexico, Seymour is moving away from land toward the west at about 14 mph. No reconnaissance flights will be going into Seymour, but satellite imagery suggests that the hurricane likely completed an eyewall replacement cycle on Monday night.

Seymour could strengthen even more in the next 24 hours, as wind shear remains very light (only about 5 knots), sea-surface temperatures are very warm (28 - 29°C), and the atmosphere remains fairly moist (mid-level relative humidities of 60 - 70%). NHC’s official forecast makes Seymour a Category 4 storm with 140-mph winds by late Wednesday. Beyond Wednesday, shear will increase and SSTs will decrease along Seymour’s path, and the hurricane will weaken fairly quickly as it begins curving toward the north-northwest. Seymour will dissipate long before it can threaten the Pacific coast of Mexico or the U.S.


Figure 1. Enhanced infrared image of Hurricane Seymour as of 10:30 am EDT Tuesday, October 25, 2016. Image credit: NOAA/NESDIS.


Figure 2. Visible satellite image of Hurricane Seymour as of 10:45 am EDT Tuesday, October 25, 2016. Image credit: NASA/MSFC Earth Science Office.


On Sunday night, NHC forecasters began noting Seymour’s potential for rapid intensification, which had become evident in both statistical and dynamical forecast models. NHC has gained skill at intensity prediction over the last few years, but the task remains much more difficult than track prediction, even at short time periods (see Figure 3 below]. Intensity changes are heavily influenced by complex, small-scale processes that are tough for computer models to accurately represent. This is especially true for rapid intensification, defined by NHC as an increase in a tropical cyclone’s maximum sustained winds of at least 30 knots (35 mph) in a 24-hour period. Models often disagree on whether a tropical cyclone might rapidly intensify. As an operational agency, NHC strives to avoid “windshield-wiper” forecasts, where the predictions lurch back and forth every few hours based on short-term trends. This means that NHC will often be cautious in predicting rapid intensification, to avoid having to pull back in a subsequent forecast.


Figure 3. Trends in intensity forecasts from the National Hurricane Center for Eastern Pacific tropical cyclones through 2015. Units are knots; add 15% to obtain miles per hour. Image credit: NHC.

As far back as its 12Z Sunday run, the HWRF model--on average, the best of the dynamical models at predicting intensity for an existing storm--was consistently predicting that Seymour would become at least a Category 3 storm by midweek. Singing a similar tune was the SHIPS statistical model, which takes into account various environmental factors to calculate the odds of a storm rapidly intensifying over various time periods. By 12Z Sunday, the SHIPS model gave Seymour (then just a 30-knot tropical storm) a 54 percent chance of gaining 55 knots of strength (i.e., becoming an 85-knot or 100-mph Category 2 hurricane) by 12Z Tuesday. With very consistent messages coming from these tools, NHC forecasters began to dramatically hike their intensity predictions for Seymour late Sunday. NHC’s early-Monday forecast called for Seymour to vault from 65-mph to 115-mph sustained winds in just 48 hours, which the storm more than accomplished.

The forecast for Seymour was made easier by its modest size. Smaller tropical storms and hurricanes can both strengthen and weaken more rapidly than large ones, since they contain less mass (air, water vapor, clouds) to spin up or slow down. As of Tuesday morning, Seymour’s tropical-storm-force winds extended out only 70 miles from its center, and hurricane-force winds extended out just 15 miles.

The signals were much more mixed, and the forecast more difficult, for Hurricane Matthew when it underwent spectacular intensification on September 29 - October 1. During that period, Matthew leapt from tropical-storm strength (70 mph) to Category 5 hurricane strength (160 mph) in just 36 hours. Matthew was an unusually large storm to undergo such rapid intensification: Matthew’s tropical-storm-force winds extended out 205 miles from its center even before the storm reached hurricane strength.


Figure 4.Tropical Storm Kyant as of 11 am EDT Tuesday, October 25, 2016. Image credit: CIRA/CSU/RAMMB.

Tropical Storm Kyant a slow grower in the Bay of Bengal
Tropical Storm 3, dubbed Kyant by the Indian Meteorological Department, is gradually strengthening as it moves west through the Bay of Bengal, with top sustained winds up to 50 mph as of Tuesday morning. SSTs are quite warm along Kyant’s path (close to 30°C or 86°F), and wind shear is light to moderate (10 - 15 knots), but the storm will be moving into relatively dry air (relative humidities around 40%), which will hinder its growth over time. Kyant is predicted by the Joint Typhoon Warning Agency to make landfall north of Chennai, India, on Friday night as a minimal tropical storm.

Debunking the 1913 global heat record at Death Valley
WU weather historian Christopher Burt has given us a masterpiece of meteorological detective work in his Monday post, “An Investigation of Death Valley’s 134°F World Temperature Record.” Chris joined forces with geographer and climatologist William Reid to dig into the background surrounding the 134°F reading taken at Furnace Creek, near Death Valley, California, on July 10, 1913. This was eclipsed as the world’s hottest air temperature by the 58.0°C (136.4°F) reading at El Azizia, Libya, on September 13, 1922. However, the latter was disqualified by the World Meteorological Organization in 2012, which re-throned the 1913 Furnace Creek report as the world’s hottest observed surface temperature. In his post on Monday, Chris lays the groundwork for why the 1913 reading ought to be disqualified as well. It’s a long but fascinating read--give yourself time to savor it!

We’ll be back with a new post on Wednesday.

Bob Henson


Figure 5. This photo of Death Valley, California, from Dante’s View shows the Badwater Basin just below (white area) and the Furnace Creek Ranch and the national park visitors area to the north where the green-shaded area is visible in the top right portion of this image. This photo is a still from the documentary film ‘Dead Heat’ produced by Weather Underground in 2012.

Hurricane

Hurricane Seymour Gains Steam in East Pacific

By: Bob Henson , 3:48 PM GMT on October 24, 2016

More than three weeks of quietude in the Eastern Pacific has come to an end with the development of Hurricane Seymour, which could become the region’s sixth major hurricane of the year. Seymour gained hurricane status about 450 miles southwest of Manzanillo, Mexico, at 11 am EDT Monday, with top sustained winds at 75 mph. As noted by Dr. Phil Klotzbach (Colorado State University), Seymour is the Pacific’s first named storm east of the International Date Line since Hurricane Ulika, which dissipated September 30, and the first named storm in the Eastern Pacific east of 140°W since Tropical Storm Roslyn, which dissipated on September 29.

It was exactly a year ago (October 22-23, 2015) that Hurricane Patricia rocketed from tropical storm to Category 5 strength in just 24 hours over the northeast Pacific. Though Seymour doesn’t appear set to challenge Patricia, it is strengthening at a robust enough pace to be considered a rapid intensifier. In the 24 hours from 11:00 am EDT Sunday to Monday, Seymour vaulted from a 35-mph tropical depression to a 75-mph hurricane, and more growth lies ahead. Showers and thunderstorms have expanded around Seymour’s compact center in the last few hours, enhanced by very low wind shear (less than 10 knots) and a fairly moist atmosphere (mid-level relative humidities of 60 - 70%).


Figure 1. Hurricane Seymour as of 10:57 am EDT Monday, October 24, 2016.

Outlook for Seymour
For the next several days, Seymour will be traveling west to west-northwest over very warm SSTs above 28°C (82°F), while other conditions remain favorable. Seymour’s peak intensity should arrive late Tuesday or Wednesday, by which point it is likely to attain at least Category 2 or 3 strength as suggested by the HWRF model and statistical guidance. The National Hurricane Center (NHC) official forecast issued at 11 am EDT Monday has Seymour peaking as a 120-mph hurricane on Tuesday evening. The 12Z Monday output from the SHIPS statistical model gives Seymour a 68% chance of attaining 105-knot sustained winds (Category 3) by Tuesday night and a 31% chance of reaching 115 knots (Category 4) by Wednesday morning. By Thursday, higher wind shear and lower SSTs will begin sounding the the death knell for Seymour as the hurricane begins recurving toward the northeast. Seymour is expected to dissipate by next weekend while still far offshore from the U.S. and Mexico. However, some of Seymour’s moisture could get entrained into a strong midlatitude storm expected to plow into northern and central California late in the weekend, bringing welcome rains and mountain snows.


Figure 2. NHC’s outlook for Seymour as of 11 am EDT Monday, October 24, 2016.

It’s been another busy year in the East Pacific
Forecasters had expected 2016 to produce a bit more tropical activity than usual in the Central and East Pacific. Factors in play included the projected transition from El Niño to La Niña (the latter tends to suppress hurricanes over the northeast Pacific Ocean), and the possibility that the global SSTs patterns that favored Central and East Pacific hurricanes in 2014 and 2015 might remain. (2014 was the region’s fourth most active season on record, as measured by named storms, and 2015 was the second most active.) As it turned out, La Niña has been slow in materializing, and SSTs over the North Pacific and North Atlantic have remained favorable for eastern Pacific hurricanes.

Back in May, Mexico’s national meteorological service (SMN) predicted 17 named storms, 9 hurricanes, and 4 major hurricanes in the Central and Eastern Pacific, which is slightly above the 1981-2010 average of 15.4 named storms, 7.6 hurricanes, and 3.2 major hurricanes. Likewise, the NOAA outlook skewed above the long-term mean, calling for a range of 13-20 named storms, 6-11 hurricanes, and 3-6 major hurricanes. With Seymour now a hurricane, the 2016 season stands at 20 named storms, 13 hurricanes, and 5 major hurricanes, which is near the top end of NOAA’s range and considerably above the SMN outlook. The NOAA range is designed to encompass 70% of potential outcomes for seasons that share the same climate conditions and uncertainties.

This is the fifth year in a row with an above-average number of both tropical storms and hurricanes in the Central and Eastern Pacific. Counting Seymour, the region has seen a grand total of 105 named storms since 2012! If that whole five-year stretch had featured the same rate of activity as the period 1981-2010, there would have been 77 named storms.

Elsewhere in the tropics
For the first time in a long time, we’re looking at a quiet week across the tropical Atlantic. NHC expects no tropical cyclone formation through Wednesday. Among ensemble guidance from 00Z Monday, the GFS ensemble continues to favor the development of a tropical depression well east of the Lesser Antilles this week, but the European ensemble shows less than a 10% chance of this outcome, and none of the leading operational models (GFS, Euro, and UKMET) show any significant development. Climatology also leans away from development in the open tropical Atlantic by late October.

In the Bay of Bengal, a depression west of Myanmar dubbed Invest 99B (see Figure 3 below) could gain some strength as it moves west toward India this week, although models are not bullish on any major development.

We’ll be back with a new post on Tuesday.

Bob Henson


Figure 3. Invest 99B as of 3:18 am EDT Monday, October 24, 2016. Image credit: CIRA/CSU/RAMMB.

Hurricane

At Least 13 Killed by Typhoon Haima; Atlantic Quiets Down

By: Bob Henson and Jeff Masters , 4:59 PM GMT on October 21, 2016

Potential tropical cyclones are having a tough go of it during these waning days of the 2016 Atlantic hurricane season. Forecasters have been watching Invest 99L for most of this week east of the Bahamas. 99L’s showers and thunderstorms (convection) have never consolidated around a single closed center of low pressure. On Friday morning, 99L consisted of a small pocket of convection near its center and weak showers and storms ringing 99L’s very broad area of low pressure. The entire system will soon accelerate north and get pulled into a midlatitude storm expected to intensify over New England on Friday night and Saturday. In its 8 am EDT Friday Tropical Weather Outlook, the National Hurricane Center gave 99L only a 40% chance of developing into a tropical or subtropical cyclone before it loses its identity, and that may be generous. Moisture feeding from 99L into the midlatitude cyclone and an associated front will produce heavy, drought-easing rains this weekend from Pennsylvania to New England, with 3” - 5” expected from central New York across much of New Hampshire and Maine.


Figure 1. A broad loop of showers and thunderstorms is spiraling into 99L, shown here in a visible satellite image from 10:45 am EDT Friday, October 21, 2016.

Another wave to watch in the tropical Atlantic
It’s very late in the season to look for any development in the central Atlantic, but a tropical wave centered around 11°N and 44°W on Friday morning bears watching. Strong wind shear is now pushing dry air into the wave, limiting the amount of convection present. The shear over the wave may lessen over the next couple of days, and sea-surface temperatures of around 28 - 29°C (82 - 84°F), about 0.5°C above average, are more than adequate to support development. All 20 of the GFS ensemble members from Thursday night (00Z Friday), and almost half of the 50 ECWMF ensemble members, develop this wave over the next 2 to 5 days into at least a tropical depression, with some support for tropical storm formation. A weak upper low east of the Lesser Antilles may interact with this wave, complicating any potential development. If the wave does develop, it would most likely move north or northwest and remain far from land, perhaps stalling in the open central Atlantic later next week.

The next name on the Atlantic list is Otto, and getting to that point would be noteworthy. Since regular naming of Atlantic tropical cyclones began in the early 1950s, we have had only 10 “O” storms, all of them developing during the active period of Atlantic hurricane activity that began in 1995:

Opal, 1995
Olga, 2001
Odette, 2003
Otto, 2004
Ophelia, 2005
Olga, 2007
Omar, 2008
Otto, 2010
Ophelia, 2011
Oscar, 2012


Figure 2. Forecasts for the total number of hurricanes in the 2016 Atlantic season, issued by the groups shown along the bottom legend. For groups that issue more than one outlook per season, the most recent outlook is shown here. The average forecast across groups was for 8 hurricanes, as compared to the 6 that have occurred through October 21. Image credit: Colorado State University/XL Catlin/Barcelona Supercomputing Center.

The Atlantic season to date
This year’s predictions of a near-average to slightly above-average 2016 Atlantic hurricane season are looking quite close to the mark as the season begins to wind down. As of October 21, the Atlantic has seen 14 named storms, 6 hurricanes, and 3 major hurricanes. This compares to the 1981-2010 average of 12.1 named storms, 6.4 hurricanes, and 2.7 major hurricanes.

The outlooks from most forecast groups (see Figure 2 above) leaned toward a higher number of hurricanes than we've actually seen. However, in terms of accumulated cyclone energy (ACE)--which integrates the lifespan and wind-speed intensity of each tropical cyclone--it’s been a more active year than one might expect from hurricane counts alone. This is mainly a result of the strength and duration of the year’s three major hurricanes: Gaston, Matthew, and Nicole. As of October 21, the 2016 Atlantic season had racked up an ACE total of 133, which is 144% of the typical ACE for the year to date and 128% of the typical total ACE for a season.



Figure 3. A resident of a home destroyed at the height of Typhoon Haima in Cabagan town, Isabela province, north of Manila on October 21, 2016. Cabagan and nearby areas on the east side of coastal mountains took the hardest hit from Hamia’s Category 4 winds. Image credit: Ted Aljibe/AFP/Getty Images)

Haima heads into China after departing the typhoon-weary Philippines
Residents of the Philippines’ northern Luzon Island are picking up the pieces and assessing damage after a powerful one-two blow from Typhoon Sarika, which made landfall as a borderline Category 3/4 storm with 130-mph winds on Sunday morning, followed by Typhoon Haima making landfall as a Category 4 storm with 140-mph winds on Wednesday night. Haima’s landfall point was only about 130 miles north-northeast of Sarika’s. At least two deaths and $80 million in damage were reported in the Philippines from Sarika. Haima is being blamed for at least 13 deaths in the Philippines, and widespread damage is expected to mount into the hundred of millions of dollars.

Haima made landfall between Hong Kong and Shantou, China, as a Category 1 storm late Friday night local time. With dry air now infiltrating the cyclone, additional heavy rains should be fairly limited as Haima moves inland and spins down below typhoon strength. The combined economic impact in China from Sarika and Haima is estimated at more than $800 million, according to Aon Benfield’s Steve Bowen. More than 6000 homes and more than a million acres of cropland have been affected in China, largely from Sarika.

In the Philippines, Baguio City (population 350,000) picked up over 14” (361 millimeters) of rain from Haima on October 20, and Tuguegarao City recorded 9.65 inches (245 mm.) Wind reports are scant across the region, but photos on the ground and satellite imagery reveal widespread destruction to the landscape and the built environment. Josh Morgerman of @iCyclone was located at Tuguegarao City, located in the Cagayan Valley about 25 miles inland. Though the city was shielded from Haima’s landfall by a coastal range of mountains, Morgerman documented widespread damage in the area (see embedded video below). Morgerman recorded a central pressure of 942 millibars at 1:24 am local time Thursday morning as Haima’s eye passed over. Thousands of people reportedly stayed in or near shelters between the landfalls of Sarika and Haima, which may have played a big role in reducing deaths and injuries from Haima. Both typhoons made landfall in relatively unpopulated stretches of coastline; this greatly limited the odds of a catastrophe along the lines of Super Typhoon Haiyan, which killed thousands in the Philippines in 2013.

We’ll be back with a new post on Monday. Have a great weekend, everyone!

Bob Henson and Jeff Masters


Figure 4. MODIS satellite image of Typhoon Haima taken at 1:30 am EDT October 20, 2016. At the time, Haima was a Category 2 storm with 105 mph winds, and was located between the Philippines’ Luzon Island and the coast of China. Image credit: NASA.



Hurricane

Drought is the Watchword as Winter 2016-17 Approaches

By: Bob Henson , 5:20 PM GMT on October 20, 2016

After a year with a record number of billion-dollar flood disasters, the United States is now heading into a period where drought may be the leading concern, according to forecasters behind NOAA’s initial winter outlook for 2016-17 that was released Thursday. “The winter forecast doesn’t bode well for [many] areas around the nation experiencing drought,” said Mike Halpert, deputy director of NOAA’s Climate Prediction Center, in a press conference Thursday. The most confident signal in the outlooks (see Figures 2 and 3) is for warmer-than-average conditions across the Sun Belt, from California to Florida, and for drier-than-average conditions across the southern tier of states, especially from the Southern Plains to the Southeast.

A five-year drought continues to grip central and southern California, and a rapidly intensifying drought now stretches from Alabama to the western Carolinas, as evident in this week’s U.S. Drought Monitor. Parts of northern Alabama and Georgia have only recorded about half of their average rainfall over the last six months, according to the Drought Monitor. New England and New York are also grappling with serious, months-long drought, although heavy rains this weekend may provide some relief.


Figure 1. Sunlight reflects on the surface of Lake Purdy in Birmingham, AL, on Tuesday, October 11, 2016. The lake's water levels have dropped several feet due to a severe drought. Image credit: AP Photo/Brynn Anderson.

More room for surprises
The winter of 2015-16 largely followed expectations for a strong El Niño event, with two big exceptions: persistent dryness in the drought-plagued Southwest and unusual warmth that prevailed across nearly all of the U.S., including areas such as the Gulf Coast that trend cool during El Niño winters. This winter, we don’t have a strong El Niño or La Niña event shaping North American climate, so there is even more room for natural variability and the potential for surprises in the mix. In its most recent monthly advisory, issued on October 13, NOAA deemed it likely that a La Niña will develop by late autumn, but odds are just slightly better than even that it will persist through winter, and computer models agree that it should be a weak event if it does develop. Overall, NOAA’s winter outlook for the contiguous U.S. largely follows the playbook for La Niña, which typically favors relatively wet, cool conditions toward the north and relatively warm, dry weather toward the south.


Figure 2. NOAA precipitation outlook for winter 2016-17, expressed as the probabilities for wetter- or dryer-than-average conditions for the winter as a whole. The probabilities are expressed in thirds, so a region with 40% odds of an outcome has a better-than-average chance of that outcome. Image credit: NOAA/NWS.


Figure 3. NOAA temperature outlook for winter 2016-17, expressed as the probabilities for warmer- or colder-than-average conditions for the winter as a whole. Image credit: NOAA/NWS.

Could another cold Midwest/East winter be in the cards?
One line of research suggests that several winters of the 2010s that featured intense cold across parts of the U.S. Midwest and Northeast, such as 2013-14 and 2014-15, may be related to a chain of events that begins with above-average October snow cover in Siberia (facilitated in part by recent losses of Arctic sea ice in autumn north of Siberia). In this view, above-average snow cover in autumn fosters high atmospheric pressure over the region. In turn, this deflects the jet stream and eventually disrupts the circulation over the Arctic, allowing cold air masses to pour southward more easily by winter.

Judah Cohen, one of the most prominent exponents of this hypothesis, leads an effort at Atmospheric and Environmental Research to predict winter temperatures across the Northern Hemisphere. Snow cover has been advancing at a faster-than-usual pace this autumn in Siberia, according to Cohen. Based on this, as well as below-average sea ice extent across the Barents and Kara Seas and the lack of a strong ENSO signal in the mix, AER issued a preliminary winter 2016-17 outlook on October 19. The outlook favors warmer-than-average conditions across the U.S. Southwest and colder-than-average conditions from central Canada to the southeastern U.S., including most areas east of the Great Plains except for Maine (see Figure 4). Last winter, AER called for most of North America to be mild, in keeping with the strong El Niño that developed, but it expected below-average readings over the eastern U.S., where they didn’t materialize.


Figure 4. The outlook for departures from average temperature for the contiguous U.S. issued by Atmospheric and Environmental Research on October 19, 2016. An update will be issued in November. The model uses October Siberian snow cover, sea level pressure anomalies, predicted El Niño/Southern Oscillation anomalies, and observed September Arctic sea ice anomalies. October Siberian snow cover has so far this month advanced at an above normal rate. This is an indication of an increased probability of a weakened polar vortex or a sudden stratospheric warming, and a predominantly negative Arctic Oscillation during the winter and cold temperatures--especially east of the Mississippi. Image credit: Judah Cohen, AER.


Meanwhile, The Weather Company called for readings to be above average for most of the contiguous U.S. during the winter of 2016-17 in an outlook released on September 23 (see Figure 5 below). Referring to the switch from El Niño to a weak La Niña, TWC chief meteorologist Dr. Todd Crawford said: "The reversal of tropical forcing suggests that the coldest weather in the eastern U.S. may occur earlier in the winter, with increasing chances for warmth during the late winter.” Crawford added: “Climate model forecasts for winter are unusually warm, likely reflecting the excess post-El-Nino global warmth, and another very warm winter is not out of the question due to this factor alone."


Figure 5. Temperature outlook for winter 2016-17 released by The Weather Company on September 23. Image credit: weather.com.


The cold winters of the 2010s in eastern North America may also have a link to the Pacific. Dennis Hartmann (University of Washington) emphasizes the role of warmth across parts of the tropical Pacific in generating an atmospheric “bridge” that can extend to cold, snowy conditions in the eastern U.S. and Canada. Hartmann and colleagues have investigated a pattern called the North Pacific Mode (NPM), which is distinct from the El Niño/Southern Oscillation (ENSO). The NPM’s positive phase features warmer-than-average SSTs extending from the western Pacific across to much of the north and northeast Pacific, where a recurrent area of warm water dubbed “The Blob” has returned this fall. This positive phase of the NPM in wintertime tends to favor a strong upper-level ridge from the U.S. West Coast to Alaska (reducing the likelihood of storms affecting California) and a deep, cold trough across eastern Canada and the U.S. Midwest and Northeast, favoring intrusions of Arctic air. Hartmann discusses the NPM in more detail in a March 2015 post at climate.gov.

Hartmann has not yet analyzed the NPM for recent weeks, but he told me in an email: “The [current] tropical SST pattern is such as to force a high anomaly in the pressure in the midlatitude Pacific this winter, and that would give more ‘blob’ and a downstream anomaly like that of January 2014, all else being equal. So dry in California and cold in the East seems like a reasonable prediction, although the uncertainty is high because the atmosphere generates a lot of random variability unrelated to tropical SST.  It will be interesting to see what develops.”


Figure 6. The two most common sea surface temperature (SST) correlation patterns in Pacific Ocean north of 30°S over time, based on EOF (empirical orthogonal function) analysis, a technique used to break down the role of multiple potential factors. The first is the classic signal of El Niño and La Niña (together referred to as the El Niño-Southern Oscillation, or ENSO), while the second is the North Pacific Mode (NPM). The contour interval is 0.1, and the zero contour is white. Red and blue show correlations between anomalies of opposite sign. When red areas have above-average SSTs, blue areas have below-average SSTs, and vice versa. Image credit: Dennis Hartmann, University of Washington, and climate.gov.


Figure 7. Departure from average in sea surface temperature (SST, shown in degrees C) for the period October 9 through October 15, 2016. Image credit: NOAA/ESRL/PSD.

What makes a season?
It’s important to note that even a winter that’s overall warmer than average in the Midwest or Northeast may include a couple of fierce cold blasts and/or major snowstorms. Take 2015-16: even though it was the warmest winter on record for the contiguous U.S. as a whole, and a top-ten warmest winter from New Jersey through New England--including the warmest Christmas Day ever experienced by millions of East Coast residents--it also included the epic blizzard of January 20-22, 2016, which dumped more than two feet of snow from West Virginia to New York, and the brief but intense cold wave of mid-February 2016, which produced Boston’s coldest weather since the 1950s. It’s an open question whether people will remember the East Coast’s winter of 2015-16 as brutal or balmy. When asked at Thursday’s press conference whether we are likely to see a “memorable” winter, Mike Halpert responded: “That’s not really what our outlook is about.”

We’ll be back with out next post on Friday, including a wrap-up on Typhoon Haima, which was heading toward the southeast coast of China on Thursday after ravaging parts of the Northern Philippines. We are also keeping an eye on Invest 99L, the long-simmering system east of the Bahamas. The National Hurricane Center gives 99L a 50% chance of briefly developing into a depression, and perhaps a subtropical or tropical storm, as it moves northward, eventually merging with a frontal system off the U.S. East Coast.

Bob Henson


Drought long range winter outlook

Haima Slams into Northern Philippines

By: Bob Henson , 3:57 PM GMT on October 19, 2016

Still raging at Category 4 strength, Typhoon Haima (dubbed Lawin in the Philippines) was moving into the northern Philippines on Wednesday night local time. As of 9:00 am EDT Wednesday (9:00 pm local time), Haima was located about 235 miles northeast of Manila, moving west-northwest at about 19 mph. Haima became Earth’s seventh Category 5 storm of the year on Tuesday, with top sustained winds peaking at 165 mph and a minimum central pressure estimated at 900 mb by the Japan Meteorological Agency. Interactions with the mountainous island of Luzon have since chipped away at Haima’s strength. Top sustained winds were down to 120 knots (140 mph) as of 9 am EDT Wednesday. As noted by Jonathan Erdman (weather.com), if Haima makes landfall with sustained winds of at least 113 knots (130 mph), it will be the first Category 4 storm to strike northeast Luzon since Naigae in September 2011.


Figure 1. Enhanced infrared image from Japan’s Himawari-8 satellite of Typhoon Haima as of 1430Z (10:30 pm local time or 10:30 am EDT) Wednesday, October 19, 2016. Image credit: NOAA/NESDIS.


Figure 2. Radar imagery from Aparri, on the north coast of Luzon, shows the center of Typhoon Haima approaching at 10:00 am EDT (10:00 pm local time) Wednesday, October 19, 2016. Image credit: PAGASA.

Haima remained a gigantic and powerful typhoon as it approached Luzon, with hurricane-force winds extending out up to 75 miles from its center and tropical-storm force winds extending up to 235 miles. Fortunately, the winds on the stronger right-hand side of Haima, north of its center, will deliver their greatest punch to a fairly sparsely populated stretch of coastline in far northeast Luzon. A storm surge of up to 10 feet is possible within bays in this region, according to the Philippine Atmospheric, Geophysical and Astronomical Service Administration. There are no cities along this coast the size of Tacloban City, where the storm surge associated with Super Typhoon Haiyan killed more than 5000 people in 2013. The largest population center of far northeast Luzon is Tuguegarao City, located in the Cagayan Valley about 25 miles inland and shielded by a coastal range of mountains.

Given the size and strength of Haima, massive amounts of rain (10” - 20”, with higher amounts locally) can be expected over most of the northern half of the island of Luzon. These rains will fall atop ground saturated by the passage of former Category 4 Typhoon Sariki, which makes inland flooding the biggest concern from Haima. After exiting the Philippines, a weakened Haima will continue northwestward, making landfall on the China coast east of Hong Kong as a tropical storm or perhaps a Category 1 typhoon around Saturday night local time.


Figure 3. This “day-night band” image of Haima from the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi NPP satellite captures the storm while it was at super typhoon strength well east of the Philippines (outlined at far left) at 1642Z (12:42 pm EDT) Tuesday, October 18, 2016. Image credit: NOAA

99L unlikely to amount to much
Major development doesn’t appear to be in the cards for Invest 99L, a loosely organized, elongated cluster of showers and thunderstorms (convection) well east of the Bahamas. There is no closed circulation with 99L, and its convection remained paltry and fragmented from Tuesday night into Wednesday morning. Strong wind shear of around 30 - 35 knots continues to plague 99L, inhibiting organization of the convection that’s managing to hang on with the help of warm sea-surface temperatures (SSTs) of around 29°C (84°F) and a fairly moist atmosphere (mid-level relative humidities around 65 - 75%).


Figure 4. Enhanced infrared image of showers and thunderstorms associated with 99L well east of the Bahamas as of 1415Z (10:15 am EDT) Wednesday, October 19, 2016. Image credit: NASA/MSFC Earth Science Office.

Outlook for 99L
As it drifts northward and then northwestward over the next couple of days, 99L will move over progressively cooler SSTs as strong wind shear continues. About half of the members of the 00Z Wednesday GFS and ECMWF ensembles develop 99L to low-end tropical storm strength for a brief period, mostly around Thursday or Friday, when a strong upper-level trough will be approaching the eastern U.S. The dynamics associated with this trough, together with an upper-level low situated near 99L, would tend to favor 99L developing as a subtropical storm (if it did intensify) and eventually merging with the front. In its 8 am EDT Wednesday Tropical Weather Outlook, the National Hurricane Center is giving 99L a 60% chance of developing into at least a tropical depression by Friday and an 80% chance by Monday. I would peg the odds of 99L becoming a named tropical or subtropical storm at less than 50%. Meanwhile, the approaching front is expected to produce heavy rains of 2” - 6” from eastern Pennsylvania across upstate New York, northern New England, and far southeast Canada.

In the Eastern Pacific, NHC is monitoring three areas of interest, none of which are likely to develop over at least the next couple of days.


Figure 5. Surface winds over and near Greenland show the circulation associated with former Nicole as of 1500Z (11:00 am EDT) Wednesday, October 19, 2016.

Ex-Nicole helps trigger fierce downslope winds over southeast Greenland
After nearly two weeks as a tropical cyclone roaming the Atlantic, including a direct hit on Bermuda as a Category 3 hurricane, the remnants of Post-Tropical Cyclone Nicole were delivering a noteworthy parting shot to Greenland in the form of a localized wind called the piteraq (“that which attacks you”). A piteraq involves very cold, dense surface air descending from the Greenland plateau and accelerating in response to strong low pressure off the east coast. The EUMETSAT agency has an excellent explainer on the piteraq. Gradually being enveloped by a larger mid-latitude cyclone and front, Nicole was approaching far south Greenland on Wednesday as a still-powerful 966-millibar low, providing the strong pressure gradient needed for a piteraq to develop. Winds were sustained as high as 47 mph and gusting up to 68 mph on Wednesday morning at Tasillaq, on Greenland’s east coast, where coastal obstructions can cause a piteraq to evolve into an even more localized wind called a neqajaq. Thanks to wunderground member barbamz for finding and posting background information on the piteraq in the comments of our last post.

We’ll be back on Thursday with a new post.

Bob Henson


Hurricane

Global Temperature Just Short of Record in September, Says NOAA

By: Jeff Masters and Bob Henson , 10:25 PM GMT on October 18, 2016

September 2016 was Earth's second warmest September since record keeping began in 1880, said NOAA's National Centers for Environmental Information (NCEI) on Tuesday. In the NOAA database, September 2016 came in 0.89°C (1.66°F) warmer than the 20th-century average for September, and just 0.04°C shy of the record set in September 2015. NASA reported the warmest September in its database, with September 2016 a mere 0.01°C above the previous record, set in September 2014.


Figure 1. Departure of temperature from average by region for September 2016, which fell just short of September 2015 in NOAA’s database as the warmest September for the globe since record keeping began in 1880. Large swaths of much-warmer-than-average conditions could be found across the Americas, Africa, Eurasia, and adjacent oceans, with pockets of record warmth scattered across the globe. Image credit: NOAA National Centers for Environmental Information (NCEI).

A year-plus streak of global records draws to an end
September 2016 marked the end of a remarkable streak of 16 consecutive months in which NOAA’s global monthly temperature record was broken, the longest such streak since global temperature records began in 1880. Ocean-only temperatures this September were 0.04°C (0.07°F) cooler than the record warmth of September 2015, while land-only temperatures were 0.11°C (0.20°F) above the previous land-only record from September 2015. (Since most of Earth’s surface is covered by ocean, the land-plus-ocean reading is dominated by the ocean-only temperatures, thus keeping September 2016 just short of the land-plus-ocean record) For the lowest 8 km of the atmosphere, global satellite-measured temperatures in September 2016 were tied for warmest with 1998 for any September in the 38-year record, according to the University of Alabama in Huntsville (UAH).

With the powerful 2015-16 El Niño event having ended early in 2016, the impressive global warmth in recent months can mostly be attributed to the steady build-up of heat-trapping greenhouse gases due to human activities. NOAA’s global surface temperature for the year so far (January-September 2016) is an eye-opening 0.78°C (1.40°F) above the 20th-century average and 0.08°C (0.14°F) warmer than the previous January-to-September record, set in 2015 (see Figure 2 below).

Temperatures would have to plummet at an almost unthinkable pace between now and December in order to keep 2016 from becoming the warmest year in global record-keeping. Gavin Schmidt, director of NASA’s Goddard Institute of Space Studies, has maintained for months that there is a better-than-99 percent chance of 2016 ending up as Earth’s third consecutive hottest year on record. On October 17, Schmidt concluded that a new annual record for 2016 now “seems locked in.”

As the end of the year approaches, it will be difficult for temperatures to top the monthly records set in late 2015 and early 2016. At the same time, even a modest dip in global temperatures would still keep readings close to the record pace of 2015-16, and above all or nearly all other years in the 136-year database.


Figure 2. Departure from the 20th-century average for the global January-through-September temperature for the years 1880 - 2016. This year has seen by far the warmest temperatures on record for the year-to-date period. Image credit: NOAA/National Centers for Environmental Information (NCEI).

NOAA expects a La Niña event this fall, but probably a weak one
Sea surface temperatures (SSTs) in the Niño3.4 monitoring region of the eastern Pacific have been near or beyond the threshold for a weak La Niña since mid-July, but the atmospheric conditions that normally accompany La Niña have been slower to evolve. In September, NOAA dropped the La Niña Watch that was in place for several months, but reinstated it on October 13, thanks to a pronounced cooling of SSTs in late September and early October that caused the atmosphere to begin responding in a La Niña-like fashion. According to the October ENSO forecast from NOAA’s Climate Prediction Center, weak La Niña conditions are now favored to exist during the remainder of the Northern Hemisphere fall (70% chance), and persist through the winter (55% chance.)

Australia’s Bureau of Meteorology retained its La Niña watch in its biweekly update on October 11, saying “the majority of international climate models indicate the tropical Pacific is likely to remain at ENSO neutral levels through to the end of the 2016–17 summer. Two of the eight models suggest brief, weak La Niña levels are possible towards the end of 2016.” (Australia’s oceanic threshold for La Niña and El Niño is higher than NOAA’s: the Niño3.4 region must be at least 0.8°C warmer or cooler than average, rather than 0.5°C, though Australia doesn’t require those temperatures to persist for months as NOAA does.) The Japan Meteorological Agency has gone further; for the second straight month, their monthly update has concluded that “it is considered that La Niña conditions are present in the equatorial Pacific.” The JMA uses the Niño3 region, which overlaps with the Niño3.4 region but extends further east.

Arctic sea ice hits its fifth lowest September extent on record
The rate of September sea ice gain in the Arctic was above average last month, after sea ice extent bottomed out at the second lowest yearly extent ever observed early in the month (see our post here on that event). As a result, September 2016 Arctic sea ice extent came in at the fifth lowest in the 38-year satellite record, according to the National Snow and Ice Data Center (NSIDC). The minimum extent for the year, set on September 10, tied with the minimum set in 2007 for the second-lowest on record. The Arctic’s sea ice has grown so slowly in recent days that the extent on October 18 was in a virtual tie with 2007 and 2012.

One billion-dollar weather disaster in September 2016: Typhoon Meranti
According to the September 2016 Catastrophe Report from insurance broker Aon Benfield, one billion-dollar weather-related disaster hit the planet in September: Typhoon Meranti, which killed 44 people in China, Taiwan and the Philippines on September 13 - 16 and did $2.4 billion in damage. Two other tropical cyclones in September fell just short of being billion-dollar disasters: Hurricane Hermine in the U.S. ($800 million in damage) and Typhoon Megi, which hit Taiwan at Category 3 strength and China at Category 1 strength, doing $940 million in damage.

Additionally, a severe weather outbreak in the U.S. Plains, Midwest and Mississippi Valley on May 7 - 10 and a flood disaster April 15 - 19 in the U.S. Plains/Rockies accumulated enough damage claims to be rated billion-dollar disasters by the end of September. Between January - September 2016, there were 27 billion-dollar weather disasters globally. This is the fifth greatest number of such disasters since 1990, with only 2013 (41), 2010 (40), 2011 (35) and 2014 (29) with more.

For the U.S., Aon Benfield and NOAA counted twelve billion-dollar weather disasters during January - September 2016, which is the second highest number of such disasters on record since 1980 (the record: sixteen in 2011.) Most interesting is that NOAA classifies four of these as inland flood events, which doubles the previous record of two inland flood events in a year. NOAA emphasizes ”This is a notable record, further highlighted by the numerous other record flooding events that have impacted the U.S. in 2016.”


Figure 3. U.S. billion-dollar weather disasters (adjusted for inflation using the Consumer Price Index, or CPI) since 1980 (colored bars, scale on the left axis) and damage done by these disasters (grey line with a shaded 95% confidence interval, scale on the right axis.) The 1980–2015 annual average is 5.2 events (CPI-adjusted); the annual average for the most recent 5 years (2011–2015) is 10.8 events (CPI-adjusted). Image credit: NOAA.

