Category 6™

97L Sweeps Toward Lesser Antilles; Nida Approaching Philippines

By: Bob Henson , 10:54 PM GMT on July 30, 2016

As it hustles westward at 25-30 mph in the western tropical Atlantic, Invest 97L is continuing to organize. In its tropical weather outlook issued at 2:00 PM EDT Saturday, the National Hurricane Center placed the tropical wave about 550 miles east of the Lesser Antilles. The wave’s envelope of shower and thunderstorm activity (convection) increased notably on Saturday, with strong convection now extending across the Leeward Islands. Upper-level wind shear is strong to 97L’s north, but light to moderate (5 - 15 knots) over the core of the wave. In addition, 97L is moving over sea-surface temperatures (SSTs) of about 28°C (82°F), which is about 0.5°C above average and more than warm enough to favor development.

Despite these supportive factors, 97L is fighting some unfavorable elements. The system is more organized aloft than at the surface, with healthy upper-level divergence but no sign yet of a closed surface circulation (see Figure 2). In addition, it’s typically more difficult for waves moving as quickly as 97L to organize. As it plows westward, 97L will be moving toward a region of moderate to strong shear (20 - 30 knots) associated with a weak upper-level trough across the central Caribbean, although it appears the shear will relax considerably as the trough shifts westward. [Update: The 0Z Sunday run of the SHIPS model keeps wind shear for 97L below 10 knots through Wednesday.] There is also a modest amount of dry air from the Sarahan Air Layer extending across the region of 97L’s track. Both the ECMWF and GFS model runs from 12Z Saturday keep 97L as an open wave during its trek across the eastern Caribbean. Ensemble guidance suggests only a modest chance of 97L traversing the eastern Caribbean as a tropical depression, based on the 12Z Saturday runs of the GFS and ECMWF ensemble models. Ensemble forecasts are produced by taking the operational high-resolution version of the model and running it at lower resolution with slight perturbations to the initial conditions in order to generate a range of possible outcomes. Only a small fraction of ensemble members develop 97L over the next several days.


Figure 1. Infrared satellite image of Invest 97L in the western tropical Atlantic as of 2115Z (5:15 pm EDT) Saturday, July 30, 2016. Image credit: NOAA/NESDIS.

In its 2 PM outlook, NHC gave 97L a 30% chance of developing into a tropical depression by Monday. Given the system’s vigorous growth today, and the mix of positives and negatives noted above, I’ll lay 50% odds on the chance that 97L will be at least a tropical depression by Monday, though it would probably struggle to maintain that status over the next several days. Squally weather, with bursts of heavy rain and wind gusts of 30-40 mph, can be expected through Sunday across the Lesser Antilles and beyond as 97L whips through the area. A flash flood watch is in effect for Sunday across Puerto Rico and the Virgin Islands, with rains of 2-4” predicted and higher amounts possible.

The long-range outlook for 97L
If 97L manages to organize even modestly over the next 2-3 days, we’ll have to keep a close eye on it. Model trends have been to route 97L on a fairly direct west to west-northwest path across the northern Caribbean, perhaps missing Hispaniola and most likely staying south of Cuba. Assuming that 97L forms a center of circulation and avoids major interaction with the high terrain of these islands, it will be well situated to strengthen--perhaps significantly--by late next week. A convectively coupled Kelvin wave (CCKW) has tended to suppress upward motion across the tropical Atlantic this week, but by later next week 97L may enter a region where the CCKW pattern favors upward motion. In addition, SSTs across the northwest Caribbean are very warm (29°C or 84°F, about 1°C above average), and there is a near-record amount of heat in the upper ocean to support rapid development if atmospheric conditions turn out to be favorable.

The SHIPS statistical intensity model is increasingly bullish on 97L, with the 18Z Saturday run of SHIPS bringing 97L to a Category 3 strength by Thursday. The last several runs of the HWRF model, which has shown increasing skill over the last several years, also project 97L to reach hurricane strength in the Caribbean (although the 12Z Saturday run appears to have had initialization problems, as noted by WU member Levi Cowan). The 12Z Saturday runs of the GFS and ECMWF models, two of the other more-trustworthy dynamical models, suggest that 97L could begin organizing just before crossing the Yucatan Peninsula and then develop further in the Bay of Campeche by late next week. It is far too soon to assign any confidence to model projections in this time range, but the available guidance indicates that 97L is well worth watching. NHC gives 97L a 60% chance of development by Thursday, August 4.


Figure 2. Surface winds across the tropical Atlantic at 1800Z (2:00 pm EDT) Saturday, July 30, 2016. The surface circulation is less organized with Invest 97L (far left) with Invest 96L (right), as 96L features weaker winds overall but a more evident surface circulation. Image credit: earth.nullschool.net.


Figure 3. Infrared satellite image of Invest 96L in the eastern tropical Atlantic as of 2045 (5:15 pm EDT) Saturday, July 30, 2016. Image credit: NOAA/NESDIS.

96L is struggling
Although the circulation of Invest 96L in the eastern tropical Atlantic is more organized than that of 97L, there isn’t much meat on the bones. There was only scattered convection on Saturday around the core of 96L, which is located about 400 miles southwest of the Cape Verdes. Although SSTs of around 28°C are more than adequate for development, wind shear of 5-10 knots along 96L’s path will increase to moderate levels (15 - 25 knots) over the next 2-4 days, and there is a large region of Sarahan dust lying ahead of 96L. Only a small fraction of ECMWF and GFS ensemble members have 96L as a depression in the central Atlantic by the middle of next week, and NHC gives 96L a 20% chance of development through Thursday.

Eighth Northeast Pacific storm of the month?
We may yet set a record for the largest number of named storms on record to develop in the eastern Pacific Ocean in the month of July. Invest 91E was gathering its forces on Saturday about 800 miles southwest of the southern tip of the Baja California peninsula, moving west-northwest at 10-15 mph. On this track, 91E should steer well clear of any major land areas, but in its tropical weather outlook issued at 2 PM EDT Saturday, NHC gave the system a 70% chance of development by Monday and a 90% chance by Thursday. If it manages to become Tropical Storm Howard before Monday, it will be the record-breaking eighth named storm this month. In the longer range, it’s possible that 91E will take a leftward-arcing path that would carry it or its remnants toward the Hawaiian Islands in about a week’s time.


Figure 4. Tropical Storm Nida as of 2130Z (5:30 pm EDT) Saturday, July 30, 2016. Image credit: RAMMB/CSU/NOAA.

Nida on track to reach the southeast China coast
Tropical Storm Nida will be sweeping across the northernmost part of the Philippines island of Luzon late Sunday. Nida’s surface winds were 50 mph as of 1800Z (2:00 pm EDT) Saturday, according to the Joint Typhoon Warning Center (JTWC). Nida has little time to strengthen before it slides across Luzon, and most areas will be on its weaker south side, but a large swath of convection will bring very heavy rains to the northern half of the island. Impacts could be considerably greater when Nida reaches the southeast China coast early next week. Models are in strong agreement on a straightforward west-northwest track for Nida, and very warm SSTs combined with only modest upper-level shear (10-20 knots) are quite favorable for strengthening. Model consensus brings Nida very close to Hong Kong by early Tuesday local time. Although many typhoons pass close enough to Hong Kong to bring high winds and heavy rain, a direct strike from a typhoon is less common. The 2100Z Saturday outlook from JTWC projects that Nida will pass directly over Hong Kong as a minimal typhoon.

We’ll be back with an update by Monday morning, or sooner if 97L develops into a tropical depression.

Bob Henson


Figure 5. WU tracking map showing the track and strength of Tropical Storm Nida projected by the Joint Typhoon Warning Center on Saturday, July 29, 2016.

Hurricane

The Big Thompson Disaster: Reverberations of a Flash Flood, 40 Years Later

By: Bob Henson , 10:20 PM GMT on July 29, 2016

What began as a celebratory Saturday in the mountains ended in tragedy 40 years ago this weekend, when a catastrophic flash flood ripped through the narrow Big Thompson Canyon of Colorado’s Front Range. A total of 144 people were killed on that Saturday evening, July 31, 1976--the eve of the 100th anniversary of Colorado’s statehood. On just about any summer weekend, the canyons northwest of Denver are packed with vacationers and day-trippers. With the state’s centennial falling on this particular weekend, the mood was especially festive, and the weather seemed no more threatening than on many other summer days. Forecasts through the day called for a 40% to 50% chance of showers and thunderstorms, but there was no particular concern about flood risk. Only a few hours later, critical gaps in weather data, communication, and public awareness had teamed up with a slow-moving deluge to create a true disaster--one that’s had a noteworthy influence on how we deal with flash floods today.


Figure 1. The irony of tragedy: a structure labeled “DREAMLAND” torn apart by the Big Thompson Canyon flood on July 31, 1976. Image credit: USGS.

Working in a data vacuum
The mountains of the U.S. West are just as prone to flash flooding as they were in 1976. However, there has been phenomenal progress in the ability to foresee, monitor, and warn people about the risks. Looking back from the vantage point of our current data-saturated world, it is astonishing how little information was available to forecasters on that fateful day. Routine satellite observations were in their infancy, and the black-and-white images that came in every 30 minutes were crude by today’s standards (see Figure 2). On the ground, there were no official weather stations or stream gauges reporting from anywhere in the Big Thompson Canyon, which starts near Rocky Mountain National Park and rolls about 25 miles eastward and downward, ending near the city of Loveland.


Figure 2. Left: A 7:30 PM CDT radar image of the flood-producing thunderstorm complex on July 31, 1976, in the Big Thompson Canyon (upper left of image), which was located near the outer edge of the radar range. Right: Satellite imagery from 7:00 PM CDT provided little detail on the Big Thompson storm, part of an arc of intense thunderstorms stretching from north-central Colorado (point A) to southeast Kansas (point C). Image credit: NOAA.

Most crucially, there was only a smattering of radar data for local forecasters to draw on. Just six years earlier, in 1970, northeast Colorado had obtained its first National Weather Service weather radar. This “conventional” unit preceded the NEXRAD Doppler network of the 1990s. The radar was located at Limon, more than 100 miles southeast of the Big Thompson Canyon, which meant the canyon fell toward the outer edge of the radar’s useful range. There were other problems as well. During this pre-Internet era, forecasters based in Denver had no way to directly view the radar observations being gathered at Limon. Instead, standard practice was for black-and-white images to be transmitted from Limon to Denver via facsimile, or “fax”. On July 30, the fax transmitter at Limon broke, meaning that no images could be transmitted to Denver until repairs could be made. This didn’t happen until August 1. As a result, the radar technician working on July 31 had to make phone calls to an NWS forecaster in Denver and summarize what he was seeing on radar--a cumbersome process at best.


Figure 3. A massive thunderstorm complex builds over the upper reaches of the Big Thompson Canyon on the late afternoon of July 31, 1976. Image credit: NOAA


The cold truth about warm rain
The gaping observational holes of 1976 were accompanied by a limited understanding of the meteorology that drives flash floods in the mountainous West. We now know that the heaviest rainfall comes from “warm rain” processes, when the atmosphere is so unusually warm and moist that much of a storm lies below the freezing level (a hard thing to achieve in this high-altitude region). The warm-rain process can yield radar returns that are misleadingly low for the amount of rain actually being produced. The official NOAA report on the event notes that NWS staff were puzzled by a seeming contradiction: the storms extended upward to an impressive 62,000 feet, but the strongest radar returns were surprisingly weak (only about 30 dbZ). We don’t know exactly how much warm-rain processes may have boosted the rain totals, but the available data suggests there was at least some impact. If a higher-resolution radar had been available and located closer to the canyon, and if the warm-rain process had been recognized at the time, forecasters might have picked up on the gravity of the threat. As it happened, the storms were addressed with a fairly routine severe thunderstorm warning and a cursory reference to potential flooding.

Unbeknownst to virtually everyone outside the canyon, torrential rain was falling at the time, with amounts topping 12” in less than five hours toward the western (higher) end of the canyon. Before long, an enormous pulse of high water cascaded down the canyon, pushing 10-foot-wide boulders ahead of it. The flood wave demolished more than 570 structures and hundreds of vehicles--as well as much of U.S. Highway 34, the primary route into and out of the canyon for some 1800 full- and part-time residents and hundreds of visitors that night. Many tried in vain to escape in their vehicles, and a highway patrolman who drove into the canyon to investigate was among those killed. Some of the worst damage occurred near the downstream end of the canyon, where relatively little rain fell. Based on the 139 bodies recovered from the flood (several others were never found), the vast majority of victims were killed by traumatic injury, not by drowning. With communication tools so limited by today’s standards, it took many hours for the full scope of the tragedy to become evident. Not until the next day did most Coloradans find out anything about the Big Thompson disaster.

While it was shocking in its own right, the Big Thompson flood came amid a decade of major flash flood disasters. More than 200 people died in Rapid City, South Dakota, on June 9-10, 1972. A valley in West Virginia was devastated by the breach of a mine-tailings dam at Buffalo Creek on February 26, 1972, which took 125 lives (see my related post from this year). And the failure of six dams in heavy rain led to 84 deaths in Johnstown, Pennsylvania, on July 19-20, 1977. These disasters--on top of more than 300 deaths in the 1974 Super Outbreak of tornadoes--helped galvanize the world of weather research and policy, serving as motivation for the massive NWS modernization efforts of the 1990s.


Figure 4. Signs like these became a fixture in Colorado’s steep canyons following the Big Thompson Flood. Image credit: Courtesy Colorado State University Water Center.


The Big Thompson flood also played a major role in bringing social science into meteorology. Eve Gruntfest, then a graduate student at the University of Colorado Boulder, ended up studying individual and institutional responses to the flood for her master’s thesis. Gruntfest concluded that many victims in the Big Thompson might have survived had they scrambled up the hillside just a few feet rather than fruitlessly staying in their vehicles. “Before that research, people didn’t realize that you can’t ‘out-drive’ a flash flood,” Gruntfest said. Her findings led to “CLIMB TO SAFETY” signs that were deployed across the state’s canyons (see Figure 4). Gruntfest later founded the landmark WAS*IS program (Weather and Society Integrated Studies). Based at the National Center for Atmospheric Research, WAS*IS brought together hundreds of meteorologists and social scientists for mutual learning and brainstorming and to help integrate social science into meteorological research and practice.

Big Thompson, take two: What went better this time
Recurrence intervals--the amount of time one would expect to elapse between floods of a given magnitude--are a risky thing to calculate. One estimate, based on geological evidence, concluded that the streamflow in the Big Thompson Canyon in 1976 was on the order of a 10,000-year event. Incredibly, another catastrophic flood struck just 37 years later, in early September 2013, when another hydrologic disaster struck a much larger swath of the Colorado Front Range. Stretching over several days, and including both flash-flood and river-flood elements, the waters of 2013 inflicted more than $1 billion in damage, with more than 350 homes demolished and almost 500 miles of roadway damaged or destroyed—including much of U.S. Highway 34 through the Big Thompson. The peak water volume flowing through the canyon was somewhat lower than in 1976, but the flood crest was sustained over a much longer period, with multiple peaks. “I never thought I would ever see cars wrapped around trees again, and certainly not in the Big Thompson Canyon,” Gruntfest told me.


Figure 5. Vehicles lie upended in a swollen Coal Creek in Lafayette, CO, during the 2013 floods that struck large parts of Colorado. Credit: Will Von Dauster, NOAA.


Figure 6. A county road in Berthoud, CO, washed away by the September 2013 Colorado Front Range floods. Credit: Lornay Hansen/Cooperative Institute for Research in Environmental Science (CIRES).

For all the psychic and physical damage it inflicted, Colorado’s flooding of 2013 was far less deadly than the Big Thompson event of 1976, with just eight deaths directly attributable to the floods. We can chalk up the much-reduced death toll to a range of factors. Despite inconsistencies in timing and location, a number of high-resolution model runs suggested more than a day in advance that torrential rains of up to 8 inches could strike parts of northeast Colorado. The NWS stressed the potential for heavy rain in local outlooks issued a day in advance. Years of coordination among federal, state, and local agencies had already led to greatly improved awareness of the flash flood risk in Colorado’s canyons. The event itself was tracked far more closely than the 1976 storms, thanks to modern radar and satellites: a total of 78 flash flood warnings were issued by NWS offices in Denver and Pueblo.

Once the event was under way, much-improved lines of communication allowed for quick road closures and other rapid responses that helped keep many thousands of residents out of harm’s way. Cellphones, websites, and social media also helped people to obtain a wealth of information on the emerging floods (although cellphone coverage remains limited in many canyons). As with tornado warnings, flash flood warnings are now transmitted directly to newer cellphones as audio and text alarms through the Wireless Emergency Alert system, provided that the phone’s owner has not opted out of this feature. More progress is on the way: for example, NOAA’s experimental Flooded Locations And Simulated Hydrography Project (FLASH), based at the National Severe Storms Laboratory, is using high-resolution rainfall data to produce flood forecasts every five minutes with a resolution of just one kilometer (0.6 mile). FLASH is one example of a new generation of tools that are likely to revolutionize severe weather warnings in the 2020s and beyond. And starting late this year, the long-awaited GOES-R satellite debut will deliver a huge advance in the tempo and resolution of U.S. imagery available for forecasters.

These advances and many others should make us grateful, yet never complacent. In 2004, it was easy to think that the United States might never again see a hurricane kill many hundreds of citizens. Just a year later, Hurricane Katrina proved that assumption horribly wrong. In 2010, one might have thought that the days of a single tornado killing more than 100 people, or an outbreak killing several hundred, were long gone--and then we saw the Super Outbreak of April 2011 and the horrific Joplin tornado of May 2011. Likewise, a flash flood striking in the wrong place at the wrong time could still wreak a catastrophic toll. On an individual level, anyone who drives around a barrier and into high water during a flash flood is taking what could be a deadly personal risk. More than 100 of the deaths in the Big Thompson canyon were vehicle-related. Doing what we can to spread awareness of water’s deadly power would be a fitting tribute to those whose lives were lost in the Big Thompson Canyon.

We'll have an update on Saturday afternoon on the two systems in the tropical Atlantic that have some potential for development over the next few days, Invest 96L and Invest 97L. See also this morning's post from Jeff Masters on the twin systems.

Bob Henson

More background:
Big Thompson Canyon Flash Flood of July 31-August 1, 1976 (NOAA Natural Disaster Survey Report, October 1976)
The Record Front Range and Eastern Colorado Floods of September 11-17, 2013 (NWS Service Assessment, June 2014)
A Deadly Flood That Helped Improve Weather Forecasting [NOAA web feature, July 29, 2016]


Figure 7. Nezette Rydell, meteorologist in charge at the NWS Denver/Boulder office, addresses a gathering held near Loveland, CO, on Friday, July 29, 2016, in honor of the 40th anniversary of the Big Thompson Flood of 1976. Organized by NOAA and the U.S. Geological Service, the event was hosted by the Sylvan Dale Guest Ranch, located at the base of the canyon. Ranch co-owner Susan Jessup, who was an eyewitness to both the 1976 and 2013 floods, also spoke, along with experts and policymakers from the State of Colorado, UCAR, USGS, and Larimer County, CO. I delivered opening remarks and introduced speakers. Image credit: Bob Henson.


Flood

Twin Invests 96L and 97L Worth Watching in the Atlantic

By: Jeff Masters , 2:41 PM GMT on July 29, 2016

There's a new threat area to discuss today in the Atlantic: a tropical wave midway between the Lesser Antilles Islands and the Cabo Verde Islands that is headed west to west-northwest at 25 mph. This disturbance was designated Invest 97L on Thursday afternoon by NHC, and should arrive in the northern Lesser Antilles by late Saturday night. The Hurricane Hunters are on call to investigate the storm on Sunday, if needed. Satellite loops on Friday morning showed 97L had a modest area of heavy thunderstorms which were poorly organized, though there was some increasing spin evident in the cloud pattern. Wind shear was a light 5 - 10 knots, and sea surface temperatures (SSTs) was an adequate-for-developement 27°C (81°F), which was about 1°C (1.8°F) above average. Water vapor satellite imagery showed that 97L had a modest amount of dry air from the Saharan Air Layer (SAL) surrounding it, which was slowing development.


Figure 1. Latest satellite image of Invest 97L in the middle Atlantic.