Here is Aon Benfield’s tally of billion-dollar weather disasters globally for January - September 2016:

1) Flooding, Yangtze Basin, China, 5/1 - 8/1, $28.0 billion, 475 killed
2) Flooding, Louisiana U.S., 8/9 - 8/16, $10 - $15 Billion, 13 killed
3) Flooding, Germany, France, Austria, Poland, 5/26 - 6/6, $5.5 billion, 17 killed
4) Drought, India, 1/1 - 6/30, $5.0 billion, 0 killed
5) Flooding, Northeast China 7/16 - 7/24, $5.0 billion, 289 killed
6) Wildfire, Fort McMurray, Canada, 5/2- 6/1, $5.0 billion, 0 killed
7) Severe Weather, Plains-Southeast U.S., 4/10 - 4/13, $3.75 billion, 1 killed
8) Severe Weather, Rockies-Plains-Southeast-Midwest U.S., 3/22 - 3/25, $2.5 billion, 0 killed
9) Super Typhoon Meranti, China, Taiwan, Philippines, 9/13 - 9/16, $2.4 billion, 44 killed
10) Flooding, China, 6/18 - 6/23, $2.3 billion, 68 killed
11) Winter Weather, East Asia, 1/20 - 1/26, $2.0 billion, 116 killed
12) Severe Weather, Plains-Midwest U.S., 4/29 - 5/3, $1.75 billion, 6 killed
13) Tropical Cyclone Roanu, Sri Lanka, India, Bangladesh, Myanmar, China, 5/14 - 5/21, $1.7 billion, 135 killed
14) Drought, China, 1/1 - 3/1, $1.6 billion, 0 killed
15) Drought, Zimbabwe, 6/1 - 8/10, $1.6 billion, 0 killed
16) Flooding and Severe Weather, Plains-Midwest-Southeast-Northeast U.S., 3/4 - 3/12, $1.5 billion, 6 killed
17) Typhoon Nepartak, Philippines, Taiwan, China, 7/8 - 7/9, $1.5 billion, 111 killed
18) Severe Weather, Plains-Southeast U.S., 3/17 - 3/18, $1.4 billion, 0 killed
19) Tropical Cyclone Winston, Fiji, 2/16 - 2/22, $1.4 billion, 44 killed
20) Flooding, Argentina and Uruguay, 4/4 - 4/10, $1.3 billion, 0 killed
21) Severe Weather, Plains-Midwest U.S., 5/21 - 5/28, $1.3 billion, 1 killed
22) Severe Weather, Plains-Midwest-Southeast-Northeast U.S., 2/22 - 2/25, $1.2 billion, 10 killed
23) Severe Weather, Netherlands, 6/23 - 6/24, $1.1 billion, 0 killed
24) Severe Weather, Plains-Rockies U.S., 7/28 - 7/29, $1.0 billion, 0 killed
25) Flooding, Texas U.S., 4/15 - 4/19, $1.0 billion, 9 killed
26) Severe Weather, Plains-Midwest-Mississippi Valley U.S., 5/7 - 5/10, $1.0 billion, 2 killed
27) Winter Weather, Eastern U.S., 1/21 - 1/24, $1.0 billion, 58 killed

And here are the three disasters from September 2016 in more detail:


Disaster 1. After topping out as one of Earth’s top-ten strongest tropical cyclones on record, with a central pressure of 890 mb and sustained winds of 190 mph, Super Typhoon Meranti weakened to Category 2 strength before making landfall in China’s Fujian Province on September 15. Meranti killed 42 people and did $2.3 billion in damage to China. In Tawian, two people were killed, and damage was over $70 million. Above, we see the eye of Meranti directly over the Philippines’ Itbayat Island in a moonlight image from Japan’s Himiwari-8 satellite taken at 17:32 UTC September 13, 2016. Itbayat recorded sustained winds of 112 mph (10-minute average) and a pressure of 934 mb at 1 am local time, 32 minutes prior to this image. At the time, Meranti was a Category 5 storm with 185-mph winds and a central pressure of 890 mb. No deaths or injuries were reported on the island, but there was heavy damage.


Disaster 2. Extreme rainfall of up to 17 inches created widespread urban flooding in Houston and surrounding suburbs April 15 - 19. Over 1,000 homes and businesses were damaged, and there were more than 1,800 high water rescues. It was the most widespread flood event to affect Houston since Tropical Storm Allison in 2001. Above, we see a drone image of flooding in north Houston on April 20, 2016. Image credit: wunderphotographer Moussifer.


Disaster 3. Tornadoes and severe storms caused widespread damage across the Plains and Central states (NE, MO, TX, OK, KS, CO, IL, KY, TN) May 7 - 10. The damage was greatest in Nebraska and Missouri. In this image, we see a rotating supercell thunderstorm with a wall cloud over Stillwater, OK, on May 9, 2016. Image credit: wunderphotographer gunhilda.

India’s monsoon season ends with slightly below-average rains
India, whose $5 billion drought was Earth's fourth most expensive weather-related natural disaster through September of 2016, received decent monsoon rains in 2016 after two straight years of poor rains. According to the India Meteorological Department, monsoon rains during the period June 1 - September 30, 2016 were about 3% below average. This year’s monsoon rains wreaked considerable death and damage, though. Through the end of August, monsoon floods had killed at least 510 people in India and caused at least $150 million in damage, with the Ganges River reaching the highest levels ever recorded at four locations in northern India. Additional heavy monsoon rains in India’s Telangana and Andhra Pradesh states led to catastrophic flooding during the second half of September, killing at least 28 people and causing $479 million in damage. The monsoon is now in steady retreat across India, but at a slower pace than usual.

Notable global heat and cold marks set in September 2016
Hottest temperature in the Northern Hemisphere: 51.2°C (124.2°F) at Mitribah, Kuwait, 4 September
Coldest temperature in the Northern Hemisphere: -38.6°C (-39.6°F) at Geo Summit, Greenland, 20 September
Hottest temperature in the Southern Hemisphere: 44.0°C (111.2°F) at Villamontes, Bolivia, 12 September
Coldest temperature in the Southern Hemisphere: -82.2°C (-116.0°F) at Dome Fuji, Antarctica, 9 September
(Courtesy of Maximiliano Herrera.)

Major weather stations that set (not tied) new all-time heat or cold records in September 2016 (Courtesy of Maximiliano Herrera)
Fez Airport (Morocco) max. 45.1°C,  5 September
Ibiza Airport (Spain) max. 38.4°C,  5 September
Lugo (Spain) max. 41.6°C, 6 September
Col Major-Mt. Blanc (Italy) max. 6.3°C, 7 September; increased to  7.2°C on 29 September
Saint Laurent do Moroni (French Guiana, France) max. 38.0°C, 27 September:  New territorial record high for French Guiana
Caravelle (Martinique) max 36.1°C, 15 September

One all-time national heat record set or tied in September 2016
One nation or territory—French Guiana--set an all-time heat record in September 2016. From January through September 30, 2016, a total of 21 nations or territories tied or set all-time records for their hottest temperature in recorded history. This breaks the record of eighteen all-time heat records in 2010 for the greatest number of such records set in one year. Also, one all-time cold temperature record has been set so far in 2016 (in Hong Kong.) "All-time" record here refers to the warmest or coldest temperature ever reliably reported in a nation or territory. The period of record varies from country to country and station to station, but it is typically a few decades to a century or more. Most nations do not maintain official databases of extreme temperature records, so the national temperature records reported here are in many cases not official. Our data source is international weather records researcher Maximiliano Herrera, one of the world's top climatologists, who maintains a comprehensive list of extreme temperature records for every nation in the world on his website. If you reproduce this list of extremes, please cite Maximiliano Herrera as the primary source of the weather records. Here are 2016's all-time heat and cold records as of October 1:

French Guiana broke its all-time hottest record on September 27, 2016, when the mercury hit 38.0°C (100.3°F) at Saint Laurent du Moroni.

The Marshall Islands set its all-time hottest record on August 24, 2016, when the mercury hit 35.6°C (96.1°F) at Utirik Atoll.

The Cayman Islands (United Kingdom territory) tied its all-time hottest record on August 21, 2016, when the mercury hit 34.9°C (94.8°F) at Owen International Airport.

The British Virgin Islands [United Kingdom territory] set its all-time hottest record on July 22, 2016, when the mercury hit 35.0°C (95.0°F] at Terrance B. Lettsome International Airport.

Iraq set its all-time hottest record on July 22, 2016, when the mercury hit 53.9°C (129.0°F) at Basrah.

Iran tied its all-time hottest record on July 22, 2016, when the mercury hit 53.0°C (127.4°F) at Delhoran.

Kuwait set its all-time hottest record on July 21, 2016, when the mercury hit 54.0°C (129.2°F) at Mitribah.

Guernsey (United Kingdom territory) tied its all-time hottest record on July 19, 2016, when the mercury hit 35.0°C (95°F) at the small island of Alderney.

Hong Kong Territory (China) tied its all-time hottest record on July 9, 2016, when the mercury hit 37.9°C (100.2°F) at Happy Valley.

Niger set its all-time hottest record on June 8, 2016, when the mercury hit 49.0°C (120.2°F) at Bilma.

Palau tied its all-time hottest record on June 8, 2016, when the mercury hit 34.4°C (93.9°F) at Koror AWS.

India set its all-time hottest record on May 19, 2016, when the mercury hit 51.0°C (123.8°F) at Phalodi.

Maldives set its all-time hottest record on April 30, 2016, when the mercury hit 35.0°C (95.0°F) at Hanimaadhoo.

Thailand set its all-time hottest record on April 28, 2016, when the mercury hit 44.6°C (112.3°F) at Mae Hong Son.

Cambodia set its all-time hottest record on April 15, 2016, when the mercury hit 42.6°C (108.7°F) at Preah Vihea.

Burkina Faso set its all-time hottest record on April 13, 2016, when the mercury hit 47.5°C (117.5°F) at Dori.

Laos set its all-time hottest record on April 12, 2016, when the mercury hit 42.3°C (108.1°F) at Seno.

Vanuatu in the South Pacific set its all-time hottest record on February 8, 2016, when the mercury hit 36.2°C (97.2°F) at Lamap Malekula.

Tonga set its all-time hottest record on February 1, 2016, when the mercury hit 35.5°C (95.9°F) at Niuafoou.

Wallis and Futuna Territory (France) set a new territorial heat record with 35.8°C (96.4°F) on January 10, 2016 at Futuna Airport. This is the second year in a row that Wallis and Futuna has beaten its all-time heat mark; the previous record was a 35.5°C (95.9°F) reading on January 19, 2015 at the Futuna Airport.

Botswana set its all-time hottest record on January 7, 2016, when the mercury hit 43.8°C (110.8°F) at Maun.

Hong Kong Territory (China) set its all-time coldest mark on January 24, 2016, when the mercury dipped to -6.0°C (21.2°F) at Tai Mo Shan (elevation 950 meters.) Tai Mo Shan has a period of record going back to 1996; the coldest temperature near sea level since record keeping began at the Hong Kong Observatory in 1884 was 0°C (32°F) on January 18, 1893.

Jeff Masters and Bob Henson

Climate Summaries

Super Typhoon Haima Takes Aim on Philippines

By: Bob Henson and Jeff Masters , 4:00 PM GMT on October 18, 2016

Now an extremely dangerous Category 5 storm, Super Typhoon Haima is en route to hammer parts of the far northern Philippines that were slammed by another typhoon less than a week ago. Packing top sustained winds of 160 mph (1-minute average) on Tuesday morning, Haima was located about 450 miles east of the Philippines, moving just north of due west at about 17 mph. Haima’s power was obvious on satellite imagery Tuesday morning, with a large ring of intense thunderstorms with very cold cloud tops completely encircling Haima’s distinct eye. Haima is not only intense but mammoth: hurricane-force winds extend more than 60 miles northeast of its center and tropical-storm-force winds extend more than 200 miles northeast.

Haima’s track should angle slightly rightward over the next 24 hours, which would bring the typhoon onto the far northeast coast of the Philippines’ Luzon Island on Wednesday night local time (Wednesday afternoon EDT). Now that Haima has completed an eyewall replacement cycle, its overall structure should remain intact up through landfall. Haima’s new eye is nearly 30 miles across, large enough to allow considerable contraction. Together with the trends evident on satellite, this suggests that Haima could intensify even more prior to landfall. The Joint Typhoon Warning Center (JTWC) has Haima approaching Luzon as a Category 5 storm on Wednesday. More than 48 million people live on the island, although the population density is larger toward the island’s southern end, where Manila is located. The sparsely populated northeast coast of Luzon appears on track for an extremely powerful hit from Haima. Fortunately, there are no cities along this coast the size of Tacloban City, where the storm surge associated with Super Typhoon Haiyan killed more than 5000 people in 2013. The largest population center of far northeast Luzon is the city of Tuguegarao, located about 25 miles inland and shielded by a coastal range of mountains.


Figure 1. Enhanced infrared image from Japan’s Himiwari-8 satellite of Super Typhoon Haima as of 1400Z (10:00 am EDT) Tuesday, October 18, 2016. Image credit: NOAA/NESDIS.


Figure 2. Forecast from JTWC for Haima as of 1500Z (11:00 am EDT) Tuesday, October 18, 2016.

Flooding a major threat over northern Philippines
It was just last Sunday local time when Tropical Storm Sarika made landfall on the east coast of Luzon shortly after attaining Category 4 strength. Sarika’s west-northwest track took it across the heart of the island, where it produced rainfall totals that topped 20 inches in spots. Sarika is now approaching far northern Vietnam and far south China as a much weaker storm, though it could still drop more than 8” of rain along its slow-moving path. Haima is likely to dump another 10 - 20” of rain, with even higher local totals, across the northern half of Luzon, along a track roughly 100-150 miles north of Sarika’s. Following in Sarika’s footsteps, Haima is expected to continue toward a second landfall on the coast of south China as a much weaker system.

Seven Cat 5 cyclones in 2016 thus far
Haima is the planet’s seventh Category 5 storm of the year. This makes 2016 Earth’s third consecutive year with an above-average number of these most dangerous of tropical cyclones. Since 1990, Earth has averaged between 4 and 5 Category 5 storms per year. The other Category 5 storms of 2016 were:

Tropical Cyclone Winston, which devastated Fiji in the Southwest Pacific in February;
Tropical Cyclone Fantala from May, in the Southwest Indian Ocean;
Super Typhoon Nepartak from July, in the Northwest Pacific Ocean;
Super Typhoon Meranti in the Northwest Pacific, which struck the small Philippine island of Itbayat Island while at peak strength in September;
Super Typhoon Chaba in the Northwest Pacific, which weakened before affecting South Korea and Japan in early October;
Hurricane Matthew in the Atlantic in October.

Meranti was the most intense Category 5 of the year thus far, with sustained winds of 190 mph and a central pressure of 890 mb.


Figure 3. Satellite image of Invest 99L as of 1408Z (10:08 am EDT) Tuesday, October 18, 2016.

Tropical storm may form in northwest Atlantic this week
The long-brewing disturbance east of the Bahamas dubbed Invest 99L has a decent shot at becoming a named storm over the next several days. 99L has a large area of fairly disorganized convection (showers and thunderstorms), with top sustained winds as high as 35 mph, but it still lacks the closed center of circulation that would qualify it as a tropical depression. In its Tropical Weather Outlook issued at 8 AM EDT Tuesday, the National Hurricane Center gave 99L a 40 percent chance of developing into at least a tropical depression by Thursday morning, and a 70 percent chance through Sunday morning.

The best shot for 99L’s development may be around Thursday, as it arcs gradually northwest around the Bahamas. Models differ on how far west this arcing path will take 99L and how strong it might become. Sea surface temperatures will remain at least marginally supportive, in the 26 - 28°C range (79 - 82°F), through Friday, and the mid-level atmosphere is reasonably moist (60 - 70%). However, 99L will be fighting wind shear now around 40 knots that will be only marginally more favorable (20-25 knots) by late in the week. The GFDL and HWRF models bring 99L to weak tropical storm strength by Wednesday and keep it there through the weekend. More than 80% of the 00Z Tuesday ensemble runs of the ECMWF, and about two-thirds of the 00Z Tuesday GFS ensemble runs, bring 99L up to tropical storm strength. There is no operational or ensemble model support for 99L becoming a hurricane, or even a strong tropical storm. The strong wind shear suggests that any development of 99L could be as a subtropical rather than a tropical cyclone.

Models are in very close agreement that 99L will turn sharply north-northeastward late next week ahead of a strong front that will be moving through the eastern U.S. It appears likely that 99L will be swept north along this front, eventually merging with a strong area of low pressure predicted to move from New England into eastern Canada over the weekend. This evolving front and low could become a major rain-producer across parts of northwest Pennsylvania, northern New York, northern and eastern New England, southern Quebec, and New Brunswick.


Figure 4. Enhanced infrared satellite image of former Tropical Storm Nicole at 0430Z (12:30 am EDT) Tuesday, October 18, 2016, just hours before it was reclassified as a post-tropical cyclone. Image credit: CIRA/CSU/RAMMB.

Nicole’s long life as a tropical cyclone comes to a close
At 5 am EDT Tuesday, the National Hurricane Center reclassified Tropical Storm Nicole as Post-Tropical Cyclone Nicole, bringing to a close nearly two weeks of NHC advisories on this venerable system. Located at 47.1°N—further north than Montreal and about 900 miles south of Greenland—Nicole was in the process of being absorbed by a midlatitude frontal system. Although Nicole’s top sustained winds remained 50 mph, the storm was barely discernible on satellite imagery, with its center elongated and virtually devoid of showers and thunderstorms.

Nicole was christened as a tropical storm at 11 AM EDT October 4, and it attained and lost hurricane status on three separate occasions, the first Atlantic storm to pull off this hat trick since Tomas (2010). According to Phil Klotzbach (Colorado State University), Nicole is the longest-lived (13.75 days) of all Atlantic tropical storms and hurricanes forming after October 1 since the destructive 1906 Florida Keys hurricane. That one was born as a tropical storm on October 8 and dissipated as a tropical depression on October 23.

The October heat wave continues
Records are dropping like autumn leaves across much of the central and eastern U.S. as an incredibly warm air mass for mid-autumn progresses across the nation. On Monday, Dodge City, KS, rocketed to 101°F, which broke the all-time high for October that had been set just the day before at 99°F. Records began at Dodge City way back in 1873. Neighboring Garden City, KS, accomplished the same feat, setting an all-time October high of 98°F on Sunday followed by 100°F on Monday. Temperatures on Tuesday were on track to soar into the 80s from Chicago, IL, to Albany, NY, and many locations are experiencing summer-like nights as well. In Moline, IL, the low on Monday was 71°F, the city’s first-ever low of at least 70°F after October 6 in records going back to 1874. If Detroit manages to stay above 69°F through midnight Tuesday night, its morning low of 70°F will stand as the warmest daily minimum achieved on any date from October through April in records going back to 1874.

We’ll be back this afternoon with our global climate wrap-up for September.

Bob Henson and Jeff Masters

Hurricane Heat

Twin Typhoons in Philippines; Nicole of the North; Hundred-Degree Heat in Plains

By: Bob Henson , 2:18 PM GMT on October 17, 2016

The northern Philippines island of Luzon may soon experience its second typhoon strike in less than a week. Typhoon Sarika rapidly intensified from tropical storm to Category 4 strength in just 30 hours before plowing across central Luzon early Sunday local time, causing widespread power outages and forcing more than 15,000 people to evacuate. At least two deaths have been attributed to Sarika, according to weather.com. Sarika is now en route to the southern Chinese island of Hainan, where it should strike as a Category 1 typhoon, then weaken before reaching far northern Vietnam on Wednesday.

An even more fearsome storm is now on its way toward the Philippines: Typhoon Haima. Another rapid intensifier, Haima zoomed from tropical storm strength at 2:00 pm EDT Saturday to Category 4 strength as of 8:00 am EDT Monday. Light wind shear, a very moist atmosphere, and extremely warm water (sea surface temperatures close to 30°C) will provide Haima with very supportive conditions for strengthening. Already boasting a large circulation--its tropical-storm-force winds extend out up to 150 miles--Haima is predicted by the Joint Typhoon Warning Service to become a super typhoon with Category 5 sustained winds of 160 mph by Tuesday, weakening only slightly before it reaches the northern tip of Luzon by Wednesday night local time.


Figure 1. Enhanced infrared Himiwari-8 satellite image of Typhoon Haima at 7:00 am EDT Monday, October 17, 2016. Image credit: NOAA/NESDIS.

Among our top three track models, the 00Z Monday GFS and UKMET runs agree closely with the JWTC forecast, while the 00Z Monday European run takes Haima just a bit further south. Any of these tracks could produce rains of 10 - 15” over much of northern Luzon. This will fall atop the heavy rains produced by Sarika over the weekend, which will greatly exacerbate the risk of flooding. Assuming that Haima only nicks the northernmost part of the island, it may still be a formidable typhoon as it begins a gradual recurvature before striking the southeast China coast around Friday, perhaps in the vicinity of Shantou as a Category 2 or 3 storm.


Figure 2. Joint Typhoon Warning Center forecast for Typhoon Haima as of 8:00 am EDT Monday, October 17, 2016.


Figure 3. Typhoons Sarika (left) and Haima (right) as captured by the Himiwari-8 satellite at 4:00 am EDT Monday, October 17, 2016. Image credit: CIRA/CSU/RAMMB.

Nicole is venturing awfully far north for a hurricane
Don’t look now, but Hurricane Nicole is making a run for Greenland. Nicole regained hurricane strength on Saturday, the first Atlantic storm to cross the hurricane threshold at least three times in its life since Hurricane Tomas in 2010 (thanks to Phil Klotzbach at Colorado State University for researching this statistic and to wunderground member Oxfordvalley for updating it]. Nicole has stubbornly retained its warm-core characteristics well north of the tropics, making it to 41°N as of 5 am EDT Monday. Nicole was heading north-northeast at about 9 mph and should accelerate in that direction. Eventually, Nicole will become a cold-core system, although that transition may happen extremely far to the north. The National Hurricane Center predicts that Nicole will become a post-tropical cyclone by Tuesday. However, a phase-space diagram produced by Robert Hart (Florida State University) for Nicole on Sunday, October 16, suggested that Nicole would remain a warm-core system (though increasingly asymmetric) until Thursday. On Thursday morning, the NHC forecast has Nicole as a post-tropical cyclone located between Greenland and Iceland, less than 70 miles from the Arctic Circle. Even then, Nicole should still be a powerful storm, with a surface pressure below 970 millibars and peak winds on the order of 60 mph. After Nicole finally dissipates somewhere near Greenland, its core of warm, moist air will continue into the Arctic, where the extent of sea ice is at its lowest mid-October level for any year on record except 2007 and 2012.

One of the few potential analogs for Nicole is Hurricane Faith (1966), which was still classified as a Category 1 hurricane at latitude 61.1°N, the furthest-north position of any tropical cyclone in the Atlantic. Faith also carved out the longest track of any Atlantic hurricane on record.


Figure 4. Visible satellite image of Hurricane Nicole as of 1245Z (8:45 am EDT) Monday, October 17, 2016.


Figure 5. NHC forecast for Hurricane Nicole as of 0900Z (5:00 am EDT) Monday, October 17, 2016. Although Nicole is predicted to maintain hurricane-strength winds through Tuesday and tropical-storm-strength winds through Thursday, the National Hurricane Center predicts it will be a post-tropical cyclone by Tuesday.

Disturbance near Bahamas may develop later this week
An area of disturbed weather that lingered over the Bahamas over the weekend continued to fester on Monday morning. NHC gives the area only a 20% chance of developing into at least a tropical depression by Wednesday, but a 50% chance by Saturday. The GFS, European, and UKMET models all showed at least modest development of this system by late in the week, as do most members of the GFS and Euro ensemble runs from 00Z Monday. If a tropical or subtropical cyclone does form, it will likely angle northwest but then get swept out to sea by the strong front crossing the U.S. this week.

Mid-October heat sweeping across the central, eastern U.S. this week
It’s not every October that Dodge City, Kansas, gets up to 99°F. In fact, until Sunday, the city had never recorded a temperature that high in any October. The same intense jet stream that brought high winds and tornadic storms to the Pacific Northwest (see below) helped to force air downward over the central and southern Great Plains, leading to an oddly scorching weekend of clear skies and summer-like highs. In records going all the way back to 1873, Dodge City’s previous latest 99°F was on September 29, 1994. Its previous high for this late in the season was 94°F.

Amarillo, Texas, rocketed to 98°F on Sunday, its hottest reading on record for so late in the year after 99°F on October 3, 2000. A few readings over the Southern Plains managed to top 100°F, including 101°F at Borger, TX (another all-time monthly high) and an amazing 102°F at the town of Slapout, OK (see Figure 4 below). Breaking a monthly high is noteworthy in itself, but it’s especially impressive to do so right in the middle of a transition-season month like October.


Figure 6. High temperatures across Oklahoma on Sunday, October 16, 2016. Image credit: Oklahoma Mesonet.


Both Amarillo and Dodge City may soar into the upper 90s again on Monday before a strong front moves through the Southern Plains. Ahead of this front, warm air will surge northeastward, plastering most of the eastern U.S. with unseasonably warm air for mid-October. Temperatures could reach the mid-80s as far north as Albany, NY, by Tuesday. Dozens of daily record highs are likely this week, and a few more locations could notch their warmest readings ever so late in the season. Among those are St. Louis, MO, where 92°F is possible on Monday (current record 94°F on October 11, 1963, followed by 90°F on October 30, 1950) and Louisville, KY, which may hit 89°F on Tuesday (current record 89°F on October 16, 1946, followed by 88°F on October 21, 1953).


Figure 7. After temperatures moderate later this week, another surge of above-average temperatures is likely to spread across most of the contiguous U.S. during the 6-to-10-day period from next Saturday, October 22, through Wednesday, October 26, 2016. Image credit: NOAA/NWS Weather Prediction Center.


Big wind in Pacific Northwest spares Seattle, Portland
The much-feared prospect of a destructive windstorm failed to materialize across Oregon and Washington this past weekend. The surface low tracking near the coast on Saturday (containing the remnants of Typhoon Songda) ended up deepening to an impressively low 969 millibars near the northwest tip of Washington’s Olympic Peninsula. However, its track was farther northwest than expected, keeping the strongest winds away from the Seattle and Portland metropolitan areas. Even so, more than 10,000 customers lost electricity across the Puget Sound area, as wind gusts topping 40 mph blew down numerous trees and branches. Gusts in Oregon reached as high as 102 mph atop Marys Peak and 55 mph at Portland International Airport. Heavy rains extended as far south into California as the Northern Sierra Nevada and even the Santa Cruz Mountains south of San Francisco (as much as 11.33” fell there).

Chastened by the weaker-than-expected storm in the Pacific Northwest, National Weather Service forecasters took pains to explain what happened. “Yes, our forecast did not turn out as predicted. We are not pleased about it either,” said the NWS/Seattle in a Facebook post on Sunday. NWS/Portland filed a similar Facebook post, explaining that the surface low was significantly weaker than expected as it passed near the Oregon coast. The office also noted that a secondary surface low, unpredicted by models, appears to have pulled energy away from the main low.

A rare significant tornado in Oregon
The weekend storm in Oregon was partially upstaged by a different kind of wind. A sizable tornadic waterspout swept onshore from the Pacific Ocean into the town of Manzanita at around 8:20 am PDT Friday morning (see embedded video at bottom; despite the caption that mentions lightning, the flashes you will see are transformers popping). Though its onshore path was just 0.7 miles long and about 700 feet wide, the tornado was rated as an EF2 twister, with a preliminary estimate of peak winds at 125 - 130 mph. No injuries were reported, although a number of structures were damaged. Another waterspout moved onshore near the town of Oceanside, OR, about 40 minutes later.

The NWS/Portland office issued 10 tornado warnings on Friday, only 3 less than the office issued in the entire 30 years from 1986 to 2015! According to the Tornado History Project, Oregon recorded a total of 106 tornadoes from December 1951 to April 2015. Only six of those were rated as significant (F2/EF2 or stronger).

We’ll be back with more on Tuesday, including our summary of global climate for September.

Bob Henson


Figure 8. An officer walks past debris on Laneda Avenue in Manzanita, Oregon, after a tornado moved into town on Friday morning, October 14, 2016. Image credit: Danny Miller/Daily Astorian via AP.


Hurricane Heat High Wind Tornado

Bermuda Endures Direct Hit from Nicole; Fierce Winds in Store for Pacific NW

By: Bob Henson , 4:09 PM GMT on October 14, 2016

Hurricane Nicole continued to scurry across the open North Atlantic on Friday after hammering Bermuda while at Category 3 strength on Thursday. As of 11 am EDT, Nicole was located about 400 miles east-northeast of Bermuda, moving east-northeast at 18 mph with top sustained winds of 80 mph. Nicole is a massive storm: its hurricane-force winds extend up to 70 miles from its center, and tropical-storm-force winds out to 205 miles. Nicole should remain sizable and powerful even after it gradually evolves into a post-tropical cyclone this weekend, posing no additional threat to land. (Nicole may retain a warm core surrounded by cooler midlatitude air for some time.)

Bermuda is accustomed to hurricanes, though Nicole was among the few in recent decades to make a direct hit on the island nation of about 65,000 residents. (See our Wednesday post for more on Bermuda’s hurricane history.) As defined by the National Hurricane Center, landfall is when the center of a hurricane’s eye reaches land, and a direct hit is when at least part of a hurricane’s inner eyewall passes over land. Radar imagery showed that the center of Nicole’s large eye just missed Bermuda, passing less than 10 miles to its southeast; satellite imagery made it appear the eye was further away because of the hurricane’s tilt from southwest to northeast with height. Since Nicole’s eye was so large, virtually all of Bermuda got the “eye experience”: winds suddenly becoming calm or very light, with birds chirping in the background.


Figure 1. Radar image of Hurricane Nicole at 1524Z (12: local time) Thursday, October 13, 2016, as the large, ragged eye (at least 50 km or 30 miles wide) encompassed the entire island, which is partially visible just to the west of the crosshatch at center that denotes the radar location. Image credit: Brian McNoldy, University of Miami, Rosenstiel School.


Figure 2. A tiki bar lays in a shamble following Hurricane Nicole, in Tobacco Bay, St. Georges, Bermuda, Thursday, October 13, 2016. Image credit: AP Photo/Mark Tatem.

The northern eyewall of Nicole tore across Bermuda at full strength, with a lesser hit from the western eyewall after the eye passed overhead. Sustained winds peaked at 87 knots (100 mph) with gusts to 111 knots (128 mph) at a Windguru observation site at Commissioner’s Point on the northwest tip of Bermuda, according to James Dodgson, deputy director of the Bermuda Weather Service. A newer low-level reporting site, installed for the upcoming America’s Cup at Pearl Island in central Bermuda, recorded 76-knot (87-mph) sustained winds, gusting to 103 knots (119 mph). (Thanks to James Dodgson for these preliminary data.) Tidal data from Esso Pier, on the south side of Bermuda’s St. Georges Island, indicate a peak storm surge of 3.73 feet at 1:30 pm Thursday local time.

Nicole’s fury caused remarkably little damage on Bermuda, a sign of the island’s resilient buildings and infrastructure. Bermuda’s national security minister, Jeff Baron, said there was significant flooding and severe road damage at points around the island, along with downed trees and power lines, according to weather.com.


Figure 3. Hurricane Nicole as captured by the MODIS instrument (Moderate Resolution Imaging Spectroradiometer) aboard NASA’s Aqua satellite at 1750Z (1:50 pm EDT) Wednesday, October 12, 2016, as Nicole was approaching Bermuda (visible as a dark spot at upper right of image). Image credit: NASA Goddard MODIS Rapid Response Team.

Potential once-in-a-decade windstorm takes shape for Pacific Northwest
The remnants of Typhoon Songda, now pushing east through the North Pacific alongside a very strong branch of the polar jet stream (see FIgure 4 below], will spring back to life this weekend in the form of an intensifying midlatitude cyclone expected to sweep near or over the west coast of Washington. The Pacific Northwest is prone to occasional damaging windstorms caused by strong midlatitude cyclones that arc northward along the coast. According to the National Weather Service in Seattle, this storm has the potential to be the worst for the region since the Hanukkah Eve windstorm of December 14-15, 2006. Arriving on the heels of weeks of record-heavy rainfall, that storm knocked out power to more than 1.8 million people (in some cases for several days) and caused damage of more than $250 million in the U.S. and more than $80 million in Canada. Other major storms in the Pacific Northwest include the Inaugural Day Storm of January 20, 1993; the February 13, 1979 storm; and the infamous Columbus Day Storm of October 12, 1962, which produced gusts to 116 mph in Portland, Oregon, and 88 mph at Tacoma, Washington (see Figures 5 and 6 below).

This weekend’s storm--already informally dubbed the Ides of October storm--is expected to develop on Saturday west of Oregon and move north-northeast to near or over the Olympic Peninsula of Washington on Saturday night. The GFS and European models agree that its central pressure will be in the range of 965 to 975 millibars near the Washington coast, comparable to the central pressures of many Category 1 and 2 hurricanes. There are still significant differences between models on the exact track and strength of the storm, and these could have big implications for the weather that results. “If our track is off by 100 miles, the forecast is radically changed at nearly all locations,” cautioned Cliff Mass (University of Washington) in a Thursday blog post. High Wind Watches for Saturday night warned of the potential for 20 - 40 mph winds in Seattle, with gusts to 65 mph in both Seattle and Portland. Similar winds could affect Vancouver, BC, depending on the storm’s track. Much higher winds will strike the Pacific Northwest at elevation, where gusts could easily exceed 100 mph.


Figure 4. The windstorm expected to strike the Pacific Northwest over the weekend will develop on the nose of a powerful jet stream segment across the central and eastern North Pacific. Sustained winds at the 250-millibar level (about 34,000 feet) will exceed 160 mph across more than 1000 miles of the jet core, with peak winds at the jet-stream level possibly topping 200 mph. Wind legend at right is in knots; multiply by 1.15 for mph. Image credit: tropicaltidbits.com.

More than wind
This weekend’s storm will be the most dramatic segment in a multi-day episode of heavy rain, high wind, and flooding along and near the Pacific Coast from northern California to British Columbia. The first salvo, on Thursday night into Friday morning, brought winds gusting as high as 55 mph in coastal Washington, along with widespread rains of 2” - 3” on the coast and more than 5” in the Olympic Mountains. More than 10,000 customers were still without power Friday morning on British Columbia’s Vancouver Island after Thursday night's powerful winds.

From Friday morning through early next week, coastal locations and coast-facing slopes could receive anywhere from 8” to 14” of additional rainfall, with especially heavy amounts likely over extreme northwest California and far southwest Oregon. The moisture will extend into parts of central California, where the Sierra Nevada will get its first major storm of the year (mostly in the form of rain, though). San Francisco could pick up an inch or more, which would make for its heaviest rain event since more than 3” fell on March 9-13.

Sarika heading toward Philippines
Our next tropical cyclone of significance to land areas is Tropical Storm Sarika, which is expected to reach at least Category 1 typhoon strength as it rolls across the northern Philippines. Sarika may continue intensifying early next week as it heads toward Southeast Asia, potentially affecting Vietnam by midweek.

See our Thursday evening post for more details on our blog’s new name, Category 6. We’ll be back on Monday with our next post. Have a great weekend, everyone!

Bob Henson


Figure 5. Damage from the Columbus Day Storm of 1962 in Seattle, WA. Image credit: Seattle Municipal Archives.


Figure 6. Damage from the Columbus Day Storm of 1962 in Newberg, Oregon. Image credit: National Weather Service/Wikimedia Commons.


Hurricane High Wind

Our New Name: Category 6™

By: Jeff Masters and Bob Henson , 10:55 PM GMT on October 13, 2016

Jeff Masters’ WunderBlog is no more. After much deliberation among ourselves and WU colleagues, as well as some jumping through logistical hoops, we are delighted to announce that we are now the Category 6 blog! From its beginning in 2005, our blog’s top mission has been covering tropical weather. We concluded that the Category 6 name (which was suggested by Jeff) harks back to those tropical roots. More broadly, the name alludes to our deep fascination with all types of weather and climate extremes, including the many important facets of our changing climate. The Category 6 blog will provide all the insight and expert analysis needed to put the extreme events of our evolving 21st-century climate into context.


We greatly enjoyed and appreciated all of the suggestions you provided during our name-the-blog invitation earlier this year. We received more than 100 suggestions, including serious nominations and a few on-the-edge possibilities. Some of our favorite names included:

Met Vets (WU member Xyrus2000)
EverWunder (WU staff member Todd Gladfelter)
Under the Rainbow with Jeff and Bob (WU member patrap)
Bob and Jeff’s Wxcellent Adventure (WU member oldnewmex)
The Storm Cellar (WU member Neapolitan)
WunderThunder (WU staff member Saeed Ezzati)
Under the Weather (WU member DCSwithunderscores and reader Jennifer Francis)
Wonders Never Cease (WU member KDDFlorida)

To find us under our new name, just look for Category 6 under “News and Blogs” in WU’s web-based pulldown menu and under “Blogs” in our app-based navigation.

Although we have a new name, we’re planning to keep the content in Category 6 mostly as you know it. You can expect the same regular, in-depth coverage of weather and climate topics, including breaking news, profiles of past weather events, and deep dives into ongoing research. Both of us will be on deck full time (and more as needed) during tropical season, with Jeff posting on a part-time basis at other times of the year. Jeff says:

“The change in blog name was past due, since Bob Henson has been doing more than half of all the posts in my blog over the past year. We also want to start bringing in more guest posts, so it made sense to have this shared blog not be named after me--thus the new “Category 6” WunderBlog is here. Mind you, with this blog name, we are not advocating that the National Hurricane Center add a new “Category 6” to the Saffir-Simpson scale. From a disaster preparedness point of view, Category 5 storms are already catastrophic--so there is little to be gained telling people there is a Category 6 storm headed their way!”

We'll be back on Friday morning with a wrap-up on Hurricane Nicole--which socked Bermuda with a direct hit at Category 3 strength on Thursday morning--and a look ahead to the potentially historic windstorm in the Pacific Northwest this weekend, which will be nourished by the remnants of Typhoon Songda. See our post from Thursday morning for more on Nicole.

This blog literally wouldn’t be the same without your many thousands of insightful comments, observations, and images. Our community of reader-contributors is what truly makes our blog stand out. Thanks as always for your loyalty and support!

Jeff Masters and Bob Henson


Figure 1. Typhoon Maysak as seen from the International Space Station at 2118Z on March 31, 2015. Image credit: NASA/Wikimedia Commons.

Wunderground News

Category 3 Hurricane Nicole Pounding Bermuda

By: Jeff Masters and Bob Henson , 2:03 PM GMT on October 13, 2016

Category 3 Hurricane Nicole is pounding Bermuda after putting on an impressive round of rapid intensification that saw the hurricane top out as a Category 4 storm with 130 mph winds early Thursday morning. At 10 am EDT (11 am ADT) Thursday, satellite imagery and radar from the Bermuda Weather Service showed that the western edge of Nicole’s large roughly 40-mile diameter eye was poised to move over the eastern end of the island by 11 am EDT. The northern eyewall of Nicole is the strongest part of the storm, and Bermuda began taking a wicked pounding from this powerful northern eyewall beginning around 9 am EDT. The Bermuda airport is located on the east end of the island, and at 9:55 am EDT measured sustained winds of 77 mph (10-minute average), gusting to 104 mph. An Air Force hurricane hunter aircraft is in Nicole, and at 9:30 am EDT found top surface winds in the northern eyewall of 102 mph. The plane did not sample the most intense part of the northern eyewall, though, and Bermuda is likely to experience higher winds than that. High wind shear is attacking Nicole and will weaken the storm today, but probably too late to provide much relief to Bermuda.