Forecast for 97L
Steering currents favor very rapid west to west-northwesterly motion at about 25 mph for 97L though Monday, and storms that move this fast typically have trouble getting organized. This motion should take the disturbance through the northern Lesser Antilles Islands on Sunday morning, over the Virgin Islands and Puerto Rico on Sunday afternoon, and into the Dominican Republic by Sunday night. All of these areas should expect to see heavy rains of 2 - 4" and wind gusts of 30 - 35 mph as 97L passes, and the NWS may end up issuing a Flash Flood Watch for portions of the Virgin Islands and Puerto Rico this weekend. The 8 am EDT Friday run of the SHIPS model shows somewhat favorable conditions for development through Saturday night, with wind shear in the light to moderate range, 5 - 15 knots, a moist atmosphere, and SSTs near 27 - 27.5°C (81 - 82°F.) However, an unfavorable factor for development will be large-scale sinking motion over the tropical Atlantic over the next few days imparted by the passage of what is called a Kelvin Wave (see the tweet by The Weather Company's Mike Ventrice on this.) On Sunday through Monday, 97L is predicted to encounter high wind shear of 20 - 30 knots, which would thwart development. At that time, the system may be undergoing interaction with the rough topography of Puerto Rico and Hispaniola, will would also inhibit development. By Tuesday, 97L should be traversing Cuba, and will slow down to a forward speed of about 10 - 15 mph, taking it into Mexico's Yucatan Peninsula by Wednesday and into the Gulf of Mexico around Thursday.

The Friday morning operational runs of our three reliable models for predicting tropical cyclone genesis, the European, GFS and UKMET models, did not show 97L developing much. The 00Z Friday runs of the GFS and European model ensemble forecasts, done by taking the operational high-resolution version of the model and running it at lower resolution with slight perturbations to the initial conditions in order to generate a range of possible outcomes, had fewer than 10% of their ensemble members predict that 97L would become a tropical depression. In their 8 am EDT Friday Tropical Weather Outlook, NHC gave 97L 2-day and 5-day development odds of 20% and 30%, respectively. When 97L reaches the Western Caribbean and Gulf of Mexico by the middle of next week, we will need to watch it, but the crystal ball is very murky on whether or not 97L might find favorable conditions for development then.


Figure 2. MODIS visible satellite image of 96L south of the Cabo Verde Islands taken on Friday morning, July 29, 2016. Image credit: NASA.

96L continues to grow more organized
A tropical disturbance that began as a strong tropical wave that moved off the coast of Africa on Wednesday morning continues to grow more organized over the eastern Atlantic, and has the potential to develop into a tropical depression by Saturday as it tracks west to west-northwestward at about 15 mph into the middle Atlantic. Satellite loops on Friday morning showed 96L had a compact area of heavy thunderstorms, and this activity was showing increasing organization. Plenty of spin was evident in the cloud pattern, and low-level spiral banding features were evident. Wind shear was a light 5 - 10 knots, and sea surface temperatures (SSTs) were warm, near 28°C (82°F), which was about 1°C (1.8°F) above average. Water vapor satellite imagery showed that the eastern tropical Atlantic was quite moist, with the dry air of the Saharan Air Layer (SAL) several hundred miles north of 96L. These conditions are favorable for development of a tropical depression.

Forecast for 96L
Steering currents favor a west to west-northwesterly motion at 15 - 20 mph for 96L over the next five days, and the storm should reach a point near 40°W, midway between the Lesser Antilles Islands and Africa, on Sunday night. The 8 am EDT Friday run of the SHIPS model predicted modestly favorable conditions for development through Saturday night, with wind shear in the light to moderate range, 5 - 15 knots, a moist atmosphere, and warm SSTs near 27 - 27.5°C (81 - 82°F.) However, by Saturday night, 96L will encounter cooler waters, with temperatures a marginal 26.5°C (80°F). The SHIPS model also predicts that wind shear over the weekend will become high, greater than 20 knots, and the atmosphere will get very dry, due to an intrusion of the Saharan Air Layer (check out the 10-day African dust forecast from NASA.) These unfavorable conditions would stymie any development of 96L. As 96L approaches the Lesser Antilles Islands later next week, the shear increases even further and the air grows drier, making 96L unlikely to be a threat to the islands.

The Friday morning operational runs of our three reliable models for predicting tropical cyclone genesis, the European, GFS and UKMET models, all supported continued development of 96L through Saturday. The 00Z Friday run of the GFS ensemble forecast had 30 - 40% of its twenty ensemble members predict that a tropical depression would form from 96L this weekend in the eastern Atlantic. Most of these forecasts had the storm dying out the middle Atlantic, due to unfavorable conditions, and none had it becoming a hurricane. Between 30 - 40% of the 50 members of the 00Z Friday European ensemble model forecasts also showed 96L becoming a tropical depression this weekend. In their 8 am EDT Friday Tropical Weather Outlook, NHC gave 96L 2-day and 5-day development odds of 40% and 50%, respectively.

A tropical cyclone-free Eastern Pacific for the first time since July 1
For the first time since July 1, there are no active tropical cyclones in the Eastern Pacific, thanks to the dissipation of Tropical Storm Frank on Thursday. The seven named storms this month tied a record set in 1985 for the most July storms on record in the basin. We have a chance to break the record with an eighth named storm, if it forms by Sunday: in their 8 am EDT Friday Tropical Weather Outlook, NHC gave a new tropical disturbance 850 miles south-southwest of the southern tip of Mexico's Baja Peninsula 2-day and 5-day development odds of 50% and 80%, respectively. This storm--which would be named Howard if it gets to tropical storm strength--is expected to move west-northwest and not impact Mexico.

This Sunday marks the 40th anniversary of Colorado's Big Thompson flash flood, one of the deadliest flooding disasters in U.S. history, with 139 people killed. Bob Henson will be back later today with a look back at this historic flood.

Wunderblogger Steve Gregory has more on the tropics in a Thursday afternoon post, HEAT WAVE ENDS AS MR & MRS ENSO FIGHT IT OUT.

The next name on the Atlantic list is Earl.

Jeff Masters

Hurricane

96L Off the Coast of Africa Growing More Organized

By: Jeff Masters , 2:01 PM GMT on July 28, 2016

A strong tropical wave that moved off the coast of Africa on Wednesday morning has become more organized over the far eastern Atlantic, and has the potential to develop into a tropical depression in the coming days as it tracks west-northwestward at 10 - 15 mph into the middle Atlantic. NHC designated this disturbance Invest 96L on Wednesday morning--the first "Invest" of the year for an African tropical wave. Satellite loops on Thursday morning showed 96L had a compact area of heavy thunderstorms, and this activity had acquired a modest degree of organization. Some spin was evident in the cloud pattern, and low-level spiral banding features had begun to appear. Wind shear was a light 5 - 10 knots, and sea surface temperatures (SSTs) were warm, near 28°C (82°F), which was about 1°C (1.8°F) above average. Water vapor satellite imagery showed that the eastern tropical Atlantic was quite moist, with the dry air of the Saharan Air Layer (SAL) several hundred miles north of 96L. These conditions are favorable for development of a tropical depression.


Figure 1. Analysis of the Saharan Air Layer (SAL) from 8 am EDT (12 UTC) Thursday, July 28, 2016, showed that the dry air and dust of the SAL lay a few hundred miles to the north of 96L. Image credit: University of Wisconsin CIMSS/NOAA Hurricane Research Division.

Forecast for 96L
Steering currents favor a west to west-northwesterly motion at 10 - 20 mph for 96L over the next five days, and the storm should reach a point near 40°W, midway between the Lesser Antilles Islands and Africa, on Sunday. The 8 am EDT Thursday run of the SHIPS model predicted modestly favorable conditions for development through Saturday morning, with wind shear in the light to moderate range, 5 - 15 knots, a moist atmosphere, and warm SSTs near 27.5 - 28°C (81 - 82°F.) However, on Saturday and Sunday, 96L will encounter cooler waters, with temperatures a marginal 26.5 - 27°C (80 - 81°F). The SHIPS model also predicts that wind shear over the weekend will become moderate to high, 15 - 25 knots, and the atmosphere will get very dry, due to an intrusion of the Saharan Air Layer (check out the 10-day African dust forecast from NASA.) These unfavorable conditions would stymie any development of 96L.

The Thursday morning operational runs of our three reliable models for predicting tropical cyclone genesis, the European, GFS and UKMET models, all supported some limited development of 96L, but stopped short of predicting it would become a tropical depression. The 00Z Thursday run of the GFS ensemble forecast, done by taking the operational high-resolution version of the model and running it at lower resolution with slight perturbations to the initial conditions in order to generate a range of possible outcomes, had more than 50% of its twenty ensemble members predict that a tropical depression would form this weekend or early next week in the eastern Atlantic. Most of these forecasts had the storm dying out the middle Atlantic, due to unfavorable conditions, and none had it becoming a hurricane. Between 10 - 20% of the 50 members of the 00Z Thursday European ensemble model forecasts showed 96L becoming a tropical depression. In their 8 am EDT Thursday Tropical Weather Outlook, NHC gave 96L 2-day and 5-day development odds of 30% and 40%, respectively. Though the long-range uncertainty on what 96L might do is high, one reasonable scenario is for the system to steadily grow in organization the next few days, come close to or achieve tropical depression status by Saturday, then get ripped up by wind shear and dry air well before reaching the Lesser Antilles Islands by the middle of next week. Should 96L become a tropical storm, the next name on the Atlantic list is Earl.

Eastern Pacific getting less active
For the first time since July 2, there is only one active tropical cyclone in the Eastern Pacific: Tropical Storm Frank, which peaked as a Category 1 storm on Tuesday. Frank is degenerating quickly over 23°C waters and is likely to dissipate by Thursday evening, potentially giving us on Friday our first tropical cyclone-free day in the Eastern Pacific since July 1. Beginning on July 2, the Eastern Pacific had Tropical Storm Agatha form, followed by Category 4 Hurricane Blas, Category 2 Hurricane Celia, Category 3 Hurricane Darby, Tropical Storm Estelle, Category 1 Hurricane Frank and Category 4 Hurricane Georgette. This puts us far ahead of climatology: the Eastern Pacific usually does not see its seventh named storm until August 7, its fifth hurricane until August 26, and its third major hurricane until September 20. An average season has 15 named storms, 8 hurricanes, and 3 major hurricanes. The quiet may not last long: in their 8 am EDT Thursday Tropical Weather Outlook, NHC gave a new tropical disturbance a few hundred miles south of the southern tip of Mexico's Baja Peninsula 2-day and 5-day development odds of 20% and 70%, respectively. This storm--which would be named Howard if it gets to tropical storm strength--is expected to move west-northwest and not impact Mexico.

Jeff Masters

Hurricane

First African Tropical Wave of the Year to Get Designated an 'Invest': 96L

By: Jeff Masters , 3:21 PM GMT on July 27, 2016

One of the strongest tropical waves of the 2016 African monsoon season moved off the coast of Africa on Wednesday morning, and has the potential to develop into a tropical depression in the coming days as it tracks westwards at 15 - 20 mph into the middle Atlantic. NHC designated this disturbance Invest 96L on Wednesday morning--the first "Invest" of the year for an African tropical wave, and something we'll see a lot more of as once the Atlantic hurricane season hits high gear during the mid-August through late September peak of the season. Satellite loops on Wednesday morning showed 96L had only a limited amount of heavy thunderstorms, which were poorly organized and had no signs of a surface circulation. Wind shear was moderate, near 10 - 20 knots, and sea surface temperatures (SSTs) were warm, near 28°C (82°F), which was about 1°C (1.8°F) above average.


Figure 1. MODIS satellite image of Invest 96L taken on Wednesday afternoon, July 27, 2016. Image credit: NASA.

Forecast for 96L
Steering currents favor a westerly motion for 96L, with the system slowing down in forward speed late this week and reaching a point near 40°W, midway between the Lesser Antilles Islands and Africa, on Monday. The 8 am EDT Wednesday run of the SHIPS model predicted modestly favorable conditions for development through Friday, with wind shear in the moderate range, 10 - 20 knots, and warm SSTs near 28°C. However, on Saturday and Sunday, 96L will encounter cooler waters, with temperatures a marginal 26°C. The SHIPS model also predicts that wind shear over the weekend will rise to the high range, above 20 knots, and the atmosphere will get very dry, due to an intrusion of the Saharan Air Layer (check out this animation of the 10-day African dust forecast from NASA.) These unfavorable conditions would stymie any development of 96L, but forecasts of dry air and wind shear this far into the future are unreliable.

The Wednesday morning operational runs of our three reliable models for predicting tropical cyclone genesis, the European, GFS and UKMET models, all supported some limited development of 96L, but stopped short of predicting it would become a tropical depression. The 00Z Wednesday run of the GFS ensemble forecast, done by taking the operational high-resolution version of the model and running it at lower resolution with slight perturbations to the initial conditions in order to generate a range of possible outcomes, had about 40% of its twenty ensemble members predict that a tropical depression would form this weekend or early next week midway between Africa and the Lesser Antilles. Most of these forecasts had the storm dying out the middle Atlantic, due to unfavorable conditions, and none had it becoming a hurricane. Less than 10% of the 50 members of the 00Z Wednesday European ensemble model forecasts showed a tropical depression forming in the Atlantic over the next ten days. In their 2 pm EDT Wednesday Tropical Weather Outlook, NHC gave 96L 2-day and 5-day development odds of 30% and 40%, respectively. Though the long-range uncertainty on what 96L might do is high, one reasonable scenario is for the system to steadily grow in organization the next few days, come close to or achieve tropical depression status by Saturday, then get ripped apart by wind shear and dry air well before reaching the Lesser Antilles Islands by the middle of next week. Should 96L overachieve, the next name on the Atlantic list of named storms is Earl.


Figure 2. Hurricane activity in the Atlantic is typically low through the end of July, but climbs steeply once we reach the third week of August.

Eastern Pacific gets its fifth hurricane of the year: Frank
The Eastern Pacific is a month ahead of schedule for hurricane activity, thanks to the intensification of Hurricane Frank into a Category 1 storm on Tuesday. There was one other active storm in the basin on Wednesday--weakening Tropical Storm Georgette, which topped out as an impressive Category 4 storm with 130 mph winds on Monday morning. Georgette was the seventh named storm to form in the Eastern Pacific this month, tying the July record for named storms set in 1985. Since July 2, the Eastern Pacific has had Tropical Storm Agatha, Category 4 Hurricane Blas, Category 2 Hurricane Celia, Category 3 Hurricane Darby, Tropical Storm Estelle, Category 1 Hurricane Frank and Category 4 Hurricane Georgette. This puts us far ahead of climatology: the Eastern Pacific usually does not see its seventh named storm until August 7, its fifth hurricane until August 26, and its third major hurricane until September 20. An average season has 15 named storms, 8 hurricanes, and 3 major hurricanes. There may be a Tropical Storm Howard joining the parade by next week: In their 8 am EDT Wednesday Tropical Weather Outlook, NHC gave a new tropical disturbance about 700 miles south of Manzanillo, Mexico 2-day and 5-day development odds of 0% and 50%, respectively. This storm is expected to move west-northwest and not impact Mexico.

Jeff Masters

Hurricane

Extreme 'Grey Swan' Hurricanes in Tampa Bay: a Potential Future Catastrophe

By: Jeff Masters , 3:54 PM GMT on July 26, 2016

A “black swan” hurricane—a storm so extreme and wholly unprecedented that no one could have expected it—hit the Lesser Antilles Islands in October 1780. Deservedly called The Great Hurricane of 1780, no Atlantic hurricane in history has matched its death toll of 22,000. So intense were the winds of the Great Hurricane that it peeled the bark off of trees--something only EF5 tornadoes with winds in excess of 200 mph have been known to do. However, hurricanes even more extreme than the Great Hurricane of 1780 can occur in a warming climate, and can be anticipated by combining physical knowledge with historical data. Such storms, which have never occurred in the historical record, can be referred to as “grey swan” hurricanes, according to research published in Nature Climate Change in 2015 by Kerry Emanuel of MIT and Ning Lin of Princeton University (press release here.) Using a detailed hurricane model embedded within six different global climate models, the scientists showed that the risk of extreme “grey swan” hurricanes for three specific locations--Tampa, Florida; Cairns, Australia; and the Persian Gulf--may increase by up to a factor of fourteen by the end of the century, thanks to our changing climate. We'll focus in this post on the results for Tampa.


Figure 1. Damage to Tampa’s Bayshore Boulevard after the 1921 Tampa Bay hurricane.


Figure 2. Track of the Tampa Bay Hurricane of 1921, one of only two major hurricanes ever recorded to hit the city. This Category 3 storm with 115 mph winds brought a storm tide of 10 - 11.5 feet (3 - 3.5 meters) to Tampa Bay.

Tampa’s hurricane history: only two major hurricanes since 1848
Tampa Bay doesn't get hit very often by hurricanes. This is because the city faces the ocean to the west, and the prevailing east-to-west trade winds at that latitude make it uncommon for a storm to make a direct hit on the west coast of Florida from the ocean. This is fortunate, since the large expanse of shallow continental shelf waters offshore from Tampa Bay (less than 300 feet deep out to 90 miles offshore) is conducive for allowing large storm surges to build. In a worst-case scenario, with a powerful hurricane traveling north-northwestwards at just the right speed parallel to the coast, the geometry of the coast creates a unique additional rise in the water level due to a phenomenon known as a coastally trapped Kelvin Wave.


Figure 3. Two possible tracks of the Great Gale of 1848, the most violent hurricane in Tampa's history, a Category 3 or 4 hurricane with 115 - 135 mph winds. A 15-foot storm surge (4.6 meters) was observed in what is now downtown Tampa.

The last time Tampa suffered a direct hit by any hurricane was 1946, when a Category 1 storm came up through the bay. The Tampa Bay Hurricane of October 25, 1921 was a the last major hurricane to make landfall in the Tampa Bay Region. This low-end Category 3 storm with 115 mph winds at landfall brought a storm tide of 10 - 11.5 feet (3 - 3.5 meters), causing severe damage ($10 million in 1921 dollars.) The only other major hurricane to hit the city occurred on September 25, 1848, when the Great Gale of 1848, the most violent hurricane in Tampa's history, roared ashore as a Category 3 or 4 hurricane with 115 - 135 mph winds. A 15-foot storm surge (4.6 meters) was observed in what is now downtown Tampa, and the peninsula where St. Petersburg lies, in Pinellas County, was inundated, making St. Petersburg an island. A large portion of what few human structures were then in the area were destroyed.


Figure 3. Predicted height above ground of the water from a worst-case Category 4 hurricane in the Tampa Bay region, as computed using NOAA's SLOSH storm surge model. Downtown Tampa Bay would be inundated by more than 20 feet of water, and St. Petersburg would become an island, as occurred during the 1848 hurricane. Image taken from our storm surge inundation maps.

Tampa fury: global warming may make grey swan hurricanes up to 14 times more likely
The risk of grey swan hurricanes increased in the models used in the study due to an increase in both the frequency and intensity of hurricanes in the future climate. While an increase in the frequency of hurricanes due to global warming is something many models run by other hurricane scientists do not show happening, there is widespread agreement among hurricane scientists that the strongest storms should get stronger, and a number of studies have shown that Cat 4/5 storms already make up an increasing proportion of tropical cyclones, at least in some basins (though the quality of our observations adds considerable uncertainty to this finding.) Stronger storms are to be expected, because hurricanes are heat engines that extract heat energy from the oceans and convert it to wind energy, and any increase in ocean heat energy due to global warming can be expected to increase the maximum potential intensity a hurricane can reach. An additional factor not considered: potential intensity theory suggests that hurricanes will increase in size; storms that have a larger diameter push up a larger and more damaging storm surge since strong winds are blowing over a larger ocean area. Also, the study did not consider the impact of sea level rise, which will steadily increase storm surge damage in the coming decades. A 2007 study by Tufts University, Florida and Climate Change, found that a 2.25 foot increase in sea level--which many sea level rise scientists expect will happen by the end of the century--would put 152,000 people in Pinellas County (where St. Petersburg is located) under water at high tide.

A ferocious upper-end Category 3 or stronger hurricane, capable of delivering a storm surge of 20 feet (6 meters) or higher, had about a 1-in-10,000 year recurrence interval in the historical climate of 1980–2005, the scientists estimated. In other words, such a storm had a 0.01 percent chance of occurring in any given year, or a 0.3 percent chance when summed up over a 30-year period. However, in a business-as-usual global warming scenario, the six climate models showed that such a storm might become between four and fourteen times more likely by the end of the century—a 1-in-2,500 to 1-in-700 year event. Summed up over a 30-year time period, a 1-in-700 year event has a 4 percent chance of occurrence—something disaster planners should definitely think about.