Figure 1. Hurricane Nicole as seen by the Bermuda radar at 9:44 am EDT October 13, 2016, when the northern eyewall was battering the island. Bermuda (under the white cross) was about to enter the eye. Image credit: Bermuda Weather Service.

Wind and storm surge damage the main threats
The main threat from Nicole is wind damage, as the island has rarely experienced the winds from a Category 3 hurricane. Storm surge is also a concern, as Nicole is expected to drive a storm surge of 6 - 8 feet to Bermuda. Fortunately, this surge will be arriving as the tide is going out. High tide was at 6:36 am (ADT) this morning, and low tide will be at 12:48 pm (ADT) this afternoon. The difference between low tide and high tide is about three feet, so the island would have had about an extra two feet of inundation had Nicole hit at high tide. See the Bermuda Esso Pier, St. Georges, Bermuda Tide Chart (thanks to WU member SPShaw for this link.)

Another missed rapid intensity forecast
Nicole put on its rapid intensification burst as it passed over the near-record-warm waters of the subtropical North Atlantic, with sea-surface temperatures of 29°C (84°F)— roughly 2°C above average. Given the warm waters and light wind shear the storm had, rapid intensification was not a big surprise, but Nicole’s rapid intensification from a tropical storm on Tuesday morning to a Category 4 hurricane Wednesday night was not anticipated by our top three intensity models—the HWRF, SHIPS and LGEM. The Tuesday morning runs of these models all predicted that Nicole would be a Category 1 hurricane at the time of its closest approach to Bermuda on Thursday morning. NHC did go higher in their Tuesday morning intensity forecast, calling for Nicole to be a Category 2 storm by Thursday morning, but their intensity forecast fell far short of predicting the actual rapid intensification that occurred. A similar situation occurred for Hurricane’s Matthew’s rapid intensification from a tropical storm to a Category 5 hurricane in the Caribbean, which was poorly forecasted by the intensity models and NHC. Hurricane intensity forecasting still has a long ways to go, unfortunately.


Figure 2. MODIS satellite image of Hurricane Nicole taken at 11:30 am EDT October 13, 2016. At the time, Nicole had just hit Bermuda as a Category 3 storm with 120 mph winds. Image credit: NASA.

A rarity for Bermuda
It’s not every day that Bermuda sees a hurricane, and it’s even more uncommon for a major hurricane to target the island directly. In a local survey going back to 1609, the Bermuda Weather Service found that tropical cyclone damage was recorded about once every 6 to 7 years. From 1900 to 2007, the only direct hits cited by the agency were the Havana-Bermuda Hurricane of 1926, the Miami Hurricane of 1948, and Hurricane Arlene (1963). Of course, a hurricane can cause havoc while passing just west or east of the island as well. According to Phil Klotzbach (Colorado State University), only one Category 4 hurricane is known to have tracked within 50 miles of Bermuda in records going back to 1851: Hurricane 5, on October 16, 1939. Nicole will fall just short of reaching that milestone, at least in the initial analysis, as it was downgraded from Category 4 to Category 3 at 7:00 am EDT Thursday while located about 55 miles southwest of Bermuda.

In the big picture of Atlantic hurricane seasons, Nicole is also a standout. It follows Hurricane Matthew, which attained Category 5 strength on October 1. Never before has the Atlantic recorded two storms of at least Category 4 strength in October, according to Klotzbach (again, in records going back to 1851). Nicole attained its Category 4 strength at 30.1°N, making it the latest Atlantic storm in the season to exhibit Category 4 strength that far north since Hazel (1954), which was a Cat 4 at 30.2°N.

Keep an eye on the Southwest Caribbean next week
A broad area low pressure is expected to form in the waters of the Southwest Caribbean off the coast of Nicaragua early next week. The computer models have been very inconsistent in their predictions on the potential timing and location of any tropical storm development that may occur in this region, but we will have to keep an eye on it.

Links
Bermuda radar.
Live Blog from BRE News (thanks to WU member DevilsIsles for this link.)
Live Stream from BER News in Bermuda (thanks to WU member Sfloridacat5 for posting this link in the blog comments.)


Figure 3. This image from the 06Z Thursday run of the GFS model shows winds exceeding 52 mph (60 mph) approaching the western Washington coast late Saturday in association with a 963 millibar low that forms from the remnants of Typhoon Songda. Image credit: tropicaltidbits.com.

Pacific Northwest bracing for the remnants of Typhoon Songda
Another high-latitude anomaly of the tropical type will make its presence felt in the U.S. Pacific Northwest and far southwest Canada this weekend. Typhoon Songda reached its peak intensity on Tuesday at an unusually far northerly latitude: 30.3°N in the Northwest Pacific, where it briefly became a super typhoon with top sustained winds of 150 mph. No longer classified as a tropical cyclone, Songda remained a powerful storm in the North Pacific on Thursday morning, whipping eastward through the North Pacific near the International Date Line just north of 40°N with a central pressure of 996 millibars. Songda will be incorporated in a train of storms heading into the Pacific Northwest, and models agree that it will deepen at least into the 960 - 970 mb range as it approaches the Olympic Peninsula of Washington (or perhaps a bit further south, if the ECMWF model proves correct]. This is a classic set-up for very heavy rain and damaging winds across western Oregon and Washington, including the Seattle area. High wind warnings are already in effect from tonight to Friday for western Oregon and Washington, where gusts may reach 75 mph along the Oregon coast, 60 mph along the Washington coast, and 55 mph in the Seattle area. Even stronger winds are liable to materialize late Saturday and/or Sunday as the remnants of Songda approach. We’ll have more details on this potential major event on Friday.

We'll have a new post this afternoon.

Jeff Masters and Bob Henson

Hurricane

A Warm Kickoff to Autumn Across Eastern U.S.

By: Bob Henson , 10:20 PM GMT on October 12, 2016

Last month was the ninth warmest September for the contiguous 48 U.S. states in records going back to 1895, according to the monthly national climate summary released by NOAA on Wednesday. While temperatures were close to average from the Great Basin to the West Coast, the central and eastern U.S. had an uncommonly warm segue to meteorological autumn. The states of Iowa, Louisiana, and every state east of the Mississippi except for Tennessee and South Carolina had a top-ten-warmest September, and it was the hottest September on record for Ohio. Average minimum temperatures (nighttime lows) were the warmest for any September in Virginia, Maryland, and Delaware, as well as the District of Columbia.

This toasty month followed the fifth hottest U.S. summer on record. September 2015 was the second warmest on record for the contiguous U.S., and it’s now been a full decade since the nation last saw a cooler-than-average September (2006).


Figure 1. Statewide rankings for average temperature during September 2016, as compared to each September since 1895. Darker shades of orange indicate higher rankings for warmth, with 1 denoting the coldest month on record and 122 the warmest. Image credit: NOAA/NCEI.


Figure 2. Statewide rankings for average precipitation during September 2016, as compared to each September since 1895. Darker shades of green indicate higher rankings for moisture, with 1 denoting the driest month on record and 122 the wettest. Image credit: NOAA/NCEI.

Precipitation in September: Another mixed bag
The national patchwork of sogginess and drought that emerged this past summer underwent some shifts in September. Even before Hurricane Matthew arrived, the Atlantic states from South Carolina to Delaware got much-needed moisture in September (too much, in some cases). It was also a very wet September from the northern Rockies to Upper Midwest. The states of North Dakota, Delaware, and South Carolina each had a top-ten wettest September. Northeast Iowa and parts of adjoining states were walloped by thunderstorm complexes in late September that led to record flood crests in some areas. More than 5000 homes were affected in the Cedar Rapids area, where the flood crest exceeded the 100-year recurrence interval. A massive sandbagging effort in the Cedar Rapids area--which had been devastated by a flood in 2008--helped reduce the damage somewhat this time around.


Figure 3. Floodwaters in late September 2016 surround the Veterans Memorial Building, which was heavily damaged by the city’s devastating 2008 flood. The building housed the Cedar Rapids City Hall from 1927 until 2008. The new location of City Hall, several blocks away, was closed after basement flooding occured during the September 2016 flood. Image credit: City of Cedar Rapids.


A regional drought intensified from New York through New England, with Maine having a top-ten-driest September. As of October 4, the coastal stretch from southeast and central Massachusetts to central Maine was in extreme drought, with moderate to severe drought covering most of the rest of New York and New England, according to the weekly Drought Monitor from October 6. (Rains of 2” - 4” associated with Matthew over Rhode Island and southeast Massachusetts may put a modest dent in the drought there.) It was also unusually dry across the lower Mississippi Valley, Colorado, and the West Coast states of Oregon and California (where September is normally a fairly dry month).


Figure 4. Hannah Swanson, assistant wine maker, samples some of the grapes being harvested at Fresh Tracks Farm Vineyard & Winery in Berlin, VT, on October 3, 2016. The dry summer weather was ideal for growing grapes in some spots in the Northeast, but the drought in southern New England and parts of New York may have decreased the crop. Image credit: AP Photo/Lisa Rathke.

Mediocre is better than awful: California wraps up water year 2015-16 and looks ahead
Precipitation for the water year 2015-16 (extending from October to September) wound up very near average for California--a relief after four years of unremitting drought. However, the statewide water-year total obscures the drying effects of continued very warm temperatures, as well as a marked a north-to-south divide: rains were generous from central California northward, while southern California largely missed out on El Niño’s bounty. Downtown Los Angeles picked up only 5.85” for the water year, compared to an average of 11.09”. San Francisco racked up a respectable 23.10”, less than half an inch below the long-term average of 23.65”.

California’s reservoirs, concentrated in the north half of the state, were only at about 80% of average capacity on September 30 (see Figure 5 below), thanks in large part to an earlier-than-average meltout of a less-than-extravagant snowpack. The state’s forests are continuing to suffer from the effects of a half-decade of drought, which has led to an estimated 66 million dead trees. “The accumulated effects of drought and warmer temperatures are likely to leave forests susceptible to diseases, pests, and further drought conditions,” wrote Jay Lund in the California WaterBlog. “There is little that water managers can do to affect drought impacts to forests, although this might be one of the drought’s biggest and most long-lasting effects.”

What about water year 2016-17? Californians are understandably leery about drawing conclusions from El Niño and La Niña, given the disappointing outcome of El Niño in Southern California this past water year. For what it’s worth, NOAA has cancelled its La Niña watch for 2016-17. Last month it pegged the odds of La Niña at around 40% for this autumn, dropping to around 30 - 35% by winter. While below 50%, those odds are far from nonzero. Temperatures in the benchmark Niño3.4 region of the tropical Pacific are down to -0.9°C below average, according to Monday’s weekly update from NOAA, and the cooler-than-average waters now extend below 100 meters (330 feet) throughout most of the central and eastern tropical Pacific. Also consistent with La Niña: Rainfall has increased across Australia, Southeast Asia, and the Maritime Continent.

Nicole continues to intensify en route to Bermuda
Hurricane Nicole is barrelling toward a potential direct hit on Bermuda. Nicole's top sustained winds were up to 110 mph as of the 5 pm EDT advisory from the National Hurricane Center, and Nicole is predicted to become a Category 3 storm tonight before weakening slightly as it approaches the island on Thursday. Direct hurricane strikes are quite unusual for Bermuda, and it's also uncommon to have a hurricane intensifying so close to an encounter with the island. We'll be back with a full update with Nicole on Thursday morning. See our post from Wednesday morning for more background on Nicole and on Bermuda's hurricane history.

Bob Henson


Figure 5. California reservoir levels as of September 30, 2016. Values shown for each reservoir are percentage of capacity (left/blue value) and percentage of the historical average for the time of year (right/red value).

Climate Summaries

Hurricane Warning in Bermuda as Category 2 Nicole Approaches

By: Bob Henson and Jeff Masters , 5:02 PM GMT on October 12, 2016

Flexing its muscle in the Northwest Atlantic, Hurricane Nicole could make a direct hit on Bermuda on Thursday. As of the 11 am EDT advisory from the National Hurricane Center, Nicole’s top sustained winds were up to 100 mph, making it a Category 2 storm. Nicole was located 295 miles south-southwest of Bermuda and moving north at 7 mph, but it is expected to accelerate toward the north and northeast tonight and Thursday, bringing it over or very near the island around midday. A Hurricane Warning is in effect, with 3” - 6” of rain, hurricane-force winds, huge surf, and coastal flooding all possible.


Figure 1. Visible satellite image of Hurricane Nicole as of 1437Z (10:37 am EDT) Wednesday, October 12, 2016. Bermuda is visible as the black speck at center top. Image credit: NASA/MSFC Earth Science Office.

Nicole weakened from Category 2 to tropical storm strength over the weekend amid strong wind shear, but the shear had relaxed to less than 10 knots by Tuesday. The light shear and a modestly moist atmosphere (mid-level relative humidity around 50 - 55%) allowed for Nicole to regroup. The hurricane is also traveling over near-record-warm waters of around 28 - 29°C (82 - 84°F), which is about 1.5 - 2.0°C above average for mid-October. After it strafes Bermuda, Nicole will continue plowing into the North Atlantic, becoming a somewhat weaker but very large hurricane by Friday and Saturday before it transitions into a post-tropical cyclone.

Nicole gives Bermuda its fourth hurricane warning in three years
For being a small island in a big ocean, Bermuda has had an inordinate amount of bad luck with hurricanes over the past three years. Nicole is the fourth storm in the past three years to put the island under a Hurricane Warning. Last year, Hurricane Joaquin passed about 65 miles west-northwest of Bermuda on October 5 as a Category 2 storm. Joaquin brought sustained winds of tropical storm force to Bermuda, and caused power outages to 15,000 of the island’s 36,000 customers. Damage was minor, though.

In 2014, two hurricanes hammered the island within a week in a damaging one-two punch. The first was Hurricane Fay, which hit Bermuda on October 12 as a Category 1 hurricane with 80 mph winds, doing at least $10 million in damage. Just six days later, on October 18, a far worse storm made another direct hit on Bermuda--Hurricane Gonzalo, which made landfall as a strong Category 2 storm with 110 mph winds. Winds at the Bermuda Airport peaked at 76 mph, with a gust to 96 mph, as the northern eyewall of Gonzalo passed overhead. After a calm lasting about an hour, when the pressure sank to 953 mb, the southern eyewall hit, with stronger winds than the northern eyewall--93 mph, gusting to 113 mph. An unofficial gust of 144 mph was recorded at Commissioners Point at an elevation of 262', a site notorious for recording strong winds due to local terrain effects. The hurricane did an estimated $200 - $400 million in damage to Bermuda, making it the second costliest storm in their history. The costliest was Category 3 Hurricane Fabian of 2003, the only hurricane to get its name retired exclusively because of its impact on the island of Bermuda. Fabian's storm surge destroyed the causeway connecting the airport to the rest of the island and did $300 million in damage. Fabian also killed four people--the only hurricane deaths ever recorded on Bermuda.

While a direct hit on Bermuda is unusual, many hurricanes and tropical storms get close enough to cause trouble. In a local survey going back to 1609, the Bermuda Weather Service found that tropical cyclone damage was recorded about once every 6 to 7 years. From 1900 to 2007, the only direct hits cited by the agency were the Havana-Bermuda Hurricane of 1926, the Miami Hurricane of 1948, and Hurricane Arlene (1963). As with Fabian, a storm passing just west of the island need not be a direct hit to produce severe damage.


Figure 2. Hurricane Gonzalo as seen from the International Space Station on October 16, 2014. Image credit: Alexander Gerst.


Figure 3. Gonzalo as seen by the Bermuda radar at 9:43 pm ADT October 17, 2014, when the eye was over the island. Image credit: Bermuda Weather Service.



Figure 4. In hard-hit Lumberton, NC, on Wednesday, October 12, 2016, people look out towards West 5th Street, still covered by floodwaters caused by rain from Hurricane Matthew. Image credit: AP Photo/Mike Spencer.

From the Carolinas to Canada, Matthew-related woes continue to mount
Extensive and severe flooding continues to afflict parts of North Carolina near rain-swollen rivers in the wake of Hurricane Matthew. Thousands of people are still being evacuated, according to weather.com, including about 9000 people forced out of the Greenville area on Tuesday. At least 19 deaths have been confirmed across the state, and power remained out for more than 140,000 customers as of Wednesday morning. The Neuse and Tar river basins are two of the areas where rivers are still rising. As of Wednesday morning, the Neuse River at Kinston, NC, was predicted to crest on Friday near or just above the record set in 1999 by Hurricane Floyd. On Tuesday, the Neuse’s flood crest broke a Floyd-era record by nearly a foot at Goldsboro.

Matthew’s indirect effects have made it all the way to the Canadian Maritimes. Moisture from Matthew’s remnants was pulled northward ahead of an existing frontal system near the U.S. East Coast, then fed into an intensifying storm that deluged eastern Nova Scotia and Newfoundland. Some 50,000 Nova Scotia customers lost power on Tuesday, and thousands of basements were reportedly flooded. According to Nova Scotia meteorologist Jim Abraham, a preliminary one-day total rainfall of 225 mm (8.86”) reported in Sydney, the province’s second-largest city, is nearly double the city’s all-time one-day record of 129 mm set on August 17, 1981. Drone footage captured the extent of flooding on Tuesday. (Thanks to Chris Fogarty, Environment Canada, for background on this event.)


Figure 5. Typhoon Songda as captured by NASA’s Aqua satellite at 0305Z Wednesday, October 12, 2016 (11:05 pm EDT Tuesday). Image credit: NASA Goddard MODIS Rapid Response Team.

Remnants of Typhoon Songda will be heading for Pacific Northwest
The next tropical cyclone to affect the United States will hit the opposite side of the country from Matthew. Now accelerating to the northeast across the remote North Pacific, Typhoon Songda will contribute to a very soggy and stormy few days across the U.S. Pacific Northwest and southwest Canada. Songda was still packing top sustained winds of 120 mph as of 06Z (2:00 am EDT) Wednesday, after briefly reaching super-typhoon strength Tuesday at an unusually high latitude--30.3°N--with peak winds of 150 mph. Songda will hitch a ride on a fast-moving segment of the jet stream and slam into the North American coast over the weekend. In his California Weather Blog, Daniel Swain notes that some recurving typhoons transition into post-tropical cyclones and strike the U.S. West Coast as identifiable storms, while others are absorbed into the jet stream and existing frontal systems. “It appeared that Songda will do a little of both--strengthening the overall storm track and persisting as a powerful remnant surface low as it treks eastward across the Pacific,” Swain wrote.

Widespread rainfall amounts of 4” to 10” associated with the remnants of Songda will extend from British Columbia to northern California. Songda is just part of a series of storms that will drench the region over the next week. All told, some locations between the shoreline and the coastal mountains could receive 15” to 25” of rain. Very little of the heavy rain will extend south of the San Francisco area, but this isn’t too surprising given that we’re just at the start of the wet season.

We’ll be back with another post this afternoon on the U.S. climate roundup for September.

Bob Henson and Jeff Masters


Hurricane

Hurricane Matthew Floodwaters Slowly Recede; Hurricane Watch for Nicole in Bermuda

By: Jeff Masters , 4:45 PM GMT on October 11, 2016

Multiple rivers continue rampage above major flood stage in North Carolina as the state reels from a multi-billion dollar flood disaster wrought by the torrential rains from Hurricane Matthew over the weekend. At least 14 deaths have been reported across the state, according to weather.com. More than 1,500 people were stranded by high flood waters in the town of Lumberton on Monday (some fleeing to rooftops), and had to be rescued by helicopter and boat. More than 650,000 customers remained without electricity on Tuesday morning in the Southeast U.S., with about half of those in North Carolina and Virginia.


Figure 1. A boat passes a church in Nichols, S.C., Monday, Oct. 10, 2016. (AP Photo/Rainier Ehrhardt) 

Several more days of flooding coming
Most rivers in North Carolina have crested and are gradually falling in the wake of Matthew’s torrential rains, but some will remain above major flood stage for several more days. The flooding is the state’s worst since catastrophic Hurricane Floyd in September 1999, and in some areas is the worst on record. Several of the peak crests on North Carolina rivers this week from Mathew:

The Black River near Tomahawk crested at a record 27.92’ on Monday evening. Old record: 27.1’ on Sept. 18, 1999.

The Neuse River at Smithfield crested at a record 29.09’ on Monday; it is expected to fall below major flood stage by Wednesday morning. Old record: 27.4’ on September 8, 1996.

The Little River at Manchester crested at a record 31.73’ on Monday; it fell below major flood stage on Tuesday. Old record: 29.0’ on Sept. 19, 1945.

The Cape Fear River at W.O. Huske Lock crested at 68.4’ on Monday; it is expected to fall below major flood stage on Wednesday. This was its 2nd highest crest on record, behind 75.5’ on Sept. 22, 1945.

The Lumber River at Lumberton crested at a record (and unknown) height above 24.39’ on Monday, and is not expected to fall below is previous record flood height until Sunday. Old record: 20.48’ on Sept. 11, 2004


Figure 2. The Lumber River is experiencing record flooding that is expected to last all week. Image credit: NOAA/NWS Advanced Hydrologic Prediction Service.

Matthew’s impact elsewhere
Recovery efforts continue in the other regions hard-hit by Matthew, including Haiti (over 1,000 dead), The Bahamas (most costly hurricane in their history), Cuba (severe wind and storm surge damage to the eastern tip) and the Southeast U.S. states of Florida, Georgia and South Carolina (twelve dead and billions in damage.) Matthew is the most expensive Atlantic hurricane since Hurricane Sandy of 2012, and the deadliest since 2005, when both Katrina and Stan killed over 1,000 people. See our post from Monday for much more detail on Matthew’s impacts and records.


Figure 3. Latest satellite image of Nicole.

A Tropical Storm Warning and Hurricane Watch for Bermuda for Nicole
A Tropical Storm Warning and Hurricane Watch are up for Bermuda as a strengthening Tropical Storm Nicole heads towards a Thursday morning encounter with the island. Satellite imagery late Tuesday morning showed that Nicole has become much more organized since Monday, with a symmetric cloud pattern and an eye beginning to appear. The latest SHIPS model forecast diagnosed that wind shear had fallen sharply to the low range, 5 - 10 knots, with mid-level relative humidity levels that were decent for development, in the 50 - 60% range. Nicole is passing over the near-record-warm waters of the subtropical North Atlantic, with sea-surface temperatures of 29°C (84°F)— roughly 2°C above average. Record warm waters in this region helped boost Hurricane Gaston to Category 3 strength at latitude 30°N in late August. The 00Z Tuesday runs of our top four track models--the GFS, European, HWRF and UKMET models--all brought Nicole 40 - 90 miles west of Bermuda on Thursday morning. Our top three intensity models, the HWRF, SHIPS and LGEM, all predicted Category 1 hurricane intensity for Nicole at that time, as did the official NHC forecast as of 11 am EDT Tuesday. The SHIPS model in its 12Z Tuesday run was giving Nicole a 22% chance of rapidly intensifying into a Category 2 or stronger hurricane by Wednesday morning. Given the low shear and record warm waters Nicole has to work with, I expect Nicole will be a Category 2 hurricane on Thursday morning when it make its closest approach to Bermuda.


Figure 4. Typhoon Songda as seen at 00:45 UTC October 11, 2016. Image credit: NASA.

Watch for development in the Southwest Caribbean early next week
A broad area low pressure is expected to form in the waters of the Southwest Caribbean off the coast of Nicaragua early next week. A tropical depression form could form there next week, according to a number of the 70 forecasts of the GFS and European model ensembles. It is too early to be confident of a direction of motion for this system, but a movement to the northwest over Nicaragua and Honduras appears to be the most likely track, with a possible motion to the north over the central or western Caribbean later in the week.

Ex-Typhoon Songda to drench Northwest U.S.
In the Northwest Pacific, Category 3 Typhoon Songda is heading northeast at 13 mph towards Alaska, and is expected to transition to a very wet extratropical storm with 45 mph winds on Thursday, when it will be a few hundred miles south of Alaska’s Aleutian Islands. Ex-Songda will then catch a ride with the jet stream and arrive off the coast of Washington on Saturday, when the storm is expected to intensify into a powerful low pressure system with a central pressure near 960 mb, bringing strong winds and heavy rains to the coasts of Oregon, Washington, and British Columbia. Rainfall of 6 to 10 inches, with local amounts over 12 inches, is possible western Washington south to northwestern California this week, due to a series of heavy rainstorms which include ex-Songa this weekend. East of the Cascades, rainfall could total 1 to 3 inches in the valleys and 3 to 7 inches in the foothills of the northern Rockies.

Jeff Masters

Hurricane

Flooding from Matthew Continues over Carolinas; Nicole Eyes Bermuda

By: Bob Henson , 6:09 PM GMT on October 10, 2016

Under brilliant blue skies, the water-logged Inner Coastal Plain of North Carolina continued to grapple on Monday with the aftermath of Hurricane Matthew and the extreme rains it deposited on the region. At least 10 deaths have been reported across the state, according to weather.com. Some 1500 people in the town of Lumberton had to evacuate their homes early Monday (some fleeing to rooftops) after a levee in the southwest part of the town was breached overnight. At least 500 structures have already been affected by flooding in Lumberton as of Monday morning, said NC Governor Pat McCrory in a news conference. Update: It now appears there may have been no major levee beach near Lumberton--simply a massive amount of water finding alternate channels, according to an excellent Capital Weather Gang report on the flood by Angela Fritz and Chico Harlan.


Figure 1. Freda Pittman holds Mark Bergstresser's hand as Bergstresser ferries her from her flooded neighborhood to waiting friends on State Highway 211 in Lumberton, NC, on Sunday, October 9, 2016. Image credit: Chuck Liddy/The Charlotte Observer via AP.

Torrential rains pushed well inland on Saturday as Hurricane Matthew churned along the SC/NC coast before heading seaward late Saturday. See our Sunday post for a recap of some of the rainfall records and storm impacts produced by Matthew across the Southeast. Matthew dropped a total of 14.87” in Fayetteville, NC, with 14.00” of that falling on Saturday--more than doubling the city’s previous all-time calendar-day record of 6.80” observed during Hurricane Floyd on September 16, 1999. In fact, there are only four entire months in Fayetteville weather history that have received more rain than Fayetteville picked up in 24 hours on Saturday! Fayetteville records extend back to 1871. The rains were fed by extremely high amounts of atmospheric moisture brought into the region by Matthew. Increased atmospheric moisture is a hallmark of our ongoing planet-wide warming, as detailed by a number of studies. See this Climate Signals summary and this study published in July in the Journal of Climate.

A week of flooding ahead
It will take days for some rivers in North Carolina to crest, and many thousands of people will continue to be affected by flooding in or near their neighborhoods. Overall, the flooding is the state’s worst since the catastrophic Hurricane Floyd in September 1999, and some areas are being hit even harder than they were in Floyd (or any other storm on record). Below are several of the peak crests in North Carolina observed and/or projected by NOAA’s Southeast River Forecast Center as of Monday morning:

Black River near Tomahawk
27.37’ observed on Monday; still rising
Old record: 27.1’ on Sept. 18, 1999

Neuse River at Smithfield
29.09’ observed on Monday
Old record: 27.4’ on September 8, 1996

Little River at Manchester
31.73’ observed on Monday; projected peak 31.8’ later Monday
Old record: 29.0’ on Sept. 19, 1945

Cape Fear River at W.O. Huske Lock
68.4’ observed on Monday
2nd highest crest on record, behind 75.5’ on Sept. 22, 1945


Figure 2. The Lumber River is experiencing record flooding, exacerbated on Monday by a levee breach within the city of Lumberton. Image credit: NOAA/NWS Advanced Hydrologic Prediction Service.

Matthew’s toll: huge and still rising
The latest reports confirm that Matthew has been one of the most deadly and destructive Atlantic hurricanes of the 21st century. Early estimates suggested that insured losses for U.S. homes and business could be in the ballpark of $6 billion. However, these estimates have generally focused on damage inflicted by storm surge and wind, rather than on the potentially huge cost of inland flooding that is still unfolding. A roughly comparable storm, Hurricane Floyd in 1999, produced about $9.5 billion in U.S. economic damage. “I’d say that is a fair starting point for Matthew, given the expansive nature of the coastal inundation impacts from Florida to North Carolina and then the ongoing inland flooding across the Carolinas and southeast Virginia,” Steve Bowen (Aon Benfield) told me. Bowen also notes that the growing population across the Southeast U.S. leads to ever-greater exposure to financial loss when hurricanes do arrive.

Meanwhile, the Bahamas’ Tribune242 news service reported on Monday that Matthew will likely produce the largest insured losses from a single hurricane in the nation’s history. According to the international disaster database, EM-DAT, the two most expensive hurricanes in Bahamian history were Hurricane Frances of 2004 ($1 billion in losses) and Hurricane Jeanne of 2004 ($550 million in damage). The chief executive of the insurance firm Bahamas First told Tribune242 that he expects the total payout from Bahama insurance companies to exceed that from Frances and Jeanne combined.

At least 23 deaths in the U.S. have been attributed to Matthew, but the most tragic blow has been to Haiti, where the death toll is now estimated at more than 1000 (the official toll was still at 372 on Monday morning). Tens of thousands of homes were destroyed, and recovery efforts will be hobbled by the nation’s ongoing cholera epidemic. At the bottom of this post is more detail on ways you can help those affected by Hurricane Matthew in Haiti and elsewhere.


Figure 3. Enhanced infrared satellite image of Tropical Storm Nicole as of 1515Z (11:15 am EDT) Monday, October 10, 2016. Image credit: NOAA/NESDIS.

Nicole a significant concern for Bermuda
Tropical Storm Nicole, barely noticed during Matthew’s tenure, is now shaping up to be a hurricane threat in its own right. A Category 2 hurricane on Friday, Nicole weakened to minimal tropical storm status over the weekend amid dry air and strong wind shear. Nicole’s top sustained winds were 60 mph as of the 11 am EDT advisory from NHC. Nicole was located about 455 miles south of Bermuda and was heading north at 6 mph after moving little for much of the weekend. On Monday morning, Nicole had only a modest amount of showers and thunderstorms (convection) around its center, with the influence of dry air evident in the patchiness of banding around Nicole.

It appears Nicole will have a one- or two-day window for significant strengthening just before it approaches Bermuda on Thursday. Wind shear will plummet from its current 20 - 30 knots to around 5 - 10 knots by midweek. Mid-level relative humidity should be in the 50 - 60% range, up from the 40 - 50% range that prevailed over much of the weekend. As these conditions evolve, Nicole will be rolling over near-record-warm waters of the subtropical North Atlantic, with sea-surface temperatures of 28 - 29°C (82 - 84°F), roughly 1 - 2°C above average. Record warm waters in this region helped boost Hurricane Gaston to Category 3 strength at latitude 30°N in late August. The 00Z Monday runs of our top three track models--the GFS, European, and UKMET models--all bring Nicole over or very close to Bermuda on Thursday, with the European and UKMET models suggesting Nicole could be at least a Category 2 storm at that point. The 06Z Monday run of our top intensity model, the HWRF, agrees. The official NHC forecast as of 11 am EDT Monday bring Nicole across Bermuda as a strong Category 1 hurricane on Thursday. Regardless of its peak strength near the island, Nicole looks set to be a very large system, especially as it evolves into a post-tropical cyclone toward the weekend.


Figure 4. A girl carries water in Port-Salut, southwest of Port-au-Prince, in Haiti, on October 9, 2016, following the passage of Hurricane Matthew. Haiti began three days of mourning on Sunday for hundreds killed in Hurricane Matthew as relief officials grappled with the unfolding devastation in the Caribbean country's hard-hit south. Image credit: Rodrigo Arangua/AFP/Getty Images.

Portlight and Lambi Fund of Haiti disaster relief charities need your help
The Portlight.org disaster relief charity, founded and staffed by members of the wunderground community, is responding to Hurricane Matthew. Portlight has been working with their partners and stakeholder organizations throughout the affected region to ensure the needs of people with disabilities are well met. It's important to note this includes people in directly impacted areas as well as the tens of thousands of evacuees. You can check out their progress on the Portlight Blog or donate to Portlight's disaster relief fund at the portlight.org website.

The Lambi Fund of Haiti is very active in disaster relief and disaster prevention, including promotion of reforestation efforts, use of alternative fuels, and infrastructure improvements at a grass-roots level to help avert future flood disasters. What Lambi Fund is doing for their Hurricane Matthew response:
    •    Utilizing Regional Monitors and the active Partner Organizations (22 projects in portfolio) to survey the immediate needs in the South and Northwest in order to provide a primary response to these urgent needs
    •    Providing $150,000 for urgent relief during the first phase of their response while completing a needs assessment of the resources needed for the second phase, which will be to “Repair and Restore” the 22 active organizations’ projects that have been devastated
  •    Support the process of repairing the infrastructure damages (already established: 4 mills down in the Northwest, need to repair gardens, supply soil and nutrients essentially starting gardens over from scratch)

You can make your donation online at http://www.lambifund.org or send your funding support to: 

Lambi Fund of Haiti
1050 Connecticut Avenue, Suite 500
Washington DC 20036

Jeff Masters will be back with our next post on Tuesday.

Bob Henson

Hurricane

Matthew Flings All-Time Surge and Rainfall Records Across Southeast

By: Bob Henson and Jeff Masters , 7:20 PM GMT on October 09, 2016

After a devastating 12-day rampage from the Caribbean to the U.S. Mid-Atlantic, Hurricane Matthew was reclassified as a post-tropical cyclone at 5 am EDT Sunday by the National Hurricane Center. Matthew wasn’t exactly slacking off--its top sustained winds remained 75 mph as of NHC’s 2 pm Sunday advisory--but it no longer had the warm core required for tropical-cyclone status. At 2 pm EDT, Matthew was located about 150 miles east of Cape Hatteras, North Carolina, moving east at 15 mph. After days of computer models suggesting a potential loop back toward Florida, it now appears Matthew will continue eastward and gradually dissipate.

It will be some time before we have a more complete sense of Matthew’s toll, but we already know that it is the deadliest hurricane in the Western Hemisphere since 2005. In Haiti, Matthew took at least 877 lives and and left entire towns across southern Haiti almost completely destroyed. A handful of deaths and significant damage were also reported in Cuba, Jamaica, The Bahamas, Colombia, Saint Vincent and the Grenadines, and the Dominican Republic. After Haiti, it was the United States that took the worst of Matthew’s wrath. At least 16 U.S. deaths have been reported, and insured damage is expected to total at least $4 billion. See our Saturday post for details on how you can provide much-needed help to those struggling with the aftermath of Matthew.


Figure 1. A police officer walks past the remnants of a home leveled by Hurricane Matthew after it hit the tiny beach community of Edisto Beach, SC, on Saturday, October 8, 2016. Image credit: AP Photo/David Goldman.

From Florida to Virginia, astounding rains and storm surge
Matthew traced a path remarkably similar to the coastline of the Southeast U.S. Although its center stayed within about 50 miles of the coast for more than 36 hours and hundreds of miles, Matthew officially came ashore only briefly as a Category 1 hurricane along the South Carolina and North Carolina coast on Saturday afternoon. Matthew’s overall path kept its strongest winds just offshore, with few or no reports of sustained hurricane-force winds along the Southeast U.S. coast. Top wind gusts compiled by weather.com included 107 mph at Cape Canaveral, FL (collected on a tower 54 feet above ground level) and 96 mph at Tybee Island, GA.

Matthew’s just-offshore track may have spared the Southeast from billions of dollars in wind damage, but it didn’t keep the hurricane from packing a phenomenal punch in the form of water. Like several other U.S. hurricanes in the last decade, including Ike (2008) and Sandy (2012), Matthew delivered a much more severe storm surge than one might expect from its landfall strength, thanks to the water built up by much higher winds earlier in its life offshore. Matthew’s track along the concave Southeast coast also enhanced its ability to produce high surge. Major storm surge was reported as far north as the Hampton Roads area of southeast Virginia, which received an unexpectedly powerful blow from Matthew that also included tropical-storm-strength sustained winds (including a peak gust of 75 mph at Oceana Naval Air Station in Virginia Beach) and torrential rain.


Figure 2. Highway A1A in Flagler Beach, Florida on Saturday, October 8, 2016, after Hurricane Matthew’s record storm surge chewed up the road. Matthew brought a record storm surge of just over three feet to the Flagler Beach area on October 7, 2016. Image credit: Red Huber/Orlando Sentinel via AP.



Figure 3. Highway A1A in Flagler Beach, Florida on Saturday, October 8, 2016, after Hurricane Matthew’s record storm surge chewed up the road. Matthew brought a record storm surge of just over three feet to the Flagler Beach area on October 7, 2016. Image credit: Joe Raedle/Getty Images.


As of 8 am EDT Sunday, October 9, here are the approximate peak storm surges observed over the preceding 48 hours at all the tide gauges with a long-term period of record (at least a few decades) along the coasts of northern Florida, Georgia, South Carolina, North Carolina, and Virginia. (Storm surge is the added water produced by a storm atop the normal tidal cycles.)

7.8’ Fort Pulaski, GA
6.4’ Fernandina Beach, FL
6.1’ Charleston, SC
4.5’ Mayport, FL
4.4’ Springmaid Pier, SC
4.1’ Wilmington, NC
4.1' Money Point (Norfolk), VA
3.5' Sewells Point (Norfolk), VA
3.3' Chesapeake Bay Bridge Tunnel, VA
2.6’ Beaufort, NC

Three tide gauges with long-term historical records along this stretch of coast set all-time records on Friday through Sunday for their highest water level (also called the storm tide, or the water level measured relative to high tide, MHHW):

Fort Pulaski, Georgia: 5.06’
Previous record: 3.40’ during the October 15, 1947 hurricane (records since 1935.)

Wilmington, NC: 3.53’
Previous record 3.47’, during Hurricane Hazel on October 15, 1954 (records since 1935.)

Mayport, FL: 3.28’
Previous record: 2.47’, during Hurricane Jeanne on September 27, 2004 (records since 1928.)

Near-record high water levels were observed at three other stations:

At Charleston SC, the water level during the Saturday morning high tide was the third highest on record: 3.53’. The record: 6.76’ during Hurricane Hugo on September 21, 1989; second highest, 4.47’ during the August 11, 1940 hurricane (records since 1921.)

At Fernandina Beach, FL, the water level during Friday afternoon’s high tide was the second highest on record: 4.17’. The record: 6.91’ during the October 2, 1898 hurricane (records since 1897.)

At Springmaid Pier, SC the water level during Saturday afternoon’s high tide was the second highest on record: 2.66’. The record 3.65’, during the January 1, 1987 nor’easter (records since 1957.)


Figure 4. Multi-sensor analysis of precipitation for the 7-day period from 8:00 am EDT Sunday, October 2, to Sunday, October 9, 2016. Nearly all of the precipitation shown across the Southeast fell during Hurricane Matthew. Image credit: NOAA/NWS Advanced Hydrologic Prediction Service.