Tampa's "Category 6" hurricane: a mind-boggling 830 mb storm with 233 mph winds
The researchers found that extreme Category 5 hurricanes capable of delivering a storm surge of 26 - 36 feet (8 -11 meters) to Tampa had an extremely low or negligible probabilities in the climate of the late 20th Century, but are projected to happen as 1-in-5,000 to 1-in-150,000-year events in the late twenty-first century. We might need to invent a "Category 6" designation for the 1-in-150,000 year storm that came up in their simulations--a run of the HADGEM climate model that showed an unimaginably intense hurricane with a central pressure of 830 mb, top sustained winds of 233 mph, traveling parallel to the coast along just the right track to generate a titanic 36-foot storm surge. Even accounting for the 15% reduction in winds that would occur due to friction over land, the winds from such a “Category 6” hurricane would be like those of the EF5 tornado that leveled Joplin Missouri--except that EF4 to EF5 damage would be along a swath 22 miles wide, instead of a few hundred yards wide! A July 2016 paper by Columbia University hurricane scientist Adam Sobel and colleagues in Science, Human influence on tropical cyclone intensity, stated that we should expect to see about a 2.2 mph (1 m/s) per decade increase in the winds of the strongest hurricanes, or about 19 mph by the year 2100. If we assume the 215 mph sustained winds of 2015’s Hurricane Patricia (off the Pacific coast of Mexico) as the current maximum potential intensity that a hurricane can reach, a 235 mph hurricane by the end of the century is definitely a possibility.

Other estimates of Tampa Bay's hurricane risk
Extreme "grey swan" hurricanes are difficult to model, since they are such rare and extreme events. Thus, we should consider all the estimates of the potential return periods of such storms as highly uncertain.

In 2010, the Tampa Bay Regional Planning Council put out the Tampa Bay Catastrophic Plan, a scenario where a Category 5 "Hurricane Phoenix" hits downtown Tampa with 160 mph winds and a 26-foot storm surge. The study projected that the city would see about 2,000 deaths and nearly $250 billion dollars in damage.

Dr. Peter Sousounis, a meteorologist for risk modeling company AIR Worldwide, told me in an email that their maximum loss-causing event for Tampa Bay is a Category 5 storm with sustained winds of 220 mph that hits Manatee County with a central pressure of 887 mb. This nightmare storm generates $220 billion in insured losses in a four county region (Manatee, Pinellas, Pasco and Hillsborough counties)--a level of loss for those counties that has a 1-in-10,000 year recurrence interval. Since uninsured losses from a hurricane strike are usually roughly as much as the insured losses, the total damage from this storm might top $400 billion dollars.

An August 2015 report by Karen Clark & Company, Most Vulnerable US Cities to Storm Surge Flooding, cited Tampa/St. Petersburg as the most vulnerable metropolitan area in the U.S. to storm surge damage. Their 1-in-100 year storm--a strong Category 4 hurricane with 150 mph winds--could be expected to cause $175 billion in damage just from the storm surge.

Two mass evacuations in Tampa in the past 35 years
Two hurricanes have prompted mass evacuations of more than 300,000 people from the Tampa Bay area over the past 35 years. The first was Hurricane Elena of 1985, a Category 3 hurricane that stalled 80 miles offshore for two days on Labor Day weekend, bringing a 6 - 7 foot storm surge, wind gusts of 80 mph, and torrential rains. On August 13, 2004, another mass evacuation was ordered for Hurricane Charley. Thanks to a late track shift, Charley missed Tampa Bay, and instead hit well to the south in Port Charlotte as a Category 4 storm with 150 mph winds. More limited evacuations of low-lying areas and mobile homes in the 4-county Tampa Bay region were ordered for three other hurricanes in the past twenty years--Hurricane Georges of 1998, Hurricane Frances of 2004, and Hurricane Jeanne of 2004.


Figure 4. A sensible hurricane awareness effort: Hillsborough County, Florida got a $30,000 grant to post 30 of these signs around the Tampa Bay area to show how high a storm surge from a major hurricane might reach. This sign by a McDonalds at 19th Ave and Highway 41 is thirteen feet above ground level. Image credit: photonews247.com.

Tampa Bay's vulnerability to hurricanes
When the 1921 hurricane hit Tampa Bay, there were 160,000 residents in the 4-county region, most of whom lived in communities on high ground. Today there are 2.8 million residents in the region, and that number is growing by about 50,000 people per year. Most of the population in the 4-county Tampa Bay region lives along the coast in low-lying areas; about 50 percent of the population lives at an elevation less than ten feet. Over 800,000 people live in evacuation zones for a Category 1 hurricane, and 2 million people live in evacuation zones for a Category 5 hurricane, according to the 2010 Statewide Regional Evacuation Study for the Tampa Bay Region. Given that only 46% of the people in the evacuation zones for a Category 1 hurricane evacuated when an evacuation order was given when 2004's Category 4 Hurricane Charley threatened the region, the potential exists for hundreds or even thousands of people to die when the next major hurricane hits.

References
Barnes, J., 1999, Florida’s Hurricane History. The University of North Carolina Press.

Weisberg, R.H, and L. Zheng, 2006, "Hurricane storm surge simulations for Tampa Bay", Estuaries and Coasts Vol 29, No. 6A, pp 899-913.

History of Pasco County: The 1921 Hurricane

A July 2016 paper in Science, Human influence on tropical cyclone intensity

The 2010 Statewide Regional Evacuation Study for the Tampa Bay Region

The Tampa Bay Catastrophic Plan for a Category 5 $250 billion hurricane

My August 14, 2012 post, The odds of a hurricane spoiling the Republican National Convention in Tampa

My February 2016 post, Hurricane Patricia's 215 mph Winds: A Warning Shot Across Our Bow

My 2013 post, Hurricanes and Climate Change: Huge Dangers, Huge Unknowns

Latest 2016 disaster planning info from the Tampa Bay Regional Planning Council.

Climate Central's interactive Risk Zone Map for sea level rise in the Tampa Bay area.


Video 1. A newscast I hope I never see the likes of: a frightening look at the potential effects of a catastrophic Category 5 hurricane making a direct landfall on the Tampa Bay metro area, as envisioned by the 2010 Tampa Bay Catastrophic Plan Hurricane Phoenix scenario.

We'll have a new post by Thursday at the latest.

Jeff Masters




Hurricane

Darby Makes the Closest Pass to Honolulu by a Tropical Storm in Recorded History

By: Jeff Masters , 3:34 PM GMT on July 25, 2016

The closest approach on record by a tropical storm to the island of Oahu resulted in torrential rains in excess of ten inches there as Tropical Storm Darby passed just 40 miles to the south and west of Honolulu, Oahu on Sunday with sustained winds of 40 mph. No other named storm on record has passed that close to Honolulu or Oahu since accurate records began in 1949. Rainfall amounts of over ten inches in the 24 hours ending at 3:45 am HST Monday were reported at five locations on the eastern half of Oahu from Darby:

11.09" Moanalua RG
10.94" Nuuanu Upper
10.81" Luluku
10.70" Waihee Pump
10.04" Palisades

Monday morning Hawaiian radar showed that Darby continued to stream bands of heavy rain over the island, and satellite loops showed that Darby still had plenty of heavy thunderstorms on the northeast side of its circulation. Over the weekend, Darby also brought rains in excess of ten inches to West Wailuaiki, Maui (12.63") and Paauilo, on the Big Island (10.19"). There have been several road closures on Oahu due to flooding, and as of 10 pm HST Sunday, the Honolulu fire department reported 59 calls from residents who needed to be evacuated from their homes due to flooding. About 1,000 customers have lost power from the storm thus far. Darby, downgraded to a tropical depression at 11 am EDT Monday, should cease deluging Oahu by Monday afternoon as the storm pulls away to the west.


Figure 1. Radar-estimated precipitation from Tropical Storm Darby as of 10:53 am EDT (14:53 UTC) Monday, July 25, 2016. A band of heavy 6 - 11" rains fell just east of Honolulu on Oahu Island in Hawaii.


Figure 2. Tracks of all tropical cyclones (tropical depressions, tropical storms, and hurricanes) to pass within 100 miles of the Hawaiian Islands, 1949 - 2016. No named storm at tropical storm strength has passed closer to Honolulu and Oahu in recorded history than Darby, though Raymond hit the island as a tropical depression in 1983. Image credit: NOAA/CSC.

Direct hits by tropical storms and hurricane are uncommon in Hawaii
Darby made a direct hit on the Big Island of Hawaii on Saturday, becoming just the fifth named storm since 1949 to make landfall on a Hawaiian Island. The others were:

Tropical Storm Iselle, which made landfall along the southeast shore of Hawaii's Big Island on August 8, 2014 as a tropical storm with 60 mph winds. Iselle killed one person and did $79 million in damage.

Hurricane Iniki, which hit Kauai as a Category 4 hurricane, killing 6 and causing $1.8 billion in damage (1992 dollars.)

Hurricane Dot, which hit Kauai as a Category 1 hurricane, causing 6 indirect deaths and $6 million in damage (1959 dollars.)

An unnamed 1958 storm that had sustained winds of 50 mph at landfall on the Big Island. The storm killed one person and caused $0.5 million in damage.

Hawaii has seen a lot of activity over the past three years, which may be a harbinger of things to come--see my August 2014 post, Climate Change May Increase the Number of Hawaiian Hurricanes.

Eastern Pacific gets its third major hurricane of the year: Georgette
We're not even into August, and the Eastern Pacific has already had as many major hurricanes as it typically gets in an entire year: three. Hurricane Georgette, which topped out as an impressive Category 4 storm with 130 mph winds on Monday morning, is the latest addition to the club. Georgette is the seventh named storm to form in the Eastern Pacific this month, tying the July record for named storms set in 1985. Since July 2, we've had Tropical Storm Agatha, Category 4 Hurricane Blas, Category 2 Hurricane Celia, Category 3 Hurricane Darby, Tropical Storm Estelle, Tropical Storm Frank and Category 4 Hurricane Georgette. This puts us well ahead of climatology: the Eastern Pacific usually does not see its seventh named storm until August 7, its fourth hurricane until August 12, and its third major hurricane until September 20. An average season has 15 named storms, 8 hurricanes, and 3 major hurricanes.


Figure 3. VIIRS visible satellite image of Tropical Storms Frank (right) and Hurricane Georgette (left) taken at 5:20 pm EDT Sunday July 24, 2016. At the time, Georgette was an intensifying Category 2 storm with 105 mph winds. Image credit: NASA.

The Atlantic is still quiet
There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for tropical cyclone formation is predicting development during the coming five days. A few recent runs of the GFS model have been highlighting the possible development this weekend of a tropical wave predicted to come off the coast of Africa around July 27. The 00Z Monday run of the GFS ensemble forecast had about 30% of its twenty ensemble members predict that a tropical depression would form this weekend or early next week midway between Africa and the Lesser Antilles. Most of these forecasts had the storm dying out the middle Atlantic, due to unfavorable conditions. There will be several impressive pulses of dry air and dust coming off the Sahara Desert over the next ten days, which will likely make it challenging for any tropical waves to develop (check out this animation of the 10-day African dust forecast from NASA.) Less than 10% of the 50 members of the 00Z Monday European model forecast showed a tropical depression forming in the Atlantic over the next ten days. I'm not expecting to see anything form in the Atlantic until August.

Jeff Masters

Hurricane

Darby Falling Apart as it Makes Landfall on Hawaii's Big Island

By: Jeff Masters , 10:57 PM GMT on July 23, 2016

Tropical Storm Warnings are flying for the Big Island of Hawaii, Maui and Oahu as Tropical Storm Darby dashes itself against the high mountains of the Big Island. Saturday evening satellite loops showed that Darby was becoming misshapen and disorganized as it made landfall on the Big Island, and radar on the Big Island showed a highly asymmetric storm, with all of the heavy rains confined to the southeast side.


Figure 1. True-color MODIS image of Tropical Storm Darby approaching the Big Island of Hawaii at 21:30 UTC (5:30 pm EDT) July 23, 2016. At the time, Darby had top winds of 45 mph. Image credit: NASA.

Forecast for Darby
On August 8, 2014, Tropical Storm Iselle of 2014 passed directly over the Big Island, and the 13,000-foot high peaks of Mauna Loa and Mauna Kea basically shredded the storm apart. I expect Darby will suffer a similar fate, and will be downgraded to a tropical depression on Sunday. Heavy rains causing flash flooding and mudslides are the main danger from Darby. Widespread rainfall amounts of 3 - 5" will likely affect all of the Hawaiian Islands, with some areas of 5 - 10" on the Big Island. High surf of 15 - 25' that will cause erosion problems on the southeast side of the Big Island are another concern. Strong wind gusts will also be an issue, as the high volcanoes of the Big Island and Hawaii will act to create damaging wind gusts in some areas, even if the sustained winds affecting land are below tropical storm strength. In their 5 pm EDT Saturday Wind Probability Forecast, the Central Pacific Hurricane Center gave Hilo on the Big Island the greatest chance of seeing tropical storm-force winds of 39+ mph: 99%. Honolulu had a 39% chance, and Kahului, Maui a 31% chance. I think these wind probabilities are too high, and that no locations in the islands at sea level will see sustained winds of 39+ mph.


Figure 2. Composite radar image of Tropical Storm Darby taken at 6:30 pm EDT (12:30 pm HST) on Saturday, July 23, 2016. Darby's heaviest rains were confined to the southeast side of the storm.


Figure 3. Tracks of all tropical cyclones (tropical depressions, tropical storms, and hurricanes) to pass within 100 miles of the Hawaiian Islands, 1949 - 2014. Hurricanes approaching from the east typically fall apart before they reach Hawaii due to the cool waters and dry air that lie to the east of the islands. Only two named storms approaching from the east have hit the islands since 1949, an unnamed 1958 tropical storm and Tropical Storm Iselle of 2014, which hit the Big Island. Hurricanes approaching from the south represent the biggest danger to the islands, due to the warmer waters and more unstable air present to the south. The only two major hurricanes to have affected the islands since 1949, Hurricane Iniki of 1992 and Hurricane Dot of 1959, both came from the south. Image credit: NOAA/CSC.

Direct hits by tropical storms and hurricane are uncommon in Hawaii
It appears likely that Darby, though weakening, will officially be a tropical storm that makes landfall on the Big Island. This would make Darby just the fifth named storm since 1949 to make landfall on a Hawaiian Island. The others:

Tropical Storm Iselle, which made landfall along the southeast shore of Hawaii's Big Island on August 8, 2014 as a tropical storm with 60 mph winds. Iselle killed one person and did $79 million in damage.

Hurricane Iniki, which hit Kauai as a Category 4 hurricane, killing 6 and causing $1.8 billion in damage (1992 dollars.)

Hurricane Dot, which hit Kauai as a Category 1 hurricane, causing 6 indirect deaths and $6 million in damage (1959 dollars.)

An unnamed 1958 storm that had sustained winds of 50 mph at landfall on the Big Island. The storm killed one person and caused $0.5 million in damage.

Hawaii has seen a lot of activity over the past three years, which may be a harbinger of things to come--see my August 2014 post, Climate Change May Increase the Number of Hawaiian Hurricanes.

The winds at 13,000 feet on Mauna Kea
The weather on top of the highest point in Hawaii, the Big Island's Mauna Kea, elevation 13,796' (4,205 m), will be interesting to follow as Darby makes landfall. Winds have risen steadily today, and several of the six anemometers reported sustained winds in excess of 30 mph on Saturday afternoon. However, beware of the data from the Canada - France - Hawaii Telescope (CFHT). The Mauna Kea webcam page says that those winds are highly exaggerated due to location of the anemometer tower between two large telescope domes. You can see this tower on Google Maps.

Links
Weather on Mauna Kea
Live stream from KHON2 TV in Honolulu
Central Pacific Hurricane Center
2-km resolution WRF model output from the University of Hawaii for Hawaii
Storm surge maps for Oahu
Storm info from Tropical Tidbits
NWS Honolulu

Jeff Masters

Hurricane

Tropical Storm Warnings in Hawaii for Darby

By: Jeff Masters , 9:18 PM GMT on July 22, 2016

Tropical Storm Warnings are flying for the Big Island of Hawaii and Maui as Tropical Storm Darby steams westwards at 11 mph towards Hawaii. An Air Force hurricane hunter aircraft was in Darby Friday afternoon, and found top surface winds near 60 mph and a surface pressure of 999 mb. Friday afternoon satellite loops of Darby showed a modest area of heavy thunderstorms that were changing little in intensity. Wind shear was a moderate 10 - 20 knots, and sea surface temperatures (SSTs) were near 26.5°C (80°F), which just at the 80°F threshold needed to sustain a tropical storm. Rainfall from Darby should appear on radar out of the Big Island by Friday night.


Figure 1. Latest satellite image of Tropical Storm Darby.

Forecast for Darby
SSTs and wind shear are predicted to remain about the same through Saturday, so no significant changes in Darby's intensity are likely to occur as the storm approaches the Big Island and Maui. Slow weakening is likely beginning on Saturday evening as Darby interacts with the high terrain of the Big Island, and I expect Darby will affect Hawaii as a weaker storm than Tropical Storm Iselle of 2014, which hit the Big Island with sustained winds of 60 mph. Iselle caused about $80 million in damage.

Heavy rains causing flash flooding and mudslides are the main danger from Darby. The 12Z Friday run of the HWRF model predicted Darby would bring widespread rainfall amounts of 4 - 8" to all of the Hawaiian Islands, with some areas of 8 - 16" on the Big Island and Maui. Strong wind gusts will also be a concern, as the high volcanoes of the Big Island and Hawaii will act to create damaging wind gusts in some areas, even if the sustained winds affecting land are below tropical storm strength. In their 5 pm EDT Friday Wind Probability Forecast, the Central Pacific Hurricane Center gave Hilo on the Big Island the greatest chance of seeing tropical storm-force winds of 39+ mph: 63%. Honolulu had a 33% chance, and Kahului, Maui a 51% chance.


Figure 2. Radar image from the South Hawaii radar at 7:49 am EDT August 8, 2014 of Tropical Storm Iselle near landfall on the Big Island. The radar beam was being intercepted by the high mountains of Hawaii, and could not "see" to the northwest.


Figure 3. Tracks of all tropical cyclones (tropical depressions, tropical storms, and hurricanes) to pass within 100 miles of the Hawaiian Islands, 1949 - 2014. Hurricanes approaching from the east typically fall apart before they reach Hawaii due to the cool waters and dry air that lie to the east of the islands. Only two named storms approaching from the east have hit the islands since 1949, an unnamed 1958 tropical storm and Tropical Storm Iselle of 2014, which hit the Big Island. Hurricanes approaching from the south represent the biggest danger to the islands, due to the warmer waters and more unstable air present to the south. The only two major hurricanes to have affected the islands since 1949, Hurricane Iniki of 1992 and Hurricane Dot of 1959, both came from the south. Image credit: NOAA/CSC.

Direct hits by tropical storms and hurricane are uncommon in Hawaii
Tropical Storm Iselle made landfall along the southeast shore of Hawaii's Big Island on August 8, 2014 as a tropical storm with 60 mph winds. Iselle was only the second tropical storm on record to hit the Big Island, and was the strongest. The Big Island's other tropical storm was an unnamed 1958 storm that had sustained winds of 50 mph at landfall. Iselle was just the fourth tropical storm or hurricane to make a direct hit on any Hawaiian Island since accurate records began in 1949. However, Hawaii has seen a lot of activity over the past three years, which may be a harbinger of things to come--see my August 2014 post, Climate Change May Increase the Number of Hawaiian Hurricanes.

Eastern Pacific ties a July activity record: 7 named storms
The Eastern Pacific's record parade of July tropical cyclones continued this week, with the formation of Tropical Storm Georgette and Tropical Storm Frank. Both storms are expected to reach Category 1 hurricane status, but neither is expected to affect land. Georgette is the seventh named storm to form in the Eastern Pacific this month, tying the July record for named storms set in 1985. Since July 2, we've had Tropical Storm Agatha, Category 4 Hurricane Blas, Category 2 Hurricane Celia, Category 3 Hurricane Darby, Tropical Storm Estelle, and now Frank and Georgette. This puts us well ahead of climatology: the Eastern Pacific usually does not see its seventh named storm until August 7, its third hurricane until July 27, and its second major hurricane until August 19. An average season has 15 named storms, 8 hurricanes, and 3 major hurricanes.