Torrential rains wallop unexpectedly large parts of the Carolinas and Virginia
Forecasters knew for days that extremely heavy rain was likely to develop on the north side of Matthew as it moved up the Southeast coast. As hurricanes move into the midlatitudes, they often interact with pre-existing frontal systems that intensify the rain-making processes on the poleward side of the storm. Matthew ended up generating torrential rain near the Southeast coast, as predicted, but it also produced record-smashing rainfall well inland and considerably further north than expected, especially over North Carolina and southeast Virginia. More than 880 rescues had taken place across North Carolina as of Sunday morning, according to Governor Pat McCrory.

Here are the highest storm totals observed in each state along Matthew’s path as of 11 am EDT Sunday:

Florida: 7.89”, Sanford/Orlando
Georgia: 17.49”, Savannah/Hunter Army Air Field
South Carolina: 14.04”, Beaufort MCAS
North Carolina: 15.65”, William O. Huske Locke 3
Virginia: 12.84”, 10 miles northwest of Chesapeake
Maryland: 5.52”, 6 miles south of Berlin
Delaware: 3.13”, Seaford


Figure 5.. A water rescue team member leads Derrick Williams out of the water at the on-ramp of the MLK Freeway after rescuing Williams from the flood waters caused by Hurricane Matthew on Saturday, October 8, 2016, in Fayetteville, NC. Image credit: Andrew Craft/The Fayetteville Observer via AP.

From Friday into Saturday, Savannah International Airport broke the city’s official 24-hour rainfall record of 11.44” on Sept. 17-18, 1928, according to WU weather historian Christopher Burt. It’s quite possible that an even higher 24-hour reading will be confirmed from one of the other Savannah-area reporting stations, as suggested by the storm total above.

Norfolk, VA, received 7.44” of rain on Saturday, making it the city’s wettest October day on record (beating 6.23” from October 17, 1999). Little more than three months ago, Norfolk set its all-time July calendar-day rainfall record with 6.98” on the 31st.

Raleigh-Durham International Airport picked up 6.45” on Saturday, beating the area’s previous all-time calendar-day rainfall record of 5.96” set on October 1, 1929. Raleigh-area records extend back to 1887.

Perhaps the single most phenomenal record on Saturday was at Fayetteville, NC, where 14.00” of rain was reported on Saturday. This demolished the city’s previous all-time calendar-day record of 6.80” observed during Hurricane Floyd on September 16, 1999. In fact, there are only four entire months in Fayetteville weather history that have received more rain than Fayetteville picked up in 24 hours on Saturday! Fayetteville records extend back to 1871. The flooding situation in the Fayetteville area was made even worse by very heavy rains observed in parts of the area during late September.

Record atmospheric moisture contributed to Matthew’s deluge
Several locations along Matthew’s path through the Southeast recorded incredibly high amounts of atmospheric moisture on Friday and Saturday. At least two sites had record amounts of precipitable water (the total amount of liquid water that would cover the ground over a given location if all the moisture in a column of air above was condensed). These readings are taken with radiosonde soundings (balloon-borne instrument packages) that have been conducted regularly since 1948.

Jacksonville, FL: 2.85” at 8 pm EDT Friday
Previous record: 2.82” on July 20, 1983

Charleston, SC: 2.93” at 2 am EDT Saturday (special sounding)
Previous record: 2.70” on August 15, 2010

October record (and 3rd highest in any month]: Newport/Cape Hatteras, NC: 2.85” at 8 pm EDT Saturday


Figure 6. A damaged home in Savannah, GA, is seen Sunday, October 9, 2016, after a tree split and fell through the roof and front wall early Friday morning as Hurricane Matthew approached. Homeowner Karen Currier said she and her husband were inside and escaped with a few scratches. Image credit: AP Photo/Kathleen Foody.

Matthew’s place in hurricane annals
Dr. Phil Klotzbach (Colorado State University) has assembled a handy list of the many records set during Matthew’s long life. Here are a few highlights:

Intensity: Matthew was the lowest-latitude Category 5 hurricane on record in the Atlantic. Its strengthening of 80 mph in just 24 hours was the third fastest on record for the Atlantic, behind only Wilma (2005) and Felix (2007).

Longevity: Matthew maintained Category 4 or 5 strength for 102 hours, the longest such stretch on record for October in the Atlantic. Its 7.25 days as a major storm (Category 3 or stronger) is the fifth longest such period for any hurricane since satellite observations began in the Atlantic in 1966.

Landfall: Matthew is the first storm on record to make landfall as a major hurricane in Haiti, Cuba, and the Bahamas. Since 1866, the only two hurricanes to strike the Bahamas at Category 4 strength in October are Matthew and last year’s Joaquin. Matthew’s landfall near Myrtle Beach made it the first hurricane to strike the U.S. Atlantic coast north of Georgia in October since Hazel (1954).


Figure 7. Enhanced infrared image of Tropical Storm Nicole as of 1745Z (1:45 pm EDT) Sunday, October 9, 2016. Image credit: CIRA/CSU/RAMMB.

A new lease on life for Nicole
Tropical Storm Nicole continues to languish in the open Atlantic. As of 11 am EDT Sunday, Nicole was nearly stationary, spinning about 575 miles south of Bermuda with top sustained winds of around 60 mph. As a blocking ridge to its north moves eastward, Nicole should begin moving north an at increasing rate over the next couple of days. By midweek, it will be over the record-warm waters of the subtropical North Atlantic, which helped boost Hurricane Gaston to Category 3 strength at latitude 30°N in late August. With wind shear over Nicole decreasing by midweek, the storm may a chance to regain much of the strength it had on Friday. The 12Z Sunday run of the HWRF, one of our best intensity models, brings Nicole back to Category 2 strength by late this week. Our best track models (the GFS, ECMWF, and UKMET) differ on whether Nicole will pass to the west or the east of Bermuda around Thursday. Given this uncertainty, as well as Nicole’s potential to intensify, Bermudians should monitor this storm closely.

We’ll be back with our next post on Monday.

Bob Henson and Jeff Masters




Hurricane

Hurricane Matthew Pounds Southeast With Record Storm Surge, Massive Flash Flooding

By: Jeff Masters and Bob Henson , 5:36 PM GMT on October 08, 2016

Hurricane Matthew made landfall near 11 am EDT Saturday about 25 miles northeast of Charleston, South Carolina as a Category 1 hurricane with 75 mph winds. During the past two high tide cycles, Matthew has pushed a historic and destructive storm surge to the coasts of northern Florida, Georgia and South Carolina, bringing coastal water levels that were the highest to third highest ever observed. The powerful hurricane, diminished to Category 2 strength with 105 mph winds early Saturday morning, nonetheless had a very large area of strong winds that were able to pile up a massive dome of water that was focused by the arc-shaped curve of the coast into a record-height storm surge. As of 8 am EDT Sunday, October 9, here were the approximate peak storm surges observed over the preceding 48 hours at all the tide gauges with a long-term period of record along the coasts of northern Florida, Georgia, South Carolina, North Carolina, and Virginia (storm surge is the added water produced by a storm atop the normal tidal cycles):

7.7’ Fort Pulaski, GA
6.4’ Fernandina Beach, FL
6.1’ Charleston, SC
4.5’ Mayport, FL
4.4’ Springmaid Pier, SC
4.1’ Wilmington, NC
4.1' Money Point (Norfolk), VA
3.5' Sewells Point (Norfolk), VA
3.3' Chesapeake Bay Bridge Tunnel, VA
2.6’ Beaufort, NC


Figure 1. In Savannah, GA, a car is stranded in waist-deep water near Ogeechee Road and Stiles Avenue on Saturday morning, October 8. Image credit: Savannah-Chatham Metropolitan Police Department.

Three tide gauges with long-term historical records along this stretch of coast set all-time records on Friday through Saturday for their highest water level (also called the storm tide, or the water level measured relative to high tide, MHHW):

Fort Pulaski, Georgia: 5.06’
Previous record: 3.40’ during the October 15, 1947 hurricane (records since 1935.)

Wilmington, NC: 3.53’ Previous record 3.47’, during Hurricane Hazel on October 15, 1954 (records since 1935.)

Mayport, FL: 3.28’
Previous record: 2.47’, during Hurricane Jeanne on September 27, 2004 (records since 1928.)

Near-record high water levels were observed at three other stations:

At Charleston SC, the water level during the Saturday morning high tide was the third highest on record: 3.53’. The record: 6.76’ during Hurricane Hugo on September 21, 1989; second highest, 4.47’ during the August 11, 1940 hurricane (records since 1921.)

At Fernandina Beach, FL, the water level during Friday afternoon’s high tide was the second highest on record: 4.17’. The record: 6.91’ during the October 2, 1898 hurricane (records since 1897.)

At Springmaid Pier, SC the water level during Saturday afternoon’s high tide was the second highest on record: 2.66’. The record 3.65’, during the January 1, 1987 nor’easter (records since 1957.)



Figure 2. Hurricane Matthew radar at 11 am EDT Saturday, October 8, 2016, as seen on our wundermap with the storm surge layer turned on. A storm surge of 5.4’ was indicated near Georgetown, South Carolina, with 3.5’ at Wilmington, North Carolina.

More high storm surges coming to SC, NC
Matthew will continue to track right along the coast of South Carolina this afternoon, then turn more to the northeast and track just south of the North Carolina coast Saturday night through Sunday morning. This track will push a dangerous storm surge of near record-high proportions to the coast, with NHC predicting inundations of 5 - 7’ possible from Charleston, SC to Cape Fear, and lower heights of 2 - 4’ for the coast of southern North Carolina farther to the east.

You can track Matthew’s storm surge using our wundermap with the “Storm Surge” layer turned on, the NOAA Tides and Currents storm page for Matthew or storm surge expert Dr. Hal Needham’s U-SURGE page for Matthew. Dr. Needham has some excellent information on the storm surge history of the north Florida to southern South Carolina coast in a Friday morning blog post, The "Protected Coast" is Now the Most Dangerous Place of All.


Figure 3. Multi-sensor analysis of rainfall for the 24 hours ending at 8:00 am EDT Saturday, October 8, 2016. Image credit: NOAA/NWS Advanced Hydrologic Prediction Service.

Record atmospheric moisture contributing to Matthew’s deluge
Weakening winds and a track just offshore hasn’t impeded the ability of Hurricane Matthew to produce vast amounts of rain along and near the Southeast coast, as the storm took advantage of all-time record levels of atmospheric moisture. A special balloon sounding launched at 2 am EDT Saturday from Charleston, South Carolina, measured the highest amount of moisture in the air ever recorded there: a precipitable water level of 2.93” (previous record: 2.70” on August 15, 2010.) The Jacksonville, Florida upper-air station also set an all-time record for atmospheric moisture in their 8 pm Friday night balloon sounding: 2.85” of precipitable water, beating the previous record of 2.82” set on July 20, 1993. Precipitable water is the total amount of liquid water that would cover the ground over a given location if all the moisture in a column of air above was condensed. Balloon soundings of the atmosphere have records extending back to 1948.

Twenty-four hour rainfall amounts from Matthew of 2” - 5” were common across the eastern half of north Florida, with much greater totals piling up toward the north. The calendar-day total of 6.28” at Jacksonville International Airport on Friday made for the city’s fifth wettest October day on record. In Savannah, Georgia, the 8.94” of rain recorded on Friday was the city’s second-largest calendar-day rainfall on any date, beaten only by 9.02” on September 16, 1924. Records in Savannah go back to 1871. Several more inches of rain fell early Saturday as the eyewall continued rolling over the city, and Savannah’s 24-hour total through 8 am EDT was 11.50”.

Some of the higher 24-hour totals reported on Saturday morning from the CoCoRaHS volunteer observing network:

13.86” - Garden City, GA
12.90” - Reevesville, SC
11.00” - Hilton Head Island, SC*
11.00” - 8 miles S of Manning, SC*
10.00” - Summerville, SC*
9.70” - 7 miles WSW of Santee, SC
9.70” - NWS/Charleston, SC
9.39” - 12 mi N of Jacksonville, FL
[* = minimum value, as the rain gauge overflowed]


Figure 4. Rainfall predicted for the two-day period from 8 am EDT Saturday, October 8, 2016 to 8 am Monday, October 10. Image credit: NHC, via NOAA/NWS/WPC.

Major flash flood threat over southeastern Carolinas this weekend
Residents of parts of North and South Carolina must be having deja vu this morning, as torrential rains from Matthew are arriving almost precisely one year after the catastrophic deluge that caused $2 billion in damage during the first week of October 2015. A swath from around Charleston to Columbia, SC, was especially hard hit during the 2015 deluge. As Matthew continues its track just offshore, heavy rains will continue to deluge areas within about 100-150 miles of the Atlantic, with the heaviest amounts closest to the coast (see Figure 4.) At midday Saturday, flash flood watches and warnings were plastered across coastal counties from Georgia to Delaware, including the Hampton Roads area of southeast Virginia. A flash flood emergency was issued for several counties near Fayetteville, NC, where Matthew has already produced more than 8” of rain. The stage for severe flooding was set by rains that topped 10” just west of Fayetteville over the prior 10 days. A separate flash flood emergency was in effect for areas near the Grand Strand series of beaches in South Carolina.

Larger-scale river flooding may become a serious concern by early next week in some areas, especially the coastal plain of North Carolina. The N.E. Cape Fear River near Chinquapin was projected to crest at 22.6 feet on Tuesday. That would tie the crest from January 1, 1928, and fall behind only the record 23.51 feet observed during Hurricane Floyd in 1999.

Forecast: Matthew will die Sunday night
Satellite loops on Saturday morning showed a quickly degrading hurricane, with a disheveled-looking area of heavy thunderstorms that were being distorted by high wind shear of 30 knots. Matthew will encounter steadily more unfavorable conditions for existence over the next three days. Wind shear will rise above 40 knots, the atmosphere will dry, and the ocean temperatures will cool. Matthew is now expected to get entangled with a front a few hundred miles south of Cape Hatteras, North Carolina on Sunday night, putting a final end to this long-lived tropical menace. The remnant non-tropical low pressure area that was Matthew may then loop to the south and southwest early next week, but will not be a high wind or heavy rain threat to The Bahamas.

Matthew was the 13th billion-dollar disaster in the U.S. this year
Insurance broker Aon Benfield, in an update sent out Friday evening, estimated that the total price tag for Matthew's damages across the U.S., The Bahamas, Cuba and Haiti would run well into the billions of dollars, and would be the 13th billion-dollar weather-related disaster for U.S. so far this year. This is now the second-most number of such disasters (adjusted for inflation) in the U.S. in one year, behind 2011, which had seventeen. Property data firm CoreLogic is estimating $4 - $6 billion in insured U.S. losses from Matthew; total losses are typically double insured losses.


Figure 5. Women walking down the street in Jeremie, southwest Haiti, after the city was devastated by Hurricane Matthew. Foto: Logan Abassi UN/MINUSTAH.

Portlight and Lambi Fund of Haiti disaster relief charities need your help
The Portlight.org disaster relief charity, founded and staffed by members of the wunderground community, is responding to Hurricane Matthew. Portlight is working with their partners and stakeholder organizations throughout the affected region to ensure the needs of people with disabilities are well met. It's important to note this includes people in directly impacted areas as well as the tens of thousands of evacuees. You can check out their progress on the Portlight Blog or donate to Portlight's disaster relief fund at the portlight.org website.

A note from Jeff Masters: For over ten years, I’ve been a big booster of and donor to the Lambi Fund of Haiti, which is very active in disaster relief and disaster prevention, including promotion of reforestation efforts, use of alternative fuels, and infrastructure improvements at a grass-roots level to help avert future flood disasters.

What Lambi Fund is doing for their Hurricane Matthew response:
    •    Utilizing Regional Monitors and the active Partner Organizations (22 projects in portfolio) to survey the immediate needs in the South and Northwest in order to provide a primary response to these urgent needs
    •    Providing $150,000 for urgent relief during the first phase of their response while completing a needs assessment of the resources needed for the second phase, which will be to “Repair and Restore” the 22 active organizations’ projects that have been devastated
  •    Support the process of repairing the infrastructure damages (already established: 4 mills down in the Northwest, need to repair gardens, supply soil and nutrients essentially starting gardens over from scratch)

You can make your donation online at http://www.lambifund.org or send your funding support to: 

Lambi Fund of Haiti
1050 Connecticut Avenue, Suite 500
Washington DC 20036

We’ll be back with our next update by Sunday afternoon.

Jeff Masters and Bob Henson

Hurricane

Matthew, Atlantic’s Deadliest Hurricane in 11 Years, Heads for Georgia, S. Carolina

By: Bob Henson and Jeff Masters , 10:15 PM GMT on October 07, 2016

Friday brought very good news and very bad news on Hurricane Matthew. The powerful storm stayed just far enough offshore to spare Florida its worst, but reports from Haiti showed that Matthew was far more of a disaster than initially thought. Now that relief workers and other offiicals have made it to Haiti’s hard-hit southwest corner, they report catastophic conditions and a mounting death toll. More than 800 people have died in Haiti, and that number is expected to grow, perhaps dramatically, as rescue and relief efforts continue.

As of 5 pm EDT Friday, the center of Matthew was located about 40 miles east of Jacksonville Beach, FL, moving north at 12 mph. Matthew’s top sustained winds had dropped to 110 mph, making it a high-end Category 2 storm. According to Phil Klotzbach (Colorado State University) Matthew’s impressive duration of just over seven days as a major hurricane (Category 3 or stronger) put it in a tie for the fifth-longest such stretch since satellite observations began in the Atlantic in 1966.


Figure 1. MODIS satellite image of Matthew taken at 12 pm EDT October 7, 2016. At the time, Matthew was a Category 3 storm with 120 mph winds. Image credit: NASA.

Matthew’s track: a parallel reality
Matthew jogged just far enough to the east over the Bahamas so that its generally well-predicted track parallel to the central and north Florida coast kept the center just offshore--far enough so that the hurricane’s western eyewall only nicked the coastline. The top wind gust reported thus far was 107 mph at Cape Canaveral, which juts out a few miles into the Atlantic and was thus closer to Matthew’s higher winds. The impact was much less than feared at Kennedy Space Center, mainly limited to scattered debris and some roof damage. Elsewhere along the Florida coast, top sustained winds were surprisingly low, generally in the tropical storm range, resulting in fairly minor damage overall. Daytona Beach received sustained winds of at least 46 mph, with gusts as high as 67 mph. Saint Augustine notched peak sustained winds of 51 mph, with gusts to 67 mph.

Matthew is carrying out a classic round-the-bend path on the west side of a zone of high pressure over the subtropical Atlantic. The latest NHC forecast keeps Matthew hugging the Southeast coast all the way to central South Carolina by Saturday afternoon. Matthew’s gradual weakening should continue, but it may still be a hurricane as it nears Charleston, SC, and a brief landfall is possible if the path arcs slightly more leftward than expected.


Figure 2. Heavy waves caused by Hurricane Matthew pounds the boat docks at the Sunset Bar and Grill, October 7, 2016 on Cocoa Beach, Florida. Image credit: Mark Wilson/Getty Images.


Figure 3. A truck negotiates around trees downed by Hurricane Matthew, Friday, Oct. 7, 2016, in Daytona Beach, Florida. Image credit: AP Photo/Eric Gay.

Storm surge and inland flooding are now the main threat from Matthew
Matthew’s track nudged ever closer to the coast on Friday afternoon, causing progressively more serious problems with storm surge. Much of historic Saint Augustine, FL, was under water for several hours close to the midday high tide on Friday (see embedded tweet below). Althena Masson (@Wx_Goddess), a meteorologist and doctoral student at the University of Toronto from the Saint Augustine area, filed numerous tweets from the scene. “Matthew, you will not take my thesis research!” she exclaimed at one point, later evacuating to the second story of her home. Water also poured across the barrier-island community of Jacksonville Beach, as captured by a news helicopter. One videographer captured a huge tree being uprooted in Jacksonville, where Matthew may deliver the most severe hurricane-related impacts since Dora in 1964.

NHC projects that inundation levels of up to 11 feet are possible along the Georgia and southern South Carolina coasts as Matthew approaches. Already on Friday afternoon, Matthew was producing once-in-a-century high water levels ahead of its track. At Fernandina Beach, FL, the early-afternoon high tide combined with the storm surge for a crest of 4.11 feet above mean high high water (MHHW) on Friday afternoon. This is the highest water observed at Fernandina Beach in more than 100 years, beating the peak MHHW of 3.9 feet observed during Hurricane Dora (1964) and topped only by the reading of 6.94 feet recorded on October 2 during the Hurricane of 1898. On Georgia’s Brunswick River, at Village Pier on St. Simons Island, Georgia, a river crest of 6.15 feet observed around 5 pm EDT Friday beat the reading of 5.93 feet observed there on February 7, 1993. Based on the surge values during low tide Friday, Fort Pulaski, Georgia, is likely to see water at least 4 to 5 feet above MLLW during the high-tide cycle centered around midnight Friday night. In records going back to the 1930s, the highest reading observed at Fort Pulaski is 3.4 feet above MLLW, recorded on October 15, 1947. Comparable levels of surge may extend to the Low Country of South Carolina, a highly vulnerable area. The National Weather Service office in Charleston is warning of the potential for life-threatening surge in some coastal locations between Charleston and the Georgia border. In its afternoon weather discussion, the office stated:

”Many beach communities will see extensive damage to beach front properties due to a combination of large breaking waves, high surge and dangerous winds. Homes at Edisto Beach [were] already being undermined at high tide earlier this afternoon and Tybee Island saw significant flooding along the beach front. Expect considerably worse conditions tonight and it can not be stressed enough that how dangerous this scenario is.”

You can monitor surge as it moves up the Southeast coast using our wundermap with the “Storm Surge” layer turned on (note that these values are relative to mean low low water rather than mean high high water). Two other good sources are the NOAA Tides and Currents storm page for Matthew, and storm surge expert Dr. Hal Needham’s U-SURGE page for Matthew. Dr. Needham has some excellent information on the storm surge history of the north Florida to southern South Carolina coast in a Friday morning blog post, The "Protected Coast" is Now the Most Dangerous Place of All.

Very heavy rains are the other looming threat from Matthew. Totals of 10” to 15” may occur along the immediate coast ahead of Matthew, and 3” - 10” can be expected over large parts of the eastern Carolinas. These rains may produce dangerous flooding well inland. Wind gusts could reach the 40-60 mph range over the eastern Carolinas from Saturday night into Sunday. Given the wet soils that preceded Matthew, compounded by any rains from the hurricane itself, many trees could be felled and widespread power outages are possible.


Figure 4. Three-day forecasts issued for Hurricane Katrina (left) on Friday, August 26, 2005, and for Hurricane Matthew (right) on Tuesday, October 4, 2016. The red circles denote the actual locations of each storm three days after the forecasts were issued. The "cone of uncertainty" is based on forecast errors over the prior five years, so it was narrower for Matthew than for Katrina. Image credit: NOAA/NWS/NHC.

Matthew’s forecast: Accuracy goes head-to-head with geometry
People along the central Florida coast can be forgiven for thinking that the NHC forecast for Matthew was a bust. Millions of folks on the coast who were warned about the potential of fierce Category 3 winds ended up with sustained winds barely above tropical-storm strength. Yet the actual forecast for Matthew--the storm itself--was remarkably accurate. The right-hand side of Figure 4 shows the 3-day forecast issued by NHC for Matthew on Tuesday morning, October 4. Matthew’s location on Friday morning was within 75 miles of the 3-day forecast position, well within the “cone of uncertainty”. The cone width is based on error statistics for the five preceding hurricane seasons; at any point in the forecast, there’s a one-third chance that the hurricane will fall outside the cone. On the left-hand side of Figure 4, we see that the forecast for Katrina issued three days before landfall (on Friday, August 26, 2005) was far less accurate, with the actual position of Katrina more than 150 miles from the 3-day forecast location. Even with the wider cone of uncertainty circa 2005 (reflecting the greater track errors of 10-15 years ago), Katrina’s 3-day position was barely within the cone.

Figure 4 also shows us the geographic challenge of forecasting Matthew. Had Florida’s coast been oriented from west to east, like the central Gulf Coast, then Matthew would have slammed directly into some point on the coast, as Katrina did, with significant wind damage a near-certainty. Instead, Matthew tracked virtually parallel to the coast, which meant that the relatively minor (but impact-significant) forecast error relative to the coast was extended over a much longer time period.


Figure 5. Small towns along the western coast of Haiti suffered extreme damage from storm surge during Hurricane Matthew. This photo was tweeted by a United Nations aerial survey. Image credit: United Nations Stabilization Mission in Haiti (MINUSTAH), via univision.com.

Yet another disastrous hurricane for Haiti
Matthew’s death toll makes it the deadliest year for hurricanes in Haiti since 2008, when four storms--Fay, Gustav, Hanna, and Ike--dumped heavy rains on the impoverished nation. The rugged hillsides, stripped bare of 98% of their forest cover thanks to deforestation, let flood waters rampage into large areas of the country. According to reliefweb.org, Haiti suffered 793 killed, with 310 missing and another 593 injured due to hurricanes in 2008. Matthew is the deadliest Atlantic hurricane since Hurricane Katrina of 2005, which killed 1833 people (though Hurricane Stan of 2005 was indirectly responsible for 1000 - 2000 flooding deaths that year, as well.) So far, Matthew does not make it on the list of the 30 deadliest Atlantic hurricanes in history, which consists of storms that killed at least 1,500 people.

We’ll be back with our next update on Matthew by Saturday morning.

Bob Henson and Jeff Masters


.

Hurricane

Hurricane Matthew Spares Florida Major Winds; Dangerous Storm Surge and Rains Arrive

By: Jeff Masters , 4:16 PM GMT on October 07, 2016

Hurricane Matthew has spared Florida the worst. A mighty Category 4 storm with 140 mph winds when it devastated Grand Bahama Island on Thursday, Matthew underwent a collapse of its inner eyewall on Thursday evening, which resulted in the hurricane weakening dramatically. Now a Category 3 storm with 120 mph winds as of the 11 am EDT Friday advisory, Matthew has yet to generate sustained winds of hurricane force anywhere in Florida, though a gust of 107 mph was recorded on Cape Canaveral this morning. Matthew’s center came within 30 miles of Cape Canaveral, but the western eyewall of the storm has, for the most part, remained barely offshore today.


Figure 1. Hurricane Matthew radar at 11:33 am EDT Friday, October 7, 2016, as seen on our wundermap with the storm surge layer turned on. Storm surge levels of 1.2 - 2.4’ were along the east coast of Florida.

Intensity forecast: a slow weakening of Matthew
Satellite loops on Friday morning showed a solid but not spectacular major hurricane, with plenty of heavy thunderstorms with cold cloud tops in the eyewall. However, the eye had gotten less prominent since Thursday, and the intensity of the thunderstorms had decreased. Matthew will encounter steadily more unfavorable conditions for intensification over the next three days. Wind shear, now a moderate 15 knots, will rise to the high range, above 20 knots, by tonight. The ocean temperature will cool as Matthew progresses to the north, and dry air will be attacking from the west. The combination of cooler ocean temperatures, high wind shear and dry air should act to significantly weaken Matthew to a Category 1 hurricane by Saturday night, when it will make its closest approach to North Carolina.


Figure 2. Heavy rainfall from Matthew will be a huge concern, particularly over coastal South Carolina and southern North Carolina, as this graphic from the NWS in Wilmington, North Carolina illustrates.

Track forecast: landfall risk is greatest in South Carolina
Matthew is tracking right along the coast of Florida today, and we can expect that portions of the coast may occasionally see the west eyewall of the storm move over. This will bring hurricane-force wind gusts, but not sustained hurricane-force winds of 74+ mph. There is perhaps a 20% chance that Matthew will take a wobble to the west that would take the core of the hurricane ashore over the coast between Daytona Beach and Jacksonville, bringing sustained hurricane-force winds to the coast, though. The greater danger of hurricane-force winds at the coast is to South Carolina. The 00Z Friday runs of our four top models for forecasting hurricane tracks—the GFS, European, UKMET and HWRF—showed that Matthew will track very close to the coast of Florida and Georgia today and early Saturday morning, then potentially make landfall on the coast of South Carolina Saturday morning near 6 am EDT. The 06Z Friday runs of the GFS and HWRF model showed this, as well. The range of solutions for these various model runs was to take the storm inland by up to 30 miles or keep it offshore by about 30 miles, just south of Charleston. In their 11 am EDT Friday Wind Probability Forecast, NHC gave highest odds of hurricane-force winds in South Carolina to Charleston (45%.) The highest odds in North Carolina were at Bald Head Island (22%), and the highest odds in Georgia were at King’s Bay (37%).

While it’s going to be a close call whether or not Matthew makes landfall in South Carolina, this drama is not going to be the major factor controlling how much total storm damage occurs there. Matthew is likely to be a weakening Category 2 storm when it makes its closest approach to the South Carolina coast, and the amount of wind damage the storm can deliver to the state will be modest, even if it makes a direct hit on Charleston. The bigger threat to South Carolina is storm surge and fresh water flooding damage, which will happen to South Carolina regardless of whether or not the eye moves ashore or remains just offshore. Rainfall amounts in excess of a foot are expected along the coast of South Carolina and into southern North Carolina, in a region where soils are saturated and rivers are high due to near-record heavy rains over the past few weeks. Matthew’s heavy rains are likely to result in major damaging flooding, which will be magnified by the fact rivers won’t be able to drain into the ocean due to storm surge.

Record to near-record storm surge possible in far north Florida, Georgia, and South Carolina
Matthew’s failure to move inland and weaken over central Florida is good news for them but bad news for the coasts of north Florida, Georgia, and South Carolina. A stronger Matthew means a larger storm surge farther to the north. Matthew’s eyewall replacement cycle (ERC) was also a good news/bad news situation: while the ERC reduced the hurricane’s peak winds from Category 4 to Category 3, strong winds have now spread out over a wider area, which will increase the storm surge, due to all the extra water that will be put in motion by an expanded wind field. To illustrate, tropical storm-force winds extended 160 miles to the northeast of Matthew’s center at 11 am Thursday, but by 11 am Friday, these winds had expanded to extend outwards 185 miles from the center. At 11 am EDT Friday, the coast from just south of Cape Canaveral, FL to just south of Wilmington, NC was under a storm surge warning under a prototype NHC system expected to become operational next year. As Matthew moves northward, the northeast winds ahead of it will pile water against the coastline, leading to what could be record or near-record storm surges in some areas. The Friday morning discussion from the NWS in Charleston, South Carolina warned that:

Persistent and strong northeast winds have allowed for numerous previous tide cycles, even at low tide, to reach far above predicted levels. This pattern will continue and get even more hazardous as Matthew approaches the area from the south later today and tonight. There will be at least moderate coastal flooding with the midday high tide, but it's the high tide around 12-2 am tonight that's the most concerning when significant coastal flooding will likely occur. Tide levels are forecast to approach or even surpass those during October of 2015, meaning levels could exceed 8.0 ft MLLW at Charleston and more than 11.0 ft MLLW at ft. Pulaski. This would be the second highest crest on record for Ft. Pulaski, exceeded only by hurricane David which produced a 12.21 foot crest in 1979. It would also be in the top 5 or 10 crests on record for Charleston. These levels will be accompanied by moderate or heavy rains, creating an extremely dangerous situation for coastal areas and in downtown Charleston. Tybee Island will become cut off!

The forecasted inundation continues to be 4-8 ft for South Carolina and 7-11 ft for Georgia. Some coastal locations could experience the worst storm surge since Hurricane Hugo with devastating impacts.


Update: The 11 am Friday NHC advisory reduced the expected peak storm surge inundation for Georgia to 6 - 9 feet.

Major storm surge flooding had yet to materialize from Matthew on Friday morning at any of our tide gauges on Friday morning--though there were reports of serious storm surge flooding occurring in St. Augustine, Florida, where we do not have a tide gauge. At 11 am EDT Friday, persistent onshore winds associated with Matthew’s circulation were pushing a storm surge of 2.4 feet to the Florida/Georgia border at Fernandina Beach, 2.0 feet to Jacksonville, Florida at Mayport Bar, 1.2 feet to Savannah, Georgia near Fort Pulaski and 1.4 feet to Charleston, South Carolina, as seen on our wundermap with the “Storm Surge” layer turned on, or the NOAA Tides and Currents storm page for Matthew, or storm surge expert Dr. Hal Needham’s U-SURGE page for Matthew. Dr. Needham has some excellent information on the storm surge history of the north Florida to southern South Carolina coast in a Friday morning blog post, The "Protected Coast" is Now the Most Dangerous Place of All.

Long range forecast for Matthew: a loop-de-loop
Our top two hurricane track models—the GFS and European—continue to show high pressure building in to the north of Matthew this weekend, blocking the hurricane’s forward path. Matthew is expected to loop back towards the south and southwest, potentially reaching The Bahamas by Tuesday. Along the way, though, Matthew may draw close enough to Hurricane Nicole to force the two storms to rotate around a common center—something known as the Fujiwhara effect. This behavior can occur when two storms get within 800 miles of each other. This potential interaction with Nicole on Sunday and Monday makes the 3 - 5 day forecast for Matthew’s track of higher uncertainty than usual-though if anything, it is most likely to reinforce the expected northward track of Nicole and southward track of Matthew. One thing we are confident of: Matthew will be a much weaker storm by Tuesday when it makes its closest approach to the Bahamas. High wind shear of 30 - 50 knots is expected to affect Matthew Sunday through Tuesday, along with very dry air—humidities at mid-levels of the atmosphere are expected to drop to 20% by Monday, which is bound to cause significant weakening of the storm. If Matthew does pass through The Bahamas on Tuesday, it would likely be no stronger than a 35 mph tropical depression.


Figure 4. Track forecasts from the four European model ensemble members [gray lines] that most closely match the operational run [red line] during the first 72 hours, starting at 00Z Friday, October 7, 2016. The red line is a version of the 00Z Friday operational model track that has been adjusted and calibrated using a proprietary technique to account for systemic model errors. All of these forecasts show Matthew doing a loop over the waters east of The Bahamas, with three of them showing Matthew moving through The Bahamas. The high-probability cluster (grey lines) perform better than other ensemble members at forecast times of five days and beyond. The grey crosses along the Gulf Coast are the locations of oil wells, as this forecast tool was designed primarily for use by the oil and gas industry. Image credit: Climate Forecast Applications Network (CFAN).

We’ll be back with our next update by late this afternoon. Meteorologist Steve Gregory is making regular updates on Matthew.

Jeff Masters

Hurricane

Matthew Toys With Florida Coast; Major Surge Threat Remains

By: Bob Henson , 5:49 AM GMT on October 07, 2016

After barreling across the Caribbean and through the Bahamas, Hurricane Matthew backed off from an immediate U.S. landfall on Thursday night, and odds were rising that the system might not come fully ashore before looping out to sea over the weekend. In its 11 pm EDT advisory, the National Hurricane Center kept Matthew’s top sustained winds at 130 mph, making it a minimal Category 4 storm. Hurricane Hunters found that Matthew’s central pressure had dropped to 937 millibars on Wednesday night. Together with radiometer-derived surface winds of 125 mph, it was clear that Matthew remained a potent hurricane, despite its somewhat disheveled appearance on satellite. Update: At 2:00 am EDT Friday, NHC downgraded Matthew to a Category 3 storm, with top sustained winds of 120 mph.


Figure 1. Enhanced infrared satellite image of Hurricane Matthew as of 12:45 am EDT Friday, October 7, 2016. Image credit: NOAA/NESDIS.


Figure 2. WU depiction of NEXRAD radar from 1:15 am EDT Friday, October 7, 2016. The predominant outer eyewall and its intense thunderstorms (yellow band just east of Port Saint Lucie) was slowly edging toward the Florida coast.

Eyewall to eyewall
Over the course of Thursday afternoon and evening, Matthew ended up with dual, concentric eyewalls--an outer one, about 70 miles wide, and an inner one, about 10 miles wide, where the strongest winds were focused. The development of dual eyewalls often heralds an eyewall replacement cycle (ERC), in which the inner eyewall collapses and the outer one gradually contracts. Matthew appeared ripe for an ERC on Thursday evening, and that process appeared to be underway late Thursday night, as a reconnaissance summary at 12:15 am EDT Friday reported a single closed eyewall, about 55 miles wide.


Figure 3. Observations gathered by a Hurricane Hunter flight through Matthew late Wednesday night into early Thursday morning. The emergence of a single large eyewall can be seen in the extended period between wind peaks (blue trace) at around 0342Z (11:42 pm EDT Wednesday) when the aircraft detected very low surface air pressures below 945 millibars (red trace, corresponding to the pressure legend at left). Image credit: tropicaltidbits.com.


Figure 4. Official NHC forecast for Matthew as of 11 pm EDT Thursday, October 6, 2016. The unusual look of the “cone” is because of the nearly complete loop that Matthew is predicted to carve out in the next five days.

A coast-scraping track that could still cause major trouble
What was always recognized as a possibility--that Matthew would never quite make landfall on the Florida coast--emerged as the most likely outcome on Thursday night, as reflected in the 11 pm NHC outlook (see Figure 4 above). Matthew’s track out of the Bahamas was angled just far enough north of northwest to keep the center rolling more or less parallel to the Florida coast. Provided that Matthew carries out the gradual curve to the right expected late Friday through Saturday, its center will likely remain between about 20 and 50 miles off the coast, perhaps all the way to Charleston, SC, by Saturday night. This path would be enough to keep Matthew’s inner core and its top sustained winds offshore, which is very good news in terms of limiting the most severe wind damage. On the down side, Matthew’s outer eyewall--which will likely be packing streaks of 60 to 90 mph sustained winds--will probably edge onto or just inland from the coast early Friday. If Matthew’s center remains offshore as the hurricane churns north and northeast toward Georgia, then its outer eyewall may be slower to weaken. People along the Florida coast from around Melbourne northward can expect several hours of high wind on Friday, fierce enough at times to topple trees and power lines. If not catastrophic (thankfully!), such damage may end up being far more widespread on this type of coast-scraping path than it would have been with a hurricane slamming onshore at a right angle.

Hurricane-force winds are possible as far north as coastal Georgia and southern South Carolina later on Friday, but the primary threat here will be high water--the most deadly aspect of U.S. hurricanes. Because of the gradual expansion of Matthew’s wind field, its direction of motion, and the largely concave geometry of the coastline, barrier islands and inlets from north FL to southern SC remain at risk of major storm surge even if Matthew remains offshore. Late Thursday night, NHC was projecting the potential for coastal inundations of 7 to 11 feet from Sebastian Inlet, Florida, to Edisto Beach, South Carolina, including parts of the St. Johns River between the coast and Jacksonville. Breaking waves of up to 20 - 25 feet are possible atop the coastal surge.

Time and again in recent years, we’ve seen hurricanes weaken in terms of peak winds as they approach the coast, yet push far more water onshore than residents expected. This is one reason why the Saffir-Simpson scale no longer directly relates its strength categories to storm surge: peak winds near the center are an unreliable index to how much surge a hurricane may actually produce. Even if Matthew weakens and stays offshore as projected, surge levels in some areas (especially far north Florida and Georgia) may be the highest observed in many decades, and I fear that many coastal residents will underestimate this risk.


Figure 5. Projected 3-day rainfall totals from 8:00 pm EDT Thursday, October 6, to 8:00 pm Sunday, October 9. Image credit: NOAA/NWS Weather Prediction Center.

Very heavy rainfall is the other water-related threat that still looms large with Matthew. Widespread totals in the 10” to 15” range are projected to fall within about 50 miles of the coast from far north Florida to southeast North Carolina (see Figure 5). The southeast half of the Carolinas can expect 3” to 10” amounts. This may be enough to cause extensive flooding, especially where 10” - 15” of rain has fallen in the last three weeks. With winds potentially gusting to 40 - 50 mph, we can expect extensive tree loss and power outages.

If Matthew fails to make landfall on Friday, or if it does come ashore below Category 3 strength, the remarkable and unprecedented U.S. “drought” in major hurricane landfalls will continue. The last hurricane to strike the U.S. with Category 3 winds was Wilma, in October 2005--nearly 11 years ago.

Beyond the Carolinas
Long-range models agree in turning Matthew gradually seaward from the Carolinas over the weekend, and it now appears that the wacky loop-de-loop solution presented by the models a couple of days ago will materialize, at least in some form or fashion. The path shown in Figure 3 above is one of the most precise and elegant circles I’ve ever seen in a five-day NHC forecast. By Tuesday, Matthew is predicted to be heading southwestward, back into the northern Bahamas. Matthew will almost certainly be a far weaker system by this point--most likely a tropical storm. It’s certainly possible that Matthew will end up crossing Florida at some point next week.


Figure 6. Enhanced infrared satellite image of Hurricane Nicole as of 12:45 am EDT Friday, October 7, 2016. Image credit: NOAA/NESDIS.

Nicole is now a Category 2 hurricane
Quietly gathering strength while Matthew hogged the spotlight, Hurricane Nicole has become a respectable storm in its own right. Nicole’s top sustained winds were bumped up to 105 mph at 11 pm EDT Wednesday, making it a strong Category 2 hurricane. Located about 340 miles south of Bermuda, Nicole was stationary, embedded in weak steering currents and in no hurry to head anywhere. Matthew may draw close enough to Nicole early next week to bring the Fujiwhara effect into play, which would tend to push Nicole to the north and Matthew toward the south--consistent with the motions now expected for both systems, although larger-scale steering will probably be the main factor at work.

NHC’s Eric Blake provided an interesting climatological tidbit in his Thursday night discussion on Nicole: “This is the first time since September 10, 1964 that two Category 2 (or stronger) hurricanes have occurred simultaneously in the Atlantic basin west of 65W. Interestingly, those hurricanes in 1964, Dora and Ethel, were in similar positions as Matthew and Nicole are now.”

Jeff Masters will be back with our next update by late Friday morning.

Hurricane

With or Without a Landfall, Category 4 Matthew Will Pose an Extreme Threat

By: Jeff Masters and Bob Henson , 12:22 AM GMT on October 07, 2016

Hurricane Hunters found on Wednesday afternoon that Hurricane Matthew was hanging on to its formidable strength, despite a less-than-textbook structure on satellite. Matthew’s central pressure was as low as 936 millibars late Wednesday afternoon. Top sustained winds dropped to 130 mph in the 8 pm EDT advisory from the National Hurricane Center. Dry air flowing into the storm from the northwest took a clear bite out of Matthew’s core of showers and thunderstorms (convection) on Wednesday afternoon, leaving the convection mostly concentrated on Matthew’s south side. However, after about 5:00 pm EDT, the convection rapidly filled in on Matthew’s north side, making for a much more symmetric hurricane.


Figure 1. A radar image from WU’s Storm app at 6:20 pm EDT Thursday showed Matthew’s center just southwest of Freeport, The Bahamas. Matthew’s small eye and eyewall were surrounded by a broader eyewall whose west side was located about halfway between Freeport and the Florida coast.


Figure 2. Visible satellite image from 5:45 pm EDT Thursday, October 6, 2016. Image credit: NOAA/NESDIS.

Complicating things: a possible eyewall replacement cycle
Matthew has been an extremely difficult storm to forecast, and was exhibiting extremely complicated and rapid changes in its structure Wednesday afternoon. In the early afternoon, Matthew began forming concentric eyewalls--typically the prelude to an eyewall replacement cycle (ERC), where the inner eyewall collapses and a new larger-diameter outer eyewall takes over. At 3 pm EDT, the Hurricane Hunters found two concentric closed eyewalls--an inner eyewall 12 miles in diameter, and an outer eyewall 75 miles in diameter. Just three hours later, the inner eyewall had shrunk to 8 miles in diameter, and the outer one to 57 miles in diameter. At this time, a portion of the inner eyewall passed over Settlement Point on Grand Bahama Island, bringing sustained winds of 75 mph, gusting to 86 mph (and as high as 105 mph at 6:11 pm EDT). Around 7 pm EDT, Miami radar indicated that the inner eyewall had reconnected to the outer eyewall via a spiral band, while the outer eyewall continued to contract. It appeared some dry air may have gotten wrapped into the circulation at this time, which would potentially cause weakening. However, at 7 pm the core of the hurricane was crossing the axis of the very warm Gulf Stream Current, which may give it a boost of energy.


Figure 2. Sea surface temperatures are exceptionally warm, in the upper 80s Fahrenheit, just east of the Florida peninsula, as shown in this map derived from data collected on October 5, 2016, by the European MetOp-B satellite. Image credit: Rutgers University Coastal Ocean Observation Lab.

If Matthew retains both eyewalls, it has the potential to strengthen before making landfall. It’s also quite possible that Matthew’s inner eyewall will collapse and the outer one will become predominant at some point before Matthew gets very near the Florida coast. If so, that would be good news and bad news. The good side: Matthew’s peak winds would likely decrease, perhaps by 10 to 20 mph. On the other hand, hurricane-force winds would expand to cover a much larger area, encompassing much of the outer eyewall. Furthermore, the large western side of the outer eyewall would give a multi-hour battering to buildings along the coast as the hurricane moved northward, increasing the chances of building failure. It’s not a sure thing that the inner eyewall will collapse before landfall; eyewall replacement cycles sometimes take several days to complete.

The bottom line: Matthew is more likely to weaken than to strengthen because of the potential ERC that is underway. If the inner eyewall completely collapses by Friday morning, landfall as a Category 3 storm instead of a Category 4 storm will be likely.


Figure 4. Official NHC forecast for Matthew as of 5:00 pm EDT Thursday, October 6, 2016.

Matthew’s track
NHC’s Hurricane Warning as of 8 pm extended from Boca Raton, FL, to South Santee River, SC, including Lake Okeechobee and Orlando. As of 8 pm EDT, Matthew was moving toward the northwest, but slightly more northward than westward, at about 13 mph. Given that Matthew was then located about 75 miles east of Palm Beach, we can be confident that Matthew will not make landfall south of Palm Beach. (A reminder: NHC defines landfall as the center of a tropical cyclone reaching the coast. A hurricane’s eyewall can move along the coast without it being considered landfall of the storm itself.)

Matthew’s path should undergo a very gradual rightward arc as it approaches the angled Florida coast, which makes it very difficult to say exactly where landfall might occur. The more important question may be where Matthew’s strongest winds come ashore. Especially if Matthew undergoes an ERC, parts of its eyewall could affect the entire coastline from around Palm Beach north to the Georgia coast for extended periods, although these winds may only be around Category 1 strength. A broader field of sustained winds above tropical-storm strength (39 mph) can be expected well inland, including Lake Okeechobee and the Orlando area. As we discussed in our our post on Wednesday morning, the most likely point for landfall--if landfall occurs--is Cape Canaveral, which juts about 10-15 miles into the Atlantic.

Extreme storm surge possible in northern Florida, Georgia, and South Carolina
Even a broader, weaker Matthew would retain its ability to produce severe storm surge north of its path, especially along Florida’s First Coast (including St. Augustine and Jacksonville) and the coast of Georgia. As of late Thursday afternoon, the entire coast from near Boca Raton, FL, to Cat Island, SC, was under a storm surge warning under a prototype NHC system expected to become operational next year. As Matthew churns northward, the northeast winds ahead of it will pile water against the coastline, leading to what could be record or near-record storm surges in some areas.


Figure 5. Potential maximum inundation (amount of water above ground) that could result from Hurricane Matthew through 5 pm EDT Sunday, October 9, 2016. Displayed flooding values indicate the water height that has about a 1-in-10 (10%) chance of being exceeded. This prototype graphic was issued by NHC at 11 am EDT Thursday, October 6. Please consult local advisories for official information about the expected storm-surge threat in particular areas. Image credit: NOAA/NHC


At 7 pm EDT Thursday, persistent onshore winds associated with Matthew’s circulation were already pushing a storm surge of 2.7 feet to the Florida/Georgia border at Fernandina Beach, 1.9 feet to Jacksonville, Florida at Mayport Bar, 1.8 feet to Savannah, Georgia near Fort Pulaski and 1.8 feet to Cape Canaveral, Florida, as seen on our wundermap with the “Storm Surge” layer turned on, or the NOAA Tides and Currents storm page for Matthew, or storm surge expert Dr. Hal Needham’s U-SURGE page for Matthew.

We’ll be back with our next update late Thursday night.

Jeff Masters and Bob Henson


Hurricane

Once Again a Cat 4 Storm, Potentially Disastrous Matthew Rolls Toward Florida Coast

By: Bob Henson and Jeff Masters , 6:27 PM GMT on October 06, 2016

Hurricane Matthew is once again an extremely dangerous Category 4 storm. Matthew’s top sustained winds were upgraded to 140 mph in the 11 am EDT advisory from the National Hurricane Center, based on surface wind data collected by dropsondes (parachute-borne instrument packages) and the SFMR radiometer aboard Hurricane Hunter aircraft. Matthew’s central pressure dropped more than 12 millibars overnight, and a jump in surface winds typically follows such a drop after 12-24 hours. Hurricane Warnings are now in place from Broward County, Florida, to Ediston Beach, South Carolina. As of 2 pm EDT Thursday, Matthew’s sustained winds were holding at 140 mph, with the storm located about 125 miles east-southeast of West Palm Beach, Florida. Update: See our post from 8 pm EDT Thursday for updated information on Matthew's strength and forecast.

Matthew’s eye, clearly visible on satellite, was approaching the north end of Andros Island in The Bahamas around noon on Thursday. The especially dangerous right-hand side of Matthew’s eyewall passed over or very near New Providence Island, including Nassau. Since the city lies on the north side of the island, it is shielded to a large extent from storm surge with a northwestward-moving hurricane such as Matthew.


Figure 1. This visible image on Oct. 6 at 1:00 p.m. EDT from NOAA's GOES-East satellite shows Hurricane Matthew as it regained Category 4 hurricane status. Hurricane Nicole is visible to the right. Image credit: NASA/NOAA GOES Project.

The northwest Bahamas getting pounded
Over the past day, The Bahamas have taken a severe pounding from Hurricane Matthew. On Wednesday evening, the hurricane passed within 50 miles of Exuma, where WU member ExumaMET had this to report: Morning all. It was an intense night here. I recorded Sustained winds over 100 and gusts way into category 4 strength with one gust hitting 153 mph before something took out my instrument. We're still in tropical storm force and it should be interesting to see what the island looks like as the sun comes up.

At 2:19 am EDT Thursday, winds at a personal weather station (PWS) on Staniel Cay, Exumas, located in the strong right eyewall of Matthew, about 30 miles east-northeast of hurricane’s center, peaked at 92 mph, gusting to 101 mph. The pressure bottomed out at 984 mb at that time, and 14.13” of rain fell in the period midnight to 1 pm EDT.

After passing Exuma, Matthew marched northwest, passing between Andros Island to the west and New Providence Island to the east. The strongest winds of the right-front quadrant of Matthew hit New Providence between 9 - 11 am today. Winds at 9 am EDT at the Nassau airport on New Providence were 58 mph, gusting to 85 mph. The airport stopped transmitting data after that, as did the four PWS’s on the island. It is likely that the island experienced a ten-foot storm surge on the south shore.

Matthew is continuing northwest, and will pass between the Berry Islands and Grand Bahama Island this afternoon and this evening. At 2 pm EDT Thursday, an automated station in the Berry Islands, located about 50 miles to the northeast of Matthew’s center, reported a sustained wind of 59 mph, with gusts to 76 mph. A personal weather station (PWS) on the Berry Islands reported sustained winds of 85 mph—but the quality of the wind data was suspect. The pressure was 971 mb.

Settlement Point on Grand Bahama Island will be in the northeast eyewall of Matthew at approximately 8 pm tonight. As of 1 pm EDT, the winds were 43 mph, gusting to 47 mph.


Figure 2. Latest NHC forecast for Hurricane Matthew as of 11 am EDT Thursday, October 6, 2016.

The forecast for Matthew through Friday
Matthew may well strengthen further on Thursday afternoon and evening, but there is only a small chance (estimated at 23% in the 12Z Thursday SHIPS model) that it will reach Category 5 strength. More likely, Matthew will approach the Florida coast tonight as a Category 4 storm, then slide up the coast on Friday with a gradual weakening trend, as greater wind shear, drier air, and land interactions take their toll. How long Matthew retains its strength depends largely on how long the center stays entirely offshore, rolls along the coast, or nudges just inland at some point.

Confidence is now very high with Matthew’s large-scale track through Saturday, as the hurricane will be tracing a very predictable loop around the west side of high pressure over the western Atlantic. The challenge is on the smaller scale, where variations of just 20 or 30 miles relative to the shore can make a great difference in terms of impact. The uncertainty in Matthew’s east-west position near the shore means that coastal residents in central and northern Florida must prepare for the possibility of receiving winds from Matthew’s eyewall, as well as the potential for record-smashing storm surge in some parts of northern Florida and Georgia (see embedded tweet at bottom).

The small-scale uncertainty in Matthew’s track does not affect the larger-scale picture, which includes:
—Winds of tropical storm strength (40 - 75 mph) across the eastern half of the Florida peninsula from Lake Okeechobee northward, including Orlando.
—Rainfall totals of 5” to 15” within 50 miles of the coast from central Florida to southern North Carolina. Rainfall of 3” - 6” could extend further north across eastern North Carolina. Falling atop ground saturated by recent rains, this could produce widespread flooding far north of Matthew’s center and will raise the risk of power outages (see Figure 4 below), as gusty winds bring down trees in soggy soil.


Figure 3. Probability of hurricane-force winds from Matthew for the 120 hours from 8 am EDT Thursday, October 6, to Tuesday, October 11. Probabilities are highest (greater than 70%) along the immediate coast from around Port St. Lucie to Cape Canaveral. There is a greater than 90% chance of tropical-storm-force winds as far west as Lake Okeechobee and Orlando. Matthew’s peak winds were upgraded following the creation of this image, but the breadth of the expected wind swath has not changed significantly. Image credit: NOAA/NHC.

A unique storm in Florida hurricane annals
There are no ideal analogs for Matthew’s expected track and strength along the Florida coast. Only a handful of hurricanes have struck Florida with winds as strong as Matthew’s current 140 mph, and the only hurricanes known to have been “coast scrapers” along the central and northern Florida coast were considerably weaker than Matthew. For most residents along the north half of Florida’s Atlantic coast, and perhaps the Georgia coast as well, Matthew will be the strongest hurricane in living memory. (The last major hurricane to affect the Jacksonville area was in 1898.) Breaking waves as high as 15 to 25 feet on top of potential major storm surge are likely to inflict severe damage to beaches and barrier islands along the central and northern Florida coast.

Matthew is on track to become the first major hurricane to make landfall on U.S. shores since Wilma in 2005. It is virtually certain to be the most destructive since Hurricane/Superstorm Sandy in 2012, and it could easily end up among the ten most expensive landfalls in U.S. history adjusted for inflation, perhaps rivaling or topping such recent storms as Wilma, Irene (2011), Ike (2008), Ivan (2004), and Charley (2004). Latest estimates from a University of Michigan-based research group are that as many as 9.6 million people from Florida to North Carolina may lose power as a result of Matthew.


Figure 4. Estimated fraction of the population that is projected to experience power outages with the passage of Hurricane Matthew, based on data from early Thursday morning. Even though Matthew will pass well south of North Carolina, strong winds below hurricane strength combined with very heavy rains will pose the risk of tree damage and outages.

A quick guide to potential impacts
Below is a general summary of potential impacts from Matthew as of midday Thursday. For the latest local details, be sure to check the NWS local statements page, and heed any evacuation advice from local authorities.

FL Treasure Coast (including Port St. Lucie and Vero Beach)
There is still a chance Matthew will make landfall as far south as Port St. Lucie, but movement trends and computer model guidance suggest that the center is more likely to be just offshore by late Thursday night, moving along the coast and very gradually toward it. This would put some or all of the Treasure Coast in the western eyewall of Matthew, where sustained winds would probably be less than Category 4 strength but still potentially very damaging. A storm surge of up to 5 to 8 feet is expected on the barrier islands of Martin and Saint Lucie counties, with the surge risk highest if Matthew does edge inland along the Treasure Coast.

FL Space Coast (including Melbourne and the Kennedy Space Center)
This is the most likely area to experience the highest winds from Matthew (see Figure 3 above) with Daytona Beach at high risk. The wind threat is especially serious at Cape Canaveral, which juts out into the Atlantic about 10-15 miles. If Matthew does make landfall along the Florida coast, this would be the most likely spot for it. Billions of dollars of facilities and equipment are at risk at Kennedy Space Center and nearby bases, which have never before experienced a major hurricane. Some of KSC’s older facilities were designed only to withstand Category 2 or 3 winds, while facilities built after Hurricane Andrew (1992) are designed to withstand Category 4 or 5 storms. Storm surge could reach 7 to 11 feet over the barrier islands of Volusia and Brevard counties. Matthew is likely to traverse the Space Coast during the overnight hours Thursday. (Ironically, the GOES-R satellite—originally scheduled to be airborne by now, where it would be gathering data on Matthew—is instead at the space center, awaiting its rescheduled launch in November.)

FL First Coast (including St. Augustine and Jacksonville)
The wind threat here will hinge not only on Matthew’s track but also on whether some or all of the storm’s eyewall makes it inland further south and is weakened by land interaction. Even if Matthew is curving slightly offshore by this point, winds of at least Category 1 strength can be expected along the immediate coast, with somewhat lesser winds toward the west side of the Jacksonville metro area. Severe flooding is possible at the coast and along the St. Johns River east of Jacksonville. The area should experience its greatest impacts from Matthew on Friday morning, although surge could intensify a number of hours before Matthew’s arrival. Storm surge flooding could reach 6 to 9 feet at St. Augustine and Jacksonville Beach, as well as Fernandina Beach and Amelia City to the north.

Georgia and South Carolina Coast
Matthew’s track should be gradually edging away from the coast by the time it nears Georgia late Friday, but the hurricane may still be at Category 1 strength less than 100 miles from Hilton Head, South Carolina, by Saturday morning. The concave angle of the GA/SC coastline combined with Matthew’s gradual approach could lead to very dangerous high-water impacts as Matthew approaches. Storm surge flooding is expected to be 7 to 9 feet over southeast Georgia, with isolated amounts up to 11 feet, and 3 to 5 feet in southeast South Carolina, with isolated amounts up to 8 feet. Heavy rains to the north of Matthew will exacerbate the risk of flooding, especially near the coast.


Figure 5. Hurricane Nicole (far right) was more than 700 miles east of Hurricane Matthew (far left) at 1:37 pm EDT Thursday, October 6, 2016. Image credit: NASA/MSFC Earth Science Office.

Nicole now a hurricane
While all eyes are on Matthew (and rightly so), the sixth hurricane of this busy Atlantic season has developed far to the east. Compact Hurricane Nicole was centered about 345 miles south of Bermuda as of 2:00 pm EDT, with top sustained winds of 80 mph. Steering currents are quite weak around Nicole, and it is likely to meander across the open Northwest Atlantic for the next several days, perhaps strengthening a bit more before it weakens early next week. Nicole and Matthew are now separated by about 1350 kilometers, which is the maximum distance where we need to take into account the Fujiwhara effect (the tendency for two tropical cyclones near each other to rotate around a common midpoint). Since Matthew is moving further away from Nicole with time, and is so much stronger than Nicole, we need not worry about the Fujiwhara effect at this point as a major steering influence on Matthew.

We’ll be back with an update on Thursday night.

Bob Henson and Jeff Masters





Hurricane

Hurricane Matthew Steadily Intensifying, Likely to be a Category 4 Storm for Florida

By: Jeff Masters , 1:25 PM GMT on October 06, 2016

Powerful Category 3 Hurricane Matthew has steadily intensified over the warm waters of The Bahamas, and is poised to become a Category 4 hurricane this afternoon. An Air Force hurricane hunter aircraft penetrated Matthew’s eye at 8:17 am EDT, and found that the central pressure had fallen to 937 mb (preliminary data, not official yet.) The surface winds measured by their SFMR instrument were unchanged from what the aircraft measured in their earlier pass through the eye at 6:08 am, but the pressure fell 7 mb between those fixes—a significant drop. Matthew’s pressure was 961 mb at 11 pm EDT Wednesday, and the 24 mb pressure fall in nine hours that has occurred since then will likely lead to a further increase in Matthew’s winds, by about 10 - 15 mph, by this afternoon. This would make Matthew a 135 - 140 mph Category 4 storm as it bears down on Florida.

There is hope, though, that the current intensification cycle may be leveling off. Satellite loops at 8 am EDT Thursday morning showed a solid but not spectacular major hurricane, with plenty of heavy thunderstorms with cold cloud tops in the eyewall. However, the eye had gotten less prominent since the early morning hours. There was no obvious cooling of the tops of the eyewall thunderstorm clouds going on, or large-scale expansion of the hurricane’s size. The 8:17 am EDT eye report from the Hurricane Hunters noted that the eyewall was open on its west side, which may halt intensification.


Figure 1. Hurricane Matthew as seen from 248-nm range Miami radar (with clutter turned off) at 8:31 am EDT Thursday, October 6, 2016. Matthew's eye was just east of Andros Island in the Bahamas, and the northern eyewall was beginning to affect Nassau, on New Providence Island.

The Bahamas getting pounded
At 2:19 am EDT Thursday, winds at a personal weather station (PWS) on Staniel Cay, Exumas, located in the strong right eyewall of Matthew, about 30 miles east-northeast of hurricane’s center, peaked at 92 mph, gusting to 101 mph. The pressure bottomed out at 984 mb at that time, and 12.95” of rain fell in the 7-hour period midnight to 7 am EDT.

WU member ExumaMET reported this from the island of Exuma, which Matthew sideswiped on Wednesday evening: Morning all. It was an intense night here. I recorded Sustained winds over 100 and gusts way into category 4 strength with one gust hitting 153mph before something took out my instrument. We're still in tropical storm force and it should be interesting to see what the island looks like as the sun comes up.

The dangerous right front quadrant with Matthew’s highest winds began pounding the most populous island in The Bahamas, New Providence, on Thursday morning around 8 am EDT. Winds at 9 am EDT at the Nassau airport were 58 mph, gusting to 85 mph, and the pressure was falling rapidly. Extreme winds are the main danger on New Providence, though a storm surge of up to ten feet is possible. Fortunately, the capital of Nassau is on the more protected north side of the island, which is less vulnerable to storm surge. High tide is at 11:46 am EDT, and the highest storm surge will likely arrive shortly before then. Tidal range between low tide and high tide is about two feet, so the timing of the high tide relative to a possible ten-foot storm surge can contribute up to a 20% increase in the observed storm tide (the height of the water above ground.)

The weaker left-side eyewall of Matthew will be punishing Andros Island late Thursday morning and into Thursday afternoon. Late Thursday afternoon, it will be Grand Bahama Island’s turn to receive a beating.


Figure 2. Enhanced infrared image of Matthew as of 8:37 am EDT Thursday, October 6, 2016.

Intensity forecast: a major hurricane for The Bahamas and Florida, but not a Cat 5
Matthew has favorable conditions for intensification: light to moderate wind shear of 5 - 15 knots, very warm ocean waters of 29.5 - 30°C (85 - 86°F) and 70 - 75% relative humidity at mid-levels of the atmosphere (as analyzed by the SHIPS model.) Matthew may get an extra bump in intensity when it crosses over the axis of the warm Gulf Stream Current Thursday evening, but the total ocean heat content will decline as the hurricane draws very near to the coast of Florida early Friday morning. Interaction with land will occur then, limiting the potential for intensification. Strong upper-level winds out of the southwest will begin bringing moderate wind shear of 10 - 20 knots on Friday, and there is plenty of dry air to the hurricane’s west that these winds will be able to drive into the hurricane’s core. By Saturday, when Matthew is near the coast of South Carolina, wind shear will rise to the high range, 20 - 25 knots, and the combination of high wind shear and dry air to the storm’s west should act to significantly weaken Matthew from Saturday through Monday as it parallels the coasts of South Carolina and North Carolina. We can expect Matthew to weaken to a Category 1 hurricane or tropical storm by Monday of next week.

The bottom line: Matthew is likely to be a major Category 4 hurricane by this afternoon, and will likely be at Category 3 or 4 strength when it affects the east coast of Florida on Friday. Matthew is not likely to become a Category 5 storm.

Florida under siege
The 00Z Thursday runs of our two top models for forecasting hurricane tracks—the GFS and European—showed that Matthew will make landfall on the coast of Central Florida early Friday morning. The 06Z Thursday run of the GFS model showed this, as well. In their 5 am EDT Thursday Wind Probability Forecast, NHC gave highest odds of hurricane-force winds in Florida to Ft. Pierce (67%), West Palm Beach (62%), and Cocoa Beach (56%).

How strong Matthew is when it affects Georgia and South Carolina is difficult to predict, as it depends strongly on how much time the hurricane spends over land in Florida. The most likely strength for Matthew at the time of its closest approach to Georgia and South Carolina is as a Category 2 storm, but a Category 1 or 3 storm is also a possibility.

We'll have much more on the threat Florida, Georgia, and South Carolina face in our next post.

Long-range track forecast for Matthew: less danger to North Carolina, no danger to New England
Thursday’s latest 00Z run of the European model and 06Z run of the GFS model predicted that Matthew would turn to the northeast and then east on Saturday, keeping the storm several hundred miles south of the coast of North Carolina. In this scenario, the coasts of Georgia and southern South Carolina would be at risk of hurricane force winds, but the coast farther north—including North Carolina and New England—would not be. In their 5 am EDT Wednesday Wind Probability Forecast, NHC was giving the coast from Jacksonville, Florida to Charleston, South Carolina 11 - 17% chances of receiving hurricane force winds. Probabilities for the coast of North Carolina were less than 10%. There is still a great danger of flooding rains in southern North Carolina, though, even if the storm passes more than 100 miles to the south. Rivers are high and the soils are saturated from heavy rains during the past two weeks, and the expected 6+ inches of rain Matthew will dump may cause widespread damaging flooding.


Figure 3. Screen shot of NHC’s interactive Storm Surge Probability product from 5 am EDT Thursday, October 6, 2016, showing the probability of inundation in excess of 5’ above ground level from Matthew. The northern Florida coast to the coast of South Carolina is expected to have a greater than 50% chance of getting inundation in excess of five feet. The highest probabilities are along the Georgia coast, where hurricane impacts are fairly infrequent. The graphic is based upon an ensemble of Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model runs created using the current National Hurricane Center (NHC) official hurricane advisory. Storm surge probabilities depend on the historical accuracy of NHC's forecasts of hurricane track, and wind speed, and an estimate of storm size.

Long range forecast for Matthew: thrown for a loop
Our top models—the GFS, European, and UKMET—continue to show Matthew missing getting picked up by the trough to its north this weekend and looping back towards The Bahamas by Tuesday next week. However, Matthew will experience high wind shear of 30 - 50 knots Sunday through Tuesday, which would make Matthew a weak tropical storm by Tuesday.


Figure 4. Track forecasts from the four European model ensemble members [gray lines] that most closely match the operational run [red line] during the first 72 hours, starting at 00Z Thursday, October 6, 2016. The red line is a version of the 00Z Thursday operational model track that has been adjusted and calibrated using a proprietary technique to account for systemic model errors. Only one of these forecasts shows Matthew entirely missing a landfall along the Southeast U.S. coast, and all of them show Matthew failing to recurve out to sea to the northeast. The high-probability cluster (grey lines) perform better than other ensemble members at forecast times of five days and beyond. The grey crosses along the Gulf Coast are the locations of oil wells, as this forecast tool was designed primarily for use by the oil and gas industry. Image credit: Climate Forecast Applications Network (CFAN).

Links
Meteorologist Steve Gregory is making regular updates on Matthew.
Rapid-scan 7-minute time resolution loop of Matthew from NASA/MSFC

We’ll have several more posts today.

Jeff Masters

Hurricane

Matthew’s Shrieking Winds Hit Bahamas

By: Bob Henson , 4:10 AM GMT on October 06, 2016

Wednesday night was a very stormy night across the heart of The Bahamas as Hurricane Matthew churned through the center of the archipelago. The worst impacts on Wednesday night were likely being felt on Long Island, Great Exuma Island, and nearby smaller islands extending to the northwest, as Matthew moved parallel to these islands and just to the west of them. At 11 pm EDT Wednesday, winds at a personal weather station (PWS) on Staniel Cay, Exumas, located about 50 miles north-northwest of Matthew’s center, were 60 mph, gusting to 67 mph. Winds in Nassau were 17 mph, gusting to 29 mph. Two weather stations on Great Exuma Island reported much higher winds, but these stations have gone offline and so the readings may not be trustworthy: Exuma International Airport (southeast at 119 mph, gusts to 144 mph) and Moss Town (south-southeast at 107 mph, gusts to 131 mph).


Figure 1. Enhanced infrared satellite image of Hurricane Matthew as of 11:15 pm EDT Wednesday, October 6, 2016. Image credit: NOAA/NESDIS.

Intensity update: Headed back to Category 4?
Officially, Matthew’s top sustained winds were at 115 mph as of the 11 pm EDT advisory from the National Hurricane Center. This makes Matthew a low-end Category 3 storm. Matthew’s efforts to reorganize and reintensify on Wednesday afternoon and evening were been a mixed bag. Hurricane Hunters found Matthew’s eyewall partially open at times, and the top surface winds had yet to rebound significantly. On the other hand, the convective core of showers and thunderstorms surrounding Matthew’s center has intensified and expanded, and Matthew’s central pressure began dropping late Wednesday night, a sign that the enhanced convection may be helping Matthew to regain intensity. An 11:03 pm Wednesday fix from the Air Force hurricane hunters found that Matthew had finally closed off its eyewall, and the central pressure had dropped to 959 mb. In its 11 pm EDT discussion, NHC noted that Matthew’s eye--once again distinct on satellite imagery--has contracted to about 17 miles wide, another sign of strengthening. It may take until midday Thursday for any substantial drop in Matthew’s pressure to result in a stronger wind field. NHC predicts that Matthew will again hit Category 4 intensity by Thursday evening. The 00Z Thursday SHIPS model forecast gave an 11% chance that Matthew would intensify enough to become a Category 5 storm again by Thursday night.


Figure 2. NHC forecast for Matthew as of 11 PM EDT Wednesday, October 6, 2016.

Track update: Still heading for Florida coast
Matthew continues heading on a northwest track that will take it just west of New Providence Island, putting Nassau in the most intense part of the storm’s dangerous right-hand side. However, Matthew may head just far enough west to avoid the worst-case impacts for Nassau, most likely tracking over parts of Andros Island. Unlike the mountainous parts of eastern Cuba and western Haiti that took a toll on Matthew as it crossed them, Andros is a very flat island, so it should have little or no effect on the storm.

Should Matthew continue on its due-northwest track, it would come uncomfortably close to making landfall along the urban corridor from Miami to Palm Beach. Our most reliable track models insist that Matthew will begin angling just to the right before landfall, which would keep the southern part of this corridor on Matthew’s weaker side. Broward County (including Fort Lauderdale) is in a hurricane warning, while Miami-Dade County is in a tropical storm warning. The risk of dangerous impacts, including hurricane-force winds, ramps up greatly from Palm Beach northward. The most recent NHC forecast (see Figure 2 above) keeps Matthew as a Category 4 hurricane as it reaches the Melbourne area on Friday morning and a strong Category 3 by Friday evening just east of Jacksonville. The 00Z Thursday run of the GFS model agrees very closely with the official NHC track. Hurricane Warnings are now in effect from Broward County to Fernandina Beach, Florida, with a Hurricane Watch extending northward to Edisto Beach, South Carolina.

If NHC’s forecast were to prove spot-on, conditions along Florida’s central and northern Atlantic coast could easily top anything observed in many decades. As we noted this afternoon, the Melbourne area--including Kennedy Space Center--has never recorded a major hurricane. Hurricane Dora struck near St. Augustine, FL, as a Category 3 in 1965, but otherwise the Jacksonville area and its 1.5 million residents have never experienced a hurricane of this magnitude. A northward-moving “coast scraper” hurricane has the potential to cause widespread damage over an enormous swath of populated area. In general, the storm surge threat with such a storm would be less than for a perpendicular landfall, but as the Atlantic coast begins curving toward Georgia, the risk of dangerous storm surge will rise markedly, with inundations of up to 8 feet possible from Sebastian Inlet, FL, to the Georgia/South Carolina border.

The bottom line: Matthew continues to pose a potentially dire threat to much of Florida’s Atlantic coast, with major impacts likely along the Georgia coast and potentially further north.

See our previous update for more background on the various threats posed by Matthew. As always, NHC is the place to turn for official warnings, watches, and local statements.

Jeff Masters will be back with our next update on Thursday morning.

Bob Henson

Hurricane

Matthew Raking Bahamas; Could Be First Major Hurricane for Florida’s Space Coast

By: Bob Henson , 10:34 PM GMT on October 05, 2016

Hurricane Warnings are in place along much of Florida’s Atlantic coastline, where Category 3 Hurricane Matthew is expected to trace a grinding path on or very close to shore on Friday. As of the 5 pm EDT advisory from the National Hurricane Center (NHC), Matthew was located about 400 miles southeast of West Palm Beach, FL, moving northwest at 12 mph. After weakening during its passage over Cuba, Matthew is gradually regaining its strength over the near-record-warm waters of The Bahamas, where sea surface temperatures of 29-30°C (84-86°F) are more than 1°C above average. A Hurricane Hunter flight observed 106-knot (122-mph) surface winds on Wednesday morning, and with little change in the storm’s overall structure since then, NHC estimated Matthew’s top sustained winds at 120 mph in the 5 pm advisory.

Matthew is already a large storm, with hurricane-force winds extending 45 miles from its center and tropical-storm-force extending out to 175 miles. Matthew’s wind field may expand further in the next several days as the hurricane matures. A Hurricane Hunter flight late Wednesday afternoon was finding Category 2 winds. Satellite imagery late Wednesday afternoon showed intense “hot towers” of thunderstorm activity beginning to develop around Matthew’s eye. Outflow channels extended southward and northward near the top of the storm, although weaker than the channels that supported Matthew’s growth to Category 5 strength in the Caribbean. Overall, Matthew could dip slightly in strength tonight before the reorganization now in process provides a chance for restrengthening on Thursday. The 18Z Wednesday SHIPS model forecast gave a 9% chance that Matthew would intensify enough to become a Category 5 storm again by Thursday afternoon.

The take-home message: it still appears likely that Matthew will approach Florida early Friday as a major hurricane. A Hurricane Warning was in effect late Wednesday from Broward County, FL, to the Flagler/Volisua county line (including the Orlando area and Lake Okeechobee), with a Hurricane Watch extending further northward to the Savannah River, including all of the Georgia coast. A Tropical Storm Warning covers much of far South Florida, including the Miami area. See the NHC update for a full rundown on warnings and watches.


Figure 1. Visible satellite image of Hurricane Matthew from 5:15 pm EDT Wednesday, October 5, 2016. Image credit: NOAA/NESDIS.

Conditions are easing in Greater Antilles, worsening in Bahamas
Matthew’s outer rainbands were still strafing Haiti, Jamaica, and much of eastern Cuba late Wednesday, but the strongest winds had moved north, out of the area. Matthew’s thread-the-needle track included only brief spells over the westernmost tip of Haiti and extreme eastern Cuba. This land-avoiding track allowed the hurricane to move into The Bahamas with its structure largely intact, but it also greatly limited the extent of strong winds over the Greater Antilles. Satellite data showed that rainfall has been intense over many areas, although surface reports are limited. Thus far, at least 25 deaths have been attributed to Matthew, according to weather.com. We can only hope these numbers stay relatively low, although they will undoubtedly rise as more damage reports come in. See the embedded video at bottom for a sense of Matthew’s rampage over eastern Cuba.

Especially if Matthew strengthens, it could bring vicious winds well above hurricane force to several Bahamian islands, depending on its exact track. Torrential rains will also plague the islands. The biggest concern for the Bahamas is storm surge, which could reach 10 to 15 feet along and east of Matthew’s track. Wunderground member ExumaMET sent this update from the southeast Bahamas early Wednesday afternoon: “Reporting in from little Exuma at the very South East of the chain. I'm able to still get cell data but we're getting frequent hurricane force gusts and the recent more NNW move I've seen on satellite is troubling and I hope not a trend. I live on high ground but I do fear for a lot of those living on the south side in particular a large settlement called Moss Town.”

Central and northern Florida bracing for a historic hurricane hit
An unusual confluence of ingredients is in place that may bring hurricane conditions to the Atlantic coast of northern Florida and Georgia, a place where major hurricane landfalls (Category 3 or stronger) are surprisingly uncommon, especially this late in the season. When Florida does get hurricanes in October, they almost always move northeast from the Gulf of Mexico and strike the Gulf Coast, rather than moving west or northwest from the Atlantic.

Thoughout the year as well, major landfalls seldom occur here, as shown in Figure 3. This may partly be a matter of dumb luck, but it’s also because the shape of the Florida coast here—angling from southeast to northwest—reduces the odds of a direct hit. The only hurricane known to have made landfall in Florida north of Port St. Lucie while maintaining Category 3 strength is Dora, which arrived with 125-mph sustained winds near St. Augustine in September 1964. It’s actually more common for hurricanes to strike the northern half of Florida’s coast after having traveled across the state—as was the case with Donna (1960) and Charley (2004), both of which entered the Atlantic just north of Palm Coast. The most recent major hurricane along the Georgia coast was in 1898.


Figure 2. Tracks of all hurricanes since 1851 that are known to have passed within 175 nautical miles miles (the shaded circle) while at Category 3 or stronger intensity. Image credit: NOAA.


FIgure 3. The official NHC forecast for Matthew as of 5 pm EDT Wednesday, October 5, 2016.

An unusual threat for the coast from central Florida to Georgia
The latest tracking map from NHC, shown above, depicts a Category Four hurricane centered just north of the Kennedy Space Center (KSC, in Titusville, FL) at 2:00 pm EDT Friday. If Matthew does move along the coast or just inland, it could bring severe hurricane conditions to a heavily populated coastal region that’s had precious little experience with such a storm. Hurricanes Jeanne and Frances (2004) caused billions in damage as they moved from the Atlantic onto the central Florida coast, and Matthew may be stronger than either of them as it nears the coast. Even though winds near KSC were only in the neighborhood of minimal hurricane strength, Frances inflicted an estimated $100 million in damage to the area’s space and military operations.