Figure 4. VIIRS visible satellite image of Tropical Storms Darby, Estelle, and Frank, plus Tropical Depression 8-E, taken at 8 pm EDT Thursday July 21, 2016. Image credit: NASA.

Atlantic still slumbering--but for how long?
As is usually the case when the Eastern Pacific is active, the Atlantic is quiet. This inverse correlation in activity occurs because the conditions over the Eastern Pacific driving this July's bounteous activity--surface low pressure and rising air--creates a compensating area of sinking air over the tropical Atlantic, creating surface high pressure and dry weather--the antithesis of conditions needed for tropical cyclone formation. There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for tropical cyclone formation is predicting development during the coming five days. However, for the first time all month, NHC is not highlighting any new areas for tropical cyclone development in the Eastern Pacific over the next five days, and the GFS model is not predicting anything new will form. That may mean it will be the Atlantic's turn to get active during the last few days of July, and a number of recent runs of the GFS model have been highlighting the possible development late this month of a tropical wave predicted to come off the coast of Africa around July 27. There will be plenty of dry air and dust from the Saharan Air Layer (SAL) around through the end of the month, though, which will likely make it challenging for any tropical waves to develop (check out this animation of the 10-day African dust forecast from NASA.)

Jeff Masters

Hurricane

Eastern Hemisphere's All-Time Temperature Record: Kuwait Fries in 54°C (129.2°F) Heat

By: Jeff Masters , 3:01 AM GMT on July 22, 2016

It was a historic day in the annals of meteorology on Thursday, July 21, 2016 in the Middle East, where the temperature in Mitribah, Kuwait soared to an astonishing 54°C (129.2°F). If verified, this would be Earth's hottest temperature ever reliably measured outside of Death Valley, California, according to wunderground's weather historian Christopher C. Burt. The temperature is likely to be verified, since Thursday's incredible heat also extended into Iraq, which set their all-time heat record: 128°F (53.4°C) at Basrah. According to Burt and Herrera, Thursday's Basrah reading ranks as the fourth highest temperature ever reliably measured outside of Death Valley; the only higher non-Death Valley temperatures were today's 54°C (129.2°F) at Mitribah, Kuwait, a 53.6°C reading at Sulaibya, Kuwait in 2011, and a 53.5°C reading at Mohenjodaro, Pakistan on May 26, 2010. Note that there is one other competitor for hottest non-Death Valley temperature ever measured: the official all-time high temperature in Israel is a 54°C (129.2°F) reading from Tirat Tsvi, Israel on June 22, 1942. The Israeli Met Office pursued an investigation of the record in 2012, prompted by an inquiry from the World Meteorological Organization (WMO) and convincing evidence from wunderground's weather historian Christopher C. Burt and weather extremes expert Howard Rainford that the actual high temperature was a full degree lower. The Israeli Met Office concluded that the record was valid, but refused to make public the details leading to their conclusions. Until they do so, the record remains suspect.


Figure 1. A photograph of the official Furnace Creek, Death Valley maximum recording thermometer at time of observation on Monday morning July 1, 2013 (which was for the maximum temperature measured on June 30). The photo shows a maximum of 129.2°F was reached, tying it with the 129.2°F reading at Mitribah, Kuwait, on July 21, 2016, for the highest reliably measured temperature on Earth, according to wunderground's weather historian Christopher C. Burt. Observations at the site are made only at 4 p.m. and 7 a.m. daily. The shelter door is not opened at any other time in order to not affect the ambient air temperature inside the shelter. You may have seen a different image of this same thermometer on the NWS-Las Vegas web site posted July 1, 2013 that shows the temperature just shy of 129°. That is because THAT photograph was taken after the thermometer had been removed from its shelter and turned vertically, which caused the mercury to slip down the tube about 0.3°F. This photograph was taken prior to the thermometer being removed from the shelter. Photo courtesy of Death Valley National Park and NWS-Las Vegas.

Comparison with Death Valley temperatures
The official world record high temperature is 56.7 °C (134.1 °F) on July 10, 1913, in Furnace Creek Ranch, California, in Death Valley. Mr. Burt has commented "the record has been scrutinized perhaps more than any other in the United States. I don't have much more to add to the debate aside from my belief it is most likely not a valid reading when one looks at all the evidence." He proposes that the highest reliably recorded temperature at Death Valley is a 54.0 °C (129.2 °F) reading on June 30, 2013--tied with Thursday's measurement in Kuwait. The 129.2°F value at Death Valley was rounded down to 129°F in the official record, though. Death Valley has also recorded 53.9°C (129°F) four times: July 20, 1960, July 18, 1998, July 20, 2005, July 7, 2007. There is no evidence that the temperature reached 129.2°F on those dates, unlike the reading on June 30, 2013.

The Middle East's heat wave continues on Friday
The Middle East's astonishing heat wave will last one more day. Friday's high in Basrah, Iraq is predicted to hit 128°F and Mitribah, Kuwait is predicted to hit 127°F. Gotvand, Iran is predicted to hit 126°F--very close to Iran's all-time heat record of 127.4°F, set most recently at Gotvand on July 17, 2014. On Saturday, the ridge of high pressure bringing the record heat will weaken, bringing temperatures about 10°F cooler to Iraq and Kuwait, and about 2 - 4°F cooler to Iran.

UPDATE: On Friday, July 22, 2016, Basrah, Iraq International Airport reported a high temperature of 53.9°C (129°F). Today's high in Basrah is the second highest reliably measured temperature in world recorded history outside of Death Valley, California. Only yesterday's 54°C (129.2°F) at Mitribah, Kuwait was hotter.

Mr. Burt plans to post an in-depth look at the new heat records in a forthcoming post.

I'll have an update on the tropics on Friday afternoon.

Jeff Masters

Heat

WU Personal Weather Stations Are Now 200,000+ Strong

By: Bob Henson , 2:42 PM GMT on July 21, 2016

For more than a decade, individuals across the United States have been collecting weather data from their houses and backyards using personal weather stations (PWSs), and sharing their data with the world via Weather Underground. Data from the WU PWS Network, which was launched in 2001, can be found in a variety of formats on the WU website and WU apps. Over the last several years, the WU PWS Network been growing by leaps and bounds, both in numbers and geographic spread. From around 30,000 stations in 2013, mostly in the United States, the WU PWS Network has now grown to include four continents and 195 nations--and we are delighted to announce that it recently passed a major milestone: 200,000 stations! Not only is this the largest PWS Network on Earth, it is also one of the world’s biggest Internet of Things (IoT) platforms. (IoT refers to groups of interconnected objects that can exchange data.)

Observations from the WU PWS Network are combined with atmospheric data collected from 40 million smartphones monthly (barometric pressure and sky/hazard reports) as well as from 50,000 flights per day, all feeding into WU’s forecast engine. Together, they help improve and refine the hyperlocal forecasts that are a WU hallmark.



More than 100 personal weather stations going to critical locations
The Weather Company, an IBM Business (of which WU is a subsidiary) announced today that WU will partner with meteorological, government, and nonprofit organizations to furnish hundreds of PWSs at key locations in Africa, Asia, and South America. The plan is to leverage the benefits of PWS Networks and IoT technology to help advance local economies, build resilience, and improve forecast technology.

--As part of IBM’s philanthropic Smarter Cities Challenge program, WU will be donating up to 100 PWSs this calendar year for deployment in Santiago, Chile, and Visakhapatnam (Vizag), India. Both cities have at least 5 million residents in their metropolitan areas, and each has its own weather-related issues:

Santiago: flooding and landslides due to heavy rainfall; potential wildfires during hot, dry, windy weather
Vizag: heavy monsoon rains each summer, along with the risk of tropical cyclones from the Bay of Bengal

The Smarter Cities Challenge sends teams of top IBM experts for three-week deployments to help cities around the world address their most critical challenges and operate more smartly and effectively. The two cities above were chosen for the PWS deployment in order to maximize the potential benefit as a function of population density, web connectivity, and current infrastructure gaps.

--In partnership with the Oregon-based nonprofit TAHMO (Trans-African HydroMeteorological Observatory), more than 300 PWSs will be deployed across Nigeria, Kenya, and various other African nations where traditional observing networks are sparse and expensive to maintain As these new stations come online, IBM and TWC researchers will assess how much each PWS helps to improve forecast accuracy. In addition, the station data will be incorporated by IBM’s Watson IoT platform for use in precision agriculture (e.g., optimizing the use of water and fertilizer) and other areas. The focus of TAHMO is on building a dense network of hydrometeorological observations across the sparsely-sampled African continent.


Figure 1. Visag, India (top) and Santiago, Chile (bottom). Image credits: Av9/Wikimedia Commons (Visag), Javmoraga/Wikimedia Commons (Santiago).

A win-win-win: local economies, societal resilience, and IoT science
The PWS donations above will provide much-needed data that can serve society in a variety of ways: informing crop growing and harvesting, optimizing critical resource management, providing advance notice of extreme weather, and much more. Local business should benefit as well, through the ability to leverage weather data to improve decision-making support and expand weather-sensitive industries. The donations will also serve as a test bed for exploring the combined power of the PWS Network and Watson IoT technology, which aims to blend cognitive science and interconnected data across a wide spectrum of disciplines.

“The private sector, including companies such as Weather Underground and The Weather Company, has played a useful role in the delivery of weather forecasts,” said Christian Blondin, head of cabinet of the secretary-general and director, external relations, World Meteorological Organization. “We welcome the role of such private sector companies in the provision of selected value-added services in complement of the services provided by national meteorological and hydrometeorological services around the world."

For more details on this initiative, see the press release.

Bob Henson



Wunderground News

June Does It Again: Global Temperature Sets 14th Consecutive Monthly Record

By: Jeff Masters and Bob Henson , 7:05 PM GMT on July 19, 2016

Even with the intense 2015 - 2016 El Niño event out of the picture, June 2016 was still the planet's warmest June since record keeping began in 1880, said NOAA's National Centers for Environmental Information (NCEI) on Tuesday. In the NOAA database, June 2016 came in 0.90°C (1.62°F) warmer than the 20th-century average for June, beating the previous record for June, set in 2015, by 0.02°C. This ties with May 2016 for the smallest margin the monthly global temperature has broken a record by since August 2015. NASA also reported the warmest June in its database--though just barely--as did the Japan Meteorological Agency. June 2016 marked the 14th consecutive month that the global monthly temperature record was broken, which is the longest such streak since global temperature records began in 1880. The record-warm June extended to both global ocean and global land temperatures in the NOAA database. For the lowest 8 km of the atmosphere, global satellite-measured temperatures in June 2016 were the 2nd warmest for any June in the 38-year record, according to the University of Alabama in Huntsville (UAH).

The impressive global warmth in recent months is due to the steady build-up of heat-trapping greenhouse gases due to human activities, plus a spike due to a large amount of heat being released from waters in the Eastern Pacific due to the powerful 2015-16 El Niño event. This event peaked in December, and NOAA’s global surface temperature for the year so far (January-June 2016) is a remarkable 0.20°C (0.38°F) warmer than the previous record, set in 2015 (see Figure 1). The departure of El Niño and the likely arrival of La Niña should allow temperatures to drop slightly, perhaps breaking our string of record-warm months sometime in the near future, but temperatures would have to plummet between now and December in order to keep 2016 from becoming the warmest year in global record keeping. In May, NASA/GISS director Gavin Schmidt laid 99% odds on 2016 setting a new global temperature record, which would make it Earth's third consecutive warmest year on record.


Figure 1. Departure from average for the global January-through-June 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).



Figure 2. Departure of temperature from average for June 2016, the warmest June for the globe since record keeping began in 1880. Pockets of record warmth were observed across every major ocean basin and over a few land areas, including parts of the Maritime Continent, the southwest U.S., northeast Africa, and much of the Middle East. The only major land-based region of cooler-than-average temperatures was in central and southern South America. The cool “blob” that had persisted for many months across the far North Atlantic weakened substantially in June. Image credit: National Centers for Environmental Information (NCEI).

El Niño is over; odds of La Niña decreasing
El Niño dissipated in May 2016, giving way to El Niño-Southern Oscillation (ENSO)-neutral conditions as sea surface temperatures continued to cool across the tropical Pacific Ocean during June. According to NOAA's July ENSO forecast from the Climate Prediction Center, a weak La Niña is favored to develop during the August - October peak of hurricane season. The La Niña odds in the July outlook were 55 - 60%, which is lower than the 75% odds given in the June forecast.


Figure 3. The year-to-date temperature in the Arctic (between 70°N and 90°N, the blue line) set a new record in 2016, at just over 3.5°C (6.3°F) above average. Note how the Arctic has warmed much more rapidly than the mid-latitudes (between 40°N and 60°N, the black line) in recent decades. This process is called "Arctic Amplification", and has been shown by climate models to occur as a result of human-emitted heat-trapping gases like carbon dioxide affecting the climate. Image credit: Dr. Jennifer Francis, Rutgers.

Arctic sea ice hits its lowest June extent on record
June sea ice extent in 2016 was the lowest in the 38-year satellite record, according to the National Snow and Ice Data Center (NSIDC). So far, March has been the only month in 2016 that has not set a new record low for Arctic-wide sea ice extent (March 2016 was second lowest, just above 2015). However, atmospheric conditions during late June 2016 extending into the first half of July favored low pressure and storminess, resulting in greater than average cloud cover and a slow-down in the Arctic sea ice melt rate. By July 1, Arctic sea was no longer at a record minimum for the date. The latest 2-week forecast from the GFS model shows a continuation of cloudier than usual conditions in the Arctic for the remainder of July, which should keep Arctic sea ice loss not quite as bad as seen during the record-setting retreat in the summer of 2012. The fact that 2016 is still challenging 2012 for lowest sea ice on record is evidence of how “the extraordinary years have become the normal years,” as NASA sea ice scientist Walt Meier stated in an interview last week with the Washington Post.

One billion-dollar weather disaster in June 2016: flooding in China
According to the June 2016 Catastrophe Report from insurance broker Aon Benfield, one billion-dollar weather-related disaster hit the planet in June: flooding in China on June 18 - 23 that cost $2.3 billion (this does not include the renewed round of Chinese flooding that began on June 30 extending into early July, which has brought the total cost of this year's monsoon flooding in China to $22 billion dollars.) Additionally, two severe weather outbreaks in the U.S. during May accumulated enough damage claims to be rated billion-dollar disasters by the end of June. However, the previously reported most expensive weather disaster of 2016—a drought in Vietnam that government of Vietnam said caused $6.75 billion in losses—was reassessed to have caused only $675 million in losses, due to an extra zero the government inadvertently put into its original damage estimate. Between January - June 2016, there have been eighteen billion-dollar weather disasters--one more than occurred during January - June 2013, the year that ended up with the most billion-dollar weather disasters on record: 41. Here is the tally of billion-dollar weather disasters for January - June 2016, updated to include the early July numbers from the Chinese monsoon flooding:

1) Flooding, China, 6/1 - 7/14, $22.0 billion, 273 killed
2) Drought, India, 1/1 - 6/30, $5.0 billion, 0 killed
3) Flooding, Germany, France, Austria, Poland, 5/26 - 6/6, $5.0 billion, 17 killed
4) Severe Weather, Plains-Southeast U.S., 4/10 - 4/13, $3.75 billion, 1 killed
5) Wildfire, Fort McMurray, Canada, 5/2- 6/1, $3.1 billion, 0 killed
6) Winter Weather, Eastern U.S., 1/21 - 1/24, $2.0 billion, 58 killed
7) Winter Weather, East Asia, 1/20 - 1/26, $2.0 billion, 116 killed
8) Severe Weather, Rockies-Plains-Southeast-Midwest U.S., 3/22 - 3/25, $1.75 billion, 0 killed
9) Tropical Cyclone Roanu, Sri Lanka, India, Bangladesh, Myanmar, China, 5/14 - 5/21, $1.7 billion, 135 killed
10) Drought, Zimbabwe, 1/1 - 3/1, $1.6 billion, 0 killed
11) Flooding, Argentina and Uruguay, 4/4 - 4/10, $1.3 billion, 0 killed
12) Severe Weather, Plains-Midwest-Southeast-Northeast U.S., 3/4 - 3/12, $1.25 billion, 6 killed
13) Severe Weather, Plains-Midwest-Southeast-Northeast U.S., 2/22 - 2/25, $1.2 billion, 10 killed
14) Severe Weather, Plains-Midwest U.S., 4/29 - 5/3, $1.1 billion, 6 killed
15) Severe Weather, Plains-Midwest U.S., 5/21 - 5/28, $1.1 billion, 1 killed
16) Flooding, Plains-Rockies U.S., 4/15 - 4/19, $1.0 billion, 9 killed
17) Severe Weather, Plains-Southeast U.S., 3/17 - 3/18, $1.0 billion, 0 killed
18) Tropical Cyclone Winston, Fiji, 2/16 - 2/22, $1.0 billion, 44 killed

And here is the one disaster from June 2016 in more detail:


Disaster 1. Southern China, including Jiangsu, Zhejiang, Anhui, Jiangxi, Gansu, Shaanxi, Qinghai, Hubei, Hunan, Guangxi Zhuang, Chongqing, Sichuan, Guizhou, and Yunnan provinces, experienced torrential monsoon rains from June 18 - 23 that caused significant flooding. At least 68 people were dead or missing in the provinces of Anhui, Jiangxi, Hubei, Chongqing, Sichuan, and Yunnan, and damage was estimated at $2.3 billion. In this image, we see an aerial view of flooded buildings in Nianyushan Town of Changjiang District, China on June 21, 2016 in Jingdezhen, Jiangxi Province of China. (Photo by VCG/VCG via Getty Images)


Figure 4. As of July 13, 2016, the southwest monsoon had progressed at a near-normal pace across all of India, and had entered into eastern Pakistan. Image credit: India Meteorological Department.

Good monsoon rains in India
India, whose $5 billion drought was Earth's second most expensive weather-related natural disaster of the first half of 2016, is finally getting a good monsoon after two straight years of poor rains. According to the India Meteorological Department, the monsoon progressed at a near-normal pace across the nation during June and July, and monsoon rains during the period June 1 - July 18 were 3% above average.

Notable global heat and cold marks set for June 2016
Hottest temperature in the Northern Hemisphere: 52.4°C (126.3°F) at Mitribah, Kuwait, 30 June
Coldest temperature in the Northern Hemisphere: -27.7°C (-17.9°F) at Geo Summit, Greenland, 2 June
Hottest temperature in the Southern Hemisphere: 39.5°C (103.1°F) at Picos, Brazil, 4 June
Coldest temperature in the Southern Hemisphere: -81.6°C (-114.9°F) at Dome Fuji, Antarctica, 13 June
(Courtesy of Maximiliano Herrera.)

Major weather stations that set (not tied) new all-time heat or cold records in June 2016
Baharia (Egypt) max. 48.8°C, 4 June
Choix (Mexico) max. 48.7°C, 5 June
Huites (Mexico) max. 50.0°C, 5 June
Beru (Kiribati) max. 34.8°C, 6 June; increased to 35.0°C on 9 June
Bilma (Niger) max. 49.0°C, 8 June; New national record high for Niger
Saragt (Turkmenistan) max. 47.3°C, 8 June
Paamiut (Greenland, Denmark) max. 23.6°C, 10 June
Tamanrasset Airport (Algeria) max. 40.2°C, 18 June 
Khamis Mushait (Saudi Arabia) max. 36.2°C, 18 June
Abha (Saudi Arabia) max. 38.1°C, 18 June
Altar (Mexico) max. 48.5°C, 19 June
Sonoyta (Mexico) max. 49.4°C, 19 June
Blythe (California,USA) max. 51.1°C, 20 June

Notes:
- On 4 June, Picos AWS in Brazil recorded 39.5°C, the highest temperature ever recorded in June in the Southern Hemisphere. Previous record was 39.3°C at Ibibobo in Bolivia.

- On 8 June, Koror AWS, Palau, hit 34.4°C (94°F), tying the highest reliable temperature ever recorded in Palau (34.4°C was also recorded on several occasions at Nekken Forestry and at Koror, most recently on 16 April, 2016.)

(Courtesy of Maximiliano Herrera.)

One all-time national heat record set in June 2016
One nation--Niger--set a record in June 2016 for its all-time hottest temperature on record. From January through July 16, 2016, a total of twelve nations or territories tied or set all-time records for their hottest temperature in recorded history. 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 July 16:

Hong Kong Territory (China) tied its all-time hottest record on July 7, 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.

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 (94.8°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.