In 1979, Hurricane David (1979) ground its way up the central and northern Florida and Georgia coastlines along a track similar to that expected with Matthew. David produced hundreds of millions in damage, even though it was only at Category 1 strength during its Florida/Georgia trek. Even if Matthew reaches Florida as a major hurricane, we can expect it to weaken during the course of Friday and Friday night as it works its way northward along or near the coast.


Figure 4. Hurricane Frances brought sustained winds of 70 mph, gusting to 94 mph, to the Kennedy Space Center, and ripped 820 panels off of the gargantuan 525-foot tall Vehicle Assembly Building (shown above). The Space Center suffered millions in damage, including heavy damage to the Thermal Protection System Facility and the Processing Control Center. Two weeks later, Category 3 Hurricane Jeanne made landfall very close to where Frances did, and took 30 more panels off the Vehicle Assembly Building. According to NASA documents, the building was designed to withstand winds of 114 miles per hour—what a weak Category 3 storm would deliver. Image credit: NASA.

An excruciating track for the Southeast U.S.
Our top track models differ on the exact location of Matthew over the next several days, but they agree that Matthew will be heading on a concave track from Florida to the Carolinas that will largely duplicate the concave outline of the Southeast U.S. This makes for an extremely challenging forecast, especially from a public-safety point of view. NHC has put it very nicely in their key-message summaries for Matthew:

“When a hurricane is forecast to take a track roughly parallel to a coastline, as Matthew is forecast to do from Florida through South Carolina, it becomes very difficult to specify impacts at any one location. For example, only a small deviation of the track to the left of the NHC forecast could bring the core of a major hurricane onshore within the hurricane warning area in Florida. However, a small deviation to the right could keep the hurricane-force winds offshore. Similarly large variations in impacts are possible in the hurricane watch area in northern Florida and Georgia.”

Main threat for the Carolinas: water
Regardless of whether Matthew hugs the coast or not, it will deliver a significant storm-surge threat, especially toward the Georgia coast. NHC projects that coastal inundation (water level above ground) could reach the following levels at high tide:

Sebastian Inlet to Savannah River...5 to 8 ft
Deerfield Beach to Sebastian Inlet...3 to 5 ft
Virginia Key to Deerfield Beach...1 to 2 ft


Figure 5. Areas of flooding expected to result from typical hurricanes of various strengths over Chatham County, Georgia. Even a Category 1 strike (4-11 foot inundation) is capable of producing extensive flooding across the county, including all of Tybee Island, where officials are urging that residents evacuate. Image credit: Chatham County Emergency Management

The latest model guidance (12Z Wednesday) suggests that Matthew will be arcing away from the Southeast coast as it approaches the Carolinas. This is very good news from the standpoint of high wind, but it does not eliminate the risk of very heavy rain and at least some coastal flooding for the Carolinas. The NOAA/NWS Weather Prediction Center is projecting 6” to 10” of rain along and near the coast from central Florida to extreme southern North Carolina. If Matthew’s arc away from shore holds up, the risk of major flooding over saturated ground from eastern North Carolina northward will be greatly reduced.

Will Matthew do the loop-de-loop?
The 12Z Wednesday suite of computer models points toward a result that seemed preposterous just days ago: Matthew may well carry out a clockwise (right-hand) loop off the Southeast coast and head back toward Florida early next week. If so, it would likely be in a much-weakened state, heading over waters it churned up. The European model has pulled back from its enthusiasm for this idea, while the GFS is more bullish. Only 8% of the 50 Euro ensemble members from 12Z Wednesday, but about half of the 20 GFS ensemble members from 18Z Wednesday, carry out tracks that bring Matthew across Florida or Cuba next week and into the Gulf of Mexico or Caribbean. The loop-de-loop back to Florida thus remains possible, but we’ll have to give the models several more days to work out these possibilities.

Links
Meteorologist Steve Gregory is making regular updates on Matthew.
Rapid-scan 7-minute time resolution loop of Matthew from NASA/MSFC

Webcams:
Bahama/Port Nassau:: http://www.portnassauwebcam.com/
Ft. Lauderdale: http://www.ftlauderdalewebcam.com/
Port Canaveral: http://www.portcanaveralwebcam.com/

Tropical Storm Nicole no threat
Tropical Storm Nicole, the fourteenth named storm of this busy 2016 Atlantic hurricane season, is not expected to be a threat to any land areas as it meanders in a circle over the central Atlantic over the next five days. Satellite imagery shows Nicole is a small storm with a modest amount of heavy thunderstorm activity. The latest SHIPS model forecast shows increasing wind shear for Nicole over the weekend, which should weaken the storm.

I'll be back with an update on Matthew between 11 PM and midnight tonight. Jeff Masters and I will be posting 2 to 3 updates a day while Matthew remains a significant threat.

Bob Henson and Jeff Masters


Figure 6. The 50 forecasts from the 12Z Wednesday European (ECMWF) model ensemble (left) and the 20 forecasts from the 18Z Wednesday GFS model ensemble (right). Ensemble model runs are produced by running the same model for the same timeslice a number of times, with the starting-point conditions for each run varied randomly in order to mimic the uncertainty in our observations of the atmosphere. This produces a better sense of the future uncertainty in a given forecast. Image credit: Image credit: Climate Forecast Applications Network (CFAN).




Hurricane

Hurricane Matthew Reorganizing Over The Bahamas; Major Shift in Long-Range Track

By: Jeff Masters , 3:40 PM GMT on October 05, 2016

Hurricane Matthew was a weakened Category 3 hurricane with 115 mph winds on Wednesday morning at 8 am EDT, thanks to the disruptions to the storm caused by landfalls in Haiti and Cuba on Tuesday. However, the storm is re-organizing over the warm waters of The Bahamas, and poses a serious threat to The Bahamas and Southeast U.S. over the next three days. Matthew's top winds had rebounded slightly, to 120 mph, as of the 11 am advisory from the National Hurricane Center.

Matthew was able to shrug off its initial landfall on the southwestern tip of Haiti near 7 am EDT Tuesday, with the hurricane’s Category 4 winds of 145 mph dropping by just 5 mph. A more protracted landfall over the eastern tip of Cuba on Tuesday evening, though, disrupted the storm’s eyewall, which suffered a partial collapse. As a result of this, plus the fact that a large part of the storm’s circulation has been over the high mountains of Cuba and Hispaniola over the past day, Matthew was looking considerably less impressive on satellite imagery on Wednesday morning. The hurricane’s heavy thunderstorms were much reduced in the northwest quadrant, and Matthew was smaller and had fewer low-level spiral bands.


Figure 1. Enhanced infrared image of Matthew as of 10:00 am EDT Wednesday, October 5, 2016. Matthew's eye had sharpened distinctly over the preceding few hours. Image credit: NASA/MSFC Earth Science Office.

Two hurricane hunter aircraft were in Matthew early on Wednesday morning, and confirmed Matthew had weakened significantly; the top surface winds of the hurricane had slowed to 115 mph and the central pressure had risen to 964 mb. A rapid-scan 1-minute time resolution satellite loop of Matthew from NASA/MSFC late Wednesday morning showed that Matthew was steadily re-organizing, though. The hurricane has rebuilt its eyewall, spiral bands were increasing in intensity and areal coverage, and Matthew was growing larger. This is to be expected, as Matthew has favorable conditions for intensification: light to moderate wind shear of 5 - 15 knots, very warm ocean waters of 29.5 - 30°C (85 - 86°F) and 70 - 75% relative humidity at mid-levels of the atmosphere (as analyzed by the SHIPS model.) In their most recent pass through the eye late Wednesday morning, the Hurricane Hunters found the pressure had dropped 2 mb, to 962 mb, and the winds had increased by 5 mph.


Figure 2. Hurricane Matthew as seen on Gran Piedra, Cuba radar at 8:20 am EDT October 5, 2016. A mostly complete eyewall had been rebuilt by this time. Image credit: INSMET.

Intensity forecast: Matthew will be big and bad again
Given the favorable conditions for intensification, and the fact that Matthew is now moving into a region with even warmer waters (though a lessening amount of total ocean heat content), I expect the storm will again be at Category 4 strength by Thursday morning. The near-record warm waters Matthew will be feeding from will allow the hurricane to greatly expand its size over the next two days, as will the fact that it will be steadily gaining latitude, allowing the hurricane to better leverage the Earth’s spin to gain more spin of its own. The unusual mass of convection to the east that persisted until it made landfall in Hispaniola has apparently been absorbed, and will also contribute to Matthew expanding in size. This is going to be a very large storm with widespread impacts by the time it approaches the Southeast U.S. on Thursday evening, and Matthew is likely to be a major Category 3 or stronger hurricane while it pounds the northern Bahamas and east coast of Florida. Matthew may take an extended path over the core of the very warm Gulf Stream current on Friday, providing an extra boost in intensity.

On Friday night, when Matthew will be moving northwards nearly parallel to the coast and approaching South Carolina, high wind shear of 20+ knots is expected to attack the storm. High wind shear plus potential interaction with land will likely lead to a weakening of Matthew to Category 2 strength by Saturday, when the hurricane will make its closest approach to South Carolina and North Carolina. As Matthew makes its expected turn to the east on Sunday and moves parallel to the North Carolina coast, wind shear will rise even further, to 40+ knots, and we can expect Matthew to weaken to a Category 1 hurricane or tropical storm by Monday of next week.

Track forecast for Matthew: very bad for the Bahamas
Matthew will move northwest through The Bahamas on Wednesday and Thursday, with the dangerous right front quadrant with the highest winds likely to affect the most populous island in the archipelago, New Providence, on Thursday morning. Extreme winds are the main danger on New Providence, though a storm surge of up to ten feet is possible. Fortunately, the capital of Nassau is on the more protected north side of the island, which is less vulnerable to storm surge. Low tide in Nassau is at 5:22 am EDT Thursday, and high tide is at 11:46 am EDT. Tidal range between low tide and high tide is about two feet, so the timing of the high tide relative to a possible ten-foot storm surge can contribute up to a 20% increase in the observed storm tide (the height of the water above ground.) In their 11 am EDT Wednesday Wind Probability Forecast, NHC gave highest odds of hurricane-force winds in The Bahamas to Great Exuma (78%), New Providence (74%), and Grand Bahama (64%).


Figure 3. This Maximum Water Depth storm surge image for The Bahamas shows the worst-case inundation scenario for a Category 3 hurricane with 120 mph winds, as predicted using dozens of runs of NOAA's SLOSH model. For example, if you are inland at an elevation of ten feet, and the combined storm surge and tide (the "storm tide") is fifteen feet at your location, the water depth image will show five feet of inundation.

Major storm-surge potential for The Bahamas
No single storm will be able to cause the level of flooding depicted everywhere in Figure 3 above, but Matthew’s maximum storm surge may reach levels portrayed in this image for some of these islands. The greatest surge danger for Exuma Island and Long Island will come on Wednesday evening shortly after Matthew passes. Large expanses of shallow water lie along the west coasts of these islands, and the counter-clockwise circulation of the storm will push water to the east and northeast into these shallow water, where they will be forced up onto land. New Providence (where the capital of Nassau is located) has its shallowest waters to the south, so their main storm surge risk will come as Matthew is approaching from the southeast. According to a Tuesday blog post by storm surge expert Dr. Hal Needham, “Many areas in this archipelago contain broad reefs that provide large pools of shallow water for hurricanes to displace and inflict storm surge damage. The impacts of these surges are often severe, sea water can overwash small islands, completely inundating them with salt. Such surges often destroy fresh water and food supplies, as saline soils can take years to lose high salt content. Of particular concern is the possibility that Matthew will track far enough east to produce a large storm surge on Crooked Island, Acklins Island and Long Cay. Hurricane Joaquin generated a devastating 15-ft (4.57-m) storm surge in this area just last October, taking advantage of a shallow reef that is open to the southwest. A second large storm surge in two years would have grave impacts for this region.” Note that the elevations of the surge heights on this map is not Mean Sea Level (MSL), but rather the vertical datum, NGVD 1929, developed by the National Geodetic Survey. See wunderground's storm surge pages for more info.

Track forecast for Matthew: Hurricane Warnings and Storm Surge Warnings for Florida
The 00Z Wednesday runs of our top models for forecasting hurricane tracks—the GFS, European, and UKMET models—all show that Matthew will approach within 50 miles of, or make landfall on, the coast of Central Florida on Friday. The 06Z Wednesday run of the GFS model showed this, as well. At 11 am EDT Wednesday, Hurricane Warnings were up for much of the east coast of Florida, including the Orlando area, and NHC had issued a new experimental Storm Surge Warning for the coast of Florida from North Palm Beach to the Flagler/Volusia County line. A storm surge warning indicates there is a danger of life-threatening inundation from rising water moving inland from the shoreline somewhere within the specified area, generally within 36 hours. NHC is advising that storm surge inundation of 3 - 5 feet could occur on Friday. Farther to the north of the warned area, extending to Fernandina Beach, a Storm Surge Watch is posted, meaning that there is the possibility of life-threatening inundation during the next 48 hours. The greater threat to Florida, though, may be wind damage. In their 11 am EDT Wednesday Wind Probability Forecast, NHC gave highest odds of hurricane-force winds in Florida to Ft. Pierce (47%), West Palm Beach (43%), and Cocoa Beach (40%).

Track forecast for Matthew: danger to North Carolina and New England lessens
Wednesday’s latest 00Z run of the European model and 06Z run of the GFS model predicted that Matthew would turn to the northeast and then east on Saturday, keeping the storm several hundred miles south of the coast of North Carolina. In this scenario, the coasts of Georgia and southern South Carolina might still be at risk of hurricane force winds, but the coast farther north—including New England and Canada—would not be. In their 11 am EDT Wednesday Wind Probability Forecast, NHC was giving the coast from Jacksonville, Florida to Charleston, South Carolina 10 - 16% chances of receiving hurricane force winds. Probabilities for the coast of North Carolina were less than 10%.


Figure 4. Screen shot of NHC’s interactive Storm Surge Probability product from 5 am EDT Wednesday, October 5, 2016, showing the probability of inundation in excess of 3’ above ground level from Matthew. The northern Florida coast to the coast of South Carolina is expected to have a greater than 50% chance of getting inundation in excess of three feet. The highest probabilities are along the Georgia coast, where hurricane impacts are fairly infrequent. The graphic is based upon an ensemble of Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model runs created using the current National Hurricane Center (NHC) official hurricane advisory. Storm surge probabilities depend on the historical accuracy of NHC's forecasts of hurricane track, and wind speed, and an estimate of storm size.

Long range forecast for Matthew: thrown for a loop
Thanks to my advancing years and a low-stress lifestyle that features daily meditation, there’s not much that can move me to profanity—except the occasional low-skill driver who endangers my life on the road. But this morning while looking at the latest weather model runs, multiple very bad words escaped my lips. I’ve been a meteorologist for 35 years, and am not easily startled by a fresh set of model results: situations in 2005 and 1992 are the only ones that come to mind. However, this morning’s depiction by our top models—the GFS, European, and UKMET—of Matthew missing getting picked up by the trough to its north this weekend and looping back to potentially punish The Bahamas and Florida next week was worthy of profuse profanity. While a loop back towards Florida and The Bahamas next week is not yet a sure thing, the increasing trend of our top models in that direction is a strong indication that Matthew will be around for a very long time. Long-range forecasts of wind shear are not very reliable, but this morning’s wind shear forecast from the 00Z run of the European model does show a low to moderate shear environment over the Bahamas and waters surrounding South Florida late next week, potentially supportive of a hurricane--if Matthew survives the high wind shear of 50+ knots expected to affect the storm early next week. The bottom line is that it currently appears that Matthew will not recurve out to sea early next week, and The Bahamas and Florida may have to deal with the storm again next week.


Figure 5. Track forecasts from the five European model ensemble members [gray lines] that most closely match the operational run [red line] during the first 72 hours, starting at 00Z Wednesday, October 5, 2016. The red line is a version of the 00Z Wednesday operational model track that has been adjusted and calibrated using a proprietary technique to account for systemic model errors. Five out of six of these forecasts show Matthew barely missing landfall along the Southeast U.S. coast, and all of them show Matthew failing to recurve out to sea to the northeast. Disturbingly, two of the tracks show Matthew looping back to punish The Bahamas and crossing South Florida to enter the Gulf of Mexico. The high-probability cluster (grey lines) perform better than other ensemble members at forecast times of five days and beyond. The black crosses along the Gulf Coast are the locations of oil wells, as this forecast tool was designed primarily for use by the oil and gas industry. Image credit: Climate Forecast Applications Network (CFAN).

Links
Meteorologist Steve Gregory is making regular updates on Matthew.
Rapid-scan 7-minute time resolution loop of Matthew from NASA/MSFC
See our post from Monday morning on how Matthew--a rare northward-moving major hurricane in the Caribbean--fits into the hurricane histories of Haiti, Jamaica, and Cuba.
Great Exuma webcam

We’ll have a new post late this afternoon.

Jeff Masters

Hurricane

Matthew Holding Its Own; Threat Shifting to Bahamas, Southeast U.S.

By: Jeff Masters and Bob Henson , 9:20 PM GMT on October 04, 2016

Mighty Hurricane Matthew has shrugged off its encounter with a landfall on the southwestern tip of Haiti between 7 - 9 am Tuesday morning, and remains an extremely dangerous Category 4 storm with 140 mph winds as it plows north at about 9 mph over the eastern tip of Cuba. Update: As of 11 PM EDT Tuesday, a Hurricane Warning is in effect for the east coast of Florida from Golden Beach northward (including all of Broward County] to Sebastian Inlet, as well as for Lake Okeechobee. A Hurricane Watch extends north from Sebastian Inlet to the Flagler/Volusia County line, and a Tropical Storm Warning extends from Chokoloskee (near Everglades City) around the south end of Florida through Miami-Dade County, as well as Florida Bay and the Florida Keys from Seven Mile Bridge northeastward. See the National Hurricane Center graphics for Matthew for other watches and warnings now in effect.

Satellite loops late Tuesday morning showed that the encounter with Haiti’s southwest peninsula weakened the storm, with the eye growing indistinct and the cloud tops of the eyewall thunderstorms warming. However, early Tuesday afternoon the eye began clearing out, and an Air Force hurricane hunter aircraft found that the central pressure had begun to drop again. At 12:38 pm Tuesday, during their final penetration of the eye, the Air Force Hurricane Hunters measured a central pressure of 949 mb, down two mb from their previous two passes through the eye. Peak surface winds measured by their SFMR instrument were 135 mph, and a dropsonde measured 141 mph winds at the surface. Matthew clearly remained a solid Category 4 storm, as reflected in the 5 pm EDT advisory from the National Hurricane Center.


Figure 1. MODIS satellite image of Matthew taken at 11 am EDT October 4, 2016, four hours after the hurricane had made landfall on the southwestern tip of Haiti as a Category 4 storm with 145 mph winds. Image credit: NASA.

Other than the land interaction going on with the eastern tip of Cuba, Matthew has favorable conditions for development. Light wind shear of 5 - 10 knots is affecting the storm, it has warm ocean waters of 29°C (84°F), and plenty of moisture--70 - 75% relative humidity at mid-levels of the atmosphere, as analyzed by the SHIPS model.


Figure 2. Radar image of Hurricane Matthew as it was approaching the eastern tip of Cuba at 3:35 pm EDT October 4, 2016. Image credit: NOAA.

Extreme rains over Haiti, Cuba and the Dominican Republic
Extreme rains from Matthew are a huge concern for eastern Cuba and the entire island of Hispaniola. The mountainous terrain of these islands creates tremendous uplift to the thunderstorms moving ashore, resulting in extremely intense rainfall. According to Oficina Nacional de Meteorología (ONAMET), the official weather service of the Dominican Republic, total rainfall amounts in the Dominican Republic on October 3 were as high as 233.9 mm (9.21”). The capital of Santo Domingo received 170.2 mm (6.81”). Additional heavy rains fell across southern portions of the country on Tuesday. The huge rainfall amounts we’ve been mentioning here from the personal weather station (PWS) in Cabo Rojo, on the southern coast of the Dominican Republic near the border with Haiti--22.89” of rain on Monday--are not mentioned on the ONAMET web site, even though they operate the station. Thus, these rainfall numbers may be unreliable.


Figure 3. Total rainfall amounts in the Dominican Republic on October 3, 2016. Rainfall amounts of up to 233.9 mm (9.21”) fell. The capital of Santo Domingo received 170.2 mm (6.81”). Image credit: Oficina Nacional de Meteorología (ONAMET), the official weather service of the Dominican Republic,

Catastrophe in Haiti?
Matthew’s extreme rains, large storm surge, and Category 4 winds were likely catastrophic for the southwestern portion of Haiti where landfall occurred. Matthew was the third strongest hurricane ever recorded in Haiti, and their strongest hurricane in 52 years. The only Haitian hurricanes stronger than Matthew were two Category 4 storms with 150 mph winds: Hurricane Cleo of 1964 and Hurricane Flora of 1963. According to a Tuesday afternoon news story from weather.com, two deaths in Haiti and four in the Dominican Republic are being blamed on Matthew so far.

We don’t have many weather stations in Haiti, so it is difficult to say what the conditions are on the ground. However, all three weather stations in southern Haiti that send us data continued transmitting through mid-afternoon Tuesday, which is a good sign. The Port-Au-Prince airport did not receive strong winds; top winds as of 2 pm EDT Tuesday were 34 mph, gusting to 52 mph. However, they did report several hours of heavy rain, which is the main danger in this heavily populated region, due to the high flash flooding risk. A personal weather station (PWS) on the south coast Haiti at Aquin, about 70 miles east of Matthew’s landfall, recorded a wind gust of 59 mph at 6:50 am EDT Tuesday. A PWS near Port-Au-Prince, Haiti recorded about 2.81” of rain for the day, ending at  3 pm EDT Tuesday.

Matthew set to carve a destructive swath across The Bahamas
Matthew’s assault on the Greater Antilles is just in the first of what could be a week-long sequence of damaging events as the massive hurricane churns toward the U.S. East Coast. The most immediate threat is to The Bahamas, where the entire nation is now under a Hurricane Warning. Matthew has a good chance of retaining its current strength, or perhaps even intensifying a bit, as it passes through The Bahamas from late Tuesday through early Thursday. Wind shear is expected to remain low to moderate (around 5 - 15 knots) through at least Thursday, with a very moist atmosphere (relative humidities at mid-levels of 70 - 80%). Moreover, the waters of The Bahamas are close to record-warm levels for early October, with sea surface temperatures around 29-30°C (84-86°F), about 1°C above average. There is also plenty of deep oceanic heat; together with the shallow undersea topography of The Bahamas, this will reduce the chance that Matthew’s fierce winds and waves will churn up enough cool water to significantly dent its strength. The fact that Matthew lost little strength during its trek across the Greater Antilles testifies to its very large and well-structured circulation. The NHC forecast issued at 11 AM EDT Tuesday keeps Matthew as a Category 4 through Thursday.

Matthew will produce very heavy rains, high winds, and huge surf across The Bahamas, but the greatest risk for the islands will be the potential for a devastating storm surge. Only a year ago, Category 4 Hurricane Joaquin looped near the easternmost islands at the start of October 2015, inflicting more than $100 million in damage and killing 33 crew members aboard the ill-fated El Faro cargo ship. There is still some uncertainty about Matthew’s path, but it is likely to slice through the heart of The Bahamas, putting many islands on its more dangerous right-hand side. Direct hits on Nassau and/or Freeport are quite possible. Since Matthew’s core of hurricane-force winds is fairly compact, it’s possible that only a few islands will experience such winds, but widespread storm surge of up to 10 - 15 feet is a major concern to the east of Matthew’s expected path. Joaquin produced a 12- to 15-foot surge on Rum Cay, Crooked Island, and Acklins Island.


Figure 4. Official NHC forecast for Matthew as of 5 PM ET Tuesday, October 4, 2016.

Southeast U.S.: Huge surf, heavy rain, high winds, and perhaps a hurricane landfall
The 12Z Tuesday morning suite of computer model guidance doesn’t exactly give us a definitive sense of whether Matthew will make landfall along the Southeast U.S. coast. Of our three top track models, the 12Z operational GFS run brings Matthew to within about 50 miles of the central Florida coast late Thursday, and even closer to the Carolinas, before taking Matthew out to sea without any landfall. The 12Z ECMWF and UKMET runs both bring Matthew ashore in central Florida. The less-reliable GFDL model produces a landfall in South Florida, followed by a track back offshore and a second landfall in North Carolina by Sunday. The HWRF run keeps Matthew more than 100 miles off the Florida coast, then brings Matthew ashore in North Carolina on Saturday. As for ensemble runs, a sizable minority of the 20 members of the GEFS (GFS ensemble) from 12Z Tuesday bring Matthew into central Florida. In the most recent ECMWF ensemble available (00Z Tuesday), all four of the high-probability ensemble members produced a central Florida landfall. Some members of the 12Z Tuesday UKMET and ECMWF ensembles, as well as the 12Z ECMWF operational run, even suggest that Matthew might actually carry out a large cyclonic (right-hand) loop, extending east and then south from the Carolinas back toward Florida--a scenario reminiscent of the huge loop carved out by Hurricane Ivan in 2004. These solutions are outliers, and we will have to wait for additional model support for this idea before considering it as a real possibility.

Forecaster Lixion Avila noted in the 5 PM Tuesday NHC discussion: “It will likely take another day or so for the potential impacts of Matthew in the United States to clarify.” If today’s model solutions haven’t yet given us clarity, they do confirm that landfall remains a very real possibility, particularly along the midsection of the Florida coast and again over eastern North Carolina.

Figure 5. In September 1999, Hurricane Floyd approached the Southeast U.S. at Category 3 strength, then carried out an arcing path that brought it ashore as a Category 2 storm at Cape Fear, North Carolina.


Because Matthew will be tracing an arcing path that echoes the coastline itself, it is impossible to tell at this point exactly where that arc will overlap the coast (as evidenced by the model disagreement above). Even in those stretches where Matthew remains just offshore, coastal locations may still experience winds of tropical-storm or even hurricane strength, as well as very heavy rain. At least some flooding can be expected along most of the Southeast coast, as Matthew’s winds drive water ashore. Any direct landfall could lead to a major storm surge. Matthew’s intensity may drop somewhat as wind shear increases after Thursday, but it will likely remain a major hurricane as it threatens the Southeast coast.

One analog for Matthew is Hurricane Floyd (September 1999--see Figure 5 above), which arrived in the Bahamas as a Category 4 storm, then carried out a path near the Southeast coast roughly similar to the one that Matthew might carve out if it were to remain offshore until North Carolina. After triggering the largest peacetime evacuation in U.S. history up to that point, Floyd inflicted close to $10 billion in damage (2016 dollars) and caused 72 U.S. deaths, making it the nation’s deadliest hurricane in more than 25 years. Floyd interacted with a frontal system over the East Coast that led to extremely heavy rains over a large area. The rains in North Carolina, which arrived after heavy rain less than three weeks earlier from Hurricane Dennis, produced all-time record flooding. The high water ruined some 24,000 homes and drowned millions of pigs and chickens. Parts of the east-central U.S. coast have experienced 10” - 15” in rain over the last two weeks (see Figure 6 below), which could exacerbate any potential flood-related impact of heavy rainfall from Matthew.


Figure 6. Observed 14-day precipitation totals (in inches) from 8:00 am EDT Tuesday, September 20, 2016, to 8 am Tuesday, October 4. Image credit: NOAA/NWS Advanced Hydrologic Prediction Service.


Figure 7. Projected 7-day precipitation totals (in inches) from 8:00 am EDT Tuesday, October 4, 2016, to 8 am Tuesday, October 11. The actual amounts will hinge on the final track of Hurricane Matthew. Image credit: NOAA/NWS Weather Prediction Center.

Could Matthew hit the Northeast U.S.?
It’s quite possible that Matthew will affect the Northeast U.S. after it swings past the Carolinas this weekend, but given the continued divergence in model solutions, it’s too soon to pin down just how likely this is or what the impacts would be. The trend over the last day or two has been for Matthew to continue northeastward past the Carolinas, which reduces the odds of a left-track hook that would produce the worst direct impacts for the Northeast and/or New England. Only a couple of GFS ensemble members from 12Z Tuesday show a direct Matthew landfall north of Virginia, and the ECMWF ensemble suggests that any path over the Northeast coast for Matthew would have a good chance of occurring after a fair bit of time inland. The official NHC outlook as of 5 PM Tuesday has Matthew located about 100 miles south of the Rhode Island coast by Sunday afternoon, still as a Category 1 hurricane (see Figure 4 above).

Coastal residents north of the Carolinas and Virginias all the way to the Canadian Maritimes need to keep an eye on Matthew, as there is plenty of time for the forecast to evolve. Even if Matthew were to weaken and/or stay offshore, very heavy rains and high winds could affect a huge swath of the East Coast if the storm heads in that direction.


Figure 8. MODIS satellite image of Tropical Storm Nicole taken at 1 pm EDT October 4, 2016. At the time, Nicole had sustained winds of 50 mph, and was headed northwest at 8 mph. Upper-level outflow clouds from Hurricane Matthew can be seen at the lower left of the image. Image credit: NASA.

Tropical Storm Nicole forms from 98L
The tropical wave about 500 hundred miles northeast of Puerto Rico that we were tracking as Invest 98L developed a well-defined surface circulation and enough persistent heavy thunderstorm activity to be upgraded to Tropical Storm Nicole at 11 am EDT Tuesday. Nicole is the fourteenth named storm of this busy 2016 Atlantic hurricane season. Satellite imagery shows Nicole has the classic appearance of a tropical storm under high wind shear, with the circulation center exposed to view and all the heavy thunderstorm activity limited to the southeast side. Strong upper-level winds out of the northwest, partially due to upper-level outflow from Hurricane Matthew, are creating 30 - 35 knots of wind shear over Nicole. The latest SHIPS model forecast shows gradually increasing wind shear for Nicole over the next five days, which should weaken the storm to a tropical depression by the weekend. Nicole is not a threat to any land areas this week.

Tropical wave approaching Lesser Antilles has a low chance of development
A large tropical wave located several hundred miles east of the Lesser Antilles Islands is moving west at 10 - 15 mph, and will spread heavy rains and gusty winds into the islands on Wednesday and Thursday. The wave is unlikely to develop over the next two days, due to high wind shear from the upper-level outflow from Hurricane Matthew. Once the wave reaches the central Caribbean on Friday, wind shear should drop, and the latest GFS model ensemble forecast has about 10% of its members showing development into a tropical depression or tropical storm sometime Friday - Sunday. In their 2 pm EDT Tuesday Tropical Weather Outlook, NHC gave this system 2-day and 5-day odds of development of 10% and 20%, respectively.

We’ll be back with our next update by late morning Wednesday at the latest.

Jeff Masters and Bob Henson


Figure 9. Enhanced infrared satellite image of Hurricane Matthew (left), much smaller Tropical Storm Nicole (top center), and a tropical wave approaching the Lesser Antilles Islands (right), as of 3:45 pm EDT Tuesday, October 4, 2016. Image credit: NASA/MSFC Earth Science Office.


Matthew Hits Haiti, Their Strongest Hurricane in 52 Years

By: Jeff Masters , 1:21 PM GMT on October 04, 2016

Powerful Hurricane Matthew made landfall on the southwestern tip of Haiti near 7 am EDT October 4, 2016 as a Category 4 storm with 145 mph winds. Matthew’s extreme rains, large storm surge, and Category 4 winds are likely to be catastrophic for Haiti. The hurricane is the third strongest one ever recorded in the impoverished nation, and their strongest hurricane in 52 years. The only Haitian hurricanes stronger than Matthew were two Category 4 storms with 150 mph winds: Hurricane Cleo of 1964 and Hurricane Flora of 1963. The last major hurricane to make a direct hit in Haiti was Category 3 Hurricane David of 1979, which crossed over the nation from east to west with 115 mph winds.


Figure 1. Infrared satellite image of Hurricane Matthew as it made landfall over the southwestern tip of Haiti at 7:19 am EDT October 4, 2016.

We don’t have many weather stations in Haiti, so it is difficult to say what the conditions are on the ground. A personal weather station (PWS) on the south coast Haiti at Aquin, about 70 miles east of Matthew’s landfall, recorded a wind gust of 59 mph at 6:50 am EDT Tuesday. A PWS near Port-Au-Prince, Haiti recorded about 1.70” of rain during the 36-hour period ending at 7 am EDT Tuesday. At the Port-Au-Prince airport, top winds on Tuesday as of 8 am EDT were 34 mph, gusting to 52 mph.

An Air Force hurricane hunter aircraft arrived at Matthew’s center near 8 am EDT Tuesday, when the eye was over land. The plane did not fly directly into the center of the eye, since that would have risked penetrating through extreme turbulence over land, but the aircraft was able to measure a central pressure of 944 mb at the edge of the eye. The peak winds measured by their SFMR instrument were 135 mph, so Matthew was definitely a solid Category 4 storm at landfall.

Satellite loops on Tuesday morning showed that the encounter with land had weakened the storm, with the eye much less distinct. Light wind shear of 5 - 10 knots is affecting the storm, and Matthew is over warm ocean waters of 29°C (84°F) and has plenty of moisture to work with--70 - 75% relative humidity at mid-levels of the atmosphere, as analyzed by the SHIPS model.


Figure 2. Microwave image of rainfall rates in Hurricane Matthew from the F-16 polar orbiting satellite taken at 5:02 am EDT October 4, 2016. At the time, Matthew was a Category 4 storm with 145 mph winds. Rainfall amounts in excess of 1”/hour (orange colors) were occurring along the coasts of Haiti and the Dominican Republic. Image credit: NRL Tropical Cyclone Page.

Extreme rains near the Haiti/Dominican Republic border
Extreme rains from Matthew are a huge concern for the entire island of Hispaniola, thanks to an unusual area of extra spin and low pressure that has been embedded on the east side of Matthew’s circulation for days. This feature began rotating ashore over southern Haiti and the Dominican Republic early Monday morning, and continues to affect the Dominican Republic this morning. The mountainous terrain of the island has caused tremendous uplift to the thunderstorms moving ashore, resulting in extremely intense rainfall. A personal weather station (PWS) in Cabo Rojo, on the southern coast of the Dominican Republic near the border with Haiti, recorded 22.89” of rain on Monday, including a remarkable 5.33" in the hour from 6 am to 7 am. An additional 3.73” fell on Tuesday as of 8 am EDT, for a storm total of 26.62”. While PWS data is often suspect, these are believable rainfall amounts based on the satellite presentation of Matthew.

Intensity forecast for Matthew
Landfall in Haiti on Tuesday morning and on eastern Cuba on Tuesday evening will disrupt the hurricane, and could cause it to weaken by one Saffir-Simpson category, to a Category 3 storm. However, Matthew is a very large and well-organized storm, and it may take it only a day to recover from its disruption. The latest SHIPS model forecast predicts that wind shear will remain light to moderate, 5 - 15 knots, through Friday. Ocean temperatures will be very warm, between 29 - 30° C (84 - 86°F) and the heat content of the ocean will be high to very high, which argues for intensification of Matthew. Our top three intensity models--the HWRF, LGEM, and SHIPS models--were predicting on Tuesday morning that Matthew would be at Category 3 or 4 strength through Friday.

Track forecast for Matthew
The significant westward shift in computer model guidance on Hurricane Matthew that occurred yesterday is holding, and we now have increased confidence that Matthew will bring severe impacts to the Southeast U.S. coast from South Florida to Cape Hatteras, North Carolina.

Matthew will continue northwards after clearing the southwest tip of Haiti Tuesday morning, then make a second landfall in eastern Cuba at about 6 pm EDT Tuesday. Matthew will turn north-northwest and then northwest on Wednesday, and traverse The Bahamas from southeast to northwest Wednesday morning through Thursday morning. In their 5 am EDT Tuesday Wind Probability Forecast, NHC gave highest odds of hurricane-force winds in The Bahamas to Great Exuma (57%), New Providence (46%), and Grand Bahama (37%).

Late Thursday morning, Matthew will be very close to the coast of South Florida, and is expected to turn more to the north-northwest, almost parallel to the coast, at that time. The latest 00Z and 06Z Tuesday runs of our top two models for predicting hurricane tracks—the GFS and European models—did not show a Florida landfall, but brought the hurricane so close to Florida—within 50 miles—that most of the coast of Florida from West Palm Beach to Daytona Beach would experience sustained winds of at least 50 mph, if these forecasts verified. Keep in mind that the diameter of NHC’s cone of uncertainty two days into the future is about 100 miles; the cone is about 130 miles across three days into the future. On average, about two-thirds of all hurricanes stay within the cone, but some hurricanes are tougher to predict than others, and Matthew certainly falls into that category. Thus, it would not be a surprise to see Matthew make landfall in Florida. Two of the four members of the Euro “high-probability” cluster--the ensemble forecasts that most closely match the operational run--depicted Matthew making landfall on Florida’s East Coast near West Palm Beach on Thursday. In their 5 am EDT Tuesday Wind Probability Forecast, NHC gave highest odds of hurricane-force winds in Florida to Ft. Pierce (22%), West Palm Beach (21%), and Cocoa Beach (19%). Update: At 11 am EDT Tuesday, NHC placed the Florida coast from Deerfield Beach to the Volusia/Brevard county line under a Hurricane Watch, with a Tropical Storm Watch in effect southward from south of Deerfield Beach to the Seven Mile Bridge in the Florida Keys, including Lake Okeechobee.


Figure 3. Track forecasts from the four European model ensemble members [gray lines] that most closely match the operational run [red line] during the first 72 hours, starting at 00Z Tuesday, October 4, 2016. The red line is a version of the 00Z Tuesday operational model track that has been adjusted and calibrated using a proprietary technique to account for systemic model errors, and shows Matthew barely missing landfall along the Southeast U.S. coast. All four of the ensemble forecasts showed Matthew making landfall in the U.S., in Florida or South Carolina (though one looked like an improbable outlier, with a looping track off the coast.) The high-probability cluster (grey lines) perform better than other ensemble members at forecast times of five days and beyond. Image credit: Climate Forecast Applications Network (CFAN).

Matthew is expected to turn more to the north and then north-northeast on Friday, which will keep the storm very close to the coasts of Georgia, South Carolina, and North Carolina. At this time, our top models suggest that the greatest probability for a U.S. landfall by Matthew is in South Carolina on Friday night or North Carolina on Saturday morning. In their 5 am EDT Tuesday Wind Probability Forecast, NHC was giving the coast of Georgia, South Carolina, and southern North Carolina 3 - 7% chances of receiving hurricane force winds. However, I expect those probabilities to rise significantly by tomorrow, given the latest model data.