Jeff Masters and Bob Henson

Climate Summaries

Could the Imminent U.S. Heat Wave Trigger a Flash Drought?

By: Bob Henson , 12:36 AM GMT on July 19, 2016

A massive upper-level high will envelop most of the contiguous U.S. in the last half of July, setting up what could be a prolonged bout of extreme heat for millions of Americans. If the scorching weather persists into August, the odds of a “flash drought” in the nation’s heartland will rise sharply (along with the odds that the U.S. will notch its hottest summer on record, in line with what’s very likely to be Earth’s warmest year on record). Even though it appears that heat and humidity will combine to put residents, pets, and livestock through the wringer, it’s quite possible that the croplands of the Midwest and Plains will fare better than one might expect, thanks to a fortunate confluence of factors.

There’s certainly no mercy in the pattern projected for the next few days at upper levels. As shown in Figure 1, the upper high at 500 millibars (about four miles up) encompasses nearly all of the contiguous U.S. by Thursday night, July 21. Because air expands as it warms, a higher 500-millibar surface is associated with a warmer air mass at lower levels. Although the most extreme 500-mb heights projected in earlier model runs have dropped just a bit, both the GFS and ECMWF models have been consistent with their portrayal of a mammoth upper ridge centered near the nation’s midsection for at least the next week to ten days, perhaps longer. The atmospheric variables predicted to take shape later this week are similar to those observed during some of the nation’s most notorious heat waves of recent decades, according to the CIPS Analog website from the Cooperative Institute for Precipitation Systems/Saint Louis University. At the time period shown below in Figure 1 (8 PM Thursday, July 21), the closest analog for conditions predicted for the Midwest (taking into account temperatures, moisture, and other factors at various layers) is July 13, 1995--the second day of a catastrophic five-day heat wave that took more than 700 lives in the Chicago area. The top analogs also include July 4, 2012, and August 7, 1980, two peak days from the devastating central U.S. drought years of 2012 and 1980. Excessive heat watches for later this week have already been issued by the National Weather Service for parts of Illinois, Iowa, Kansas, Minnesota, Nebraska, North Dakota, and South Dakota. We can expect many other areas to follow suit as the week unfolds.


Figure 1. 500-millibar heights (in decameters, or tens of meters) predicted for 8:00 PM Thursday, July 21, 2016, by the 12Z Monday GEFS (the ensemble run of the GFS model). The colors show how much the predicted 500-mb height deviates from the average for this time of year. Image credit: tropicaltidbits.com.

Blazing temps and wilting humidity: a risky combo
With such strong model support for a high-end upper ridge, one might expect surface temperatures to be correspondingly extreme. Indeed, readings near or above the century mark (100°F) are likely to encompass large parts of the Great Plains by midweek--perhaps even topping 110°F in some spots--with 90°F to 100°F readings over a far larger part of the nation. As an upper-level impulse rides along the north side of the ridge later this week, a burst of heat and humidity will be shunted eastward, approaching the East Coast toward the weekend. In a post on Monday, Capital Weather Gang observed that both the GFS and ECMWF models are predicting highs in the vicinity of 105°F in the Washington, D.C., area for Saturday, perhaps approaching the city’s all-time high of 106°F (set on August 6, 1918 and July 20, 1930). It’s important to keep in mind that long-range models often struggle in nailing down the exact location and strength of high temperatures this extreme, especially beyond two or three days. The key message here isn’t the precise forecast for Saturday, but the overall signals pointing toward an intense and possibly historic round of heat affecting most of the central and eastern U.S.

Another important element of this heat wave: some of the energy that would otherwise go into heating up the lower atmosphere will be diverted into evaporating moisture. Plants and soils are quite moist in many areas thanks to recent rains, especially through a belt from the Central Plains into the Ohio Valley. That moisture is a mixed blessing: while it’ll help to keep surface air temperatures a notch lower than they’d otherwise be, it will also help pump up the amount of water vapor in the air. In addition, the Midwest’s vast corn crops are at a stage where they add moisture to the air through evapotranspiration, a process dubbed “corn sweat”. As a result, heat index values will soar to uncomfortable and even dangerous levels as this week progresses over large parts of the central and eastern U.S., especially toward the south. The atmospheric moisture will also help boost nighttime lows, which exacerbates the potential risk to human and animal health from a multi-day heat wave. (Climate Central recently documented the long-term rise in summertime atmospheric moisture across the U.S. as measured by surface dew points.)


Figure 2. In this 4-day outlook from Monday, July 18, 2016, daily heat indices on Friday, July 22, are projected to exceed 105°F (magenta) over large parts of the central and eastern U.S. The highest indices will shift toward the Southeast by early next week. Image credit: NOAA/NWS Weather Prediction Center.

Watching for flash drought
It wasn’t too long ago--in 2012--that a promising-looking spring morphed into a terrible summer for the U.S. Midwest. A long-term drought that began in late 2010 had intensified over the Southern Plains in 2011, punishing farmers and ranchers and facilitating the loss of roughly 10% of all trees in Texas. The real shocker was how quickly drought conditions took hold further north across the Midwest in the summer of 2012, leading to the most widespread U.S. drought conditions since the 1930s. “Nobody called that [in advance],” said Mark Svoboda (National Drought Mitigation Center). Even NOAA’s 30-day and seasonal drought outlooks from June 2012 failed to predict that month’s emergence of drought in the Midwest, according to Svoboda. It appears this wasn’t a simple northward extension of the ongoing drought further south, but something else--a classic case of what’s increasingly known as a flash drought, a rapid-onset drying of the landscape (there is not yet a standard definition). Svoboda first brought the term to a general audience when he used it in 2000 in a USA TODAY interview. but it was the 2012 Midwest event that gave the flash-drought concept much more prominence.

While long-term drought can emerge simply through a lack of precipitation, a flash drought is closely linked to hot summer weather. The type of flash drought most often observed in the Midwest develops as a torrid air mass sweeps in for a period of a few days to several weeks. At first, the landscape may not be particularly dry, in which case large amounts of water vapor flow from vegetation and soils into the scorching surface air (as is expected later this week). If the heat is strong and sustained enough, the landscape quickly dries out and a flash drought takes hold.


Figure 3. Frequency of occurrence of five-day periods of two types of flash drought--heat wave flash drought (top) and precipitation-deficit flash drought (bottom)--in an ensemble of four models employed to replicate land-surface conditions for the climate from 1916 to 2012. Image credit: Figs. 4a and 4b from Kingtse C. Mo and Dennis P. Lettenmaier, “Precipitation Deficit Flash Droughts over the United States,” Journal of Hydrometeorology 2016 17:4, 1169-1184, ©American Meteorological Society.  Used with permission.


In a paper published this spring in the Journal of Hydrometeorology, Kingtse Mo (NOAA Climate Prediction Center) and Dennis Lettenmaier (University of California, Los Angeles) label the above sequence of events a “heat wave flash drought.” The scientists also identified another, more common flavor--what they call a “precipitation deficit flash drought”--that’s most frequent in the Southern Plains. In this type of flash drought, a lack of precipitation allows the local landscape to heat up quickly under the strong summer sun, which leads to additional drying and further heating. Both types of flash drought are dangerous, the scientists warn: “Even though flash droughts tend not to persist, they initiate the depletion of soil moisture, and the persisting deficits can cause large damages to the agriculture community.”

Better late than sooner
If there’s any potential for a heat wave flash drought over the next few days, at least the timing is on our side. The heat is arriving several weeks later than the worst conditions in 2012, which means that major crops are further along and better able to handle the heat. In addition, the nation’s corn and soybean crops have been maturing more quickly than usual this year (see Figure 4 below). According to USDA meteorologist Brad Rippey, this is largely due to the unusual warmth of June (the warmest on record for the 48 contiguous states) together with early planting in some areas. “Corn typically has a very short period of time--ten days or so--when it is acutely sensitive to air temperature and moisture availability,” Rippey told me. Temperatures above 95°F and/or a lack of moisture are detrimental to the pollination process. However, Rippey said, “by the time the heat wave hits the western and southern Corn Belt this week, a decent amount of the corn will have passed through its most sensitive stage.” Further to the northeast, in Wisconsin, Indiana, Ohio, and Michigan, corn planting was delayed due to the cool, wet May. However, temperatures there should stay below critical thresholds during the coming week.

One concern is the potential impact of very warm nights in the 70s and 80s, which can lower corn yields by depleting sugars produced by daytime photosynthesis. “Today’s drought-tolerant varieties are really quite good at overcoming weather challenges, although nighttime heat seems to be a particular problem,” Rippey said. He adds that soybeans--another hugely important U.S. crop–are more flexible in dealing with flash droughts, since they have a wider reproductive window and can slow or halt their growth processes as needed to conserve energy and moisture.


Figure 4. The nation’s corn and soybean crops have grown more quickly than usual in 2016. Left: percent of corn crops silking in each state by July 17 (top numbers), together with the percentage difference (bottom numbers) from the five-year average for this date. Right: percent of soybean crops blooming by state. Image credit: USDA, courtesy Brad Rippey.

Two new tools for tracking flash drought
A burst of research has led to the emergence of new monitoring efforts that may help identify and even predict flash droughts. The National Drought Mitigation Center has been leading a multiyear effort to develop the Quick Drought Response Index (QuickDRI), which will monitor changes in vegetation over periods of a week or two. QuickDRI is building on VegDRI, an operational product that uses satellite and climate data to map vegetation change at the seasonal scale. Funded by NASA, QuickDRI is being tested this year and may become “pseudo-operational” as soon as 2017, according to NDMC’s Mark Svoboda.

Meanwhile, a group led by Michael Hobbins (NOAA/ESRL Physical Science Division) and Dan McEvoy and Justin Huntington (Desert Research Institute) has developed the Evaporative Demand Drought Index (EDDI), which focuses on the weather that drives both flash drought and long-term drought. Rather than assessing the landscape itself, or recent rainfall, EDDI looks solely at evaporative demand--the impact of atmospheric temperature, humidity, wind, and solar radiation over a particular time period--and how it compares to climatology. A positive EDDI indicates drier-than-average conditions. In evaluations thus far, EDDI appears to work well in providing advance notice of drought development, often ahead of other commonly used indexes. The EDDI is spotlighted in the June issue of the Journal of Hydrometeorology, where a pair of papers explains the rationale for the index and a U.S.-based evaluation of its skill. The EDDI will be moving toward operational use at NOAA’s National Water Center over the next two to three years, according to Hobbins. “The three sectors or drought types for which we think EDDI holds out the greatest hope for warning capabilities are flash drought, sustained long-term agricultural and hydrologic drought, and wildfire risk,” he added. In the meantime, regularly updated EDDI maps for various time frames are available for download. The most recent 4-week EDDI map suggests that the eastern Great Lakes, New York, and western New England have experienced drought-favorable weather over the last month. Patches of moderate drought in these areas are now showing up in the weekly U.S. Drought Monitor.

We’ll be back with our next post by Tuesday afternoon.

Bob Henson


Figure 5. EDDI values for the four weeks ending on July 13, 2016. EDDI categories are similar to those used in the U.S. Drought Monitor, although EDDI is designed to monitor the weather that leads to drought rather than to diagnose existing drought. EDDI does not incorporate precipitation or soil conditions--only atmospheric and solar variables. Image credit: Courtesy Michael Hobbins, NOAA/ESRL/PSD.

Heat Drought Extreme Weather

Eastern Pacific Hurricane Parade Continues; Record Ocean Heat Energy in the Atlantic

By: Jeff Masters and Bob Henson , 3:04 PM GMT on July 18, 2016

The Eastern Pacific's unending parade of tropical cyclones continues. The latest member of the show is Tropical Storm Estelle, which got its name Friday night. Joining the party since Tropical Storm Agatha started on July 2 have been Category 4 Hurricane Blas, Category 2 Hurricane Celia, Category 3 Hurricane Darby, and soon-to-be Category 1 Hurricane Estelle (Estelle was a high-end tropical storm with 70 mph winds at 11 am EDT Monday.) This puts us well ahead of climatology: the Eastern Pacific usually does not see its fifth named storm until July 22, its fourth hurricane until August 12, and its second major hurricane until August 19. An average season has 15 named storms, 8 hurricanes, and 3 major hurricanes.


Figure 1. VIIRS visible satellite image of ex-Hurricane Celia, Hurricane Darby, and Tropical Storm Estelle taken on Sunday afternoon, July 17, 2016. Image credit: NASA.

Frank and Georgette on the way?
In their 8 am EDT Monday Tropical Weather Outlook, NHC identified two more areas of possible tropical cyclone formation in the Eastern Pacific off the Pacific coast of Mexico. They gave 2-day and 5-day odds of development of 0% and 20% to one area, and 0% and 50% to the other. Both the European and GFS models show the potential for these areas of concern to become Tropical Storm Frank and Tropical Storm Georgette by late this week or early next week--though the models are not as gung-ho about developing these systems as they were for Agatha, Blas, Celia, Darby, and Estelle. The two potential new storms are expected to take a track to the west or west-northwest away from or parallel to the coast of Mexico. The July record for named storms forming in the Eastern Pacific is seven, set in 1985, according to NHC hurricane scientist Eric Blake. If we get a Tropical Storm Georgette this year, that would tie the July record.

The Atlantic remains quiet--but beware of this year's ocean heat content!
As is usually the case when the Eastern Pacific is active, the Atlantic is quiet. This inverse correlation in activity occurs because the conditions over the Eastern Pacific driving this July's bounteous activity--surface low pressure and rising air--creates a compensating area of sinking air over the tropical Atlantic. This sinking air creates surface high pressure and dry weather--the antithesis of conditions needed for tropical cyclone formation. There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for tropical cyclone formation is predicting development during the coming five days. Don't expect to see much activity in the Atlantic until the Eastern Pacific's burst of activity slows down. When we finally do get the surface low pressure, rising air, low wind shear, plentiful low to mid-level moisture and an African tropical wave needed to spawn an Atlantic hurricane, watch out. Record to near-record levels of heat energy are in the Atlantic in the Caribbean, Gulf of Mexico and waters surrounding the Bahamas (Figure 2), exceeding even the heat energy that was available during the notorious Hurricane Season of 2005. This year's high levels of ocean heat content in the Atlantic increases the odds of dangerous rapidly-intensifying major hurricanes if the other conditions needed for intensification are present.


Figure 2. Total oceanic heat content (called the Tropical Cyclone Heat Potential, or TCHP) in kilojoules per square centimeter (kJ/cm^2), for July 15 for the years 2005 - 2016. TCHP was at near-record or record values over much of the Caribbean, Gulf of Mexico, and waters surrounding the Bahamas in July 2016. TCHP in excess of 90 kJ/cm^2 (orange colors) is commonly associated with rapid intensification of hurricanes. Image credit: NOAA/AOML.

Bob will be back with a new post on this week's U.S. heat wave later today.

Jeff Masters and Bob Henson

Hurricane

Earth's 5th Costliest Non-U.S. Weather Disaster on Record: China's $22 Billion Flood

By: Jeff Masters and Bob Henson , 4:14 PM GMT on July 15, 2016

A historic flood event continues in China, where torrential monsoon rains along the Yangtze River Valley in central and eastern China since early summer have killed 237 people, left 93 people missing, and caused at least $22 billion in damage, the Office of State Flood Control and Drought Relief Headquarters said on Thursday. According to the International Disaster database, EM-DAT, this would make the 2016 floods China's second most expensive weather-related natural disaster in history, and Earth's fifth most expensive non-U.S. weather-related disaster ever recorded. Only China's 1998 floods, with a price tag of $44 billion (2016 dollars), were more damaging than the 2016 floods. According to the June 2016 Catastrophe Report from insurance broker Aon Benfield, Earth's only deadlier weather disaster in 2016 was an April heat wave in India that claimed 300 lives. Some 147,200 houses have been destroyed by this summer's floods in China, and over 21,000 square miles of farmland had been inundated--an area the size of Massachusetts and Vermont combined. An additional $1.3 billion in flood damage from Typhoon Nepartak occurred in China in July.


Figure 1. A stadium in Wuhan, China on July 6, 2016, after the city received 7.09” (180 mm) of rain in the twelve hours ending at 8 am July 6. Wuhan received over 560 mm (1.8 feet) of rain over the ten day period before the July 6 deluge, causing widespread damage and chaos. (Photo by Wang He/Getty Images)


Figure 2. Flood waters inundate a village in Xuancheng, in east China's Anhui province, on July 7, 2016. Image credit: STR/AFP/Getty Images.

Monsoon season in China
It's been a severe monsoon season in China this year. As we noted in a June 23 post, the heavy rains in China have occurred along the Mei-yu (or baiu) front, a semi-permanent feature that extends from eastern China across Taiwan into the Pacific south of Japan, associated with the southwest monsoon that pushes northward each spring and summer. The Mei-yu rains typically affect Taiwan and southeastern China from mid-May to mid-June, then migrate northwards to the Yangtze River region and southern Japan during June and July (the Mei-yu is known as Baiu in Japan), and then further northward to northern China and Korea (known as Changma in Korea) during July and August. A number of studies have found that the Mei-yu rainfall tends to be particularly heavy in the summer following an El Niño event, as is occurring in 2016--and occurred in 1998, the only year to experience more damaging flooding in China.


Figure 3. This summer's floods in China are the fifth most expensive weather-related natural disaster on record outside of the U.S., according to the International Disaster database, EM-DAT.


Figure 4. The U.S. has seen twelve weather-related disasters costing at least $20 billion, with eleven of them more expensive than the 2016 Chinese floods. Data source: NOAA/NCEI.

Heavier Mei-yu rains are expected in a warming climate
As the planet’s oceans and atmosphere warm up due to increased amounts of heat-trapping gases like carbon dioxide, more water vapor is entering the lower atmosphere, which provides more fuel for heavy rain. Observations show that the heaviest periods of precipitation have become more intense in many parts of the globe, and climate models agree that this trend should continue as our planet continues to warm. The Yangtze Valley of China is among the locations where a significant increase in summer precipitation was found to occur during the 20th century, as described in a 2007 paper in the International Journal of Climatology. A multiyear series of studies using high-resolution global circulation models (20 km), led by Shoji Kusunoki (Japan’s Meteorological Research Institute, or MRI) and colleagues, found that both average and extreme precipitation in the Mei-yu zone will increase during the 21st century (see this 2011 paper in Climate Dynamics). Subsequent modeling has only strengthened this finding. In the 2015 book “The Monsoons and Climate Change: Observations and Modeling,” Hirokazu Endo (MRI) and Akio Kitoh (University of Tsukuba, Japan) conclude: “State-of-the-art climate models project that both the amount and intensity of Asian summer monsoon rainfall are likely to increase under global warming, and that the rates of increase will be higher than those in other monsoon regions…Considering the improvements in CMIP5 (climate models) compared to CMIP3 in simulating present-day characteristics, we now have more confidence in future projections.”


Figure 5. Rainfall for the 30-day period ending on July 14, 2016 over China. Rainfall amounts in excess of 15.75" (400+ mm, dark blue color) fell over a large swath of the Yangtze River basin in China from Wuhan to just west of Shanghai. Image credit: National Meteorological Center of CMA.


Figure 6. Predicted total precipitation over China for the 16-day period ending at 00 UTC July 31, 2016, from the 00 UTC Friday, July 15, 2016 run of the GFS model. A wide swath of 12+" (305 mm) monsoon rains (light orange colors) is predicted to fall over portions of the Yangtze River basin. Image credit: tropicaltidbits.com.

More damaging flooding to come this summer in China
The flooding damage in China is likely to grow this month, as new rounds of torrential monsoon rains hit the nation in the coming weeks. "Although the water levels in middle and lower reaches of the Yangtze River are slowly dropping, most are still above warning levels," Zhang Jiatuan, a spokesperson for the Office of State Flood Control and Drought Relief Headquarters, told reporters on Thursday. He said the situation was "still quite critical" as central and eastern parts of China are expected to see a fresh round of heavy rain over the days to come. The latest precipitation forecast from the GFS model predicts a wide swath of 12+" of rain will fall over much of the flood-affected area through the end of July (Figure 6.)

Jeff Masters and Bob Henson

Flood

Two Flavors of Record Heat: Deadhorse and Houston

By: Bob Henson and Jeff Masters , 4:38 PM GMT on July 14, 2016

If you glance at a temperature map for North America, as shown below, you might get the impression that we’re in the midst of a fairly typical midsummer week. The north central United States and south central Canada are basking in relative comfort, thanks to a strong upper-level low and an accompanying surface high moving across the northern tier of U.S. states. Readings on Thursday morning dipped into the 50s and 60s Fahrenheit across the Northern Plains. This air will be sliding eastward over the next several days, bringing a refreshing “mild-down” across the Midwest and Northeast. What’s noteworthy right now isn’t at the core of the continent: it’s along the fringes, where some exceptional heat has been produced in recent days.


Figure 1. Temperature anomalies (departures from normal) for Thursday, July 15, 2016, as extrapolated from the 00Z Thursday GFS model output. Image credit: Climate Reanalyzer/University of Maine.


Big heat in northernmost Alaska
A pulse of warm air invaded the North Slope of northern Alaska on Wednesday, bringing some of the warmest air ever recorded there. Even with the 24-hour sunlight it receives during most of July, the North Slope typically experiences highs only in the 50s and lows in the 30s. Much warmer air can filter into the region on occasion, though, typically as a mild air mass sweeps in aloft and then warms further as it descends (the same process that can produce very mild winter conditions along the east slopes of the Rockies via “chinook” winds). On Wednesday, the tiny town of Deadhorse, AK--located about 200 air miles southeast of Barrow, and just 10 miles from the Arctic Ocean--rocketed to a high of 85°F, which is an all-time high for the Deadhorse/Prudhoe Bay area. Records there only go back to 1968, but climatologist Brian Brettschneider adds that the Deadhorse reading was the highest ever reported at any location within 50 miles of Alaska’s Arctic coast. The COOP station in Kuparuk, a few miles west of Deadhorse, also reported 85°F, according to Brettschneider. Meanwhile, Barrow topped out at 66°F on Wednesday, well short of the daily record of 79°F—which also happens to be its all-time record high, set in 1993. Update: On Thursday, July 14, Kuparuk topped its all-time record set just the day before, soaring to 86°F.


Figure 2. Temperatures at 4 PM AKDT Wednesday, July 13, 2016, along the Arctic Ocean coast of northernmost Alaska. Image credit: Brett Brettschneider.

Hot nights in Houston
The eye-opener this month in southeast Texas isn’t that it got up into the 80s—it’s that the temperature has had trouble getting below that range. Last week, on July 5, Houston’s Bush Intercontinental Airport tied its all-time warm minimum with a steamy low of just 83°F. This came midway through a five-day stretch of lows at or above 80°F, all of them setting daily records. Weather records at the airport began only in 1969, but the only higher daily minimum in the city’s official record is the 84°F low notched more than a century ago, on July 29, 1895. For this month through Wednesday, July 13, Houston has scored a remarkable nine days with low temperatures at or above 80°F. The most such lows in a single month is 14, in August 1964, so the city has a reasonable shot at breaking that record, as noted by Eric Berger at Space City Weather. Houston’s average temperature for the month through Wednesday (counting both highs and lows) is a sweltering 88.3°F, which is running almost a degree higher than the warmest July on record (87.5°F, set in 1980).

Further west, extreme heat has also been plaguing the High Plains of eastern New Mexico and west Texas for days on end. The town of San Jon, NM, set an all-time record high of 111°F on Wednesday, beating the previous record of 110°F set on June 24, 1990 (records in San Jon go back to 1907). Portales, NM, beat its July record and tied its all-time record high of 109°F from June 25, 2011 (records in Portales go back to 1905). In Lubbock, TX, the average high temperature this month has been a blazing 100.3°F, more than 7 degrees above average. On July 7, Lubbock tied its all-time monthly record of 109°F.

Torrid conditions for the heartland next week
After being shunted to the far sides of the continent, record or near-record heat will invade the center of North America next week, perhaps for an extended period. Long-range computer models continue to insist that a very strong and large ridge of high pressure will develop next week, encompassing most of the contiguous U.S. by the weekend of July 23-24. Temperatures will soar well into the 90s across most of the central U.S., with large areas above 100°F possible by late next week, especially over the Great Plains. Some runs of the GFS and ECMWF models have predicted that the height of the 500-mb pressure surface (roughly the vertical midpoint of the atmosphere) will exceed 600 decameters (6 km, or about 3.7 miles) near the center of the ridge. This would be a noteworthy event, typically seen only during the most intense U.S. heat waves. Because warm air expands, a deep layer of warm air at low levels pushes the 500-mb height upward.


Figure 3. Temperature anomalies (departures from average) in degrees C, projected by the GFS model run from 06Z Thursday, July 14, 2016, for 18Z (2:00 pm EDT) Thursday, July 21, 2016. For readings in degrees Fahrenheit, multiply the Celsius readings shown by 1.8. Image credit: tropicaltidbits.com.

Seemingly endless parade of storms continues in the Eastern Pacific
The Eastern Pacific is in the midst of an extraordinary period of July activity, thanks to favorable genesis conditions created by the presence of the Madden-Julian Oscillation (MJO), which has created rising air and low pressure over the region. Beginning on July 2, Tropical Storm Agatha formed, and since then, three hurricanes have joined the parade: Category 4 Hurricane Blas (now dissipated), Category 2 Hurricane Celia (now a tropical storm), and Category 1 Hurricane Darby (predicted to stay below Category 2 strength through the weekend, then weaken.)


Figure 4. VIIRS visible satellite image of ex-Hurricane Blas, Hurricane Celia, Tropical Storm Darby, and Invest 98E taken on Wednesday afternoon, July 13, 2016. Image credit: NASA.

Estelle on the way--and perhaps Frank
Tropical Storm Estelle is also likely on the way--both the European and GFS models indicate that an area of disturbed weather several hundred miles southwest of Acapulco, Mexico (Invest 98E) will develop into a tropical depression by Saturday, and become Tropical Storm Estelle early next week. In their 8 am EDT Thursday Tropical Weather Outlook, NHC gave 98E 2-day and 5-day odds of development of 50% and 90%, respectively. Future Estelle is expected to follow a path similar to Agatha, Blas, Celia and Darby--generally west to west-northwest, away from Mexico. If the Eastern Pacific manages to spit out a Tropical Storm Frank before the end of the month--which is quite possible, given the latest long-range forecasts from the GFS and European models--this would give us six named storms for the month, one short of the July record of seven named storms for Eastern Pacific set in 1985, according to NHC hurricane scientist Eric Blake.

The Atlantic remains quiet
As is usually the case when the Eastern Pacific is active, the Atlantic is quiet. This anti-correlation in activity occurs because rising air over the tropical Eastern Pacific typically creates a compensating area of sinking air over the tropical Atlantic. This sinking air creates surface high pressure and dry weather--the antithesis of conditions needed for tropical cyclone formation. There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for tropical cyclone formation is predicting development during the coming five days. Don't expect to see a serious threat area develop in the Atlantic until the Eastern Pacific's burst of activity slows down.

Bob Henson (heat), Jeff Masters (tropical)

Heat Extreme Weather Hurricane

The U.S. Summer is Off to a Record-Hot Start

By: Bob Henson and Jeff Masters , 4:58 PM GMT on July 12, 2016

Last month was the warmest June in 122 years of U.S. recordkeeping, beating out June 1933, according to the monthly climate roundup released on Wednesday by NOAA’s National Centers for Environmental Information (NCEI). Each of the 48 contiguous states came in above its average temperature for June, with Arizona and Utah setting all-time June records for heat. Thirteen other states had a top-ten-warmest June, stretching across the nation from California to Florida.


Figure 1. Statewide rankings for average temperature during June 2016, as compared to each June 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 June 2016, as compared to each June 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.

The nation’s biggest weather calamity of June was the catastrophic flash flood in West Virginia that took at least 23 lives and destroyed more than 1500 homes. In contrast, the month as a whole was marked by unusual dryness across most of the country: it was the 14th driest of the 122 Junes on record. Only one state (Wyoming) had a top-ten-driest June, but the general lack of moisture was most evident across the northern Great Basin, the northern and central Great Plains, and the states from New Jersey and Pennsylvania northeastward. Grand Island, Nebraska, saw just 0.05” of rain, smashing its dry-June record of 0.43” from 1922.

Could this end up as the hottest summer in U.S. history?
In line with a global climate that’s being warmed by greenhouse gases, the contiguous United States has seen six of its ten warmest summers on record in just the last 15 years. On that basis alone, 2016 has a reasonable shot at becoming our hottest summer yet, especially with the head start provided by a record-warm June. On the other hand, there is plenty of inherent variability from week to week and month to month, even in weather that’s averaged across the country.


Figure 3. Top ten hottest summers (June-August) for contiguous U.S., with the rankings of each month and the summer as a whole for the period 1895-2015 (1 = hottest). Data courtesy NOAA/NCEI.

At right, Figure 3 shows how each month played out during our ten warmest summers on record. Each of those blazing summers had at least one month that fell below the top-ten list for that respective month, showing how difficult it is to maintain the kind of unusual warmth we saw in June for an entire summer.


Figure 4. Departures from average temperature (anomalies) across the contiguous U.S. for the period July 1-10, 2016. Image credit: NOAA Climate Prediction Center.

As shown in Figure 4 (right), the first third of July was relatively cool across the Pacific Northwest, Midwest, and New England, with above-average heat continuing across the South and much of the West. This week should continue on the mild side across the northern U.S. as an unusually potent upper-level low for midsummer progresses eastward. This low has already generated a wild variety of weather over the last several days, including a round of torrential rains, flash floods, and tornadoes on Monday centered in Minnesota and Wisconsin. A phenomenal 24-hour rainfall total of 10” reported on Tuesday morning at Wascott, WI, isn’t too far from the state’s 24-hour record of 11.72”, set in 1946. The storms were fueled by extremely high amounts of atmospheric moisture: the dew point at Sioux Falls, SD, hit 82°F on Monday, apparently setting a new all-time record high dew point for the city (h/t to Minnesota meteorologist Paul Douglas for this statistic). On its way to the Midwest, the upper low delivered a blitz of accumulating snowfall and freezing temperatures to the northern Rockies, including parts of Yellowstone National Park and the Grand Tetons above 7000 feet.

As for next week, the ECMWF and GFS models have been remarkably consistent on developing a very strong upper-level high sprawling across much of the nation during the latter half of July. It’s too soon to know exactly how fierce the heat will be, or where its epicenter will be located, but the models suggest that temperatures may challenge the 100°F mark as far north as the Dakotas by later next week, with 90s enveloping most of the nation east of the Rockies for what could be an extended period. The 8-14 day outlook from the NWS Weather Prediction Center shows high odds for above-average temperatures over the entire contiguous U.S. except for the Pacific Northwest, with odds favoring below-average precipitation for most of the Plains and mid-South. If the heat manifests as expected, it may be enough to counterbalance the northern mildness so far in July and keep 2016 in the running for warmest U.S. summer on record, particularly if August stays on the hot side.


Figure 5. An ominous cloud associated with fast-moving thunderstorms sweeps across Aberdeen, South Dakota, on Monday, July 11, 2016. Image credit: wunderphotographer stuswan.


Figure 6. Enhanced infrared image of Hurricane Celia (left) and the smaller Tropical Storm Darby (right) as of 1530Z (11:30 AM EDT) Tuesday, July 12, 2016. Image credit: NOAA/NESDIS.

Celia weakens; Darby develops
The procession of tropical cyclones across the eastern North Pacific that began with the formation of Tropical Storm Agatha on July 2, followed by Hurricane Blas (named on July 3) and Hurricane Celia (named on July 8), continued on Tuesday morning with the formation of Tropical Storm Darby. As of 11 AM EDT Tuesday, Darby was located about 500 miles south of the southern tip of Baja California, moving west at 10 mph with top sustained winds of 40 mph. Although it will be heading west atop very warm sea-surface temperatures, Darby may also encounter cold water churned up in the wake of Hurricanes Blas and Celia. The National Hurricane Center outlook brings Darby to Category 1 strength by Friday, then weakens it by the weekend.

Meanwhile, Hurricane Celia is now a Category 1 storm, located about 1300 miles west-southwest of southern Baja California as of 11 AM EDT Tuesday, with top sustained winds of 90 mph. Celia topped out as a Category 2 hurricane with peak winds of 100 mph on Monday night. Now angling toward the northwest at 12 mph, Celia is expected to gradually bend back westward while slowly weakening over cooler waters during the next couple of days. Based on long-range runs of the GFS and ECMWF models, there is still a chance that a weakened Celia or its remnants could pass just north of the Hawaiian Islands early next week, bringing some high surf and a chance of squalls, but it is too soon to assign any confidence to this possibility.

Both the European and GFS models show an area of disturbed weather will develop several hundred miles southwest of the coast of Mexico by the end of this week, and this disturbance has the potential to intensify into a tropical storm over the weekend. In their 8 am EDT Tuesday Tropical Weather Outlook, NHC gave this future disturbance 2-day and 5-day odds of development of 0% and 60%, respectively. Both Darby and the next potential storm (which would be named Estelle) are expected to follow paths similar to Agatha, Blas, and Celia--generally west to west-northwest, away from Mexico. If the Eastern Pacific manages to spit out a Tropical Storm Frank before the end of the month--which is quite possible, given the long-range forecasts of the continued presence of the MJO over the Eastern Pacific into the end of July--this would give us six named storms for the month, which would approach the July record (from 1985) of seven named storms forming in the Eastern Pacific, according to NHC hurricane scientist Eric Blake.

Bob Henson and Jeff Masters

Hurricane Climate Summaries Heat

The Eastern Pacific is Sizzling; Nothing Cooking in the Atlantic

By: Jeff Masters , 3:36 PM GMT on July 11, 2016

The Eastern Pacific, which got off to its second slowest start on record on July 2 when Tropical Storm Agatha formed, is in the midst of an extraordinary period of July activity, thanks to favorable genesis conditions created by the presence of the Madden-Julian Oscillation (MJO.) Hurricane Blas, which reached Category 4 strength last week, but has since become post-tropical, has now been replaced by Hurricane Celia, which formed on Friday morning. Celia is expected to become a Category 2 hurricane late Monday before reaching cooler waters less than 26°C (79°F). These cooler waters that Celia will encounter beginning on Tuesday should induce a long-term weakening trend. Long-range runs from the GFS and European models on Monday morning predicted that a weak Tropical Storm Celia would pass within 500 miles of the Hawaiian Islands on Monday July 18, potentially giving the islands some high surf and heavy rains. However, it is too early to assess the odds of this happening.


Figure 1. VIIRS visible satellite image of ex-Hurricane Blas, Hurricane Celia, and Invest 97E taken on Sunday afternoon, July 10, 2016. Image credit: NASA.


Figure 2. Wind forecast for 2 am EDT Sunday, July 17, 2016, from the 8 pm EDT Sunday, July 10, 2016 forecast of the GFS model. The GFS model was predicting that there would be three simultaneous named storms in the Eastern Pacific. Image created using our wundermap with the "Model Data" layer turned on.

Darby and Estelle on the way
Tropical Storm Darby is expected to join Celia soon, as Monday morning satellite imagery showed that an area of disturbed weather located about 350 miles south-southwest of Manzanillo, Mexico (97E) was getting close to tropical depression status. In their 8 am EDT Monday Tropical Weather Outlook, NHC gave 97E 2-day and 5-day odds of development of 80% and 90%, respectively.

Tropical Storm Estelle is also likely on the way--both the European and GFS models show an area of disturbed weather will develop several hundred miles southwest of the coast of Mexico by the end of this week, and this disturbance has the potential to intensify into a tropical storm over the weekend. In their 8 am EDT Monday Tropical Weather Outlook, NHC gave this future disturbance 2-day and 5-day odds of development of 0% and 20%, respectively. These potential future Darby and Estelle storms are expected to follow a path similar to Agatha, Blas, and Celia--generally west to west-northwest, away from Mexico. If the Eastern Pacific manages to spit out a Tropical Storm Frank before the end of the month--which is quite possible, given the long-range forecasts of the continued presence of the MJO over the Eastern Pacific into the end of July--this would give us six named storms for the month, which would approach the July record (from 1985) of seven named storms forming in the Eastern Pacific, according to NHC hurricane scientist Eric Blake.


Figure 3. The tropical Atlantic is dominated by dry air and dust from the Saharan Air Layer (SAL), seen in orange colors in this satellite analysis from the Meteosat bird. Continued outbreaks of dust and dry air from the SAL are expected over the tropical Atlantic into next week, according to recent model runs. Image credit: University of Wisconsin/CIMSS.

Nothing cooking in the Atlantic except African dust
As is usually the case when the Eastern Pacific is active, the Atlantic is quiet. This anti-correlation in activity occurs because rising air over the tropical Eastern Pacific typically creates a compensating area of sinking air over the tropical Atlantic. This sinking air creates surface high pressure and dry weather--the antithesis of conditions needed for tropical cyclone formation. There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for tropical cyclone formation is predicting development during the coming five days. I'd be surprised to see a serious threat area develop in the Atlantic until the Eastern Pacific's spasm of activity slows down.


Figure 4. A woman cleans mud and debris after flooding in China's Fujian Province on July 10, 2016 after Tropical Storm Nepartak's landfall. Image credit: Zhang Guojun/XInhua via AP.

Typhoon Nepartak's aftermath: 12 dead, $200 million in damage
Typhoon Nepartak sloshed ashore as a weakening tropical storm over China's Fujian Province on Saturday, July 9, bringing heavy rains of 4 - 8" in this region of China closest to Taiwan. The resulting flooding is being blamed for 9 deaths in China. Eighteen people are missing, and damage is estimated at $135 million. In Taiwan, where Nepartak powered ashore on July 7 as a Category 4 super typhoon with top sustained winds of 150 mph, three deaths are being blamed on the storm, with over $62 million in damage.

Jeff Masters

Hurricane

Typhoon Nepartak Drenches Taiwan, Killing 2; Now Headed For China

By: Jeff Masters , 3:40 PM GMT on July 08, 2016

Typhoon Nepartak powered ashore over the southeastern shore of Taiwan at approximately 6:30 pm EDT (22:30 UTC) July 7 as a Category 4 super typhoon with top sustained winds of 150 mph, as estimated by the the Joint Typhoon Warning Center (JTWC). The Japanese Meteorological Agency (JMA) estimated that Nepartak had a central pressure of 930 mb shortly before landfall. Nepartak hit a relatively unpopulated portion of Taiwan, limiting the damage from the storm. At this writing, two deaths from drowning and 72 injuries had been blamed on the storm. The nearest large city to the storm's landfall location, Taitung (population 107,000), measured sustained 10-minute winds of 81 mph, gusting to 114 mph, at 21 UTC Thursday, in the northwest eyewall of Nepartak. Taitung's pressure sank as low as 964 mb. Lanyu, on an island just off the coast, saw sustained winds (10-minute average) of 101 mph, with a gust to 160 mph, at 02:15 UTC July 8, when the station was in the south eyewall of Nepartak. Several locations in southeast Taiwan received over 15" of rain in less than 24 hours from Nepartak: Tianxiang (19.05" or 484 mm) and Yuli (17.48" or 444 mm.) National Taiwan University (NTU) buoy NTU2 (located about 170 km southeast of Taitung, Taiwan) recorded a surface pressure of approximately 897 mb as the eye passed over near 8 am EDT Thursday. If verified, this may rank as the lowest surface pressure ever measured by a buoy in world history. A team from National Taiwan University is working to verify that the calibration of the pressure on this buoy was correct.


Figure 1. Radar image of Super Typhoon Nepartak making landfall in southeastern Taiwan taken at 5:30 pm EDT July 7, 2016 (5:30 am local time on Friday in Taiwan.) Image credit: http://www.cwb.gov.tw/V7e/observe/radar/>Taiwan CWB.


Figure 2. Super Typhoon Nepartak approaching landfall in Taiwan on the evening of July 7, 2016. Image credit: NOAA/RAMMB/Colorado State.

Nepartak dramatically weaker after hitting Taiwan
The encounter with the high mountains of Taiwan destroyed the inner core of Nepartak, resulting in the surface circulation separating from the circulation at mid-levels of the atmosphere. The surface circulation moved to the southwest and then west to the southwest corner of Taiwan, while the mid-level circulation continued moving more to the west and west-northwest. Whenever a tropical cyclone loses vertical alignment like this, weakening results, and Nepartak was rated a mere Category 1 storm with 80 mph winds and a 970 mb surface pressure by JTWC and JMA at 8 am EDT Friday. Satellite loops on Friday morning from NOAA/SSED and NOAA/RAMMB showed a very disorganized storm with heavy thunderstorms occurring only along its southern flank, over southern Taiwan.


Figure 3. MODIS visible satellite image of Typhoon Nepartak at 03:10 UTC July 8 (11:10 pm EDT July 7), 2016. At the time, Nepartak was a Category 2 typhoon with 105 mph winds. Image credit: NASA.

Nepartak's impact on Taiwan and China
Nepartak had slowed down to a northwest motion at 4 - 5 mph on Friday morning (U.S. EDT), and the typhoon will make landfall in eastern China on Saturday and dissipate by Sunday. Given the slow movement of the typhoon, heavy rains from the storm will be confined primarily close to the coast. This is good news for China, since the coastal region has seen relatively light rains of 1 - 4 inches over the past ten days, and flooding from Nepartak's expected 4 - 8" of rain will likely not be catastrophic there. Had Nepartak been able to penetrate several hundred miles inland and reach the region between Wuhan and Shanghai, where over 16" of rain has fallen over the past ten days, a multi-billion dollar flood disaster would have resulted. According to insurance broker Aon Benfield, heavy monsoon rains since June 30 in the Yangtze River Basin have already killed nearly 200 people and cost $8.7 billion. The hardest-hit areas were in Hubei Province, where up to 1,295 millimeters (4.24 feet) of rain have fallen since June 30.

Taiwan's recent typhoon history
Nepartak is not the strongest typhoon to hit Taiwan. At least two typhoons have hit Taiwan at Category 5 strength: Super Typhoon Joan, which made landfall in 1959 with 185 mph winds, and Super Typhoon Bilis, which intensified from a Category 2 storm with 105 mph winds to a Category 5 storm with 160 mph winds in the 30 hours before making landfall on the island on August 22, 2000. Bilis killed 14 people and did $134 million in damage to Taiwan. The island was hit by two major typhoons last year: Category 4 Typhoon Dujuan and Category 3 Typhoon Soudelor. The Central Weather Bureau of Taiwan has a list (in Chinese) of all the typhoons that have affected Taiwan.

Nepartak: Earth's third Category 5 storm of 2016
Nepartak is the third Category 5 storm on Earth so far in 2016. Its 900 mb minimum surface pressure makes it the strongest tropical cyclone of the year (by pressure), and its peak 175 mph winds are tied for the second strongest winds of the year. The other two Category 5 storms earlier this year were in the Southern Hemisphere: the Southwest Indian Ocean's Tropical Cyclone Fantala, which topped out with 175 mph winds and a 910 mb central pressure on April 17, and the Southeast Pacific's Tropical Cyclone Winston, which devastated Fiji on February 20 with sustained winds of 180 mph. Winston's lowest central pressure was 915 mb. Both storms were tied for the strongest tropical cyclones ever observed (by sustained winds) in their respective ocean basins. On average, Earth sees 4 - 5 Category 5 storms per year, with over 50% of these being typhoons in the Northwest Pacific. It is rare to have the first named storm of the year in an ocean basin make it to Category 5 strength. This has happened at least twice before in the Northwest Pacific--in 1958, when Category 5 Super Typhoon Ophelia formed in January, and in 2000, with Super Typhoon Damrey (thanks to WU member 1900hurricane for this stat). The Atlantic has had two cases where the first named storm of the year made it to Cat 5--Hurricane Allen in 1980, and Hurricane Andrew in 1992 (thanks go to WU member Tcwx2 for reminding me of Andrew).


Figure 4. Storm Chaser James Reynolds rode out Nepartak in Taitung, and took this photo of an overturned car during the storm. His Twitter feed has more photos and videos.

Storm chasers ride out Nepartak
Storm Chaser Josh Morgerman of iCyclone rode out the storm in Taitung, and had this eyewitness account: "In the early-morning darkness the NW eyewall raked downtown Taitung with terrifying ferocity. The howling was deafening as the air filled with lethal swirling debris. My ears popped painfully during the peak gusts. The hotel's front entrance took a beating, and we thought the front doors would smash-- but instead the winds tore apart the restaurant at the back of the lobby-- all the windows completely blew out-- so that furniture and debris blew into the elevator area.

Then the center made a funny S hook just before landfall-- very typical of Taiwanese typhoons-- so the eye just missed us. From there, the pressure started to rise-- from a low of around 960 mb-- and the winds are now slowly lessening. It's a mess outside. The driveway is filled with every kind of wreckage from God knows where, including signs, branches, tin, a nice old chair, etc. The school across the street has lost almost all of its roof.

This typhoon was a beast-- definitely one of the worst I've been in. The JTWC's final intensity estimate before landfall-- 130 knots, a strong Cat 4 USA-- seems reasonable. And it seems like this city of 107K people felt its full force. An older man I talked to in the lobby-- a Taiwanese dude who's been in many typhoons-- said he never saw wind this strong or felt so frightened during a typhoon.

I'm exhausted and looking forward to sleep. Deep, deeeeep, cyclone-freeee sleeeeeeeeep."


Nepartak Links
Brian McNoldy has a continuously updating radar loop of Nepartak. It is interesting to watch as the storm makes landfall, it gets deflected to the southwest by the high mountains of Taiwan.

Stunning zoomed-in visible animation of Nepartak from July 7, 2016, from NOAA/RAMMB/Colorado State.

Spectacular zoomed-out visible animation of Nepartak from July 7, 2016, from NOAA/RAMMB/Colorado State.



Figure 5. VIIRS visible satellite image of Hurricane Blas taken at 21:40 UTC (5:40 pm EDT) July 7, 2016. At the time, Blas was a Category 3 storm with 115 mph winds. Image credit: NASA.

Eastern Pacific remains active
The Eastern Pacific, which got off to its second slowest start on record on July 2 when Tropical Storm Agatha formed, now has two more named storms. Hurricane Blas peaked as a Category 4 storm with 140 mph winds at 11 pm EDT July 6, but is headed west-northwest into a region with cool waters and more stable air, which will make the storm dissipate by Sunday without affecting any land areas. Tropical Storm Celia formed on Friday morning, but is having trouble with the wake of cold water left behind by Blas. However, Celia should be able to eventually intensify into a hurricane as it heads west to west-northwest over the next week. Long-range runs from the GFS and European model do show a weakening Celia coming within 500 miles of Hawaii on July 16 - 17, so the islands should keep an eye on the storm. And we could have Tropical Storm Darby coming: both the European and GFS models show an area of disturbed weather will develop several hundred miles southwest of the coast of Mexico by Tuesday, and this disturbance has the potential to intensify into a tropical storm late in the week. In their 8 am EDT Friday Tropical Weather Outlook, NHC gave this future disturbance 2-day and 5-day odds of development of 0% and 20%, respectively.

The Atlantic is quiet
There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for tropical cyclone formation is predicting development during the coming five days. On July 12 - 13, an area of low pressure is expected to form off the coast of North Carolina, and it is possible that this low could acquire some tropical characteristics as it moves northeastwards out to sea. The low should not impact any land areas in the U.S.

Have a great weekend, everyone, and I'll be back with a new post by Monday at the latest.

Jeff Masters

Hurricane

Nepartak Holding on to Category 5 Strength Just Hours Before Landfall in Taiwan

By: Jeff Masters , 4:06 PM GMT on July 07, 2016

Super Typhoon Nepartak is holding on to Category 5 strength just hours before landfall in southern Taiwan. At 8 am EDT Thursday, the Japanese Meteorological Agency estimated that Nepartak had a central pressure of 900 mb, and the Joint Typhoon Warning Center (JTWC) estimated top sustained winds of 160 mph. Buoy NTU2 (located about 170 km southeast of Taitung, Taiwan) recorded a surface pressure of approximately 897 mb as the eye passed over between 7:50 - 8:20 am EDT Thursday. Satellite loops from NOAA/SSED and NOAA/RAMMB showed that Nepartak had weakened slightly on Thursday morning, with the eye warming and the area of heaviest eyewall thunderstorms shrinking in size. The storm still remained a very formidable Category 5 storm, though, and its annular structure--with a large donut-like central area of heavy thunderstorms with very little in the way of spiral banding--will make the typhoon more resistant to weakening than typical tropical cyclones.


Figure 1. Radar image of Super Typhoon Nepartak taken at 11:30 am EDT July 7, 2016 (11:30 pm local time in Taiwan.) Image credit: Taiwan CWB.


Figure 2. MODIS visible satellite image of Super Typhoon Nepartak at 02:30 UTC July 7 (10:30 pm EDT July 6), 2016. At the time, Nepartak was a Category 5 super typhoon with 175 mph winds. Image credit: NASA.


Figure 3. Buoy NTU2 (located about 170 km southeast of Taitung, Taiwan) recorded a surface pressure of approximately 897 mb as the eye passed over between 7:50 - 8:20 am EDT Thursday. Image credit: Institute of Oceanography, Taiwan National University. Thanks go to Brian McNoldy and WU member Carnivorous for these links.

Nepartak's impact on Taiwan and China
Nepartak had slowed down to a west-northwest motion at 10 mph on Thursday morning (U.S. EDT), and the typhoon will make landfall in the southern portion of Taiwan later on Thursday. Passage over the high mountains of Taiwan will significantly disrupt Nepartak, and the typhoon is likely to make a second landfall in mainland China on Saturday as a tropical storm.

About 1 - 2" of rain has fallen over Taiwan during the past ten days, so the soils should be able to absorb some of the expected 5 - 15" of rain Nepartak will dump over much of the island. Nevertheless, damaging flooding from the torrential rains of Super Typhoon Nepartak will likely cause tens of millions of dollars in damage to agriculture in Taiwan. The bigger concern for heavy rainfall from Nepartak is in mainland China, though. Exceptionally heavy monsoon rains affected large portions of central and eastern China over the past ten days, bringing rampaging floods that killed at least 140 people since June 30 and caused billions in damage. The soils are still saturated from these rains, and Nepartak's rains will trigger additional damaging flooding. The largest city in central China--Wuhan, with a population of 10.8 million--received over 560 mm (1.8 feet) of rain over the past ten days, with an additional 7.09” (180 mm) of rain falling in the twelve hours ending at 8 am July 6, causing widespread chaos there. However, the Thursday morning run of the HWRF model (Figure 5) showed the heaviest rains of Nepartak would likely remain south of the area flooded by last week's rains.


Figure 4. A stadium in Wuhan, China on July 6, 2016, after the city received 7.09” (180 mm) of rain in the twelve hours ending at 8 am July 6. Wuhan received over 560 mm (1.8 feet) of rain over the ten day period before yesterday's deluge, causing widespread damage and chaos. (Photo by Wang He/Getty Images)


Figure 5. Swath of total rainfall from Nepartak as predicted by the 06 UTC (2 am EDT) Thursday, July 7, 2016 run of the HWRF model. The model predicted widespread rains of 8 - 16" (light yellow colors) over much of Taiwan and Eastern China. Image credit: NOAA/NCEP/EMC.


Figure 6. Rainfall for the 10-day period ending on July 6, 2016 over China. Rainfall amounts in excess of 15.75" (400+ mm, dark blue color) fell over a large swath of China from Wuhan to just west of Shanghai. Image credit: National Meteorological Center of CMA.

Taiwan's recent typhoon history
Only one typhoon has hit Taiwan at Category 5 strength since accurate satellite records began in the 1970s: Super Typhoon Bilis, which intensified from a Category 2 storm with 105 mph winds to a Category 5 storm with 160 mph winds in the 30 hours before making landfall on the island on August 22, 2000. Bilis killed 14 people and did $134 million in damage to Taiwan. The island was hit by two major typhoons last year: Category 4 Typhoon Dujuan and Category 3 Typhoon Soudelor. Typhoon Dujuan made landfall on the island on September 28, 2015, with 140 mph winds, killing three, injuring 376, but causing less than $10 million in damage. Dujuan brought heavy rains to eastern China that caused $652 million in damage, but did not kill anybody there. On August 7, 2015, Typhoon Soudelor hit Taiwan as a Category 3 storm with 120 mph winds. Souledor killed eight, injured 420, and caused over $100 million in damage. At the peak of the storm, 4.85 million households lost electricity--the largest blackout on record in Taiwan due to a typhoon (previous record: 2.79 million customers blacked out by Typhoon Herb in 1996.) Taiping Mountain in eastern Taiwan's Yilan County saw the heaviest rains from the typhoon, with accumulations peaking at 1,334 mm (52.52".) Souledor brought heavy rains to eastern China that killed 26 people and caused $3.08 billion in damage. The Central Weather Bureau of Taiwan has a list (in Chinese) of all the typhoons that have affected Taiwan.

Nepartak: Earth's third Category 5 storm of 2016
Nepartak is the third Category 5 storm on Earth so far in 2016. Its 900 mb minimum surface pressure makes it the strongest tropical cyclone of the year (by pressure), and its peak 175 mph winds are tied for the second strongest winds of the year. The other two Category 5 storms earlier this year were in the Southern Hemisphere: the Southwest Indian Ocean's Tropical Cyclone Fantala, which topped out with 175 mph winds and a 910 mb central pressure on April 17, and the Southeast Pacific's Tropical Cyclone Winston, which devastated Fiji on February 20 with sustained winds of 180 mph. Winston's lowest central pressure was 915 mb. Both storms were tied for the strongest tropical cyclones ever observed (by sustained winds) in their respective ocean basins. On average, Earth sees 4 - 5 Category 5 storms per year, with over 50% of these being typhoons in the Northwest Pacific. It is rare to have the first named storm of the year in an ocean basin make it to Category 5 strength. This has happened at least once before in the Northwest Pacific--in 1958, when Category 5 Super Typhoon Ophelia formed in January. The Atlantic has had two cases where the first named storm of the year made it to Cat 5--Hurricane Allen in 1980, and Hurricane Andrew in 1992 (thanks go to WU member Tcwx2 for reminding me of Andrew).

Nepartak Links
Storm Chaser James Reynolds' Twitter feed is documenting Nepartak's landfall from Taitung, Taiwan, near where the eye is expected to make landfall.

Storm Chaser Josh Morgerman of iCyclone is also reporting from Taitung.

Brian McNoldy has a continuously updating radar loop of Nepartak.

Stunning visible animation of Nepartak from July 7, 2016, from NOAA/RAMMB/Colorado State.

Stunning visible animation of Nepartak from July 6, 2016, from NOAA/RAMMB/Colorado State.

The Himawari-8 Floater satellite loops have some impressive animations of Nepartak during daylight hours in the Western Pacific.

Eastern Taiwan observations from CWB. A Taiwanese station to follow is the Ludao on Green Island (which lies directly in the path of Nepartak). Thanks go to WU member Carnivorous for this link.


Figure 7. VIIRS visible satellite image of Hurricane Blas taken at 21:55 UTC (5:55 pm EDT) July 6, 2016. At the time, Blas was a Category 3 storm with 125 mph winds. Image credit: NASA.

Eastern Pacific remains active
The Eastern Pacific, which got off to its second slowest start on record on July 2 when Tropical Storm Agatha formed, now has two more tropical cyclones. Hurricane Blas, which spun into life on July 3 about 700 miles south of the southern tip of the Baja Peninsula, peaked as a Category 4 storm with 140 mph winds at 11 pm EDT July 6. Blas is headed west-northwest into a region with cool waters and more stable air, and will dissipate early next week without affecting any land areas. Tropical Depression 4-E, soon to become Tropical Storm Celia, is one Hawaii should keep an eye on, though Celia will have trouble with the wake of cold water left behind by Blas. And we could have Tropical Storm Darby next week: both the European and GFS models show an area of disturbed weather will develop several hundred miles southwest of the coast of Mexico early next week, and will intensify into a tropical storm late next week. In their 8 am EDT Thursday Tropical Weather Outlook, NHC gave this future disturbance 2-day and 5-day odds of development of 0% and 20%, respectively.

The Atlantic is asleep
There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for tropical cyclone formation is predicting development during the coming five days. Much of the tropical North Atlantic is dominated by a large area of dry air and dust from the Sahara Desert, which is common in early July.

I'll have a new post on Friday.

Jeff Masters

Hurricane

Category 5 Nepartak Headed for a Thursday Landfall in Taiwan

By: Jeff Masters , 3:31 PM GMT on July 06, 2016

Category 5 Super Typhoon Nepartak is steaming towards a Thursday landfall in Taiwan after putting on a phenomenal display of rapid intensification on Monday and Tuesday. Nepartak went from a tropical storm with 70 mph winds on Monday afternoon to a Category 4 super typhoon with 150 mph winds on Tuesday afternoon, in just 24 hours. Since then, the typhoon has continued to take advantage of light wind shear of 5 - 15 knots and extremely warm ocean waters of 31°C (88°F) to intensify into a ferocious Category 5 storm. These waters are about 1 - 2°C (1.8 - 3.6°F) above average. At 8 am EDT Wednesday, the Japanese Meteorological Agency estimated that Nepartak had a central pressure of 900 mb, and the Joint Typhoon Warning Center (JTWC) estimated top sustained winds of 175 mph. Over the past two days, unusually warm waters have extended to great depth below the storm, creating some of the highest oceanic heat content readings one sees for a tropical cyclone--near 150 kJ/cm**2 (Figure 2). Satellite loops from NOAA/SSED and NOAA/RAMMB show a fearsome storm with huge area of heavy thunderstorms with cold cloud tops reaching high into the atmosphere, surrounding a prominent eye. The storm has taken on an annular appearance, with very little in the way of spiral banding. These type of storms are more resistant to weakening than typical tropical cyclones.


Figure 1. MODIS visible satellite image of Super Typhoon Nepartak at 04:50 UTC (12:50 am EDT) July 6, 2016. At the time, Nepartak was a Category 5 super typhoon with 175 mph winds. Image credit: NASA.


Figure 2. Total Ocean Heat Content (in kilojoules per square centimeter) on July 6, 2016. The past track and forecast track of Super Typhoon Nepartak from the 2 am EDT July 6, 2016 JTWC advisory are overlaid. After traveling over a long stretch of ocean with very high heat content, Nepartak will be moving over a relatively cool area on Wednesday afternoon (U.S. EDT time.) This reduced heat energy means that Nepartak will likely be unable to strengthen further on Wednesday. On Thursday morning, typhoon will be passing over another area of relatively high oceanic heat content, which will likely prevent rapid weakening before landfall in Taiwan occurs. Image credit: University of Wisconsin/CIMSS.

Nepartak's impact on Taiwan and China
Nepartak was headed west-northwest at 18 mph on Wednesday morning (U.S. EDT) on a track that will take it over Taiwan on Thursday afternoon. Our two top global models for predicting tropical cyclone tracks, the GFS and European models, both predicted that Nepartak would make landfall in Taiwan between 18 - 21 UTC (2 pm - 5 pm EDT) on Thursday. Later that day, a trough of low pressure passing to the north of the storm is expected to pull Nepartak to the northwest and then north, taking the storm on a path that should bring it just west of Shanghai, China on Sunday, when the storm will likely dissipate. Nepartak will continue to be over very warm ocean waters of 31°C (88°F) with light wind shear of 5 - 15 knots until about 6 - 12 hours before landfall in Taiwan on Thursday. In the final 12 hours before landfall, increasing wind shear, decreasing ocean temperatures, and interaction will land should act to weaken Nepartak to Category 4 strength.


Figure 3. Swath of total rainfall from Nepartak as predicted by the 06 UTC (2 am EDT) Wednesday, July 6, 2016 run of the HWRF model. The model predicted widespread rains of 8 - 16" (light yellow colors) over much of Taiwan and Eastern China. Image credit: NOAA/NCEP/EMC.


Figure 4. Rainfall for the 10-day period ending on July 5, 2016 over China. Rainfall amounts in excess of 15.75" (400+ mm, dark blue color) fell over a large swath of China from Wuhan to just west of Shanghai. Image credit: National Meteorological Center of CMA.

Heavy rains a huge concern for Taiwan and China
About 1 - 2" of rain has fallen over Taiwan during the past ten days, so the soils should be able to absorb some of the expected 5 - 15" of rain Nepartak will dump over much of the island. Nevertheless, damaging flooding from the torrential rains of Super Typhoon Nepartak will likely cause tens of millions of dollars in damage to agriculture in Taiwan. The bigger concern for heavy rainfall from Nepartak is in mainland China, though. Exceptionally heavy monsoon rains affected large portions of central and eastern China over the past ten days, bringing rampaging floods that killed at least 170 people and caused over $5 billion in damage. The soils are still saturated from these rains, and Nepartak's rains will trigger additional damaging flooding. The largest city in central China--Wuhan, with a population of 10.8 million--received over 560mm (1.8 feet) of rain over the past ten days, causing widespread chaos there. However, the Wednesday morning run of the HWRF model (Figure 3) showed the heaviest rains of Nepartak would likely miss Wuhan. The main concern is for the region between Wuhan and Shanghai, where another 8 - 16" of rain is likely to fall on regions where more than 8" of rain fell last week.

Taiwan's recent typhoon history
If Nepartak hits Taiwan at Category 4 strength, as currently forecast by JTWC, this will not necessarily be catastrophic for the island. Taiwan is no stranger to powerful typhoons, and has endured many strikes by major typhoons without suffering catastrophic impacts. The island was hit by two major typhoons last year: Category 4 Typhoon Dujuan and Category 3 Typhoon Soudelor. Typhoon Dujuan made landfall on the island on September 28, 2015, with 140 mph winds, killing three, injuring 376, but causing less than $10 million in damage. Dujuan brought heavy rains to eastern China that caused $652 million in damage, but did not kill anybody there. On August 7, 2015, Typhoon Soudelor hit Taiwan as a Category 3 storm with 120 mph winds. Souledor killed eight, injured 420, and caused over $100 million in damage. At the peak of the storm, 4.85 million households lost electricity--the largest blackout on record in Taiwan due to a typhoon (previous record: 2.79 million customers blacked out by Typhoon Herb in 1996.) Taiping Mountain in eastern Taiwan's Yilan County saw the heaviest rains from the typhoon, with accumulations peaking at 1,334 mm (52.52".) Souledor brought heavy rains to eastern China that killed 26 people and caused $3.08 billion in damage.

Nepartak: Earth's third Category 5 storm of 2016
Nepartak is the third Category 5 storm on Earth so far in 2016, and tied for the second strongest tropical cyclone of the year (by wind speed). The other two Category 5 storms earlier this year were in the Southern Hemisphere: the Southwest Indian Ocean's Tropical Cyclone Fantala, which topped out with 175 mph winds and a 910 mb central pressure on April 17, and the Southeast Pacific's Tropical Cyclone Winston, which devastated Fiji on February 20 with sustained winds of 180 mph. Winston's lowest central pressure was 915 mb. Both storms were tied for the strongest tropical cyclones ever observed (by sustained winds) in their respective ocean basins. On average, Earth sees 4 - 5 Category 5 storms per year, with over 50% of these being typhoons in the Northwest Pacific.

Links
Stunning visible animation of Nepartak from July 6, 2016, from NOAA/RAMMB/Colorado State.

The Himawari-8 Floater satellite loops have some impressive animations of Nepartak during daylight hours in the Western Pacific.

Taiwan radar

I'll have a new post on Thursday.

Jeff Masters

Hurricane

Super Typhoon Nepartak Takes Aim at Taiwan

By: Jeff Masters , 10:13 PM GMT on July 05, 2016

Residents of Taiwan are turning worried eyes eastwards, where Super Typhoon Nepartak is steaming towards them after putting on a phenomenal display of rapid intensification. Nepartak went from a tropical storm with 70 mph winds on Monday afternoon to a Category 4 super typhoon with 150 mph winds in just 24 hours, as estimated by the Joint Typhoon Warning Center (JTWC). The typhoon took advantage of light wind shear of 5 - 10 knots and extremely warm ocean waters of 31°C (88°F) to fuel its rapid intensification. Unusually warm waters extended to great depth below the storm, creating some of the highest oceanic heat content readings we see for a tropical cyclone--near 150 kJ/cm**2 (Figure 2). Satellite loops from NOAA/SSED and NOAA/RAMMB show a mighty storm with a large area of heavy thunderstorms with cold cloud tops reaching high into the atmosphere, surrounding a 15-mile diameter eye. The storm has taken on an annular appearance, with very little in the way of spiral banding. These type of storms are more resistant to weakening than typical tropical cyclones. The Japanese Meteorological Agency estimated that Nepartak had a central pressure of 925 mb at 2:45 pm EDT Tuesday.


Figure 1. Infrared VIIRS image of Super Typhoon Nepartak at 2:10 pm EDT July 5, 2016. At the time, Nepartak was a Category 4 super typhoon with 150 mph winds. Image credit: NOAA/NASA.


Figure 2. Total Ocean Heat Content (in kilojoules per square centimeter) on July 5, 2016. The past track and forecast track of Super Typhoon Nepartak from the 2 pm EDT July 5, 2016 JTWC advisory are overlaid. After traveling over a long stretch of ocean with very high heat content, Nepartak will be moving over a relatively cool area on Wednesday afternoon (U.S. EDT time.) This reduced heat energy may be responsible for the HWRF model's forecast of a dip in the typhoon's intensity on Wednesday afternoon, followed by a re-strengthening on Thursday morning as the storm passes over another area of relatively high oceanic heat content (see Figure 3). Image credit: University of Wisconsin/CIMSS.


Figure 3. Predicted winds (top) and minimum central pressure (bottom) for Super Typhoon Nepartak made by the Joint Typhoon Warning Center (red) and five computer models at 8 am EDT (12Z) July 5, 2016. The HWRF model (purple) is predicting the typical pattern one might see in an eyewall replacement cycle--a double maximum in the winds (145 kt or 165 mph at 8 pm EDT July 5 and again at 2 am EDT July 7), accompanied by a double minimum in central pressure. However, although the HWRF model is capable of simulating eyewall replacement cycles, this is probably not what is going on in this case, since the zoomed-in graphics from the HWRF model do not show concentric eyewalls forming. Image credit: NOAA/NCEP/EMC.

Nepartak a threat to Taiwan, China, South Korea, and Japan
Nepartak was headed west-northwest at 21 mph on Tuesday evening on a track that will take it very close to Taiwan by Thursday afternoon (U.S. EDT.) Our two top global models for predicting tropical cyclone tracks, the GFS and European models, both predicted that Nepartak would make landfall in Taiwan between 18 - 21 UTC (2 pm - 5 pm EDT) on Thursday. Later that day, a trough of low pressure passing to the north of the storm is expected to pull Nepartak to the north and then northeast, potentially allowing Nepartak to affect the Chinese coast just south of Shanghai, South Korea, and/or Southwest Japan late this week. Nepartak will continue to be over very warm ocean waters of 31°C (88°F) with light wind shear of 5 - 10 knots until about six hours before its expected landfall in Taiwan. Though the total heat content of the ocean will be only roughly half of what the storm fed off during its rapid intensification phase, Nepartak still has nearly ideal conditions for intensification, and will likely become a Category 5 storm on Wednesday.

The Himawari-8 Floater satellite loops have some impressive animations of Nepartak during daylight hours in the Western Pacific.

I'll have a new post on Wednesday.

Jeff Masters

Hurricane

East and West Pacific Tropical Cyclone Seasons Begin With a Bang

By: Jeff Masters , 12:53 AM GMT on July 05, 2016

The longest tropical cyclone-free period in Northwest Pacific history--200 days--ended on Saturday July 3, with the formation of Tropical Storm Nepartak in the waters just south of Guam. The previous tropical cyclone in the basin was Typhoon Melor , which fell below tropical storm strength on December 16, 2015. According to Colorado State University hurricane expert Dr. Phil Klotzbach, the previous longest tropical cyclone drought in the Northwest Pacific was two days shorter--198 days--during December 1972 - June 1973. The July 3 start date for the 2016 season's first named storm is the second latest start date in the 66-year period of record. Only 1998, with a July 8 start date, had a later start. All three of these late-starting years--2016, 1998, and 1973--featured strong El Niño conditions transitioning to neutral or La Niña conditions later in the year.  The upper-level atmospheric circulation associated with such a transition brings an unfavorable environment for tropical cyclones--sinking air, surface high pressure, and dry conditions. Surface pressures over the past month in the waters east of the Philippines extending to the date line have been 0.5 - 1.5 mb above average.


Figure 1. Tropical Storm Nepartak (70 mph winds) at 23 UTC July 4, 2016. Image credit: NOAA.

Nepartak a potential threat to Taiwan, China, South Korea, and Japan
Nepartak was headed northwest at 22 mph on Monday evening on a track that will take it very close to the northern portion of Taiwan by Thursday afternoon (U.S. EDT.) At that time, a trough of low pressure passing to the north of the storm may pull the storm to the north and then northeast, potentially allowing Nepartak to affect the Chinese coast just south of Shanghai, South Korea, and/or Southwest Japan late this week. Nepartak is over very warm ocean waters of 31°C (88°F) with moderate wind shear of 10 - 15 knots. On Tuesday, Nepartak will cross over a region of ocean with very high heat content, and wind shear is expected to drop to the low range, 5 - 10 knots. These nearly ideal conditions for intensification will likely allow the storm to strengthen into a major Category 3 typhoon by Wednesday.

The Himawari-8 Floater satellite loops have some impressive animations of Nepartak during daylight hours in the Western Pacific.


Figure 2. MODIS visible satellite image of Hurricane Blas taken on the afternoon of July 3, 2016. At the time, Blas was a Category 1 storm with 75 mph winds. Image credit: NASA.

Second latest start to the Eastern Pacific hurricane season on record
It's also been a near-record late start to the Eastern Pacific hurricane season, which finally got its first named storm on July 2 when Tropical Storm Agatha formed in the waters over 1000 miles south of the tip of Mexico's Baja Peninsula. Agatha's formation made 2016 the second latest-starting Eastern Pacific hurricane season (east of 140°W) since accurate satellite records began in 1971. The latest first tropical storm on record was Tropical Storm Ava of 1969, which strengthened to a tropical storm at 00 UTC on July 3. Agatha has now been joined by Hurricane Blas, which spun into life on July 3 about 700 miles south of the southern tip of the Baja Peninsula. Agatha and Blas are likely to be joined by Tropical Storm Celia late this week, since both the European and GFS models predict that an area of disturbed weather located several hundred miles south of Acapulco, Mexico will develop. In their 8 pm EDT Monday Tropical Weather Outlook, NHC gave this new disturbance 2-day and 5-day odds of development of 0% and 70%, respectively. Agatha and Blas are not a threat to any land areas, but Hawaii should keep an eye on the disturbance expected to become Celia. Steering currents next week may favor a more westerly track than Agatha and Blas are taking.

Quiet in the Atlantic
There are no tropical cyclone threat areas in the Atlantic to discuss, and none of the reliable models for tropical cyclone formation is predicting development during the remainder of the week. Much of the tropical North Atlantic is dominated by a large area of dry air and dust from the Sahara Desert, which is common in early July.

I'll have a new post on Wednesday.

Jeff Masters

Hurricane

Chinese Floods Kill 186: Earth's Costliest and 2nd Deadliest Weather Disaster of 2016

By: Jeff Masters , 3:33 PM GMT on July 04, 2016

Torrential monsoon rains along a stalled frontal boundary near the Yangtze River in China have killed 186 people, left 45 people missing, and caused at least $7.6 billion in damage. In the Hubei Province, 1.5 million people have been evacuated or are in need of aid, almost 9,000 houses have collapsed or are seriously damaged and more than 710,000 hectares of crops have been affected, the provincial civil affairs department said. According to the May 2016 Catastrophe Report from insurance broker Aon Benfield, the $7.6 billion in damage from these floods would make them the world's most expensive and second deadliest weather-related disaster so far in 2016. The only deadlier weather disaster in 2016 was an April heat wave in India that claimed 300 lives.


Figure 1. Aerial view of the flooded houses at Rongshui Miao Autonomous County on July 3, 2016 in Liuzhou, Guangxi Province of China. (Photo by Long Tao/VCG via Getty Images) 

A deadly monsoon season in China
It's been a severe monsoon season in China this year. On June 22, a tornado hit near the city of Yancheng in Jiangsu province, about 500 miles south of Beijing, killing 98 and injuring 800. As our Bob Henson noted in a June 23 post, this tornado occurred along the Mei-yu (or baiu) front, which typically persists for a few weeks in late spring and early summer. This semi-permanent feature extends from eastern China across Taiwan into the Pacific south of Japan, associated with the southwest monsoon that pushes northward each spring and summer. The AMS Glossary notes: “The mei-yu/baiu front is very significant in the weather and climate of southeast Asia as it serves as the focus for persistent heavy convective rainfall associated with mesoscale convective complexes (MCCs) or mesoscale convective systems (MCSs) that propagate eastward.” A number of studies have found that the Mei-yu rainfall tends to be particularly heavy in the summer following an El Niño event, as is occurring in 2016. More heavy rain is likely in the flood-affected areas later this week.

I'll be back with a post on the tropics later today.

Jeff Masters

Flood

Heat vs. Cold: Which Is More Dangerous for Kids in Cars?

By: Bob Henson , 4:33 PM GMT on July 01, 2016

Not long ago, a friend’s simple query on Facebook triggered my own curiosity: why don’t we hear about children dying after being left in a vehicle on a very cold day? It’s a pertinent question, given the tragic consequences when small children (or pets) are inadvertently left in the car on a sunny, warm day. When it comes to the environment inside a closed vehicle, it appears that warm weather is indeed far riskier than cold weather, for a variety of reasons.

Jan Null (Department of Meteorology and Climate Science, San Jose State University) has tracked close to 700 deaths of children left in cars since 1998. However, he knows of only a couple of cases where children died from being in a cold vehicle. Null suggested I check with Dr. Leticia Ryan, an assistant professor of pediatrics at Johns Hopkins Children’s Center. Ryan agreed that the question was a good one: “Children are at increased risk for both hyperthermia [elevated body temperature] and hypothermia [reduced body temperature] in comparison to adults.” However, like Null, Ryan wasn’t aware of any research focused on the different responses to heat vs. cold in vehicle interiors.

To explore the question further, I held an email brainstorm with Rebecca Morss and Julie Demuth, both of whom study the intersections of weather, warnings, and society at the National Center for Atmospheric Research. Morss and Demuth pointed out several factors that would presumably lead to a greater risk to children and pets left in cars during warmer times of the year. 

Sunshine can only warm a vehicle, regardless of the temperature outside. This is why it doesn’t have to be a scorching-hot day to produce deadly heat inside a closed car (see Figure 1). On a bright, cold winter day, the same effect could help keep a vehicle’s interior less chilly than it would otherwise get.


Figure 1. Even when temperatures outside are only 80°F, sunshine entering a closed vehicle can push the temperature to 109°F in just twenty minutes. After an hour, the car’s interior air can reach a blistering 123°F. Cracking windows does not reduce the ability of the air to reach such high temperatures. The sunshine entering the car rapidly heats up surfaces (the dashboard or steering wheel can reach 180 – 200°F on an 80°F day). These surfaces, in turn, heat up the interior through convection and conduction as well as by longwave radiation, in much the same way that an asphalt parking lot sends heat upward. An hour’s worth of warming is depicted in this QuickTime animation. Image credit: GM and Jan Null.


Being in a closed vehicle minimizes the effect of wind chill, which could otherwise exacerbate the bodily heat loss for a given air temperature.

—Unless a cold front is moving in, the outdoor temperature will typically rise during the course of a winter day, thus reducing the potential temperature drop within a vehicle.

—Morss speculates: “I can imagine why one is less likely to leave a child in a car on a cold day, because you'd be more likely to go back into your car to grab something (coat, mittens), or you'd have a cue when you got out of the car and felt the bitter cold that would make you think ‘did I give my child warm enough clothes today?’ and thus think about your child.”

A few stats and safety tips
Last year (2015) saw 24 vehicular heat stroke deaths, the least for any year since Null began compiling data in 1998. However, 2016 is off to a bad start, according to Null, with 16 deaths already recorded as of June 30. Null’s website noheatstroke.org includes a set of frequently updated statistics that bring home the problem vividly. Of the 661 such deaths recorded from 1998 through 2015, just over half involved children who were “forgotten,” many of them left in a vehicle by a parent or caregiver rushing to work in the morning. Latitude is not a guaranteed defense, as 2016 has already seen confirmed deaths as far north as Iowa and New York.

Here are Null’s safety recommendations:

Never leave a child unattended in a vehicle—not even for a minute!
—If you see a child unattended in a hot vehicle, call 911.
—Be sure that all occupants leave the vehicle when unloading. Don't overlook sleeping babies.
—Always lock your car and ensure children do not have access to keys or remote entry devices. Teach children that vehicles are never to be used as a play area.
—If a child is missing, always check the pool first, and then the car, including the trunk.
—Keep a stuffed animal in the carseat, and when the child is put in the seat, place the animal in the front with the driver. Or place your purse, briefcase, or cell phone in the back seat as a reminder that you have your child in the car.
—Make "look before you leave" a routine whenever you get out of the car.
—Have a plan that your childcare provider will call you if your child does not show up for school.


Don’t forget your furry companion!
Hundreds of pets are believed to die around the country after being left in hot cars. The Humane Society offers these tips on how you can help if you see a pet in a parked car on a sunny summer day:

—Take down the car's make, model and license-plate number.
—If there are businesses nearby, notify their managers or security guards and ask them to make an announcement to find the car's owner.
—If the owner can't be found, call the non-emergency number of the local police or animal control and wait by the car for them to arrive.

The American Veterinary Medicine Association suggests: “Before you put your pet in the vehicle, ask yourself if you really need to take your pet with you--and if the answer is no, leave your pet safely at home.”

Several states now have Good Samaritan hot-car laws that allow private citizens, in some circumstances, to break into motor vehicles if they notice a child or an animal is in jeopardy. Various types of hot-car laws are now on the books in 21 states, and bills are now pending in California and Michigan. The Animal Legal Defense Fund has compiled a useful state-by-state overview of the protections now in force and those being considered.

Eastern North Pacific is primed for tropical development next week
Long-range forecasts from the ECMWF and GFS models continue to flag the possibility of one or more tropical cyclones developing next week over the eastern North Pacific. This region will be under the influence of a strong convectively coupled Kelvin wave (CCKW) as well as an active Madden-Julian Oscillation (MJO), both of which will favor rising motion and tropical development in the eastern Pacific over the first few days of July. (See our Wednesday post for more background on CCKW and MJO activity.) Wind shear is weak to moderate across the region, and sea surface temperatures are 0.5°C to 2°C above average throughout the area north of about 8°N, despite the presence of cooler-than-average waters closer to the equator associated with the trend toward La Niña.


Figure 2. Infrared GOES-East satellite image for the eastern North Pacific, valid at 1515Z (11:15 AM EDT) Friday, July 1, 2016. The disturbed weather stretching from west to east is associated with an active monsoon trough. Image credit: NASA Earth Science Office.

The first in our potential series of East Pacific tropical cyclones is likely to be Invest 94E, now located well south of Acapulco, Mexico. In its 10 AM EDT Friday tropical weather outlook, the National Hurricane Center gave 94E a 30 percent chance of development by Sunday and an 80 percent chance by Wednesday. Another disturbance located further west has only a limited amount of convection (showers and thunderstorms) with it, but NHC gives it a 20 percent chance of development over the next five days. Several other weak centers of low pressure extend east along the monsoon trough that includes both of these systems (see Figure 2), yet it remains unclear which one(s) will have the best chance of development. NHC summed it up nicely in its 10 AM EDT Friday tropical weather discussion for the eastern Pacific: “Model guidance is consistently showing further development of one or more of these low pressure areas, but continues to be inconsistent regarding the details such as when, where and to what extent.” Whatever does develop over the next few days across the region will likely track well offshore and pose little or no threat to land.

Meanwhile, in the U.S., there are no large areas of significant severe weather anticipated for the holiday weekend. Very heavy rains (locally 4” to 6”) and a few severe storms are expected as a weak upper impulse traverses a frontal zone from Kansas to southern Illinois and Indiana, moving into the central Appalachians by Monday and Tuesday. Residents of West Virginia hard-hit by flooding last week will need to monitor this threat.

Jeff Masters will be back on deck next week. In the meantime, have a great weekend, everyone. If you’re in the U.S., Happy Fourth of July--and if you're a Canadian, Happy Canada Day!

Bob Henson


Figure 3. Central surface pressures in potential tropical cyclones depicted by members of the GEFS ensemble run from 06Z Friday, July 1, 2016, valid at 06Z Thursday, July 7. Each central pressure is in millibars, with the preceding “9” or “10” lopped off. Colors indicate the normalized spread, or how much the central pressures deviate from typical surface pressure. The predicted centers toward the west are associated with Invest 94E. Image credit: tropicaltidbits.com


Figure 4. Members of the GEFS ensemble run from 06Z Friday, July 1, 2016, show a variety of potential tracks for Invest 94E, all of which would take the system well away from the Mexican coastline.

Hurricane Heat


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

Category 6™

About

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