After its closest approach to the coast of North Carolina, we have a number of reliable models predicting that Matthew will continue north-northeast and hit New England on Sunday, with eastern Massachusetts being at greatest risk. Landfall in New England would very likely not be at hurricane strength, due to the potential for Matthew to pass over a lot of land before getting there. The risk to New England is not clear at this point, though, since we have some model guidance predicting a more northeasterly path for Matthew, keeping the center of the storm several hundred miles east off the Northeast U.S. coast.

Links
Meteorologist Steve Gregory is making regular updates on Matthew.
See our post from Monday morning on how Matthew--a rare northward-moving major hurricane in the Caribbean--fits into the hurricane histories of Haiti, Jamaica, and Cuba.
Guantanamo Bay, Cuba radar

We’ll be cranking out 2 - 3 updates on Matthew per day throughout the next five days. Our next update, early this afternoon, will also discuss 98L, which is close to tropical storm strength.

Jeff Masters

Hurricane

Matthew Slamming Hispaniola; Southeast U.S. Landfall a Growing Threat

By: Bob Henson and Jeff Masters , 12:23 AM GMT on October 04, 2016

Colossal amounts of rain are soaking Haiti and the Dominican Republic as Category 4 Hurricane Matthew heads for an encounter with the western end of Hispaniola. As of the National Hurricane Center’s update at 8:00 pm EDT Monday, Matthew was located about 200 miles south of Port-au-Prince, Haiti, moving just east of due north at 8 mph. Matthew’s top sustained winds were holding at 140 mph, solidly in the Category 4 range. Just before 8 PM EDT, a Hurricane Hunter flight found a minimum surface pressure of 934 millibars, down from the 940 mb reported in the 8 PM EDT advisory. However, surface winds measured by the SFMR instrument had not yet increased. Matthew may be completing an eyewall replacement cycle, with the original small eye decaying and a larger outer band taking over. Hurricane Hunters described the new eye as ragged, elliptical and kidney-shaped, about 17 by 30 miles across. Depending on how soon this cycle is completed, it’s possible that Matthew's winds could either increase or decrease by 5 - 10 mph prior to the storm making landfall in southwest Haiti around 8 am EDT Tuesday.


Figure 1.Hurricane Matthew’s eye was clearly evident in this enhanced infrared satellite image from 2345Z (7:45 pm EDT) Monday, October 3, 2016. Image credit: NOAA/NESDIS.

As of late Monday, Hurricane Warnings were in effect for Haiti, Cuba’s eastern provinces, and the southeastern and central Bahamas. Matthew’s center is likely to pass over or very near the western tip of Haiti. This will likely spare Jamaica from widespread winds above hurricane force, although very heavy rains can still be expected. On the other hand, Matthew’s track is close to a worst-case scenario for the beleagured nation of Haiti, as it will bring the hurricane’s more dangerous right-hand side across Hispaniola. Far southwest Haiti may experience Matthew’s small core of intense hurricane-force winds, and a much larger area of powerful south winds slamming against tall mountainsides will lead to phenomenal rains over Haiti as well as much of the Dominican Republic (DR). The rains will likely be enhanced by moisture associated with a persistent band of showers and thunderstorms that has flanked Matthew’s east side for days (see this discussion of the mysterious “blob” from Marshall Shepherd). This feature’s rapid movement toward Hispaniola has actually led to heavier rains thus far in the Dominican Republic than in Haiti. A personal weather station in Cabo Rojo, on the southern coast of the Dominican Republic near the border with Haiti, recorded 22.91” of rain in thirteen hours between 3 am and 4 pm on Monday, including a remarkable 5.33" in the hour from 6 am to 7 am. While PWS data is often suspect, these are believable rainfall amounts based on the satellite presentation of Matthew.



Figure 2. Flooding and coastal damage in Jacmel, Haiti on Monday afternoon, October 3, 2016. Jacmel is on the south coast of Haiti, about 25 miles southwest of the capital of Port-Au-Prince. Image credit: Ruth Chervil.

NHC warns that localized rainfall amounts could total 40” over southern Haiti and the southwestern DR, with widespread 15” - 25” amounts. Massive flooding and landslides are a virtual certainty, with the impacts especially severe on Haiti’s deforested landscape. As discussed in Jeff Masters’ post this morning on the hurricane history of Matthew’s targets, one of the few analogs for this northward-moving major hurricane is Hazel (1954), which killed more than 1000 people in Haiti.


Figure 3. Visible satellite image of 2145Z (5:45 pm EDT) Monday, October 3, 2016. Very intense rainbands associated with the mysterious “blob” east of Matthew can be seen at far right. Image credit: Naval Research Laboratory.

Models are in fairly close agreement in taking Matthew across the eastern tip of Cuba late Tuesday. This would keep most of the island on the hurricane’s weaker western side, but only a slight change in track could make a huge difference in the impacts on Cuba. On Wednesday into Thursday, Matthew will be charging across the central and northwest Bahamas. The intensity forecast for Matthew at this point is tough, with both high- and low-end possibilities. Matthew could be cut back to Category 2 or 3 strength by its brief passage over the high mountains of Haiti and/or Cuba. However, it will then have a chance to restrengthen over the deep, warm waters of the Bahamas. Matthew will be surrounded by a very moist atmosphere (relative humidities around 80%) and will pass over sea-surface temperatures close to record highs for early October. It's possible to envision Matthew striking the central Bahamas on Wednesday at anywhere from Category 2 to Category 4 strength. The offficial NHC forecast has Matthew at Category 3 strength through at least Friday.

A growing threat for the Southeast U.S.
A significant westward shift unfolded Monday in computer model guidance on Hurricane Matthew, and this has big implications for the hurricane’s potential impact on the U.S. East Coast. The main reason appears to be stronger ridging south of 98L and north of Matthew than earlier predicted, which may help to nudge Matthew far enough west for major impacts along the Southeast U.S. coast. Last night’s 50 ensemble runs from the 00Z Monday European model included a number of tracks making landfall along the U.S. East Coast. Most concerning was that all four members of the Euro “high-probability” cluster--the members that most closely match the operational run--depicted Matthew making landfall on Florida’s East Coast. Today’s 12Z Monday Euro ensemble continued along the same lines (see Figure 4 below).


Figure 4. Track forecasts from the four European model ensemble members [gray lines] that most closely match the operational run [red line] during the first 72 hours, starting at 12Z (8:00 am EDT) Monday, October 3, 2016. The red line is a version of the 12Z Monday operational model track that has been adjusted and calibrated using a proprietary technique to account for systemic model errors. The high-probability cluster (grey lines) perform better than other ensemble members at forecast times of five days and beyond. Image credit: Climate Forecast Applications Network (CFAN).


A track mirroring the Southeast coastline?
Other models have now moved into the Euro ensemble’s camp. The 12Z and 18Z GFS brought Matthew considerably closer to the Florida coast than earlier runs, with a projected landfall in northern South Carolina this weekend (see Figure 4 below) and a second landfall on Cape Cod less than 36 hours later. The 18Z GFS nudged Matthew’s track so that it arrives very near the central Florida coast on Thursday night, then hugs the coast all the way to Cape Hatteras, North Carolina, on Sunday morning. The 12Z and 18Z Monday GFS ensembles (GEFS) featured a majority of runs making landfall somewhere between Florida and North Carolina, a major shift west from previous GFS ensembles. The 12Z Monday run of the HWRF model tracked about 1 degree (roughly 60 miles) west of its previous two runs, now showing a potential landfall in eastern North Carolina by late Friday.

Obviously, a direct landfall from Matthew could inflict a devastating blow. The key variable in Matthew’s track later this week is how far north and west the hurricane moves before it begins the expected northeastward motion that will take it toward the Northeast U.S. and Canadian Maritimes. A gradual, arcing turn near the coast, as depicted in the 18Z GFS, would avoid a perpendicular, head-on landfall (the type that occured in New Jersey with Hurricane/Superstorm Sandy). This would act to reduce the intensity of storm surge at any given point. Such a track would also keep the mainland primarily on the less-intense western side of Matthew. On the other hand, such a track would bring hurricane-related impacts, including strong winds and heavy rains, to many millions of coastal residents. One particular concern is the risk of very heavy rain from eastern North Carolina into the Delmarva region. The last two weeks have already left totals exceeding 10” in some areas (see Figure 6 below). Any rains from Matthew would fall atop saturated soil, and even strong tropical-storm-force winds could lead to widespread tree uprooting. We can also expect major beach erosion as Matthew churns northeastward.

The governors of Florida and North Carolina have already declared states of emergency for all of FL and parts of central and eastern NC.


Figure 5. Total rainfall as observed by radar and rain gauges over the 14-day period ending at 12Z (8:00 am EDT) Monday, October 3, 2016. Image credit: NOAA/NWS Advanced Hydrologic Prediction Service.


Figure 6. The 50 forecasts from the 12Z Monday European (ECMWF) model ensemble (left) and the 20 forecasts from the 18Z Monday GFS model ensemble (right) agree that Matthew could make landfall almost anywhere from Florida to Nova Scotia late this week, over the weekend, or early next week. The GFS ensemble has been more tightly clustered than the ECMWF ensemble throughout Matthew’s life. Ensemble model runs are produced by running the same model for the same timeslice a number of times, with the starting-point conditions for each run varied randomly in order to mimic the uncertainty in our observations of the atmosphere. This produces a better sense of the future uncertainty in a given forecast. Image credit: Image credit: Climate Forecast Applications Network (CFAN).

98L: probably no steering influence on Matthew
An area of low pressure associated with a tropical wave (Invest 98L) is over the central tropical Atlantic several hundred miles north-northeast of the northern Lesser Antilles. In their 8 pm EDT Monday Tropical Weather Outlook, NHC gave this system 2-day and 5-day odds of development of 60%. High wind shear will likely keep any development of 98L rather limited, and we doubt 98L will be able to exert a significant steering influence on Matthew.

Northeast impacts: Still too soon to tell
The outlook for Matthew beyond the Southeast coast remains quite uncertain. Model solutions vary in how close Matthew’s northeast track might come to the Mid-Atlantic, Northeast, and New England, ranging from well inland to well offshore. We’ll also need to see how strong Matthew is by the time it passes the Outer Banks. A track just off the Southeast coast would keep Matthew over the warm waters of the Gulf Stream, whereas an inland track would lead to more rapid weakening.

The bottom line
Matthew poses an unusually widespread threat to the U.S. East Coast, with impacts possible from Florida to Maine. Residents should monitor the National Hurricane Center’s five-day outlooks (as shown below), as well as any local statements posted to the NHC’s webpage dedicated to Matthew.

We’ll be back with our next update by Tuesday morning at the latest. Meteorologist Steve Gregory is making regular updates on Matthew.

Bob Henson and Jeff Masters


Figure 7. WU depiction of official National Hurricane Center forecast for Matthew as of 5:00 pm EDT Monday, October 3, 2016.

Hurricane

Matthew Dumping Extreme Rains; Threat to Southeast U.S. Growing

By: Jeff Masters and Bob Henson , 6:14 PM GMT on October 03, 2016

Very dangerous Hurricane Matthew is maintaining Category 4 strength as it heads northwards at 6 mph, and is already dumping potentially catastrophic rains on Haiti and the Dominican Republic. An unusual area of extra spin and low pressure that has been embedded on the east side of Matthew’s circulation for days is generating intense rains in excess of one inch per hour, as seen on microwave imagery (Figure 1.) A portion of this feature rotated ashore over southern Haiti and the Dominican Republic early Monday morning, and the mountainous terrain of this region undoubtedly caused additional uplift that resulted in rainfall rates much higher than one inch per hour. A personal weather station in Cabo Rojo, on the southern coast of the Dominican Republic near the border with Haiti, recorded 20.05” of rain in eleven hours between 3 am and 2 pm on Monday, including a remarkable 5.33" in the hour from 6 am to 7 am. While PWS data is often suspect, these are believable rainfall amounts based on the satellite presentation of Matthew. The outer spiral bands of Matthew are also affecting Jamaica, as seen on Jamaican radar (see long loop saved by Brian McNoldy, Univ. of Miami, Rosenstiel School.)


Figure 1. Microwave image of rainfall rates in Hurricane Matthew from the F-16 polar orbiting satellite taken at 5:16 am EDT October 3, 2016. At the time, Matthew was a Category 4 storm with 130 mph winds. Rainfall amounts in excess of 1”/hour (orange colors) were occurring along the coasts of Haiti and the Dominican Republic. This intense area of rainfall moved ashore a few hours later, bringing 5.33” of rain in one hour to Cabo Rojo. Image credit: NRL Tropical Cyclone Page.

An Air Force hurricane hunter aircraft made four passes through the eye of Matthew on Monday morning and early Monday afternoon, and found surface winds as high as 140 mph. The central pressure stayed in the 940 - 941 mb range during all the passes, so it does not appear that Matthew is undergoing intensification. Satellite loops on Monday morning showed that Matthew’s eye was clearing out and becoming more distinct, and the hurricane’s cloud pattern was becoming more symmetric--signs the storm may be about to intensify, though. Light wind shear of 5 - 10 knots is affecting the storm, and Matthew is over warm ocean waters of 29°C (84°F) and has plenty of moisture to work with: 70 - 75% relative humidity at mid-levels of the atmosphere, as analyzed by the SHIPS model.

Matthew passed over NOAA buoy 42058 early Monday morning, and top winds during passage of the weaker portion of the eyewall were 74 mph, gusting to 92 mph. Seas were 34 feet, and the buoy recorded a minimum pressure of 943 mb. The wind measurement height on the buoy was 5 meters, so an upwards correction of about 10 mph is needed to adjust these numbers to the standard 10-meter observing height for winds.


Figure 2. The GOES East satellite captured this image of Hurricane Matthew, located about 220 miles southeast of Kingston, Jamaica, at 9:15 am EDT on October 3, 2016.  Image credit: NOAA Visualization Lab.

Intensity forecast for Matthew
The latest SHIPS model forecast predicts that wind shear will remain light to moderate, 5 - 15 knots, for the next five days. Ocean temperatures will be very warm, between 29 - 30° C (84 - 86°F) and the heat content of the ocean will be high to very high, which argues for intensification of Matthew. At any time, though, Matthew could undergo an eyewall replacement cycle (ERC), where the inner eyewall collapses and is replaced by a larger-diameter eye, with a new eyewall formed from an outer spiral band. This process usually causes a weakening to the storm’s top winds for a day or so. The down side of an ERC is that is spreads out the storm’s hurricane-force winds over a wider area, resulting in severe impacts over a wider area. Our top three intensity models--the HWRF, LGEM, and SHIPS models--were predicting on Monday morning that Matthew would be at Category 3 or 4 strength for the next four days. The SHIPS model gave Matthew an 11% chance of rapid intensification of 30 mph or more by Tuesday morning. Landfall in eastern Cuba/northwest Haiti on Tuesday could act to disrupt the hurricane and destroy its inner core, which might knock Matthew down to Category 2 strength for several days. However, Matthew will probably re-intensify by at least 20 mph in the two days after its landfall in Cuba/Haiti.

Three-day track forecast for Matthew
Matthew will make landfall or pass very close to the southwest tip of Haiti early Tuesday morning, then make a second landfall in eastern Cuba on Tuesday afternoon. Matthew will then traverse The Bahamas from southeast to northwest Tuesday evening through Thursday morning. In their 11 am EDT Monday Wind Probability Forecast, NHC gave highest odds of hurricane-force winds to Les Cayes in southwest Haiti (35%) and to Guantanamo Bay, Cuba (41%). Lower odds were given to Kingston, Jamaica (0%)  and Port-Au-Prince, Haiti (2%). In The Bahamas, hurricane-force wind odds of 39% were given to Great Exuma, 24% to New Providence, and 35% to San Salvador. See our post from earlier Monday morning for more on how Matthew--a rare northward-moving major hurricane in the Caribbean--fits into the hurricane histories of Haiti, Jamaica, and Cuba.

98L: probably no steering influence on Matthew
An area of low pressure associated with a tropical wave that (designated Invest 98L by NHC on Sunday morning) is over the central tropical Atlantic several hundred miles north-northeast of the northern Lesser Antilles. Over 50% of the members of the 00Z Monday European ensemble forecasts predicted that this system would develop into a tropical depression or tropical storm as it heads west-northwest to northwest at 10 - 15 mph; the GFS model showed virtually no development. In their 2 pm EDT Monday Tropical Weather Outlook, NHC gave this system 2-day and 5-day odds of development of 50%. Satellite loops on Monday morning showed that 98L had a very limited amount of heavy thunderstorm activity that had acquired a respectable amount of spin. High wind shear of 30 knots was affecting 98L, and the 12Z Monday SHIPS model forecast predicted wind shear would rise even higher by Tuesday--in excess of 45 knots. This level of shear will likely keep any development of 98L rather limited, and we doubt 98L will be able to exert a significant steering influence on Matthew.


Figure 3. Track forecasts from the four European model ensemble members [gray lines] that most closely match the operational run [red line] during the first 72 hours, starting at 00Z Monday, October 3, 2016. The red line is a version of the 00Z Monday operational model track that has been adjusted and calibrated using a proprietary technique to account for systemic model errors. Four out of five of these forecasts showed Matthew making a double landfall in the U.S.: first in Florida, then farther north. The high-probability cluster (grey lines) perform better than other ensemble members at forecast times of five days and beyond. Image credit: Climate Forecast Applications Network (CFAN).

Beyond The Bahamas: landfall threat for Southeast U.S. increasing
A significant westward shift in computer model guidance on Hurricane Matthew has occurred, and this could have big implications for the hurricane’s potential impact on the U.S. East Coast. The main reason appears to be stronger ridging south of 98L and north of Matthew than earlier predicted, which may help to nudge Matthew far enough west for major impacts along the Southeast U.S. coast. Last night’s 50 ensemble runs from the 00Z Monday European model included a number of tracks making landfall along the U.S. East Coast. Most concerning is that, for the first time in Matthew’s life, all four members of the Euro “high-probability” cluster--the members that most closely match the operational run--depict Matthew making landfall on Florida’s East Coast. (The 12Z Monday run of the NAM model also depicts the stronger ridge and suggests a Florida landfall, but the NAM is not designed to handle tropical cyclones and should be avoided for hurricane prediction, unless perhaps you’re Bart Simpson.)

Lending further credence to the westward shift are the latest 12Z Monday operational runs of our other two top track models, the GFS and UKMET. The 12Z UKMET brings Matthew into the East Coast of Florida, while the GFS brings Matthew considerably closer to the Florida coast than earlier runs, with a projected landfall in northern South Carolina this weekend (see Figure 4 below) and a second landfall on Cape Cod less than 36 hours later. The several previous operational GFS runs had suggested that a Southeast landfall would be limited to the NC Outer Banks at most. Likewise, the 12Z Monday GFS ensembles (GEFS) now include a majority of runs making landfall somewhere between Florida and North Carolina, a major shift west from previous GFS ensembles. In addition, the 12Z Monday run of the HWRF model is tracking about 1 degree (roughly 60 miles) west of its previous two runs, now showing a potential landfall in eastern North Carolina by late Friday.


Figure 4. Comparison of GFS operational model output from (left) 06Z Monday and (right) 12Z Monday. Black lines denote surface air pressure; colors denote the height of the 500-millibar surface, roughly the midpoint of the atmosphere, in tens of meters. The more recent guidance (right) shows a stronger ridge (deeper orange colors) to the east and north of Matthew, keeping it further to the west as it moves northward. Long-range models such as the GFS are much less skillful at projecting hurricane intensities than hurricane tracks. Image credit: tropicaltidbits.com

In our next update this evening, we’ll look at results from the 12Z Euro and GFS ensemble runs and the 12Z Euro operational run. For now, it’s important to keep in mind that the uncertainty “cones” produced by NHC are not tailored specifically for a given hurricane: they are based on the average error in NHC forecasts over the preceding five years. On average, about two-thirds of all hurricanes stay within the cone, but some hurricanes are tougher to predict than others. Given the wide range of model guidance on Matthew, and the recent westward shift, the actual uncertainty for this hurricane may be wider than the 120-hour cone location implies. In any event, there is enough model support for various possibilities that people all the way from Florida to Maine should continue to take seriously the possibility of impacts from Matthew. As always, the NHC is the place to turn for official 5-day forecasts, including intensity and track guidance and cones of uncertainty.


Figure 5. WU depiction of official NHC hurricane forecast through 12Z (8:00 am EDT) Saturday, October 8.

Category 5 Super Typhoon Chaba threatening Japan, South Korea
Previously a Category 5 itself, Matthew has a Category 5 cousin over the Northwest Pacific today: Super Typhoon Chaba, which passed just south of Okinawa early Monday. Chaba intensified into a 165 mph Category 5 storm with a central pressure of 905 mb on Monday morning, becoming Earth’s sixth Category 5 storm of the year. The planet averages about 4 - 5 Cat 5’s per year, so we are above average for the third year in a row. Both 2015 and 2014 had nine Category 5 storms, tied for the second most on record (the record was twelve, set in 1997.)


Figure 6. Super Typhoon Chaba passing just south of Okinawa at 1:45 am EDT October 3, 2016. At the time, Chaba was a Category 5 storm with 165 mph winds. Image credit: NASA.

Chaba’s northern eyewall passed very close to Kumejima, on an island just west of Okinawa. Kumejima reported sustained winds of 87 mph (10-minute average) with a pressure that bottomed out at 960 mb at 1 am local time Monday. According to Jon Erdman of weather.com, Chaba was the third Category 5 super typhoon to track within 65 nautical miles of Kumejima Island, in records dating to the 1960s, and will be the strongest on record there. Chaba is expected to recurve to the north and northeast, passing very close to South Korea and Japan as a Category 3 storm Tuesday afternoon (early Wednesday morning, Japan time.)

Links
Meteorologist Steve Gregory is making regular updates on Matthew.
CIMMS Satellite Blog has an interesting post on airglow gravity waves observed in Hurricane Matthew during its rapid intensification phase.
Jamaican radar
Long Jamaica radar loop saved by Brian McNoldy, Univ. of Miami, Rosenstiel School.)

Jeff Masters and Bob Henson

Hurricane

Hurricane History of Matthew's Targets: Haiti, Eastern Cuba and Jamaica

By: Jeff Masters , 12:29 PM GMT on October 03, 2016

Very dangerous Category 4 Hurricane Matthew is churning northwards towards Haiti, Jamaica, and eastern Cuba, and is poised to deliver a historic pounding on Monday and Tuesday to these unfortunate nations. At 8 am EDT Monday, an Air Force hurricane hunter aircraft passed through the eye of Matthew, and found the storm was a little stronger: Matthew's surface pressure was approximately 940 mb (extrapolated from their 10,000' flying altitude), and surface winds as high as 140 mph were seen with their SFMR instrument. Matthew passed over NOAA buoy 42058 early Monday morning, and top winds during passage of the eyewall were 74 mph, gusting to 92 mph. Seas were 34 feet, and the buoy recorded a minimum pressure of 943 mb. The outer spiral bands of Matthew are already drenching the south coasts of Haiti and the Dominican Republic, as seen on Jamaican radar (see long loop saved by Brian McNoldy, Univ. of Miami, Rosenstiel School.) An unusual area of extra spin and low pressure that has been embedded on the east side of Matthew’s circulation for days is generating intense rains in excess of 1”/hour that are now deluging the coasts of Haiti and the Dominican Republic, as seen on microwave imagery (Figure 1.) A personal weather station in Cabo Rojo, on the southern coast of the Dominican Republic, recorded 7.90" of rain from midnight to 8 am Monday, including 5.33" in the hour from 6 am to 7 am.


Figure 1. Microwave image of rainfall rates in Hurricane Matthew from the F-16 polar orbiting satellite taken at 5:16 am EDT October 3, 2016. At the time, Matthew was a Category 4 storm with 130 mph winds. Rainfall amounts in excess of 1”/hour (orange colors) were occurring along the coasts of Haiti and the Dominican Republic. Image credit: NRL Tropical Cyclone Page.

I’ll need some time this morning to digest and formulate a post on the latest sets of model forecasts for Matthew, and will be back around noon today with a detailed look at the long-range forecast for Matthew. Until then, I wanted to detail the hurricane history of the three nations under immediate threat from Matthew—Haiti, Cuba, and Jamaica. Haiti will take the brunt of Matthew’s heavy rains, and will suffer the most from the storm. In the wake of the great 2010 earthquake, over 50,000 people still live outdoors in makeshift shelters consisting of tarps or tents, and are highly vulnerable to Matthew's floods and winds.


Figure 2. Track of all hurricanes that are known to have passed through the shaded circle with at least Category 3 intensity. The only major hurricanes that took a south-to-north track similar to the forecast for Matthew were Sandy (2012), which briefly attained Category 3 strength before striking eastern Cuba, and Hazel (1954), which struck southwest Haiti as a Category 3 storm. Up to 1,000 Haitians died as a result of Hazel, and the nation’s economy was hobbled for years afterward. NOAA’s hurricane data base extends back to 1851. Both Hazel and Sandy were October hurricanes that went on to affect much of the U.S. East Coast. Image credit: NOAA

Haiti’s hurricane history
Haiti has been hit by 8 major Category 3 or stronger hurricanes since 1851 (see Figure 2). Two of these hurricanes were Category 4 storms with 150 mph winds: Hurricane Cleo of 1964 and Hurricane Flora of 1963. The last major hurricane to make a direct hit in Haiti was Category 3 Hurricane David of 1979, which crossed over the nation from east to west with 115 mph winds after devastating the Dominican Republic as a Category 5 storm with 170 mph winds.

Haiti has been relatively fortunate with hurricanes since the great 2010 earthquake, which killed over 200,000 people and forced hundreds of thousands of people to live outside for multiple years in makeshift shelters highly vulnerable to hurricanes. The deadliest hurricane in Haiti since the 2010 earthquake was Hurricane Sandy of 2012, which did not make a direct hit on the nation, but still killed 75 people and did over $250 million in damage. In the month following Sandy, a resurgence of cholera linked to the storm killed at least 44 people and infected more than 5,000 others.


Figure 3. Satellite-estimated rainfall amounts from NASA's TRMM satellite show that portions of Haiti received over 12.75" (325 mm) of rain (pink colors) from Hurricane Sandy. The capital of Port-au-Prince received 8 - 10" (200 - 250 mm.) Image credit: NASA.

Prior to the earthquake, the hurricane season of 2008 was the cruelest natural disaster ever experienced in Haiti. Four storms--Fay, Gustav, Hanna, and Ike--dumped heavy rains on the impoverished nation. The rugged hillsides, stripped bare of 98% of their forest cover thanks to deforestation, let flood waters rampage into large areas of the country. Particularly hard-hit was Gonaives, the fourth largest city. According to reliefweb.org, Haiti suffered 793 killed, with 310 missing and another 593 injured. The hurricanes destroyed 22,702 homes and damaged another 84,625. About 800,000 people were affected--8% of Haiti's total population. The flood wiped out 70% of Haiti's crops, resulting in dozens of deaths of children due to malnutrition in the months following the storms. Damage was estimated at over $1 billion, the costliest natural disaster in Haitian history up to that time. The damage amounted to over 5% of the country's $17 billion GDP, a staggering blow for a nation so poor. (This would be roughly equivalent to the United States experiencing an $800-billion-dollar hurricane, eight times more costly than Sandy.)

The year 2008 was only one of many years hurricane have brought untold misery to Haiti. Hurricane Jeanne of 2004 passed just north of the country as a tropical storm, dumping 13 inches of rain on the nation's northern mountains. The resulting floods killed over 3,000 people, mostly in the town of Gonaives. Jeanne ranks as the 12th deadliest hurricane of all time on the list of the 30 most deadly Atlantic hurricanes . Unfortunately for Haiti, its name appears several times on this list. Hurricane Flora killed over 5,000 people in 1963. An unnamed 1935 storm killed over 2,000, and Hurricane Hazel killed over 1,000 in 1954. More recently, Hurricane Gordon killed over 1,000 Haitians in 1994, and in 1998, Hurricane Georges killed over 400 while destroying 80% of all the crops in the country.


Figure 4. Devastation in Haiti after Hurricane Hazel in 1954. Image credit: Bertrand Roy.

Why does Haiti suffer a seemingly disproportionate number of natural disasters? The answer in that in large part, these are not natural disasters--they are human-caused disasters. Haiti is the poorest nation in the Western Hemisphere. With oil too expensive for the impoverished nation, charcoal from burnt trees has provided 85% or more of the energy in Haiti for decades. As a result, Haiti's 9 million poor have relentlessly hunted and chopped down huge amounts of forest, leaving denuded mountain slopes that rainwater washes down unimpeded. Back in 1980, Haiti still had 25% of its forests, allowing the nation to withstand heavy rain events like 1987's Category 3 Hurricane Emily, without loss of life. But as of 2004, only 1.4% of Haiti's forests remained. Jeanne and Gordon were not even hurricanes--merely strong tropical storms--when they stuck Haiti, but the almost total lack of tree cover contributed to the devastating floods that killed thousands. And it doesn't even take a tropical storm to devastate Haiti--in May of 2004, three days of heavy rains from a tropical disturbance dumped more than 18 inches of rain in the mountains, triggering floods that killed over 2,600 people.


Figure 5. The flooded city of Gonaives after Hurricane Hanna, September 3, 2008. Image credit: Lambi Fund of Haiti.

What can be done to reduce these human-worsened natural disasters? Education and poverty eradication are critical to improving things. In addition, reforestation efforts and promotion of alternative fuels are needed. If you're looking for a promising way to make a charitable donation to help Haitian flood victims, I’m a big booster and donor to the Lambi Fund of Haiti, which is very active in promoting reforestation efforts, use of alternative fuels, and infrastructure improvements at a grass-roots level to help avert future flood disasters.

Eastern Cuba’s hurricane history
Six major hurricanes have hit the eastern coast of Cuba over the past 100 years, according to NOAA’s Historical Hurricane Tracks website:

Hurricane Sandy of 2012. Sandy was low-end Category 3 storm when it struck just west of Santiago de Cuba from the south. Sandy destroyed tens of thousands of homes and killed at least 11 people on Cuba. However, Sandy was not a top-ten most expensive hurricane for Cuba.

Hurricane Dennis of 2005. Dennis was the strongest hurricane on record to hit eastern Cuba: a Category 4 storm with 140 mph winds. Dennis was the fourth most expensive Cuban hurricane on record, with damages of $1.4 billion (2005 dollars.)

Hurricane Inez of 1966 (Category 3, 115 mph winds.)

Hurricane Cleo of 1964 (Category 3, 115 mph winds.)

Hurricane Flora of 1963 (Category 3, 120 mph winds.) Flora wandered over Cuba as a hurricane for four days, dumping prodigious rains. Flora was by far the deadliest hurricane in Cuban history, with 1750 deaths.

Hurricane Ella of 1958 (Category 3, 115 mph winds.)

Jamaica’s hurricane history
Despite being in a part of the Caribbean prone to hurricanes, Jamaica has suffered only three direct hits by hurricanes since 1950:

Hurricane Charlie of 1951. This Category 3 storm plowed along the length of the island, killing 154 people. According to EM-DAT, the international disaster database, this was Jamaica’s deadliest hurricane (NHC lists the death toll at 259.)

Hurricane Gilbert of 1988. The mighty Category 3 storm also took a path over the length of the island with sustained winds of 125 winds, killing 49 and causing over $2 billion in damage—by far Jamaica’s most expensive hurricane on record.

Hurricane Sandy of 2012. Sandy hit the island as a Category 1 storm with 85 mph winds, killing two and causing $100 million in damage. About 70% of the residents of Jamaica lost power.

Hurricanes have a funny way of taking 11th-hour course changes that spare the island a direct hit. Category 5 Hurricane Allen took an odd wobble around the island. Category 4 Hurricane Dean of 2007 was headed straight for the island, but also wobbled just to the south, keeping the dangerous northern eyewall just south of Jamaica. Dean caused plenty of damage, though, bringing sustained Category 2 hurricane winds to the coast. Damage was estimated at $350 million, and 3 people died.

Perhaps the remarkable turn of an approaching hurricane was by Hurricane Ivan 2004, as it headed directly for the island with 145 mph Category 4 winds. Ivan took a sudden turn 35 miles from the island, traced out an exact outline of the island's coast 35 miles offshore, then resumed its previous track. In the Jamaica Observer, Custos of Kingston, Reverend Carmen Stewart, contended that prayer was responsible. "It has happened time and time again," Reverend Stewart said. "I know people have been praying and I don't see any other reason why it (the hurricane) would make such a drastic turn…God hears prayer." Ivan still did $760 million in damage, making it Jamaica’s second costliest hurricane on record.


Figure 6. Hurricane Ivan about to take its miraculous wobble around the island of Jamaica.

I’ll be back around noon today with a detailed look at the long-range forecast for Matthew.

Jeff Masters

Hurricane

Category 4 Hurricane Matthew Continues Northwest Toward Greater Antilles

By: Bob Henson , 12:00 AM GMT on October 03, 2016

Short-term ups and downs in Category 4 Hurricane Matthew continued on Sunday afternoon, as the storm drifted northwest toward an expected destructive encounter with Haiti, Jamaica, and Cuba. As of the 8 pm EDT Sunday advisory from the National Hurricane Center (NHC), Matthew’s top sustained winds were 145 mph, a slight increase from Sunday morning but still down from Matthew’s peak of 160 mph on Friday night. It’s typical for hurricanes as strong and mature as Matthew to experience minor fluctuations in intensity, sometimes several times in a day. A more substantial drop in intensity lasting a day or more can occur when a major hurricane’s eye shrinks so much that a secondary eyewall forms around it, eventually replacing the original eyewall. Thus far, Matthew has avoided a classic eyewall replacement cycle (ERC), although there are signs that a secondary feature may have developed Sunday without causing a significant intensity drop, as noted by wunderblogger Steve Gregory.

The puzzling batch of intense showers and thunderstorms (convection) located more than 100 miles east of Matthew continued through the day Sunday (see Figure 2). At times over the weekend, this feature has been larger and more intense than the convection around Matthew itself. NHC forecaster Richard Pasch referred to this as a “persistent, but inexplicable, cluster of deep convection” in NHC’s Sunday morning discussion of Matthew, adding that “the effect of this feature on Matthew's intensity evolution is unknown.”


Figure 1. MODIS satellite image of Matthew taken at 11:30 am EDT Sunday, October 2, 2016. At the time, Matthew was a Category 4 storm with 145 mph winds. Image credit: NASA.


Figure 2. Enhanced infrared image of Matthew as of 7:15 pm EDT Sunday, October 2, 2016. Image credit: NOAA/NESDIS.

It appears that Matthew has a very tight core of peak winds surrounded by much-less-strong winds. NOAA buoy 42058 has been located less than 50 miles from Matthew’s center for most of the day Sunday, yet its top sustained winds remained just below 60 mph through 5 pm EDT (see Figure 3]. NOAA reports that Matthew’s hurricane force winds extend out to 35 miles from Matthew’s center, with tropical storm force winds extending out up to 205 miles.


Figure 3. Top sustained winds observed at NOAA buoy 42058 over the past five days. Hurricane Matthew was passing less than 50 miles south of the buoy on Sunday afternoon, when sustained winds topped 45 knots (52 mph). Image credit: NOAA/National Buoy Data Center.

Serious threat for Jamaica, Cuba, and Haiti in next 48 hours
We will likely be talking about Matthew throughout the upcoming week, but the most immediate concern is for the western Greater Antilles. Now moving northwest at about 5 mph, Matthew is expected to arc north-northwest or north as it approaches the islands. Hurricane Warnings are in effect for Haiti, Jamaica, and the eastern Cuban provinces of Guantanamo, Santiago de Cuba, Holguin, Granma, and Las Tunas. The official NHC forecast, and the prevailing view from our top forecast models, is for Matthew to pass somewhere between eastern Jamaica and western Haiti on Monday night and to cross easternmost Cuba on Tuesday.

Matthew has the potential to strengthen en route to Jamaica and Haiti, especially if an upper-level outflow channel develops on its south side, as suggested by data on Sunday afternoon. Satellite imagery late Sunday afternoon showed a sharpening eye, and a region of very high oceanic heat content is located below Matthew’s expected path on Sunday night and Monday (see Figure 4 below). It is not out of the question that Matthew could regain Category 5 strength en route to Jamaica and Haiti, a truly frightening prospect. Assuming Matthew largely avoids the high mountains of Jamaica and Haiti, it is likely to hit eastern Cuba as one of the region’s most intense landfalling hurricanes in decades.


Figure 4. Tropical cyclone heat potential, an index of the amount of heat in the upper ocean, for the Caribbean as of October 1, 2016. Matthew’s position at 5 pm EDT October 2, 2016 is shown as the magenta hurricane symbol with a “4” in it. The hurricane is about to enter a region with high oceanic heat content, in excess of 100 kilojoules per square centimeter (orange colors), which may aid in intensification. Image credit: NOAA/AOML.

A rare northward-mover
A northward track into the Greater Antilles would be very rare for a hurricane as strong as Matthew. The only two analogs in the last few decades happen to be two other October storms: Sandy (2012) and Hazel (1954), neither of which reached the islands at Category 4 strength. As Matthew approaches, phenomenal rainfall rates can be expected, especially east of Matthew’s center, as southerly winds slam against south-facing mountains and hillsides. NHC is warning that rainfall could total as much as 40” in parts of southern Haiti and the southwest Dominican Republic, with widespread 5” - 15” totals expected elsewhere across Haiti, parts of Jamaica, and eastern Cuba.

It’s possible that Matthew will continue on its northwest course and turn north a bit later than models are predicting, which could bring the center over or close to eastern Jamaica rather than westernmost Haiti. This would greatly increase the potential impact on Jamaica, which has experienced only three direct hits from hurricanes of any strength in the past 65 years. In any event, Haiti--a nation where deforestation has made the landscape extremely vulnerable to flooding and landslides--is almost certain to experience Matthew’s extremely heavy rains, which are expected to extend well east of the center (especially if the batch of intense convection well east of Matthew retains its identity). Storm surge may also be a significant concern, perhaps as high as 7 to 11 feet on the far southeast coast of Cuba and 7 to 10 feet on the south coast of Haiti.


Figure 5. Projected total rainfall from Hurricane Matthew over Jamaica, Haiti, the Dominican Republic, and eastern Cuba as of Sunday afternoon, October 2. Image credit: Greg Carbin, NOAA/NWS Weather Prediction Center (WPC), @GCarbin.

The Bahamas and beyond
Little has changed in the prognosis for The Bahamas, which are likely to be hit hard by Matthew. A Hurricane Watch is now in effect for the southeastern Bahamas as well as the Turks and Caicos Islands. Matthew is expected to move north across the heart of The Bahamas from Wednesday into Thursday. Even if Matthew has weakened to a Category 3 hurricane by then, it could easily restrengthen, as wind shear should remain low through at least midweek (around 10 knots or less) mid-level relative humidity will remain high (70% or more), and sea-surface temperatures will be at near-record levels around 29-30°C (84-86°F). Ample deep oceanic heat throughout the Bahamas would help sustain Matthew even if it moved slowly and churned up deeper waters.

Beyond midweek, the outlook for Matthew remains fairly murky. The operational runs of the GFS and European models both take Matthew on a curving northeastward path that parallels the Southeast U.S. coast, drawing within 100 miles of the North Carolina coast by Saturday or Sunday before moving further offshore. The 12Z Sunday UKMET model--the other of our best three track models--is the outlier, bringing Matthew northwest from the Bahamas toward central Florida by next weekend. The 50 members of the Euro ensemble runs from Sunday (see Figure 6) continue to indicate the possibility of a landfall along the U.S. Mid-Atlantic or Northeast coast (or the south coast of Nova Scotia, Canada) a week or more from now, although most of the members keep Matthew offshore north of North Carolina. The 18Z GFS ensemble shows only a small minority of runs producing any U.S. landfall, mainly in the Outer Banks of NC.

For now, Matthew’s track beyond the Bahamas is still uncertain enough that coastal residents from Florida to Canada should be on the alert for possible impacts in a few days, especially given this hurricane’s strength and breadth. Note that long-range computer models may overestimate Matthew’s strength north of the Carolinas. Much cooler waters there would likely bring Matthew below major-hurricane strength in less than a day’s time, although it could still be a strong hurricane or post-tropical cyclone with huge surf as far north as Canada. Beach erosion may become a major issue later this week if Matthew takes its time moving northward off the East Coast.

Jeff Masters will be back on Monday morning with our next update on Matthew, as well as more background on the hurricane history of Jamaica, Cuba, and Haiti. Meteorologist Steve Gregory is making regular updates on Matthew.

Bob Henson


Figure 6. The 70 forecasts from the 12Z Sunday European (ECMWF) model ensemble (top) and 18Z Sunday GFS model ensemble (bottom). Image credit: Climate Forecast Applications Network (CFAN).

Hurricane

Matthew Stalls and Weakens, but Expected to Head North; Threat to U.S. Increases

By: Jeff Masters , 4:02 PM GMT on October 02, 2016

Hurricane Matthew is weaker as it meanders over the central Caribbean south of Haiti, but the mighty Category 4 hurricane is expected to move northwards later today and deliver a punishing blow to the islands of Hispaniola, Cuba, and Jamaica on Monday and Tuesday. An Air Force hurricane hunter aircraft made three passes through the eye of Matthew on Sunday morning, and found that Matthew’s winds had weakened to 140 mph and the central pressure had risen to 947 mb. This weakening may be partially due to the fact Matthew has essentially stalled, allowing the storm to bring up cooler waters from below. In addition, satellite loops on Sunday morning showed that Matthew had wrapped some dry air into its circulation, and this may have contributed to weakening of the storm. Moderate wind shear of 10 - 20 knots is affecting Matthew, and the storm is over warm ocean waters of 28.5°C (83°F) and has plenty of moisture to work with: 75 - 80% relative humidity at mid-levels of the atmosphere, as analyzed by the SHIPS model. The outer spiral bands of Matthew can be seen on Jamaican radar. Matthew will pass within 50 miles of NOAA buoy 42058 late this afternoon. At 9:50 am EDT Sunday, winds at the buoy were 47 mph, gusting to 56 mph, and seas were 23 feet.


Figure 1. Latest satellite image of Matthew.

Two-day track forecast for Matthew
Despite Matthew drifting a bit further westward than expected on Sunday morning, the models are very unified in their two-day track forecasts for Matthew. A large upper-level low pressure system over east-central U.S. will pull Matthew to the north through Tuesday, resulting in a landfall or a near-miss in southwest Haiti on Monday night, followed by a second landfall in eastern Cuba/northwest Haiti on Tuesday morning. Matthew will then continue northwards into the southeastern Bahamas on Tuesday afternoon. In their 11 am EDT Sunday Wind Probability Forecast, NHC gave highest odds of hurricane-force winds to Les Cayes in southwest Haiti (35%) and to Guantanamo Bay, Cuba (31%). Lower odds were given to Kingston, Jamaica (6%) and Port-Au-Prince, Haiti (6%).


Figure 2. View of Matthew’s eye as seen from the Air Force Hurricane Hunters on their Saturday morning flight. Image credit: ARWO Lt Froelich, Air Force hurricane hunters.

Two-day intensity forecast for Matthew
The latest SHIPS model forecast predicts that wind shear will steadily drop during the next two days, becoming very low, less than 5 knots, by Monday afternoon. At the same time, ocean temperatures will warm to 29° C (84°F) and the heat content of the ocean will increase, which ordinarily would argue for re-intensification of Matthew. However, this morning’s observation that dry air was getting wrapped into the circulation may mean that intensification will struggle to occur today and Monday. Furthermore, this morning’s hurricane hunter flight showed evidence of a secondary maximum in winds outside of the eyewall. This may be an indication that Matthew could undergo an eyewall replacement cycle (ERC), where the inner eyewall collapses and is replaced by a larger-diameter eye, with a new eyewall formed from an outer spiral band. This process usually causes a weakening to the storm’s top winds for a day or so. The down side of an ERC is that it spreads out the storm’s hurricane-force winds over a wider area, resulting in severe impacts over a wider area. Our top three intensity models—the HWRF, LGEM, and SHIPS models—were predicting on Sunday morning that Matthew would be at Category 3 or 4 strength at landfall on Monday evening. The SHIPS model gave Matthew a 0% chance of rapid intensification of 30 mph or more by Monday morning. All factors considered, a Category 3 hurricane at landfall Monday night is probably the most likely scenario. It is unknown what role, it any, the unusual blob of heavy thunderstorms that has persisted on Matthew’s east side might play in the future evolution of the storm. If this intense area of thunderstorms remains intact through Monday night, it could result in catastrophic rains for Haiti.


Figure 3. MODIS satellite image of Matthew taken at 2:30 pm EDT October 1, 2016. At the time, Matthew was a Category 4 storm with 150 mph winds. Image credit: NASA.

Longer-range intensity forecast for Matthew
Matthew’s anticipated landfall over Jamaica/Cuba/Haiti on Monday will weaken the storm, due to the high mountains it will interact with. However, it now appears that Matthew will have limited time over land, due to the storm’s expected track mostly over the water areas between Haiti and Cuba. While this is good news for those nations, this would be bad news for The Bahamas. Matthew inner core may be able to survive the land interaction, resulting in a much stronger storm in the Bahamas. The latest 12Z Sunday SHIPS model forecast predicts low to moderate wind shear, a very moist atmosphere and near-record warm ocean temperatures near 30°C (84°F) for Matthew later this week when it is over The Bahamas, so we can expect strengthening. Matthew is likely to be a major Category 3 or stronger hurricane for at least a portion of its trek through The Bahamas. As Matthew moves north of the Bahamas, waters will cool and the shear is likely to increase, resulting in some weakening late this week.





Figure 4. The 70 forecasts from the 00Z Sunday European (ECMWF) model ensemble (top) and GFS model ensemble (bottom) were beginning to converge on a solution for the track of Matthew that would put the storm very close the U.S. East Coast late this week. In their 11 am EDT Sunday Wind Probability Forecast, NHC gave highest 5-day odds of tropical storm-force winds in the U.S. to West Palm Beach and Fort Lauderdale, Florida (24%), with probabilities of 15 - 20% along most of the North Carolina coast.

Longer-range track forecast for Matthew: risk increases to U.S. East Coast
Over the past two days, our two best computer models have been trending towards a more westerly track for Matthew late this week, increasing the odds that Matthew will make a direct hit somewhere along the U.S. East Coast. Sunday’s 00Z European model and 06Z GFS model had Matthew coming very close to or making landfall in North Carolina 6 - 7 days from now. As one can see from the latest set of ensemble model runs (Figure 4), just about any location along the East Coast could potentially see a hurricane landfall this week. Since the hurricane is expected to be moving roughly parallel to the coast, a long stretch of the coast may receive strong winds and heavy rain from Matthew. We do have three decent models predicting a path for Matthew well away for the U.S. coast late in the week, though—the HWRF, Canadian and GFDL—so it is not yet a foregone conclusion that Matthew will impact the U.S. coast.

98L: A potential steering influence on Matthew?
An area of low pressure associated with a tropical wave that (designated Invest 98L by NHC on Sunday morning) is over the central tropical Atlantic several hundred miles east-northeast of the northern Lesser Antilles, and may alter the steering currents for Matthew. Over 50% of the members of the 00Z Sunday European ensemble forecasts predicted that this system would develop into a tropical depression or tropical storm as it heads northwest at about 15 mph early this week; the GFS model showed virtually no development. In their 8 am EDT Sunday Tropical Weather Outlook, NHC gave this system 2-day and 5-day odds of development of 20% and 30%, respectively. If this storm develops significantly, it may exert a steering influence on Matthew that could help pull it out to sea. Satellite loops on Sunday morning showed that 98L had a very limited amount of heavy thunderstorm activity that was poorly organized, thanks to dry air and high wind shear of 25 - 30 knots. The 12Z Sunday SHIPS model forecast predicted wind shear would rise even higher by Tuesday—in excess of 50 knots—so I doubt 98L will be able to develop.


Figure 5. Track forecasts from the four European model ensemble members [gray lines] that most closely match the operational run [red line] during the first 72 hours, starting at 00Z Sunday, October 2, 2016. The red line is a version of the 00Z Sunday operational model track that has been adjusted and calibrated using a proprietary technique to account for systemic model errors. Four out of five of these forecasts showed Matthew hitting the U.S. The high-probability cluster (grey lines) perform best at forecast times of five days and beyond. Image credit: Climate Forecast Applications Network (CFAN).

We’ll be back this afternoon with an update on Matthew. Meteorologist Steve Gregory has also been making regular updates on Matthew,

Jeff Masters

Hurricane

Hurricane Warnings for Haiti, Jamaica as Category 4 Matthew Restrengthens

By: Bob Henson , 10:55 PM GMT on October 01, 2016

Despite its unorthodox structure, Hurricane Matthew remains a formidable hurricane in the southern Caribbean Sea and an increasing threat to parts of Haiti, Jamaica, and Cuba. Matthew briefly attained Category 5 intensity late Friday, when its top sustained winds hit 160 mph--only 36 hours after Matthew was still a tropical storm. By early Saturday afternoon, Matthew’s peak winds had were at 140 mph, but they have since resurged to 150 mph as of the 5 pm EDT advisory from the National Hurricane Center. Matthew is now a high-end Category 4 hurricane.

As noted by Jeff Masters in our morning post, only a few hurricanes in the Atlantic have bolted from tropical storm to Cat 5 intensity in less than two days. Hurricane Wilma of 2005 and Hurricane Patricia of 2015 accomplished the feat in 24 hours; Hurricane Felix of 2007 did it in 30 hours; Hurricane Rita of 2005 and Hurricane Andrew of 1992 did it in 36 hours; and the Great Labor Day Hurricane of 1935 did so in 42 hours.


Figure 1. Enhanced infrared satellite image of Matthew at 2115Z (5:15 pm EDT) Saturday, October 1, 2016. Image credit: NOAA/NESDIS.

Menacing yet quirky
For such a powerful hurricane, Matthew has quite an odd structure. The most unusual feature is the persistent swath of intense showers and thunderstorms (convection) well east of its center, as evident in Figure 1 above. This feature has been in place for most of Matthew’s life as a tropical cyclone, and it may have played a role (yet to be determined) in its rapid intensification. For much of Saturday afternoon, this area of convection was actually larger and stronger than the convection around Matthew itself.

Hurricane Hunters on Saturday afternoon continued to find Matthew bearing a closed, fairly small eye that was just 8 nautical miles in diameter. Eyewall replacement cycles, which are fairly common with intense hurricanes, can produce a weakening for a day or so as the inner eye decays and the outer one gradually takes over. There was some evidence on Saturday that Matthew was trying to form a secondary eyewall further from its center, but this had not yet happened by late Saturday afternoon. Outside of rain-contaminated areas, the strongest near-surface winds detected by the Hurricane Hunters using the SFMR radiometer were around 130 knots (150 mph), and peak flight-level winds were around 135 knots (155 mph).

A dire situation for Haiti
After moving mainly west-southwest for the past day, Matthew carried out a very tight cyclonic (counterclockwise) loop on Saturday afternoon--most likely a prelude to its long-expected northward turn. At 5 pm EDT, Matthew was drifting northwest at just 3 mph. Assuming Matthew’s northward motion picks up as expected on Saturday night, we should soon have a better sense of which parts of the Greater Antilles will be most at risk from Matthew. The most immediate threat is to Jamaica and Haiti, which Matthew is expected to be approaching by early Monday. It is very rare for hurricanes this strong to strike either nation from the south, an angle of approach that would maximize the storm-surge potential along south-facing coasts.

Extremely heavy rains will occur around Matthew, and in particular on its right-hand (eastern flank), where fierce southerly winds will slam into south-facing mountains and hillsides. Rainfall east of Matthew’s center could be even more widespread and heavier than with other hurricanes of this size and strength because of the massive slug of convection and moisture well east of its center, as discussed above.


Figure 2. All hurricanes that are known to have passed through the shaded circle with at least Category 3 intensity. The only major hurricanes that took a south-to-north track similar to the forecast for Matthew were Sandy (2012), which briefly attained Category 3 strength before striking eastern Cuba, and Hazel (1954), which struck southwest Haiti as a Category 3 storm. Up to 1000 Haitians died as a result of Hazel, and the nation’s economy was hobbled for years afterward. NOAA’s hurricane data base extends back to the mid-1800s. Both Hazel and Sandy were October hurricanes that went on to affect much of the U.S. East Coast. Image credit: NOAA


The 12Z Saturday runs of our best track models--the GFS, European, and UKMET models--all bring Matthew between Jamaica and Haiti, as reflected in the latest official NHC track. This path would reduce the risk for Jamaica but heighten it for Haiti, where deforestation greatly enhances the potential for devastating floods and landslides. I’m especially concerned about the mountainous Tiburon Peninsula of southwest Haiti, which is most likely to experience the strongest winds and heaviest rains. NHC warns that rainfall could total 15” to 25” in southern Haiti, with localized amounts as high as 40” possible. Given Haiti’s extreme poverty (the nation is still recovering from its catastrophic earthquake of 2010), Matthew could produce a truly devastating blow. Heavy rains of 10” - 20” will also affect parts of eastern Jamaica and the Dominican Republic. A Hurricane Warning is now in effect for all of Jamaica and for southern Haiti, with a Hurricane Watch for northern Haiti.


Figure 3. NHC track forecast for Hurricane Matthew as of 5 pm EDT Saturday, October 1, 2016.

If Matthew threads the needle between eastern Jamaica and western Haiti, it will largely avoid disruption from mountains that exceed 6000 feet in height in both areas. This would allow Matthew to retain most or all of its strength as it approaches easternmost Cuba late Monday. Most of Cuba should experience the less-intense west side of Matthew, but a Hurricane Watch is in effect from Camaguey to Guantanamo province. Matthew could make landfall very close to Guantanamo Bay, where some 700 U.S. military personnel and family members were preparing on Saturday night for evacuation to Pensacola, Florida. Although Sandy was barely a Category 3 when it struck just west of Santiago de Cuba in 2012 from the south, it was the strongest hurricane to hit eastern Cuba in half a century, destroying tens of thousands of homes and taking at least 11 lives.

Longer-term outlook for Matthew
Models have converged somewhat on Matthew’s future track in the western Atlantic, but there remains plenty of uncertainty on critical points. Chances are that Matthew will be at least partially disrupted from its trek through the Greater Antilles. However, our top intensity models agree that it will likely restrengthen once it reaches The Bahamas. Conditions will remain very supportive for Matthew over The Bahamas on Tuesday and Wednesday, with very low wind shear, record-warm sea surface temperatures, and a moist atmosphere to work with. Residents of The Bahamas would be well advised to start making preparations, as hurricane watches could be required as soon as Sunday. Right now it appears the eastern Bahamas are most at risk of being affected by Matthew’s more dangerous east side, but very heavy rains and high winds could overspread many of the islands on Tuesday or early Wednesday.


Figure 4. The 70 forecasts from the 18Z Saturday GFS model ensemble (top) and 12Z European (ECMWF) model ensemble (bottom) continued to show a wide variety of solutions for the track of Matthew. The two models have grown closer together in their solutions compared to Friday. Both models indicated that Matthew could remain a major hurricane well into the northwest Atlantic, although model skill at intensity prediction drops markedly over time. Image credit: Climate Forecast Applications Network (CFAN).

Big questions on Matthew’s track later next week
Models agree very closely on Matthew’s general track into the Bahamas, but they strongly suggest that Matthew could slow down or angle toward the northwest by midweek as steering currents weaken. The next step in the Matthew saga will then be determined by two main influences. One is an area of low pressure about 600 miles east of the Leeward Islands, moving slowly west-northwest. NHC gives this area only a 20% chance of developing into at least a tropical depression by Thursday. Regardless of its status, it could give Matthew a pathway to move northeast and out to sea from the Bahamas. The other influence on Matthew’s long-term future is a strong mid-latitude upper trough that will be plowing toward the eastern U.S. by later next week. Models generally agree that the upper-level trough will pick up Matthew and cart it north and northeastward, but there is crucial disagreement on how far west its track might extend. Among the 20 members of the 18Z Saturday ensemble run of the GFS and the 50 members of the 12Z Saturday European (ECMWF) ensemble, a number of members haul Matthew along the U.S. East Coast at various points, with several tracks moving well inland. A number of other GFS and ECMWF ensemble members keep Matthew just off the East Coast without any direct landfall.


Figure 5. Track forecasts from the five European model ensemble members [gray lines] that most closely match the operational run [red line] during the first 72 hours, starting at 12Z Saturday, October 1, 2016. The red line is a version of the 12Z Saturday operational model track that has been adjusted and calibrated using a proprietary technique to account for systemic model errors. Image credit: Climate Forecast Applications Network (CFAN).


We cannot yet rule out the possibility of Matthew moving close enough to the Florida coast to produce major impacts. Among the five members of the “high-probability” Euro ensemble from 12Z Saturday (see Figure 5), two members take Matthew sharply westward across South Florida by next weekend and up Florida’s West Coast. The 12Z Saturday UKMET model also brings Matthew to the vicinity of South Florida by Thursday. Considering that the Euro, GFS, and UKMET are our top three track models, it’s clear there is still plenty of uncertainty in how Matthew may affect the U.S. later next week.

The bottom line:

Matthew poses a dire threat to the western Greater Antilles, especially Haiti. All residents should prepare as best they can for what could be the strongest northward-moving hurricane in living memory across the region.

The Bahamas may experience prolonged impacts from Matthew next week. The official NHC forecast brings Matthew through the islands as a Category 3, and it could be stronger. The duration of Matthew’s impact, and its exact track, are increasingly uncertain beyond Tuesday.

Models continue to indicate the potential for Matthew to affect any part of the U.S. East Coast from Florida to Maine later next week into the weekend. The bulk of model solutions keep Matthew just offshore, but a significant minority bring Matthew onshore, possibly as a strong hurricane. It is too soon to know exactly how the mid-latitude steering currents will evolve, so the range of potential landfall locations remains very wide.

Jeff Masters will be back with our next update by late Sunday morning. Wunderblogger Steve Gregory posted a Saturday afternoon update on Matthew, CAT 4 HURRICANE MATTHEW: THREAT TO US CONTINUES.

Bob Henson

Hurricane

Hurricane Matthew Now a Category 4 After Topping Out at Category 5 Strength

By: Jeff Masters , 3:47 PM GMT on October 01, 2016

Hurricane Matthew weakened slightly on Saturday morning to a still-ferocious Category 4 storm after topping out Friday night as the Atlantic’s first Category 5 storm in nine years. Matthew put on a spectacular and wholly unexpected display of rapid intensification on Friday, strengthening from a tropical storm to a Category 5 hurricane in a remarkably short period of time—just 36 hours. It’s a good thing this unexpected rapid intensification burst did not occur as the hurricane was approaching landfall in a heavily populated area, with a population unprepared for a catastrophic hurricane strike. There have been other storms that have intensified even more rapidly from tropical storm strength to Category 5 than Matthew, though. For comparison, Hurricane Wilma of 2005 and Hurricane Patricia of 2015 accomplished the feat in 24 hours; Hurricane Felix of 2007 did it in 30 hours; Hurricane Rita of 2005 and Hurricane Andrew of 1992 did it in 36 hours; and the Great Labor Day Hurricane of 1935 did so in 42 hours.


Figure 1. Latest satellite image of Matthew.

What made Matthew’s rapid intensification so surprising was that it occurred despite the presence of strong upper-level winds out of the southwest that created high wind shear of 20 knots. The NHC official forecast and the intensity models failed to predict Matthew’s rapid intensification—though the SHIPS model did give a 12% chance that we would see intensification into a Category 5 hurricane. We don’t have much data over ocean areas to be able to diagnose the detailed flow pattern around the core of a hurricane, and it is likely the shear was actually much lower near Matthew’s center, which allowed the storm to organize more quickly than our models anticipated. The rapid intensification process was also aided by the fact Matthew was moving into a moister atmosphere—the upper-level winds hitting Matthew from the southwest were advecting in air that had high humidity, which did not disrupt the storm like low humidity air would have done.

Another surprise regarding Matthew’s rapid intensification was that the central pressure that supported the Category 5 winds of the storm was relatively high—941 mb. Category 5 storms usually have pressures quite a bit lower. According to meteorologist Sam Lillo, Matthew had the third highest pressure observed in an Atlantic category 5 hurricane. For comparison, Hurricane Andrew had a 933 mb central pressure when it was a Category 5, and Hurricane Felix had a 935 mb central pressure when it achieved Category 5 status. Matthew’s strongest winds have been focused over a relatively narrow region near the core of the storm, which has allowed it to have extreme winds without an extremely low pressure.


Figure 2. Radar view of Matthew’s eye as seen from the Air Force Hurricane Hunters on their Friday night flight that found Category 5 winds. Image credit: Pilot Maj Roundtree, Air Force hurricane hunters.

Current observations of Matthew
An Air Force hurricane hunter aircraft made two passes through the eye of Matthew on Saturday morning, and found that Matthew’s central pressure had risen to 947 mb during their second pass at 8:48 am EDT. Flight-level winds at 10,000 feet hit 135 mph and surface winds measured by their stepped frequency microwave radiometer (SFMR) were as high as 124 mph, which would make Matthew a borderline Category 3/Category 4 storm. Infrared satellite loops on Saturday morning showed that Matthew had weakened some, with the eye less distinct and the cloud tops of the eyewall thunderstorms warmer. At upper levels, high cirrus clouds streaming to the north of Matthew showed the continued presence of a powerful outflow channel, which was helping ventilate the storm and allowing it to fight off the high wind shear of 20 - 30 knots affecting it. Aiding development today were warm ocean waters of 28.5°C (83°F) and 70 - 75% relative humidity at mid-levels of the atmosphere, as analyzed by the SHIPS model. Heavy rains from Matthew were affecting the coast of South America near the Colombia/Venezuela border, as seen on Venezuela radar.

Two-day intensity forecast for Matthew
Matthew is about to turn the corner around the Azores-Bermuda High, and will head north-northwest on Sunday towards Jamaica and southwestern Haiti. The latest SHIPS model forecast predicts that wind shear will steadily drop during the next two days, reaching the low range, less than 10 knots, by Sunday morning. At the same time, ocean temperatures will warm to 29° C (84°F) and the heat content of the ocean will increase, which ordinarily would argue for re-intensification of Matthew. However, this morning’s hurricane hunter flight found that the eye of Matthew had shrunk to eight miles in diameter, and the aircraft showed evidence of a secondary maximum in winds outside of the eyewall. This may be an indication that Matthew is about to undergo an eyewall replacement cycle (ERC), where the inner eyewall collapses and is replaced by a larger-diameter eye, with a new eyewall formed from an outer spiral band. This process usually causes a weakening to the storm’s top winds for a day or so. It is possible that we will see little net change in Matthew’s strength before the storm makes its closest pass to Jamaica and southwestern Haiti on Monday--perhaps a decrease in peak winds today into Sunday, with some rebound possible by Monday if an eyewall replacement cycle is completed in time. The down side of an ERC is that is spreads out the storm’s hurricane-force winds over a wider area, resulting in severe impacts over a wider area.

Our top three intensity models—the HWRF, LGEM, and SHIPS models—were predicting on Saturday morning that Matthew would have top sustained winds of 120 - 130 mph on Monday. The SHIPS model gave Matthew a 0% of rapid intensification of 30 mph or more by Sunday morning. In their 11 am EDT Saturday Wind Probability Forecast, NHC gave highest odds of hurricane-force winds to Guantanamo Bay, Cuba (29%) and Kingston, Jamaica (25%.)

Two-day track forecast for Matthew
Differences continue in the two-day model track forecasts for Matthew, though the differences between our two best models—the GFS and European model—have shrunk since Friday’s runs. This may be because of dropsonde data taken by the NOAA jet on Friday evening, which was ingested into the 00Z Saturday runs of the models. A large upper-level low pressure system over east-central U.S. will begin pulling Matthew sharply to the north-northwest by Sunday, but the exact timing of the turn is in doubt. An later turn is being predicted by the 06Z Saturday run of the GFS model, with the storm passing between Jamaica and southwestern Haiti on Monday afternoon, and hitting eastern Cuba early Tuesday morning. The 00Z Saturday European model run has Matthew heading northwards a little sooner, with a landfall in southwest Haiti on Monday afternoon, and then in northwest Haiti early Tuesday morning.

Longer-range intensity forecast for Matthew
Matthew’s anticipated landfall over Jamaica/Cuba/Haiti on Monday will weaken the storm, due to the high mountains it will interact with. This process may completely disrupt the inner core of Matthew, reducing the storm to Category 1 or 2 strength for several days, as it traverses The Bahamas. The storm may be able to re-intensify to major hurricane status in 2 - 3 days, though, over the exceptionally warm waters surrounding The Bahamas. The LGEM and HWRF models predict a 25 - 30 mph increase in Matthew’s winds between Tuesday and Thursday. However, our ability to make intensity forecasts this far in advance is limited.





Figure 3. The 70 forecasts from the 00Z Saturday European (ECMWF) model ensemble (top) and GFS model ensemble (bottom) continued to show a wide variety of solutions for the track of Matthew. The two models have grown closer together in their solutions compared to Friday, but the GFS model showed a much greater threat to the U.S. In their 11 am EDT Saturday Wind Probability Forecast, NHC gave highest odds of tropical storm-force winds in the U.S. to West Palm Beach, Florida (24%).

Longer-range track forecast for Matthew: the U.S. East Coast at risk
Matthew will likely to punish a large portion of The Bahamas on Wednesday and Thursday. The threat to the U.S. East Coast remains highly uncertain, though, as one can see from the latest set of ensemble model runs (Figure 3). Our two best models, the GFS and European, differ considerably in their handling of the upper-level low pressure system that will be guiding Matthew northwards next week. The European model prefers a track for Matthew out to sea, while the GFS model keeps Matthew perilously close to the U.S. coast. Bolstering the GFS model’s case is the latest 00Z Saturday run of the UKMET model, which brings Matthew to a landfall in South Carolina in seven days. However, the Canadian, HWRF, and GFDL models show a track for Matthew more like the European model’s track, out to sea, so it’s anybody’s guess where Matthew will be five days from now. One wild card: an area of low pressure associated with a tropical wave has formed over the central tropical Atlantic several hundred miles east of the Lesser Antilles, and may alter the steering currents for Matthew. About 50% of the members of the European ensemble predicted that this system would develop into a tropical depression or tropical storm as it heads northwest next week; the GFS model showed virtually no development. In their 8 am EDT Saturday Tropical Weather Outlook, NHC gave this system 2-day and 5-day odds of development of 10% and 20%, respectively. If this storm develops significantly, it may exert a steering influence on Matthew that could help pull it out to sea.


Figure 4. Track forecasts from the five European model ensemble members [gray lines] that most closely match the operational run [red line] during the first 72 hours, starting at 00Z Saturday, October 1, 2016. The red line is a version of the 00Z Saturday operational model track that has been adjusted and calibrated using a proprietary technique to account for systemic model errors. Only one of these forecasts showed Matthew hitting the U.S. Image credit: Climate Forecast Applications Network (CFAN).

Bob will be back this afternoon with an update on Matthew. Wunderblogger Steve Gregory posted a Saturday afternoon update on Matthew, CAT 4 HURRICANE MATTHEW: THREAT TO US CONTINUES.

Jeff Masters

Hurricane

Matthew Becomes the Atlantic's First Category 5 Hurricane in Nine Years

By: Bob Henson and Jeff Masters , 4:01 AM GMT on October 01, 2016

Extending a jaw-dropping stretch of rapid intensification, Hurricane Matthew has become the Atlantic's first Category 5 hurricane since Felix in 2007. Matthew's top sustained winds were set at 160 mph in the 11 pm EDT update from the National Hurricane Center. The upgrade was based on radiometer-measured near-surface winds as high as 143 knots (165 mph] gathered in a Hurricane Hunter flight on Friday evening. Now located less than 100 miles north of the Colombian coastline, Matthew continues to move just south of due west at about 7 mph.


Figure 1. Enhanced infrared satellite image for Matthew as of 11:15 pm EDT Friday, September 30, 2016. Image credit: NOAA/NESDIS.

Matthew is the planet’s fifth Category 5 storm of the year. The others were Tropical Cyclone Winston, which devastated Fiji in the Southwest Pacific in February; Tropical Cyclone Fantala from May, in the Southwest Indian Ocean; Super Typhoon Nepartak from July, in the Northwest Pacific Ocean; and Super Typhoon Meranti in the Northwest Pacific, which struck the small Philippine island of Itbayat Island while at peak strength in September. Super Typhoon Meranti was the most intense Category 5 of the year, with sustained winds of 190 mph and a central pressure of 890 mb. The globe averages between 4 and 5 Category 5 storms per year.

In records going back to 1924, only five Atlantic hurricanes are on record as having Category 5 strength this late in the year--all of them in the Caribbean, the region where sufficiently warm waters and favorable atmospheric conditions are most likely to occur this late in the season. Shown with their date spans at Category 5 strength, these are:

"Cuba": October 19, 1924
"Cuba": November 5-8, 1932
Hattie: October 30-31, 1961
Mitch: October 26-28, 1998
Wilma: October 19, 2005

More background from our earlier post
There's been little change so far in the outlook for Matthew, although we'll be watching tonight's 00Z Saturday model runs closely to see what comes next. Below is more context on Matthew's past, present, and future, mostly brought over from our post earlier this afternoon. We will be posting regular updates through the weekend, typically between 10 am and noon EDT and between 6 and 8 pm EDT. For those new to our blog, the comments section is packed with valuable insights from our many members, including meteorologists as well as dedicated laypeople.

Bob Henson and Jeff Masters

How did Matthew get so strong so quickly?
Vertical wind shear of up to 20 knots has plagued Matthew for most of the last two days, yet the storm has not only maintained its structure but grown at a ferocious rate. Dissertations may be written on how this happened! Working in Matthew’s favor has been a steadily moistening atmosphere along its westward path, which means that the shearing winds didn’t push too much dry air into Matthew. Once it developed a central core, Matthew was able to fend off the wind shear much more effectively. In addition, water temperatures are unusually warm throughout the Caribbean (and the entire western North Atlantic), with an area of high oceanic heat content directly beneath Matthew’s path. Such deep oceanic heat allows a storm to strengthen without churning up cooler waters from below that could blunt the intensification.

Matthew’s ascent highlights the nagging challenge of predicting hurricane intensity. NHC statistics for the past few years show a steady improvement in track forecasts and much more erratic progress in intensity forecasts (see Figure 2 below). The typical 48-hour track error has been cut in half since the late 1990s, dropping from around 150 nautical miles (170 miles) to around 75 nautical miles today. Meanwhile, the 48-hour intensity forecast error has averaged about 12 knots (15 mph) in the last several years, which is not much better than the 15-knot errors that were typical in the mid-to-late 1990s. Much of that error is the result of just a few rapidly intensifying storms, such as Matthew.


Figure 2. Trends in track and intensity forecasts from the National Hurricane Center for Atlantic hurricanes through 2015. Units are nautical miles (left) and knots (right); add 15% to obtain miles and miles per hour. Image credit: NHC.

Although Matthew strengthened far more quickly than projected in the official outlook--and expected by most observers--there were signs that rapid intensification was possible, as we discussed on Wednesday afternoon. The 18Z (2:00 pm) Wednesday run of the SHIPS statistical model included a 44% chance that Matthew’s strength would increase by 55 knots in 48 hours. In fact, this is exactly how quickly Matthew intensified: from 50 knots (60 mph) at 18Z Wednesday to 105 knots (120 mph) at 2:00 pm Friday. SHIPS is only one tool used by forecasters to assess potential intensity change. Dynamical forecast models were generally less gung-ho on rapid intensification on Wednesday, and even subsequent SHIPS runs pulled back a bit.


Figure 3. Radar image of Hurricane Matthew as seen from NOAA’s P-3 Orion hurricane hunter aircraft at 1:40 pm EDT September 30, 2016. At the time, Matthew was a rapidly intensifying Category 3 hurricane with 120 mph winds. Image credit: NOAA/AOML/HRD, via tropicalatlantic.com

Figure 4. Visible satellite image of Matthew (1-kilometer resolution) at 1945Z (3:45 pm EDT) Friday, September 30, 2016. The Colombian and Venezuelan coastlines are outlined in yellow. Image credit: CSU/RAMMB/CIRA.


Matthew poses a major threat to Jamaica
Matthew is moving just south of due west at 9 mph. Its location about 75 miles north of Punta Gallinas, Colombia, puts it about as close to South America as any major hurricane is known to have gotten (even about 50 miles closer than 2004’s Hurricane Ivan).

Although Matthew’s westward track will keep it offshore of Colombia and Venezuela, a Tropical Storm Warning is in effect for the Colombian coast from the Venezuelan border west to Riohacha. The Columbian coast will remain on the less-intense left-hand side of Matthew, reducing the odds of hurricane-force winds and limiting the heaviest rains. Riohacha’s Almirante Padilla reported sustained winds of less than 20 mph on Friday afternoon.

Models agree strongly that Matthew will begin taking a fairly sharp right turn on Saturday, heading north-northwest through the central Caribbean. Conditions should be very favorable for maintaining Matthew's strength at this point. Wind shear is projected to drop dramatically (perhaps below 10 knots by Sunday), the deep atmosphere will moisten further (close to 80% relative humidity), and Matthew will be passing over waters with extremely high oceanic heat content. Now that Matthew is a Category 5 hurricane, we can expect ups and downs in its strength from day to day as internal processes such as eyewall replacement cycles kick in.

The threat to the Greater Antilles from Matthew is becoming increasingly worrisome. The most immediate concern is for Jamaica, where a Hurricane Watch has been posted. The latest NHC outlook brings Matthew over the eastern tip of Jamaica on Monday afternoon. A westward shift of just 50 miles--well within the range of uncertainty at this point--would put the city of Kingston in Matthew’s dangerous right-hand side. A major hurricane striking Jamaica from the south would be a virtually unprecented event. Figure 5 shows the tracks of all major hurricanes passing over or very near Jamaica since 1851. All of the prior events involved storms tracking on a classic west-northwest path except for an unnamed 1912 hurricane that crossed the northwest tip of the island on a northeast path, then made a 180-degree turn. Among all hurricanes since 1851 (not shown), the only one to have crossed Jamaica on a primarily northward track during the last 80 years is Sandy (2012), which struck eastern Jamaica at Category 2 strength. Sandy caused an estimated $100 million in damage in Jamaica and knocked out power to most of the island. Matthew could be much stronger than Sandy, and a northward-oriented path through central Jamaica could bring a severe storm surge into the highly vulnerable Kingston area.

Next in Matthew’s sights on the NHC-predicted track would be Cuba, whose excellent history of hurricane awareness and preparation would likely reduce potential impacts. Matthew may also be weakened by any direct passage over mountainous Jamaica, although it could easily strike Cuba as a major hurricane.

A Tropical Storm Watch is in effect for the western coast of Haiti from Port-au-Prince to the Dominican Republic border. If Matthew were to trend eastward rather than westward, the risk to western Haiti would rise dramatically. Model guidance has trended gradually west over time, which gives some hope that Haiti will escape the worst of Matthew. Still recovering from the devastation of the 2010 earthquake, and plagued with deforestation and poverty, Haiti would be highly vulnerable to the impacts of a major hurricane.


Figure 5. Tracks of all major hurricanes passing within the shaded circle encompassing Jamaica during the period from 1851 to 2015. Each of these was moving from right to left (east to west), except for the 1912 hurricane, which moved east-northeast and then backtracked toward the west-southwest as it weakened. Image credit: NOAA.


Figure 6. WU depiction of National Hurricane Center track and intensity forecast for Matthew as of 11:00 pm EDT Friday, September 30, 2016.

Long-term outlook for Matthew
If anything, the prospects for Matthew later next week have become more uncertain over time. Models continue to take Matthew north through The Bahamas, but then we have major divergence among our top models. As just one example, the 12Z Friday operational run of the GFS model pulls Matthew almost due north, slamming it into eastern Maine as a significant hurricane or very intense post-tropical storm by next weekend. In stark contrast, the 12Z run of the ECMWF model strands Matthew in the Bahamas, where it lingers through next weekend and into the following week as a major hurricane. The 12Z run of the UKMET, our other top track model, also stalls Matthew in the Bahamas, then angles it northwest toward the Southeast U.S. coast.

Why such profound disagreement? The simplest explanation is that track errors increase markedly over time, and there is little skill beyond about 5-7 days. In this case, there is a great deal of uncertainty over how the mid-latitude steering features over the United States and the western Atlantic will evolve over the next week. NOAA’s Gulfstream-IV jet has been flying regular missions to sample the environment around Matthew, which has likely led to improvements in the short-term track forecasts. The problem is that the upper-level trough that will be a key influence on Matthew’s track next week is still thousands of miles away--moving through the northeast Pacific, where observations are scarce. It is far too soon to know with confidence how the upper-level features will evolve next week, so we need to keep our expectations very modest for confidence in any East Coast forecast.

The bottom line:

--Matthew poses a very serious risk to the western Greater Antilles early next week.

--A trek over the mountainous terrain of Jamaica, Cuba, and/or Haiti would dramatically weaken Matthew. At least some restrengthening would be possible over the Bahamas.

--Matthew could affect any part of the U.S. East Coast from Florida to Maine at some point from the middle of next week into the weekend.

--Long-range forecasts will vary, perhaps several times each day. Because the key features that will steer Matthew are very uncertain at this point, any given model shift may not mean much until the evolution of these features becomes better defined, which could take several days.

Bob Henson


Figure 7. The 70 forecasts from the 12Z Friday European (ECMWF) model ensemble (left) and 18Z GFS model ensemble (right) continued to show a wide variety of solutions for the track of Matthew that pose various threats along the U.S. East Coast. (The tracks from the ECMWF that previously targeted the Gulf Coast have almost completely disappeared.) Image credit: Climate Forecast Applications Network (CFAN).

Hurricane


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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About

Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather