Category 6™

Early, Late, and Far-Flung: The Eclectic 2016 Atlantic Hurricane Season

By: Bob Henson and Jeff Masters , 8:11 PM GMT on November 30, 2016

After three relatively quiet seasons, the hurricane-generating waters of the North Atlantic, Gulf of Mexico, and Caribbean returned in 2016 to the busy production schedule they’ve maintained in most years since the mid-1990s. Assisted by the switch from a record-strong El Niño to a borderline La Niña, which reduced vertical wind shear, the 2016 season ended up above the long-term average for all of the most commonly tracked indices, with the largest number of hurricanes observed since 2012, the most major hurricanes since 2011, and the Atlantic’s first Category 5 hurricane since 2007. Persistent dryness in mid-levels of the atmosphere likely kept this season from being even more active, noted Dr. Phil Klotzbach (Colorado State University, CSU) in his end-of-season recap.

Here are the numbers for 2016 through November 30, the official last day of the Atlantic season. In parentheses are the average values for the period 1981 - 2010. Below the tally, you’ll find our look at a few noteworthy aspects of this prolonged, wide-ranging season.

Tropical cyclones (including depressions):  16
Named storms:  15 (average 12.1)
Hurricanes:  7 (average 6.4)
Major hurricanes:  3 (average 2.7)
Accumulated cyclone energy (ACE), as reported by CSU:  134 units (average 108)


Figure 1. Forecasts of the expected number of Atlantic hurricanes in 2016 as issued by a variety of forecast groups shown at the bottom of the chart. The actual total number of hurricanes through November 30 was 7, which falls within the outlooks from almost every group that issued its forecast as a range rather than a single number. Forecasts in pale blue were based on statistical models, those in red on dynamical models, and those in purple on hybrid models. Image credit: Colorado State University/Barcelona Supercomputing Center/XL Catlin.

•    The Atlantic’s deadliest hurricane in more than a decade: Matthew
The main story of the 2016 Atlantic hurricane season was Hurricane Matthew, the Atlantic’s first Category 5 storm since Felix of 2007. Matthew lasted as a major hurricane for eight days from Sept. 30 to Oct. 7, and devastated Haiti as a  Category 4 storm on October 4. Matthew killed 546 in Haiti, according to the insurance broker Aon Benfield, making it the Atlantic’s deadliest hurricane in 11 years. Damage in Haiti was estimated at $1.9 billion--a staggering 21% of the impoverished nation’s GDP, and by far Haiti’s costliest hurricane on record, according to the international disaster database, EM-DAT (previous record: $400 million 1980 dollars from Hurricane Allen.) Matthew battered Cuba as a Category 4 storm, causing $2.6 billion in damage (3.2% of their GDP.) Matthew was Cuba’s second most expensive hurricane on record, behind Hurricane Georges of 1998 ($3 billion in damage in 2016 dollars.) The Bahamas suffered $600 million in damage from Matthew (6.8% of GDP), making it their third most expensive hurricane on record behind Hurricane Frances of 2004 ($1.28 billion in losses, 2016 dollars) and Hurricane Jeanne of 2004 ($700 million in damage).

Matthew grazed the coast of Florida and Georgia before making landfall in South Carolina on October 8 as a Category 1 hurricane with 75 mph winds. Matthew’s storm surge brought water levels that were the highest ever observed along portions of the coasts of Northern Florida, Georgia and North Carolina, beating records that had been set as long ago as 1928. Near record-warm ocean waters contributed to atmospheric moisture levels that were the highest on record over portions of Florida and South Carolina as Matthew moved up the coast, allowing the hurricane to dump 1-in-1000 year rains in some areas of South Carolina and North Carolina. Matthew killed 49 people in the U.S., 28 of them in North Carolina, and U.S. damage was estimated at up to $10 billion. This would make Matthew the 17th most expensive hurricane in U.S. history. Remnant moisture from Matthew also brought flooding rains and high winds to parts of the Maritime Provinces of Canada, causing tens of millions of dollars in damage.


Figure 2.Fuel tanks are surrounded by booms to capture leaking fuel on October 12, 2016, in Lumberton, NC, in the wake of flooding from Hurricane Matthew. The Lumberton River hit an all-time record flood crest of 24.39’ on October 9, 2016. Image credit: AP/Chuck Burton.


Figure 3. Twenty-four hour rainfall amounts from Hurricane Matthew on October 6 - 10, 2016 over portions of South Carolina and North Carolina were so extreme, that one could expect them to have a recurrence interval of 1-in-1000 years based on past climatology (dark blue colors). The calculations do not incorporate general trends toward more extreme rainfall related to climate change. Image credit: NOAA/NWS.

•    A phenomenally prolonged season. On January 14, Hurricane Alex became the Atlantic’s first January hurricane since 1955. Alex maintained Category 1 strength for almost 24 hours, peaking at 85 mph winds, before weakening to a tropical storm with 65 mph winds and making landfall on January 15 on the island of Terceira in the central Azores, roughly 1000 miles west of Portugal. No major damage or casualties were reported from Alex’s landfall. Only one other time since records began in 1851 has a January tropical cyclone made landfall in the Atlantic: Hurricane Alice, which moved from northeast to southwest over the islands of Saint Martin and Saba on January 2, 1954. The only other January hurricane in the Atlantic was Hurricane One on January 4, 1938. Alex’s ascension to hurricane strength was likely aided by sea surface temperatures that were up to 1°C above average for that time of year--near 22°C (72°F.)


Figure 4. MODIS visible satellite image of Tropical Storm Alex at 9:20 am EST Friday, January 15, 2016. About an hour earlier, Alex’s western eyewall passed over the Azores island of Terceira (black outline below the center of Alex). Image credit: NASA.

The season’s other bookend (assuming no other tropical cyclones form by December 31) was deadly Hurricane Otto, the first hurricane known to make landfall on Thanksgiving Day (November 24 this year) as well as the Atlantic’s strongest hurricane on record so late in the calendar. After its landfall in far southern Nicaragua, Otto weakened to tropical storm strength while moving over northwest Costa Rica, where it killed 10 people. Only one other Atlantic tropical cyclone in recorded history has killed people later in the year: Tropical Storm Odette, whose floods killed eight people in the Dominican Republic after making landfall on December 6, 2003. Otto is the first named storm on record to pass directly over Costa Rica, and as it moved into the Pacific, it became the first tropical cyclone to keep its name while moving from one ocean basin to another. (Several other storms have successfully crossed basins, but previous policy was to change the name when this occurred.)
 
The only year with anything close to this prolonged a tropical cyclone season--January 12 to November 24--was 1938, whose activity extended from January 3 to November 10. Even if we discount January storms by arguing that they represent the tail ends of prior seasons, this year’s activity still ran from May 27 to November 24. That span is just one day shorter than the classic June-to-November season, and it’s only a month shorter than the infamous 2005 season, which went from June 8 to January 6.


Figure 5. MODIS satellite image of Otto taken at approximately 11 am EST, November 24, 2016--Thanksgiving Day. At the time, Otto was a Category 2 storm with 110 mph winds about to make landfall in Nicaragua as the strongest Atlantic hurricane ever observed so late in the year. Image credit: NASA.

•    Record amounts of oceanic fuel. The very strong 2015-16 El Niño, playing out on top of relentless long-term warming associated with human-produced greenhouse gases, led to record-warm sea surface temperatures across many parts of the globe, including the North Atlantic. Many of this year’s storms developed or intensified over waters that were 1°C - 2°C (1.8° - 3.6°F) above the local seasonal average. The widespread oceanic warmth most likely played a role in extending the season, as well as supporting greater intensification in locations and time frames where it otherwise might not have occurred. Several of this year’s hurricanes hit their peak strength near or north of 30°N, where especially warm waters prevailed during peak season.


Figure 6. Large swaths of the world’s oceans experienced record-warm sea surface temperatures for the year 2016 through October, including most of the Northwest Atlantic and Caribbean. Image credit: NOAA/NCEI.

•    A year littered with landfalls. From the first named storm to the last, 2016 saw an unusually large number of its tropical cyclones (13 out of 16) passing over or near land. Actual landfalls were also numerous, and their locations were remarkably diverse, including the Azores (Alex); South Carolina (Bonnie); Florida (Colin); Mexico (Danielle); Belize (Earl); Haiti, Cuba, The Bahamas, and South Carolina (Matthew); Bermuda (Nicole); and far south Nicaragua (Otto). Tropical Storm Julie jumped the gun on landfall by becoming a named storm while it was located over eastern Florida, making it the first tropical storm on record to develop within the Sunshine State. The five landfalling storms in the United States were the most since 2008, when six storms struck.

•    The intensity challenge, circa 2016. Over the last few years, forecasters and computer models have made some real headway in the devilishly difficult challenge of predicting rapid hurricane intensification, but 2016 gave us two humbling examples of how far we still have to go. As Hurricane Matthew drifted across the southern Caribbean Sea, it rocketed in strength from Category 1 to Category 5 in just 24 hours (from 80 mph sustained winds at 03Z on September 30 to 160 mph at 03Z on October 1). The official NHC forecast at the start of this day-long burst was for Matthew to take three days to top out at high-end Category 2 strength (105 mph). Less dramatic but still eye-opening was Nicole’s surge from Category 1 to Category 4 strength in the Northwest Atlantic over just 21 hours (from 90 mph sustained winds at 06Z on October 12 to 135 mph at 03Z on October 13). Like Matthew, Nicole had also been predicted at the start of its rapid strengthening to remain just below the major hurricane threshold (Category 3). NHC often reminds users in their discussions and statements that a particular hurricane could strengthen more rapidly than indicated in the official forecast.

•    Warning woes on the East Coast. The year’s two most significant East Coast hurricane threats, Matthew and Hermine, proved to be unusually challenging from the warning perspective. Nearly the entire East Coast from Florida to Massachusetts ended up in a hurricane or tropical storm warning as a result of the two storms. Matthew’s concave coastal track cut down on the amount of wind damage, especially in Florida, while Hermine lingered just far enough off the mid-Atlantic so that many coastal stretches from Delaware to New York that had been largely abandoned for the Labor Day weekend ended up with oddly picture-perfect weather in the midst of tropical storm warnings. In both cases, the high-end risks painted by computer forecast models were enough to justify alerting residents. Strong winds, high surf, rip tides, and coastal erosion hammered the mid-Atlantic and Northeast coast during Hermine’s leisurely decay, and Matthew’s record storm surge along the Southeast coast and its catastrophic rains inland will not soon be forgotten.


Figure 7. Waves crash ashore at Atlantic City, New Jersey, on Sunday, September 4, 2016, as Tropical Storm Hermine spins well offshore. Image credit: Jessica Kourkounis/Getty Images.

•    Florida’s hurricane “drought” is over--but another record string continues. Florida got its first hurricane landfall in nearly 11 years (3966 days) with the arrival of Category 1 Hermine, which struck the state’s northeast Gulf Coast on September 2. The landfall ended a string of good fortune unprecedented in Florida records. Hermine was also the first hurricane observed in the Gulf of Mexico since Ingrid in 2013, curtailing the Gulf’s longest hurricane-free stretch on record. Hurricane Matthew’s track just off the Southeast coast until its South Carolina landfall kept it from ending yet another remarkable “drought”: the longest period between major hurricane landfalls (Category 3 or stronger) in U.S. hurricane data going back to 1851. This ongoing stretch began after Hurricane Wilma struck Florida in October 2005. A number of observers, including Robert Hart (Florida State University) and colleagues, have noted that this record is somewhat arbitrary, especially since two large landfalling systems with lesser winds but major storm surge were the nation’s second and third most costly hurricanes on record: Sandy in 2012 and Ike in 2008, respectively. In October, Capital Weather Gang’s Jason Samenow declared the U.S. major-hurricane drought to be the “most overblown statistic in meteorology.”

Still, it’s undeniably impressive that all 29 major hurricanes recorded in the Atlantic from 2006 through 2016 managed to avoid bringing Category 3 winds to the shores of the United States. Even if this is nothing more than a fluky natural variation, the major-hurricane drought reminds us that it’s been a long time since we’ve seen what truly devastating hurricane winds can do to the nation’s Gulf and Atlantic coasts.

Addendum: Louisiana’s no-name storm
One other event deserves mention here, even though it’s not officially part of the 2016 tropical season: the slow-moving disturbance that dumped colossal amounts of rain on southern Louisiana in mid-August, causing 13 deaths and an estimated $10 - 15 billion in damage. Because surface winds were light and the surface low stayed generally onshore, the system was never declared a tropical cyclone by the National Hurricane Center. At the same time, for much of its life the storm was a symmetric warm-core low, the same type of structure associated with tropical cyclones. Regardless of its classification, the storm behaved much like other tropical depressions, tropical storms, and hurricanes that have taken their time moving through the Gulf Coast region. Some parts of Louisiana recorded more than 20" of rain in 48 hours, which qualifies as a 1-in-1,000 year rainfall event (having a 0.1 percent chance of occurring at a particular location in any given year), according to the NWS Lower Mississippi River Forecast Center. The highest rainfall total from the storm was 31.39” in Watson, Louisiana. The storm system carried near-record amounts of atmospheric moisture, drawn from the Gulf of Mexico and northwest Atlantic, where sea-surface temperatures (SSTs) were at near-record levels.

For more perspective on the 2016 Atlantic season, check out Dr. Brian McNoldy’s wrap-up (Capital Weather Gang) and Dr. Phil Klotzbach’s seasonal summary at Colorado State University. We’ll be back with a new post on Friday.

Bob Henson and Jeff Masters


Figure 8. Major flooding in Prairieville, Louisiana on Friday, August 12, 2016. Image credit: @presleygroupmk/twitter.com.

Hurricane

On Giving Tuesday, Support Increasingly Embattled Climate Scientists

By: Jeff Masters , 10:33 PM GMT on November 29, 2016

Climate science and climate scientists in the United States are likely to be under unprecedented assault by powerful politicians in the coming four years. Climate-change-denying politicians are already in high positions in Congress, and soon we will have a president who has publicly denied climate change science. On Giving Tuesday, November 29, I urge you to make a tax-deductible donation to the nonprofit Climate Science Legal Defense Fund (CSLDF) to help protect the crucial research of climate scientists from political interference.

Multiple climate scientists are currently involved in litigation in state and federal courts across the United States. Most noteworthy have been the cases brought by Lamar Smith (R-Texas), head of the House Committee on Science, Space, and Technology, and a major recipient of campaign contributions from the fossil fuel industry. According to Wikipedia, Smith’s House Science committee issued more subpoenas in his first three years than the committee had for its entire 54-year history; many of these subpoenas demanded the records and communications of scientists who published papers that Smith disapproved of. In one of his 2016 subpoenas, Smith called on court decisions defending the work of the House Un-American Activities Committee in the 1950s as valid legal precedent for his investigation—explicitly equating his investigation with the dark McCarthy era in our history when the government trampled on civil liberties.


Figure 1. Dr. Michael Mann addresses an audience at a fund raiser on behalf of the Climate Science Legal Defense Fund (CSLDF) in 2014. Dr. Mann will be featured at a CSLDF legal symposium on open records laws on Wednesday morning, December 14, from 8am - 1pm at the San Francisco Marriott Marquis as part of the American Geophysical Union (AGU) conference. For those not already attending AGU, tickets are available for $25 here.

Trump has little knowledge of climate science, and low regard for climate scientists
President-elect Trump’s remarks on climate change last week to the New York Times demonstrate that the president-elect has little knowledge of climate science, and low regard for climate scientists. Some examples from the interview:

Trump on climate change: “You know the hottest day ever was in 1890-something, 98. You know, you can make lots of cases for different views."

My commentary: Climate change is a matter of scientific fact. Based on the evidence, more than 97% of climate scientists have concluded that human-caused climate change is happening. The hottest day on Earth since records began probably came in 2016--Earth's third consecutive warmest year on record. The year 1898 was one of the coldest years in global recorded history, ranking as the 18th coldest year since 1880. The hottest day globally is a statistic that is not computed by climate scientists, and is largely irrelevant to the discussion of climate, which is measured on timescales of many years.

Trump on wind turbines: "They’re made out of massive amounts of steel, which goes into the atmosphere, whether it’s in our country or not, it goes into the atmosphere."

My commentary: Steel in the atmosphere? That's completely insignificant.

Trump on climate scientists: “They also have those horrible emails that were sent between the scientists…. Terrible. Where they got caught, you know, so you see that and you say, what’s this all about. I absolutely have an open mind.”

My commentary: seven independent inquiries concluded that the hacked climate scientists’ emails that were made public in 2009 showed that the researchers' work was scientifically correct. And as I wrote in our post-election post, Trump’s Proposals: Dangerous to our Climate’s Future, the president-elect has surrounded himself with top officials who are climate change deniers, and these are the people who will be influencing his "open mind." In comments made to the media on Sunday, Trump’s new White House chief of staff, Reince Priebus, confirmed that climate change denial will be the official policy of Trump’s administration.



Enter the Climate Science Legal Defense Fund
The nonprofit Climate Science Legal Defense Fund (CSLDF) was created five years ago to help climate scientists fight back against politically-motivated harassment. CSLDF works to help raise funds for scientists’ legal defenses, serves as a resource in finding pro bono legal representation, and provides support during difficult litigation proceedings as well as when legal action is threatened. I'm proud to say that I'm a founding board member of the charity, which has helped nearly a hundred researchers across the country since 2011. Check out their website at climatesciencedefensefund.org, and please consider making a tax-deductible donation to this worthy cause.

CSLDF at the AGU Meeting in San Francisco, December 12 - 16
The Climate Science Legal Defense Fund will have a booth (booth number 1523) in the exhibit hall in this December's American Geophysical Union meeting in San Francisco, where climate scientists can set up a free one-on-one session with a lawyer; these free sessions can also be set up with an email to lawyer@climatesciencedefensefund.org. CSLDF is also hosting a legal symposium on open records laws on Wednesday morning, December 14, from 8am - 1pm at the San Francisco Marriott Marquis, Salon 2. For those not already attending AGU, tickets are available for $25 here.

Links
See my 2009 blog post, The Manufactured Doubt industry and the hacked email controversy.

My fellow CSLDF board member, Naomi Oreskes, has co-authored the excellent book, Merchants of Doubt, which has also been made into a fascinating documentary (available on Netflix.)


Figure 3. Women walking down the street in Jeremie, southwest Haiti, after the city was devastated by Hurricane Matthew. Foto: Logan Abassi UN/MINUSTAH.

Portlight and Lambi Fund of Haiti disaster relief charities need your help
If your giving instincts favor disaster relief, consider a donation to the Portlight.org disaster relief charity, founded and staffed by members of the wunderground community. Portlight is responding to needs of the disabled in the wake of the $10 billion in damage Hurricane Matthew brought to the Southeast United States, and is also continuing their work in Louisiana, which suffered an even more devastating flooding disaster in August, with damages estimated at $10 - $15 billion. You can check out their progress on the Portlight Blog or donate to Portlight's disaster relief fund at the portlight.org website.

For over ten years, I’ve been a big booster of and donor to the Lambi Fund of Haiti, which is very active in disaster relief and disaster prevention, including promotion of reforestation efforts, use of alternative fuels, and infrastructure improvements at a grass-roots level to help avert future flood disasters. Category 4 Hurricane Matthew devastated Haiti on October 4, killing 546, making it the Atlantic’s deadliest hurricane in 11 years. Damage in Haiti was estimated at $1.9 billion—a staggering 21% of the impoverished nation’s GDP, and by far Haiti’s costliest hurricane on record. Here’s what the Lambi Fund is currently doing for their Hurricane Matthew response:
• Protecting food security by replanting the fields with beans, corn and vegetables so that a consumable harvest occurs in three months.
• Ensuring that women who lost their assets receive funding through micro-credit to reignite their small businesses.

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

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

Note: My views are my own and not necessarily representative of The Weather Company or IBM. I am a founding board member of the Climate Science Legal Defense Fund.

Jeff Masters

Climate Change Politics

Catastrophic Fire Hits Southeast Tennessee Homes and Resorts

By: Bob Henson , 4:28 PM GMT on November 29, 2016

What appears to be the most damaging wildland fire to strike a Southeast U.S. community in many decades tore into the tourist mecca of Gatlinburg, Tennessee, on Monday night. The Chimney Top Fire has burned hundreds of structures in and near this much-loved city and has injured at least four people. Nearby Pigeon Forge, home of the Dollywood theme park, has also been affected by the fire, which began in the adjacent Great Smoky Mountains. At least 14,000 people were evacuated from the area, and an estimated 1000-plus people were in shelters on Tuesday morning. At 9:03 PM EST Monday night, the Sevier County Emergency Management Agency sent this message:

“THE CITY OF GATLINBURG AND NEARBY COMMUNITIES ARE BEING EVACUATED
DUE TO WILDFIRES. NOBODY IS ALLOWED INTO THE CITY AT THIS TIME. IF
YOU ARE CURRENTLY IN GATLINBURG AND ARE ABLE TO EVACUATE...EVACUATE
IMMEDIATELY AND FOLLOW ANY INSTRUCTIONS FROM EMERGENCY OFFICIALS.
IF YOU ARE NOT INSTRUCTED TO EVACUATE...PLEASE STAY OFF THE ROADS.”


Figure 1. Fire erupts on the side of The Spur on Highway 441 between Gatlinburg and Pigeon Forge, TN, on Monday night, November 28, 2016. In Gatlinburg, smoke and fire caused the mandatory evacuation of downtown and surrounding areas. Image credit: Jessica Tezak/Knoxville News Sentinel via AP.


Figure 2. Thick smoke from area forest fires spread over Gatlinburg, TN, at midday Monday, November 28, 2016, a few hours before fire moved into parts of town. Image credit: Brianna Paciorka/Knoxville News Sentinel via AP.

Large swaths of the hillsides surrounding downtown Gatlinburg were ravaged by the fire on Monday night, including several major hotel and resort facilities. Conflicting reports on social media, and the fluid nature of the disaster as the fire continued on Tuesday, made it hard for news organizations to determine exactly what areas had been damaged. For example, there were widespread rumors that the resort of Ober Gatlinburg was destroyed, but on Tuesday morning, Ober Gatlinburg reported on Facebook: “Our property is okay. Please keep Sevier County in your thoughts and prayers!”

“The center of Gatlinburg looks good for now," Newmansville Volunteer Fire Department Lt. Bobby Balding told the Knoxville News Sentinel on Monday night. "It's the apocalypse on both sides (of downtown)."

The southern Appalachians have endured their hottest and driest autumn on record, setting the stage for dozens of wildfires across the region that culminated in Monday’s blazes. As of Monday, 20 large fires across the Southeast, including 4 new ones, were affecting more than 130,000 acres, according to the National Interagency Fire Center. The Gatlinburg disaster occurred as winds gusted to more than 70 mph ahead of a strong cold front. The same front and upper-level system that brought the winds also delivered more than 0.50” of rain to nearby Knoxville after midnight Monday night. Intense thunderstorms will erupt from Louisiana to central Tennessee and eastern Kentucky on Tuesday afternoon, with an enhanced risk of severe weather--including the possibility of significant tornadoes--over much of Mississippi. These lightning- and wind-bearing storms may reach southeast TN by late Tuesday. Conditions should improve markedly over the next several days over much of the Southeast, thanks to the expected generous rains and cooler temperatures. However, many fires continued to burn on Tuesday, and to many residents of the Gatlinburg area, the damage has already been done. “Even with the rain that is currently falling there, the fires continue to burn and structures remain engulfed with little hope that the rainfall will bring immediate relief,” said the Tennessee Emergency Management Agency in a statement at 9 AM EST Tuesday.


Figure 3. Ranking of stations across the Southeast for the period from September 1 to November 28, 2016, in terms of temperature (left) and precipitation (right). Many locations across the region, including the Knoxville/Gatlinburg area, have seen their hottest and driest autumn on record through Monday. Enough rain may arrive over the next couple of days to keep autumn precipitation records from being set at some spots. Image credit: Southeast Regional Climate Center.

A toxic mix of fire-friendly elements
Moisture is typically plentiful across the Southeast, including Gatlinburg, which averages 56” of rain per year. Droughts here are not typically as prolonged as they are in the U.S. West. When they do strike, their impact on the lush, normally-well-watered landscape can quickly become intense. In its section on the Southeast, the U.S. National Climate Assessment noted: “The southeastern U.S. (data include Texas and Oklahoma, not Puerto Rico) leads the nation in number of wildfires, averaging 45,000 fires per year, and this number continues to increase. Increasing temperatures contribute to increased fire frequency, intensity, and size, though at some level of fire frequency, increased fire frequency would lead to decreased fire intensity.”


Figure 4. Fires along the north edge of Great Smoky Mountains National Park near Wears Valley, TN, illuminate storm clouds as photographed from the town of Seymour, about 10 miles northwest of Gatlinburg. Photo credit: Jeremy Kwasney, On Location Photography. Thanks to Julie Carles-Witt for obtaining permission.


Figure 5. Firefighter Valarie Lopez is followed by Mark Tabaez as they climb down a hill after cooling hot spots from a wildfire that burned a hillside in Clayton, GA, on November 15, 2016. Image credit: AP Photo/John Bazemore.


Making matters worse is the state of the forest in the Great Smoky Mountains National Park, where fire has been largely suppressed for nearly a century. Studies led by the University of Tennessee have examined the history of fire in the forests just south of Gatlinburg within the national park. Analyses of trees that date back as far as the early 1700s show that smaller, less-intense fires triggered by lightning and/or human activity were once quite frequent, clearing out the landscape for new growth every few years. “In most areas of the park, it’s very clear when this pattern of regular fires stopped: in the early 1930s, the park began suppressing fire, and tree rings changed,” notes the National Park Service.

Decades of fire suppression allowed species that are less fire-tolerant, such as maple and hickory, to take hold. On top of this, southern pine beetles have ravaged more than 90% of native short-leaf pines in some areas over the last several decades, leaving huge stands of dead trees. (As winter temperatures grow warmer in our greenhouse-altered climate, southern pine beetles have been thriving, making it as far north as New Jersey.)

Taking stock of our future fire risks
I have fond memories of a childhood visit to Gatlinburg, and it’s painful to contemplate the agony that residents are going through. The Red Cross of East Tennessee has already called this “the worst disaster involving displaced people in our area since Hurricane Katrina.” Unfortunately, the Gatlinburg fire may be a harbinger of increased fire risk across the Southeast in the decades to come, as suggested by the U.S. National Climate Assessment. A 2015 study led by Renaud Barbero (University of Idaho) suggests that the number of week-long periods with very large fires over the southern and central Appalachians may double by the 2040s - 2060s as a result of climate change. Population growth is also adding to the region’s risk. As more people move to the fringes of towns and cities, more than half of the nation’s wildland-urban interface is now located within the Southeast.

Gatlinburg is the second catastrophic wildfire this year to strike a sizable North American community in an unexpected fashion. It follows the disastrous blaze that swept across Fort McMurray, Canada, in early May, after record-setting mid-spring temperatures close to 90°F came on the heels of a very early snowmelt. The Fort McMurray fire was the costliest disaster in Canadian history, with more than $3 billion US in damage. As I wrote in a post on that event: “We have much more to learn about exactly why and how the atmosphere is moving in directions that favor devastating fire--but for now, perhaps it’s enough simply to know that the dice are being loaded. Together with the many other threats posed by climate change, this should be more than enough motivation to get serious about emission cuts. The vast and profound effects of human-produced greenhouse gases--from intensified downpours and drought impacts to ocean acidification and sea-level rise--call for a sustained commitment to change that transcends any single disaster.”

The Knoxville News Sentinel has been providing excellent in-depth coverage of the Gatlinburg fire, including a live blog with many photos and updates. Jeff Masters will be back later today with a post on Giving Tuesday.

Bob Henson



Video 1. Above: A terrifying escape from cabins near Gatlinburg, Tennessee, on Monday night, November 28, 2016. The drivers made it through the fire unscathed. Language alert: this video has several f- and s-bombs. Video credit: @VolBlood




The Upcoming Benefits of GOES-R for Hurricane Monitoring and Forecasting

By: Bob Henson , 4:56 PM GMT on November 28, 2016

A new era in satellite monitoring of the Western Hemisphere began on November 19 with the successful launch of the GOES-R satellite. GOES-R is the latest in a sequence of GOES (Geostationary Operational Environmental Satellite) satellites that began in 1975. Both polar-orbiting and geostationary satellites gather crucial data for incorporation in computer forecast models, but it’s the geostationary birds--stationed at fixed spots tens of thousands of miles above the surface--that furnish most of the satellite imagery we’ve seen on television and the Internet since the first GOES satellite was sent into space in 1975. The new satellite and three more that will follow (collectively referred to as the Geostationary Operational Environment Satellite–R Series) will provide a huge leap forward in temporal and spatial resolution, with more frequent and precise images than ever before gathered by a U.S. geostationary satellite.


Figure 1. A rocket bearing the GOES-R satellite hurtles into space from NASA’s Kennedy Space Center at 6:42 PM EST Saturday, November 19, 2016. As with previous launches, NASA worked with NOAA to develop and launch GOES-R. See embedded video of the launch at bottom. Image credit: NOAA.

When do we see the first pictures?
Although GOES-R will be in a test mode until about one year after launch (i.e., till November 2017), we won’t have to wait that long to get a peek at its offerings. The satellite should begin providing researchers with initial imagery in the next couple of months from its vantage point 22,500 miles above the equator near 89.5°W, roughly the longitude of St. Louis, Memphis, and New Orleans. This location will allow GOES-R to observe tropical cyclones in both the western North Atlantic and eastern North Pacific. According to the GOES-R Product Readiness and Operations Team, data from 16 wavelength channels, including visible and infrared images, will be made public starting in May 2017 at the following tempos:

Full-disk images (spanning most of the Western Hemisphere): every 15 minutes
Continental U.S.:  every 5 minutes
Mesoscale (regional) areas of interest:  every minute

Once operational, GOES-R will be able to provide high-resolution mesoscale images as often as every 30 seconds in rapid-refresh mode.

The Advanced Baseline Imager (ABI) aboard GOES-R is comparable to the Advanced Himawari Imager aboard Japan’s Himawari-8 and -9 satellites. Tropical weather watchers have been marveling at the crystal-clear images of Northwest Pacific typhoons and Southwest Pacific cyclones gathered from Himawari-8 since July 2015 (Himawari-9 was launched on November 2 of this year). Himawari’s visible images boast a top horizontal resolution of 500 meters (1640 feet). That’s about four city blocks!


Figure 2. Visible (top) and infrared (bottom) images of Super Typhoon Meranti in the Philippine Sea on September 11, 2016, as gathered by Japan’s Himawari-8 satellite. The GOES-R Advanced Baseline Imager is expected to gather data of comparable quality. Image credit: CIMSS Satellite Blog.

The crisp, frequent imagery from GOES-R is expected to be a particular boon to forecasters keeping tabs of fast-changing weather features, including supercell thunderstorms as well as the cores of rapidly intensifying tropical storms and hurricanes.  “We are hopeful that the improved resolution will help in resolving tropical cyclone features such as emerging eyes, which should lead to better analyses of current intensity,” said Chris Velden (University of Wisconsin–CIMSS) in an email.

GOES-R also includes a Geostationary Lightning Mapper (GLM), a groundbreaking operational sensor--the first of its type on any geostationary satellite--that will detect in-cloud, cloud-to-cloud, and cloud-to-ground activity throughout the Americas. The GLM also will allow forecasters to monitor lightning activity over the open ocean where traditional land-based lightning mapping systems can’t operate. With a resolution of around 10 kilometers (6 miles), GLM data will help forecasters watch for pockets of strong thunderstorms that may help contribute to the intensification of a tropical cyclone.


Figure 3. At top is two different modes of simulated GOES-R satellite imagery for Hurricane Wilma (October 19, 2005), as compared to the same type of output from the lower-resolution GOES-12 satellite (bottom). GOES-R infrared data, as depicted in (b), will feed into a new Hurricane Intensity Estimation (HIA) algorithm, the latest iteration of the Advanced Dvorak Technique that allows for automated estimates of tropical cyclone intensity based on infrared satellite imagery. Image credit: GOES-R.

Giving the models more to chew on
Over time, GOES-R should pay big dividends for numerical forecasting models, which often lean heavily on satellite data for their starting-point initializations. Scientists are still exploring the best ways to assimilate various types of satellite data into existing models, including the smorgasbord of new data soon to come from GOES-R. In a paper recently accepted by Monthly Weather Review, Velden and colleagues describe a new technique designed to allow the HWRF model to assimilate winds inferred from cloud motion (atmospheric motion vectors, or AMVs) of the type that GOES-R will produce. “These enhanced AMVs can provide a better initial state for the model,” said Velden. Since GOES-R has more imaging bands than its predecessors, it will be able to better specify the heights of AMVs.


Figure 4. Left: Atmospheric motion vectors (AMVs) for Hurricane Katrina (2005) as produced from GOES-12 data (4 km resolution, every 15 minutes). Right: a simulation of the enhanced AMVs that GOES-R will be able to produce (2 km resolution, every 5 minutes). Image credit: “GOES-R Impacts on Satellite Data Assimilation,” UCAR/COMET (free registration required to view module).

One feature that didn’t make it to GOES-R from the previous GOES generation is the sounder, an instrument designed to produce vertical profiles of atmospheric conditions similar to those gathered by balloon-borne radiosondes. The original plan was to include an advanced sounder aboard GOES-R, but the sounder was dropped in 2006 because of tight budgets. Along with its many other benefits, the wealth of high-resolution data from the GOES-R imager will help fill in some of the information that the aborted sounder would have provided for assimilation into computer models.

Next in the queue
Three more satellites in the GOES-R series are forthcoming: GOES-S, GOES-T, and GOES-U. If all goes well, forecasters will be drawing on data from these four launches until at least 2036. After its year-long testing phase, GOES-R will be shifted to serve as either the western or eastern satellite in the GOES constellation (GOES West or GOES East). That choice will depend on how well the two current satellites in those positions, GOES-15 and GOES-13, continue to function. (Each satellite has both a numeric and alphabetic suffix, with GOES-R to be designated as GOES-16 once it goes into geostationary orbit.) Another satellite, GOES-14, remains in space as a backup but isn’t being used at present. NOAA’s satellite agency, NESDIS, is structured to accommodate 24/7 operational data from only two satellites at a time.

We’ll be back with a new post on Tuesday. Thanks go to Chris Velden (UW/CIMSS/SSEC) and Michael Folmer (NOAA Center for Weather and Climate Prediction) for background used in this post. You can follow the steps in GOES-R’s transition to data-gathering mode at an updates page maintained by NOAA/NESDIS.

Bob Henson


Video 1. GOES-R heads into space aboard a United Launch Alliance Atlas V rocket on November 19, 2016, from Cape Canaveral Air Force Station in Florida. Image credit: NASA.

Satellites Mesoscale Forecasting Hurricane

Otto Shifts from Atlantic to Pacific after Historic Landfall in Central America

By: Jeff Masters and Bob Henson , 6:14 PM GMT on November 25, 2016

Tropical Storm Otto is now in the Eastern Pacific, headed westwards away from Central America, after making landfall on Thursday as a top-end Category 2 storm with 110-mph winds over southern Nicaragua. Otto’s heavy rains are being blamed for four deaths on November 22 in Panama, and at least five others are missing there. These deaths are the second latest deaths on record from an Atlantic named storm that we are aware of; the only killer storm on record later in the year was Tropical Storm Odette, whose floods killed eight people in the Dominican Republic after making landfall on December 6, 2003. Damage from Otto may be relatively light for its strength given that the hurricane made landfall in a very sparsely populated part of far southern Nicaragua.

Otto’s circulation survived its trek over Central America remarkably well, as the center emerged from the west coast of Costa Rica as a 70-mph tropical storm. In records dating back to 1851, Otto is the only tropical storm or hurricane whose center moved over any part of Costa Rica. Otto is also the Atlantic’s latest hurricane landfall in any year, and the latest Atlantic hurricane to reach Category 2 strength in any year.


Figure 1. MODIS satellite image of Otto taken at approximately 11 am EST, November 24, 2016--Thanksgiving Day. At the time, Otto was a Category 2 storm with 110 mph winds about to make landfall in Nicaragua as the strongest Atlantic hurricane ever observed so late in the year. Image credit: NASA.


Figure 2. Civil Defense workers look at the area where a couple was killed after their home was destroyed by a mudslide in Arraijan on the outskirts of Panama City, Panama on Nov. 22, 2016. Image credit: AP Photo/Arnulfo Franco.

According to insurance broker Aon Benfield, at least four people were killed in Panama, including two who were trapped in a landslide that struck just west of Panama City. Seven people were rescued from the slide. The third fatality was reported as the result of a toppled tree in Panama City while the fourth was as the result of drowning in the swollen Utivé River. Five people were officially listed as missing.

Otto’s future
As of 10 AM EST Friday, Otto was located more than 150 miles west of Costa Rica, with top sustained winds still at 65 mph. Few tropical storms traverse the East Pacific this far southeast, and computer models have been struggling to capture Otto’s initial state and come into agreement on its future. The rough consensus is for a steady-state tropical storm over the next several days, with some weakening thereafter. Otto will be moving over warm water with sea surface temperatures of 28 - 29°C (82 - 84°F, or about 1 - 2°C above average) with moderate wind shear of 15 - 20 knots and a reasonably moist atmosphere (mid-level relative humidity around 60%). The 06Z Friday run of our most reliable intensity model, the HWRF, projects a gradual weakening, with Otto close to the bottom threshold of tropical storm strength by next Wednesday. Meanwhile, statistical models, including the 12Z SHIPS run, suggest that Otto could actually gain some strength by early next week. The 10 AM EST Friday outlook from the National Hurricane Center (NHC) predicts that Otto will weaken to a post-tropical remnant low between Tuesday and Wednesday.

From Atlantic to Pacific: a first in hurricane naming
Tropical Storm Otto is the first storm on record to carry the same name while moving from the North Atlantic to the Northeast Pacific or vice versa. In all such prior events, NHC policy was to assign a different name when an identifiable tropical cyclone moved from one basin to another. NHC’s subsequent name-retention policy was adopted more than a decade ago, but Otto is the first storm to put the rule into practice. Under the old rule, five tropical storms or hurricanes--including the most recent, Hurricane Cesar-Douglas (1996)--underwent a name change when moving from Atlantic to Pacific or vice versa. A few other “crossover” tropical cyclones have been recorded, most of them moving from Atlantic to Pacific rather than vice versa. Some of these were no more than a tropical depression in one or the other basin, which meant that only one name was used during the entire life cycle. The most recent of these was Hermine (2010), which formed as an East Pacific tropical depression before entering the western Gulf and striking the northeast coast of Mexico as a tropical storm.

As part of the new naming convention, Otto in the East Pacific has been assigned a different ID than Otto in the Atlantic under the U.S. Automated Tropical Cyclone Forecasting System (ATCF), even though the storm has the same name and is considered the same cyclone in both basins. This is playing havoc with various online platforms that map and archive tropical cyclones. At the National Hurricane Center’s website, and on our own site, you’ll see a Hurricane Otto in the Atlantic and a Tropical Storm Otto in the Pacific depicted as two separate tropical cyclones. It appears that the two life stages of Otto will be considered separately when calculating storm totals and Accumulated Cyclone Energy for the 2016 Atlantic and East Pacific seasons.

Hurricane landfalls from January to November?!
Between the landfall of Hurricane Alex in the Azores in January and Otto's landfall in Central America this week, 2016 will break the record for the most prolonged calendar-year hurricane season in Atlantic history (the 1938 season is close behind, although that one wasn’t bracketed by landfalls). "WX Geeks" host Marshall Shepherd reflects on this "year-long" hurricane season in a Forbes essay published Friday.

We’ll be back with our next post on Monday. Enjoy the weekend, everyone!

Jeff Masters and Bob Henson

Hurricane

Cat 2 Otto Slams Nicaragua, Costa Rica; Strongest Late-Season Hurricane on Record

By: Jeff Masters and Bob Henson , 6:12 PM GMT on November 24, 2016

Small but potent Hurricane Otto plowed into the Caribbean coast around 1 PM EST Thursday less than 20 miles north of the border between Nicaragua and Costa Rica, making history in the process. As Otto approached the Central American coast, the storm’s eye was clearly visible on satellite--a compelling sight any time of year, but especially on the same day that people in the United States were celebrating Thanksgiving and putting thoughts of hurricane season out of their minds. With top sustained winds of 110 mph at the top of the Category 2 range as of 1 PM Thursday, Otto was in a three-way tie as the strongest Atlantic hurricane ever recorded this late in the year (see Figure 3 below). Otto is also the latest hurricane to make landfall anywhere in the Atlantic basin in records going back to 1851. A Category 1 storm passed about 30 miles north of the Turks and Caicos Islands on November 28, 1887. In addition, Otto now holds the mark for the southernmost hurricane landfall on record for Central America. No hurricane or tropical storm has ever been recorded in Costa Rica, but it is possible Otto's center will pass over parts of northwestern Costa Rica while Otto is still a tropical storm or hurricane (see below).

Otto’s small size allowed it to vault to top-end Category 2 strength from Wednesday night to Thursday morning after it had weakened to tropical storm strength earlier on Wednesday. As Otto approached the coastline, its hurricane-force winds only extended out to 15 miles from its center and tropical-storm-force winds extended out to 70 miles. Because the more powerful winds are on the right-hand side of a Northern Hemisphere hurricane, this meant Nicaragua would bear the brunt of Otto’s winds, although parts of far northeast Costa Rica were experiencing much rougher conditions than they are accustomed to.


Figure 1. Enhanced infrared image of Hurricane Otto as it approached the coast of southern Nicaragua and northern Costa Rica at 1515Z (10:15 am EST) Thursday, November 24, 2016. Image credit: NOAA/NESDIS.


Figure 2. Two children are embraced by their father in Bluefields, Nicaragua, as Hurricane Otto approached on November 23, 2016. Image credit: INTI OCON/AFP/Getty Images.

Otto’s impact on people and structures was minimized by its landfall location, as the storm was moving across the sparsely populated area encompassed by the Indio Maiz Biological Reserve and the Punta Gorda Natural Reserve. There may be significant damage to the reserves themselves, though. The small town of San Juan de Nicaragua (formerly Greytown, population about 1300) may have experienced hurricane conditions as Otto’s eye passed just to the north of it. Later on Thursday, winds up to tropical-storm force may affect the more populated region around Nicaragua’s capital, Managua. There are no weather stations in Weather Underground’s PWS network within 50 miles of Otto’s landfall location, and the last Hurricane Hunter foray into Otto’s inner core was just after 11Z Thursday (6:00 am EST), so we will have to depend mainly on satellite estimates for Otto’s intensity at landfall.

Rainfall will be a significant threat with Otto from Thursday into Friday. Localized torrents of up to 15” - 20” are possible along Otto’s track across southern Nicaragua and northern Costa Rica. The outer fringes of Otto’s circulation may produce rains of 5” or more along higher elevations along the Caribbean coast of Honduras and the Pacific coast of western Panama and southern Costa Rica.


Figure 3. Tracks of all Atlantic tropical storms and hurricanes recorded between 1851 - 2016 on November 24 or later. A total of 50 storms have been observed this late in year; only three of these reached Category 2 strength prior to Otto. Otto is tied for strongest Atlantic hurricane ever observed this late in the year, along with a 1934 storm that had 110 mph winds at 7 am EST November 24, and an 1853 hurricane that also had 110 mph winds at 7 am EST November 24. Image credit: NOAA.

Otto may become the first storm to keep its name from Atlantic to Pacific
A ridge of high pressure to Otto’s north will keep the storm rolling westward on Thursday afternoon and evening across southern Nicaragua and northern Costa Rica, which are far less mountainous than other parts of Central America. In fact, part of Otto’s northern circulation could pass over Lake Nicaragua, one of the top-ten biggest freshwater lakes in the Americas. With land influence at a relative minimum, Otto is projected by NHC to be a tropical storm when it enters the Pacific early Friday. If Otto does maintain its identity as a named storm, as expected, it will keep the name Otto in the Pacific. Should Otto dissipate but its remnants manage to redevelop in the Pacific, the new storm would take the name Virgil from the Eastern Pacific list.

More than a dozen “crossover” tropical cyclones have been recorded, most of them moving from Atlantic to Pacific rather than vice versa. The most recent was Hermine (2010), which formed as an East Pacific tropical depression before entering the western Gulf and striking the northeast coast of Mexico as a tropical storm. Otto would be the first crossover storm in modern records to keep its name in going from one basin to another, since NHC’s previous practice was to rename such systems. All of Otto’s predecessors in this realm--including Hurricane Cesar-Douglas (1996)--underwent a name change when moving from Atlantic to Pacific or vice versa.

We won’t need to worry about Otto once it enters the East Pacific, as conditions do not favor reintensification and the storm will be moving away from land areas.


Figure 4. Tracking map for Hurricane Otto as of 10 AM EST Thursday, November 24, 2016.

Otto’s ascension to hurricane status gives the Atlantic 15 named storms, 7 hurricanes, and 3 intense hurricanes for the year. The Accumulated Cyclone Energy (ACE) in the Atlantic for 2016 has now reached 133--the Atlantic’s highest ACE value since 2010. The long-term averages for the period 1971 - 2010 in the Atlantic were 12 named storms, 6.5 hurricanes, 2 major hurricanes, and an ACE of 92, so the Atlantic hurricane season of 2016 is above average in all categories. If Otto proceeds into the East Pacific as a named storm, it will be that region’s 22nd tropical storm, which would put 2016 in a tie with 2014 for fifth place for the most number of named storms in the Eastern and Central Pacific.

A rare Thanksgiving Day storm
This is the second Thanksgiving Day in a row that’s kept NHC forecasters busy issuing storm advisories. In 2015, record-warm ocean waters helped Hurricane Sandra off the Pacific coast of Mexico become only the second Thanksgiving Day hurricane in modern records for the Atlantic or Eastern Pacific, and the first major hurricane. Sandra set the record for the latest major hurricane ever observed in the Western Hemisphere, as the storm maintained at least Category 3 strength from 00 UTC November 26 through 00 UTC November 27 (previous record: an unnamed Atlantic hurricane in 1934 that held on to Category 3 status until 00 UTC November 24.) When Sandra peaked as a Category 4 storm with 150 mph winds at 1 am EST (06 UTC) Thanksgiving Day, November 26, it became the latest Category 4 storm ever observed in either the Eastern Pacific (previous record: Hurricane Kenneth on November 22, 2011) or the Atlantic (previous record: ”Wrong Way" Lenny on November 18, 1999.) The only other Thanksgiving Day hurricane ever recorded in the Western Hemisphere was Hurricane Karl of 1980, which spun harmlessly as a minimal Category 1 hurricane far out in the central North Atlantic on Thanksgiving Day that year.

Otto is the first named storm in the Atlantic known to make landfall on Thanksgiving, but several other weaker storms have had NHC forecasters issuing advisories on Thanksgiving Day. This includes 1988’s Tropical Storm Keith, which struck Florida as a tropical storm on Wednesday, November 23, and persisted as a strong tropical storm east of Florida until midday Thanksgiving Day (November 24). In 1998, minimal Tropical Storm Nicole weakened to a depression east of Bermuda early on Thanksgiving Day (November 26), with advisories discontinued at 10 am EST. Nicole did get a new lease on life several days later, becoming a hurricane on November 30 and persisting to become one of just five Atlantic hurricanes on record during the month of December. In the hyperactive Atlantic season of 2005, Tropical Storm Delta roamed the eastern Atlantic on Thanksgiving Day (November 24). And in 2011, a weakening Tropical Storm Keith well out to sea in the eastern Pacific prompted advisories on Thanksgiving Day (November 24). Prior to the establishment of NHC as we know it, an unnamed tropical storm dissipated on Thanksgiving Day 1953 (November 26) well east of Bermuda. Hawaii takes the cake for the worst U.S. hurricane-related impacts during Thanksgiving Week: Hurricane Iwa passed near Kauai on Tuesday, November 23, 1982, during the run-up to the “super” El Niño of 1982-83. Iwa caused one death and inflicted $250 million in damage in Kauai.

We hope all of our U.S. readers have a safe and enjoyable Thanksgiving. We’ll be back with an update on Otto on Friday.

Jeff Masters and Bob Henson

Hurricane

Record-Setting Otto to Bring Thanksgiving Flooding to Central America

By: Jeff Masters and Bob Henson , 4:07 PM GMT on November 23, 2016

The latest hurricane ever recorded to form in the Caribbean Sea, Hurricane Otto, has thankfully weakened to a tropical storm, but is still poised to make a most unwelcome visit to Central America on Thursday, when it will move ashore over southern Nicaragua. Otto will become the first Atlantic tropical cyclone on record to make landfall on (U.S.) Thanksgiving Day. Otto’s intensification to a hurricane on November 22 came about a day later than the previous latest hurricane observed in the Caribbean, Hurricane Martha of 1969. The last time a hurricane was seen this late in the year anywhere in the Atlantic was in 2005, when Hurricane Epsilon meandered across the Central Atlantic as a Category 1 hurricane on December 2 - 7. Otto became a hurricane at a latitude of 10.5°N—unusually far to the south in the Caribbean. Only Hurricane Martha, which became a hurricane at latitude 10.3°N on November 22, 1969, and maintained Category 1 strength as it moved south to 10.0°N on November 23, was a hurricane at a lower latitude in the Caribbean.


Figure 1. MODIS satellite image of Hurricane Otto taken at 1:24 pm EST November 22, 2016. At the time, Otto was a Category 1 storm with 75 mph winds, and was the latest-forming hurricane ever observed in the Caribbean Sea. Image credit: NASA.

Hurricane Hunters find a weaker Otto
An Air Force hurricane hunter aircraft finished a mission into Otto around 9 am EST Wednesday, and found that the eyewall of Otto had collapsed. NHC rated Otto’s top surface winds at 70 mph at 10 am EST Wednesday, but the Hurricane Hunters did not find any surface winds in excess of 60 mph, and the NHC conceded in their discussion that their 70 mph estimate may have been too high. Moderately high wind shear of 15 - 20 knots was likely to credit for Otto’s weakening, as strong upper-level winds out of the south-southeast were able to drive dry air to the south of Otto into its core. Satellite loops on Wednesday morning showed a considerable reduction in Otto’s heavy thunderstorm activity near its core, but there was an increase in heavy thunderstorms along a band well to the north of the center, and these thunderstorms will bring very heavy rains to Nicaragua and Honduras on Wednesday and Thursday. Otto had decent moisture to work with—about 65% relative humidity at mid-levels of the atmosphere, and sea surface temperatures (SSTs) were very warm, near 29°C (84°F), which was about 1°C (1.8°F) above average. Panama radar showed that Otto’s heavy rain bands were mostly offshore from that nation on Wednesday morning.

Track forecast for Otto
The track forecast for Otto is straightforward. A ridge of high pressure is building in to the north of the storm, and this ridge will guide Otto west-northwest and then west at an increasing forward speed. Otto will make landfall in southern Nicaragua late Thursday morning. It should take about a day for Otto to cross southern Nicaragua, which is much less mountainous than other parts of Central America. In fact, much of Otto’s path could be over Lake Nicaragua, one of the top-ten biggest freshwater lakes in the Americas. With land influence at a relative minimum, Otto is expected to be a tropical storm when it enters the Pacific on Friday. In this case, Otto would keep its name in the Pacific. Should Otto dissipate, but its remnants manage to redevelop in the Pacific, the new storm will take the name Virgil from the Eastern Pacific list.

More than a dozen “crossover” tropical cyclones have been recorded, most of them moving from Atlantic to Pacific rather than vice versa. The most recent was Hermine (2010), which formed as an East Pacific tropical depression before entering the western Gulf and striking the northeast coast of Mexico as a tropical storm. Otto would be the first crossover storm in modern records to keep its name in going from one basin to another, since NHC’s previous practice was to rename such systems. All of Otto’s predecessors in this realm--including Hurricane Cesar-Douglas (1996)--underwent a name change when moving from Atlantic to Pacific or vice versa.

Intensity forecast for Otto
Conditions favor slow intensification of Otto until landfall. Sea surface temperatures will be unusually warm for this time of year--around 29°C (84°F). The atmosphere will be moistening through Thursday, and vertical wind shear is expected to abate slightly, to 10 - 15 knots, by Thursday morning. Our most reliable intensity model, the HWRF, predicted in its 06Z (1 am EST) Wednesday run that Otto would make landfall as a strong Category 1 hurricane with 90 mph winds. The 12Z Wednesday run of the SHIPS model gave Otto a 12% chance of reaching Category 2 strength with top sustained winds of 90 knots (105 mph) by Thursday morning. Regardless of how much intensification occurs, heavy rain will be the main threat from the storm, with rainfall amounts in excess of 10” in mountainous areas very likely to cause dangerous flash flooding and mudslides in parts of Central America.


Figure 2. Tracks of all hurricanes recorded in the Caribbean Sea in November and December between 1851 and 2016. Image credit: NOAA.

A rare Thanksgiving Day storm
Forecasters at the National Hurricane Center will be issuing storm advisories on Thanksgiving Day for the second year in a row on Thursday. Last year, record-warm ocean waters helped Hurricane Sandra off the Pacific coast of Mexico become only the second Thanksgiving Day hurricane in modern records for the Atlantic or Eastern Pacific, and the first major hurricane. Sandra set the record for the latest major hurricane ever observed in the Western Hemisphere, as the storm maintained at least Category 3 strength from 00 UTC November 26 through 00 UTC November 27 (previous record: an unnamed Atlantic hurricane in 1934 that held on to Category 3 status until 00 UTC November 24.) When Sandra peaked as a Category 4 storm with 150 mph winds at 1 am EST (06 UTC) Thanksgiving Day, November 26, it became the latest Category 4 storm ever observed in either the Eastern Pacific (previous record: Hurricane Kenneth on November 22, 2011) or the Atlantic (previous record: ”Wrong Way" Lenny on November 18, 1999.) The only other Thanksgiving Day hurricane ever recorded in the Western Hemisphere was Hurricane Karl of 1980, which spun harmlessly as a minimal Category 1 hurricane far out in the central North Atlantic on Thanksgiving Day that year.


Figure 3. VIIRS satellite image of the Eastern Pacific’s Hurricane Sandra taken on November 25, 2015—the day before Thanksgiving—when Sandra was an intensifying Category 3 storm. Image credit: NASA.

Several other weaker storms have had NHC forecasters issuing advisories on Thanksgiving Day. This includes 1987’s Tropical Storm Keith, which struck Florida as a tropical storm on Wednesday, November 23, and persisted as a strong tropical storm east of Florida until midday Thanksgiving Day (November 24). In 1998, minimal Tropical Storm Nicole weakened to a depression east of Bermuda early on Thanksgiving Day (November 26), with advisories discontinued at 10 am EST. Nicole did get a new lease on life several days later, becoming a hurricane on November 30 and persisting to become one of just five Atlantic hurricanes on record during the month of December. In the hyperactive Atlantic season of 2005, Tropical Storm Delta roamed the eastern Atlantic on Thanksgiving Day (November 24). And in 2011, a weakening Tropical Storm Keith well out to sea in the eastern Pacific prompted advisories on Thanksgiving Day (November 24). Prior to the establishment of NHC as we know it, an unnamed tropical storm dissipated on Thanksgiving Day 1953 (November 26) well east of Bermuda. Hawaii takes the cake for the worst U.S. hurricane-related impacts during Thanksgiving Week: Hurricane Iwa passed near Kauai on Tuesday, November 23, 1982, during the run-up to the “super” El Niño of 1982-83. Iwa caused one death and inflicted $250 million in damage in Kauai.

Have a great Thanksgiving holiday, everyone, and we’ll be back on Thursday to look at how Central America will do with Otto.

Jeff Masters and Bob Henson

Hurricane

Otto Expected to Strike Central America as a Hurricane

By: Bob Henson and Jeff Masters , 5:14 PM GMT on November 22, 2016

One of the strongest tropical cyclones on record so far south in the Caribbean, Tropical Storm Otto, was on the verge of becoming a hurricane Tuesday morning. In its 10 AM EST advisory, the National Hurricane Center pegged Otto’s top sustained winds at 70 mph, just short of the hurricane threshold. Otto was christened on November 21, an unusually late date for a Caribbean tropical storm; only eleven Caribbean storms since 1851 have had a later formation date.

Still holding stationary less than 100 miles north of the coast of Panama on Tuesday morning, Otto is expected to begin moving west on Wednesday. The storm will likely make landfall as a Category 1 or 2 hurricane on the coast of southern Nicaragua or northern Costa Rica on Thursday. A hurricane watch extends along the entire Caribbean coast of Costa Rica northward to south of Bluefields, Nicaragua. A tropical storm warning is in effect along the central coast of Panama from Nargana to Colon, with a tropical storm watch westward to the border of Costa Rica. These are startling locations for tropical cyclone advisories--understandably so. A storm of Otto’s expected strength has never made landfall so far south in the Caribbean, and there is no record of any hurricane striking Costa Rica.


Figure 1.Latest visible satellite image of Otto.


Figure 2. Enhanced infrared image of Otto as of 1545Z (10:45 AM EST) Tuesday, November 22, 2016. Image credit: NASA/MSFC Earth Science Office.

Over the past day or so, Otto has largely shaken off the elongating influence of the frontal zone on which it developed, which extends far to the northeast into the Atlantic. Showers and thunderstorms have become stronger and much more symmetric around Otto’s center since Monday night. The storm remains quite compact, with tropical storm force winds extending out to only 70 miles from the center. That small size is both good news and bad news, as it will allow Otto to either intensify or weaken more quickly than a larger storm would. Otto will be moving through a very concave section of the Central American coast, and the rugged topography may help impart some extra spin to Otto’s circulation as the storm gradually enlarges.

Intensity outlook for Otto
Otto is in a very favorable spot to intensify. Sea surface temperatures remain unusually warm for this time of year--around 29°C (84°F), or about 1°C above the seasonal average. The atmosphere will be moistening over time, with the 12Z Tuesday SHIPS model predicting that mid-level relative humidities around Otto will increase from about 60% to greater than 70%. The main negative factor for Otto is vertical wind shear of 15 - 20 knots resulting from upper-level southeasterly winds blowing over the storm as it sits and spins. However, that shear may abate slightly on Wednesday and Thursday, and it is not enough in itself to keep Otto from intensifying. Otto should reach Central America as at least a Category 1 hurricane, and Category 2 or even higher strength cannot be ruled out. The most reliable intensity model for existing tropical cyclones, the HWRF, has consistently projected that Otto will become a solid Category 2 storm. The SHIPS model gives Otto a 30% chance of reaching top sustained winds of 90 knots (105 mph) by Tuesday morning, and an 18% chance of reaching 115 knots (135 mph, minimal Category 4 strength) by Wednesday morning. The latest Category 3 storm ever observed in the Atlantic occurred at 00 UTC November 24, 1934, so Otto has a chance of beating the record for latest major hurricane ever observed in the Atlantic (thanks go to WU member Ryan1000 for this info.)


Figure 3. Track forecast for Otto as of 10 AM EST Tuesday, November 22, 2016.

Otto’s track: Central America, and perhaps the East Pacific
Stubbornly stationary Otto began to show signs at midday Tuesday of a long-awaited westward movement. Our most reliable track models--the European, GFS, and UKMET--are now consistent in bringing Otto onshore across southern Nicaragua or northern Costa Rica on Thursday. It should take about a day for Otto to cross southern Nicaragua, which is much less mountainous than other parts of Central America. In fact, much of Otto’s path could be over Lake Nicaragua, one of the top-ten biggest freshwater lakes in the Americas. With land influence at a relative minimum, Otto has a shot at retaining its identity as a tropical cyclone when it enters the Pacific on Friday. In this case, Otto would keep its name in the Pacific. Should Otto dissipate, but its remnants manage to redevelop in the Pacific, the new storm will take the name Virgil from the Eastern Pacific list.

More than a dozen “crossover” tropical cyclones have been recorded, most of them moving from Atlantic to Pacific rather than vice versa. The most recent was Hermine (2010), which formed as an East Pacific tropical depression before entering the western Gulf and striking the northeast coast of Mexico as a tropical storm. Otto would be the first crossover storm in modern records to keep its name in going from one basin to another, since NHC’s previous practice was to rename such systems. All of Otto’s predecessors in this realm--including Hurricane Cesar-Douglas (1996)--underwent a name change when moving from Atlantic to Pacific or vice versa.

Heavy rains a major threat from Otto
Otto is likely to bring torrential rains, landslides, and flooding to parts of Central America. The region’s complex topography may lead to several widely dispersed areas of extremely heavy rain. The most straightforward part of the outlook is for several inches of rain over nearly all of Nicaragua, with a core of 10” - 15” amounts very possible just north of Otto’s circulation as it makes landfall and moves inland. The broad circulation enveloping Otto has been impinging on parts of Costa Rica and Panama, a process leading to very heavy rain that could go well beyond 15” in some areas, especially western Panama. Another narrow zone of torrential rain (again, 15” or more possible) is projected by models to develop later this week as Otto’s outer circulation moves along the north coast of Honduras, perhaps extending into far southern Belize and extreme eastern Guatemala.


Figure 4. Total rainfall for the 150-hour period ending at 7:00 AM EST Sunday, November 27, 2016, projected by the 06Z Monday run of the GFS model. Image credit: tropicaltidbits.com.

Climatology of November and December Atlantic tropical cyclones
Since the active hurricane period we are in began in 1995 (including 2016), 13 of the 21 years (62%) have seen one or more Atlantic named storms form after November 1, for a total of eighteen November/December storms:

2016: Tropical Storm Otto on November 21
2015: Hurricane Kate on November 8
2011: Tropical Storm Sean on November 8
2009: Hurricane Ida on November 4
2008: Hurricane Paloma on November 6
2007: Tropical Storm Olga on December 11
2005: the "Greek" storms Gamma, Delta, Epsilon, and Zeta
2004: Tropical Storm Otto on November 29
2003: Odette and Peter in December
2001: Hurricane Noel on November 5 and Hurricane Olga on November 24
1999: Hurricane Lenny on November 14
1998: Hurricane Nicole on November 24
1996: Hurricane Marco on November 19

Only three of these storms caused loss of life: Hurricane Ida of 2009, which killed one boater on the Mississippi River; Tropical Storm Odette of 2003, whose floods killed eight people in the Dominican Republic; and Hurricane Lenny of 1999, which killed fifteen people in the Lesser Antilles. "Wrong-way Lenny" was the second deadliest and the second strongest November hurricane on record (Category 4, 155 mph winds).

There have been only seven major Category 3 or stronger hurricanes in the Atlantic after November 1. Part of the reason for the relatively low loss of life for November storms is that they tend to form from extratropical low pressure systems that get cut off from the jet stream and linger over the warm waters of the subtropical Atlantic. These type of systems typically get their start in the middle Atlantic, far from land, and end up recurving northeastwards out to sea. Tropical Storm Sean of 2011 was an example of this type of storm. However, as noted in the wake of Hurricane Tomas of November 2010 in our blog post, Deadly late-season Atlantic hurricanes growing more frequent, "It used to be that late-season hurricanes were a relative rarity--in the 140-year period from 1851 - 1990, only 30 hurricanes existed in the Atlantic on or after November 1, an average of one late-season hurricane every five years. Only four major Category 3 or stronger late-season hurricanes occurred in those 140 years, and only three Caribbean hurricanes. But in the past twenty years, late-season hurricanes have become 3.5 times more frequent--there have been fifteen late-season hurricanes, and five of those occurred in the Caribbean. Three of these were major hurricanes, and were the three strongest late-season hurricanes on record". Dr. Jim Kossin of the University of Wisconsin published a 2008 paper in Geophysical Research Letters titled, "Is the North Atlantic hurricane season getting longer?" He concluded that yes, there is an "apparent tendency toward more common early- and late-season storms that correlates with warming sea surface temperature but the uncertainty in these relationships is high". The recent increase in powerful and deadly November hurricanes would seem to support this conclusion.

We’ll be back with an update on Wednesday and will be tracking Otto throughout the Thanksgiving holiday period.

Bob Henson and Jeff Masters
 

Figure 5. The second strongest hurricane on record in the Atlantic in November, Hurricane Lenny, takes aim at the Lesser Antilles on November 17, 1999. Image credit: NOAA. (Thanks go to WU member elioe for pointing out that the November 1932 Cuba hurricane, which peaked at 170 mph winds, was the strongest and deadliest hurricane to occur in November.)

Hurricane

Slow-Strengthening Tropical Depression Forms in Southwest Caribbean

By: Bob Henson , 5:07 PM GMT on November 21, 2016

A gradually organizing disturbance about 300 miles east of Nicaragua was designated Tropical Depression 16 early Monday morning. Little change in TD 16 was noted in the National Hurricane Center’s advisory at 10 AM EST Monday, with the depression nearly stationary and top sustained winds remaining at 35 mph. TD 16 is located in a “col” area between weather features, resulting in upper-level winds so weak that there is no definitive steering influence. As it sits and spins over very warm water (sea surface temperatures of 29°C, or 84°F, are about 1°C above average), TD 16 is very gradually becoming better organized. Showers and thunderstorms are consolidating around TD 16’s center, with upper-level outflow becoming more evident toward the west and north. Heavy rains on the periphery of TD 16 continue to affect parts of Costa Rica and Panama, as the depression pulls in moisture from the tropical Pacific.



Figure 1. Latest visible satellite image of TD 16.


Figure 2. Infrared satellite image of TD 16 at 1615Z (11:15 AM EST) Monday, November 21, 2016. Image credit: NOAA/NESDIS.

The outlook for TD 16
TD 16 is expected to become Tropical Storm Otto within the next day or so. Vertical wind shear will be in the light to moderate range (15 - 20 knots), and minor drying of the atmosphere will bring mid-level relative humidities down to about 60%, but neither factor should impede TD 16’s development. An upper-level high is projected to strengthen over the western Caribbean by midweek, which should hasten TD 16’s growth. Steering around the high will gradually impart a westward motion to the cyclone. NHC brings TD 16 to hurricane strength by Thursday as it approaches the Caribbean coast near the border of Nicaragua and Costa Rica, where landfall is currently expected on Thursday afternoon or evening. While all of our most reliable track models bring TD 16 toward Nicaragua, the 00Z Monday European run and its ensemble members are the further south (near or just south of the Costa Rica border), while the UKMET and GFS runs project a landfall closer to central Nicaragua. The ECMWF is also considerably weaker, with none of its ensemble members bringing TD 16 to hurricane strength; most of the GFS ensemble members call for a strong tropical storm or minimal hurricane before landfall. As TD 16 develops, we’ll want to start keeping a closer eye on the HWRF model, the most reliable intensity model once a system has developed.


Figure 3. Tracking map for TD 16 as of 10 AM EST Monday, November 21, 2016.

How rare is a hurricane landfall in Nicaragua?
Tropical storms and hurricanes move into Nicaragua from the east every few years, but one as far south as TD 16 is a more uncommon event. If a Hurricane Otto develops and strikes as currently predicted, it could be the southernmost hurricane landfall on record in Central America. There are no recorded Atlantic hurricane landfalls in Costa Rica or Panama. A weak tropical storm made landfall in Costa Rica in December 1887, and Panama: Hurricane Martha, which struck as a strong tropical storm in Veraguas Province, Panama, on November 24, 1969. “Undoubtedly, there have been other tropical cyclones that moved into Panama, but this was the first one that was definitely tracked,” said Robert Simpson and NHC colleagues in their roundup of the 1969 Atlantic hurricane season.

Noteworthy landfalls in Nicaragua, shown here in rough order from north to south, include:

Felix (September 4, 2007): Cat 5, landfall just south of the Nicaragua-Honduras border
Ida (November 5, 2009): Cat 1, landfall near La Barra del Rio Grande
Beta (October 30, 2005): Cat 2, landfall near La Barra del Rio Grande
1906 Florida Keys Hurricane (October 10, 1906): Cat 3, landfall on central Nicaragua coast
Cesar (July 28, 1996): Cat 1, landfall north of Bluefields
Gert (September 15, 1993): tropical storm, landfall near Bluefields
Joan (October 22, 1988): Cat 4, landfall south of Bluefields
Irene (September 19, 1971); Cat 1, landfall south of Bluefields
Bret (August 10, 1993): tropical storm, landfall near Punta Gorda Natural Reserve

Heavy rains the big threat from TD 16
TD 16 is likely to bring torrential rains, landslides, and flooding to parts of Central America. The region’s complex, rugged topography may lead to several widely dispersed areas of extremely heavy rain. The most confident outlook is for several inches of rain over nearly all of Nicaragua, with a core of 10” - 15” amounts very possible within TD 16’s circulation as it makes landfall and moves inland. The westerly flow south of TD 16 will impinge into parts of Costa Rica and Panama, leading to very heavy rain (10” or more) already under way on some of the region’s south- and west-facing slopes. Another core of torrential rain (again, 10” or more possible) is projected by models to develop later this week as TD 16’s outer circulation moves along the north coast of Honduras, perhaps extending into southern Belize and eastern Guatemala.

We’ll be back with our next update by midday Tuesday. Our post on GOES-R will appear after the threat from TD 16 has passed.

Bob Henson


Figure 4. Aerial picture taken on September 6, 2007, in the village of Sandy Bay, Nicaragua, after the passage of Hurricane Felix. The southernmost Category 5 Atlantic hurricane on record prior to Matthew in 2016, Felix caused 133 deaths, nearly all in Nicaragua, and destroyed thousands of homes in the city of Bilwi. Image credit: Oscar Navarrette/AFP/Getty Images.





Hurricane

Little Change in 90L; Tropical Development Still Possible East of Nicaragua

By: Bob Henson , 7:17 PM GMT on November 20, 2016

On Sunday, the tropical disturbance dubbed Invest 90L in the southwest Caribbean Sea continued its leisurely evolution toward possible development into a tropical depression or tropical storm over the next few days. Shower and thunderstorm activity in the vicinity of 90L had decreased a bit since Saturday. The system remained without a low-level center of circulation, although there was plenty of spin in the envelope surrounding 90L. Conditions remain favorable for 90L to intensify if and when it develops a low-level center. Sea surface temperatures around 29.5°C (85°F) are roughly 1°C (1.8°F) above average, and a very moist atmosphere surrounds 90L, with mid-level relative humidities around 80%. Vertical shear is moderate, around 15 knots, and it may decrease a bit to 10 - 15 knots over the next several days. Air Force Hurricane Hunters were en route to investigate 90L on Sunday afternoon.


Figure 1. Visible satellite image of 90L east of Central America at 1817Z (1:17 pm EST) Sunday, November 20, 2016. A separate system is located to the northeast of 90L near Hispaniola.


Figure 2. Infrared satellite image of 90L from 1745Z (12:45 pm EST) Sunday, November 20, 2016. Image credit: NASA/MSFC Earth Science Office.

Outlook for 90L
Computer models remain supportive of 90L intensifying over the upcoming week as it drifts around the southwest Caribbean east of Nicaragua. High pressure will be strengthening at upper levels over the northern Caribbean, and a weakening cool front moving into the region may help strengthen the low-level pressure gradient and the associated easterly winds rotating around 90L. All three of our most reliable operational models for tropical cyclone genesis--the European, GFS, and UKMET models--develop 90L into a tropical depression by Tuesday and intensify it to near hurricane strength by Thursday. All three models bring 90L into Nicaragua around the end of the week, with the UKMET distinctly slower than the Euro and GFS. Almost every member of the Euro and GFS ensemble runs from 00Z Sunday develops 90L into a tropical depression by Tuesday. Most of the ensemble members go on to strengthen 90L into Tropical Storm Otto, but only 1 of the 50 Euro ensemble members, and just 1 of the 20 GFS members, produce a hurricane. Both the Euro and GFS ensemble runs agree strongly that 90L will eventually track west toward Nicaragua, reaching the coast around the end of the week. In its 1:00 pm EST Sunday Tropical Weather Discussion, the National Hurricane Center gave 90L 50-50 odds of developing into at least a tropical depression by Tuesday afternoon, with 70 percent odds through Friday afternoon.

Even if it ends up as no more than a tropical depression or tropical storm, 90L will still be capable of causing major trouble in Central America. The slow-moving system will be capable of bringing days of heavy rain to Panama, Costa Rica, and Nicaragua. Torrential rains could spread into parts of Honduras, Belize, and Guatemala by late in the week assuming 90L moves west and strengthens as expected.

Heavy rains lead to national emergency in Dominican Republic
A separate area of showers and thunderstorms along a remnant front several hundred miles northeast of 90L has led to days of heavy rain across the Dominican Republic (see photos in embedded tweet at bottom). At least five people have been killed, with more than 20,000 people displaced and more than 4000 homes damaged, according to government officials. Parts of the Puerta Plata province on the north coast received more than 600 mm (23.62”) of rain from November 6 to 16, according to floodlist.com, which also noted that six provinces were under a state of national emergency.


Figure 3. Projected rainfall (in inches) from the GFS model run at 12Z (7:00 am EST) Sunday for the 180-hour period ending at 00Z Monday, November 28, 2016 (7:00 pm EST Sunday, November 27). Image credit: tropicaltidbits.com.


Figure 4. The first GOES-R satellite lifts off from Kennedy Space Center on Saturday night, November 19, 2016. Image credit: NASA/Kim Shifltett.

GOES-R is a go!
After a one-hour delay, a NASA rocket sent the first entry in NOAA’s Geostationary Operational Environmental Satellite-R series (GOES-R) into space at 6:42 pm EST Saturday, November 19. Once in orbit after about two weeks, GOES-R will be renamed GOES-16. We’ll have more on Monday about the benefits GOES-R is expected to provide to tropical cyclone monitoring and prediction. We will also be covering 90L as it evolves, with posts throughout the holiday week as needed.

Bob Henson


Hurricane Flood

90L Near Nicaragua Closer to Tropical Depression Status; GOES-R Going Up

By: Jeff Masters , 8:30 PM GMT on November 19, 2016

An area of disturbed weather in the extreme southern Caribbean off the coast of Nicaragua (Invest 90L) became much more organized on Saturday morning and afternoon, and is likely to develop into a tropical depression by Tuesday. Satellite loops on Saturday afternoon showed a considerable increase in 90L’s heavy thunderstorm activity, and the storm had plenty of spin—though no low-level circulation center was present. The disturbance had plenty of moisture to work with (about 75% relative humidity at mid-levels of the atmosphere), and water vapor satellite imagery showed no large-scale areas of dry air that 90L might have to contend with. Wind shear was marginally favorable for development, about 15 - 20 knots. Sea surface temperatures (SSTs) were very warm, near 29.5°C (85°F), which was about 1°C (1.8°F) above average.


Figure 1. MODIS satellite image of 90L taken late Saturday morning, November 19, 2016. Image credit: NASA.

Track forecast: 90L a heavy rain threat to Central America
Steering currents are weak in the region, and 90L will move erratically over the next five days. Most of the models predict a slow westward motion by Wednesday and Thursday, which would bring 90L ashore over Nicaragua late in the week. Heavy rains over Panama, Costa Rica and Nicaragua are a major concern from 90L, as even a weak tropical depression or tropical storm meandering in this area for multiple days could cause significant flooding and landslides.

Our three reliable models for prediction of tropical storm genesis—the European, GFS and UKMET models—continued to forecast in their 12Z Saturday operational runs that 90L would develop into a tropical depression by Tuesday. At least 65% of the 70 forecasts from the 0Z Saturday European and GFS model ensembles predicted that 90L would eventually become Tropical Storm Otto. However, less than 10% of these forecasts showed 90L becoming a hurricane. In their 1 pm EST Saturday Tropical Weather Outlook, NHC gave 90L 2-day and 5-day development odds of 50% and 70%, respectively. An Air Force hurricane hunter aircraft is scheduled to investigate 90L on Sunday afternoon.

GOES-R launch is today!
The new GOES-R satellite is scheduled to be launched at 5:42 pm EST Saturday. Sky and Telescope has details on how to watch the launch in person or online. I’m super excited to see this bird go up!

Jeff Masters

Hurricane

Crazy Cryosphere: Record Low Sea Ice, An Overheated Arctic, and a Snowbound Eurasia

By: Bob Henson , 6:07 PM GMT on November 18, 2016

There are weather and climate records, and then there are truly exceptional events that leave all others in the dust. Such has been the case across Earth’s high latitudes during this last quarter of 2016, on track to be the planet’s warmest year on record. Sea ice extent and area have both plummeted to record lows for this time of year in both the Arctic and Antarctic. Such dramatic losses rarely occur at the same time, which means that the global total of sea ice coverage is phenomenally low for this time of year. The weirdness extends to midlatitudes: North America as well as the Arctic have been bathed in unusual mildness over the last several weeks, while Eurasia deals with a vast zone of above-average snowfall and below-average temperatures. Let’s look at each of these to see what’s up and where they may (or may not) be related.


Figure 1. Global sea ice area, including both Arctic and Antarctic. Sea ice extent is typically larger than sea ice area because it includes all data cells with at least 15 percent ice coverage (see NSIDC definitions). Global sea ice extent is experiencing a similar departure from average as global sea ice area. Experts usually analyze Arctic and Antarctic sea ice separately rather than together (see discussion below). Image credit: Wipneus, using data from National Snow and Ice Data Center. (NSIDC was not involved in producing this image.)


Figure 2. The normalized value of global sea ice area as of November 17, 2016, was so far from any other total in the 37-year record that it represented a departure of about 8 standard deviations below the average! Image credit: Wipneus, using data from National Snow and Ice Data Center. (NSIDC was not involved in producing this image.)


Figure 3. Departures from the 1981-2010 average for sea ice extent, in millions of square kilometers, across the Arctic (blue) and Antarctic (green) in the year 2016 through November 17. The departures from average were almost equally large by mid-November, leading to a total global sea ice extent of more than 4.2 million sq km below average. Image credit: Zachary Labe, based on data from the National Snow and Ice Data Center. (NSIDC was not involved in producing this image.)

Strange times at both poles: coincidence or connection?
Round-the-clock darkness usually forces a rapid growth in sea ice across the Arctic by November, but that process has been much slower than normal over the past month or so. There is now far less mid-November sea ice in the Arctic than in any other year since satellite records began in 1979. For the five-day average ending November 17, the difference in Arctic sea ice extent between this year and the next-lowest year (2012) was 582,000 square kilometers, an area about a third larger than California. It’s an especially dramatic example of the long-term decline in sea ice across the Arctic that’s been evident for upwards of 20 years.

Experts agree that the laggard sea ice this month around Antarctica is a separate matter from the Arctic, because sea ice in the northern and southern polar regions is produced by two markedly different circulation regimes and geographies. “At NSIDC, we generally frown on the practice of looking at the global sea ice extent,” said Mark Serreze, director of the National Snow and Ice Data Center, “the reason being that ice in the two hemispheres tends to behave rather differently; while Arctic extent shows clear downward trends in all months, the pattern for the Antarctic has been much more complex.” Serreze and several other ice experts I contacted agreed that there was no obvious explanation for why sea ice extent would suddenly dip in unison in both the Arctic and Antarctic when the two processes are typically so uncorrelated. Previous record-warm years didn’t behave this way. Could some previously dormant or absent connection be popping up just now? If so, it’s not an obvious one. NSIDC’s Ted Scambos: “I’d say that to link the two poles with a single causality chain at the seasonal/annual level is probably about a decade of research in the future.”

Unlike the Arctic, sea ice extent around Antarctica has actually shown a slight increasing trend over the last couple of decades. This might seem odd in a global climate that’s warming, but there are several plausible explanations, as we discussed in an October 26 post. Just two years ago, in September 2014, Antarctic sea ice extent hit the highest values observed at any time of the year since monitoring began in 1979. We’re now seeing the lowest values on record for mid-November, and the margin between this year and all other years has been increasing. For the five-day average ending November 17, the difference in Antarctic sea ice extent between this year and the next-lowest year (1986) was an enormous 1.12 million square kilometers.

An Arctic that’s having trouble cooling down
Temperatures north of 80°N smashed records for warmth throughout the winter of 2015-16. Now they’re on an even more torrid pace. In mid-November, temperatures across the high Arctic spiked to readings more typical of September, about 40°F above average for this time of year (see Figure 3 in our November 17 post). “Continued persistence of this pattern may significantly affect sea ice thickness into 2017,” tweeted Zach Labe (@Zlabe, University of California, Irvine) on Monday.

It’s difficult to measure sea ice thickness and volume in a continuous way, but the University of Washington’s PIOMAS model, which estimates sea ice volume using the available data, dove into record-low territory this month, just weeks after a rapid refreeze took place early in the autumn. “Whatever the respective roles of natural variability and [anthropogenic global warming], these wild swings do not inspire confidence in a semi-stable system,” noted Neven Acropolis in an early-November update on the Arctic Sea Ice Blog.


Figure 4. The huge contrasts between a far-warmer-than-average Arctic and a much-colder-than-average North Asia are projected to continue for the period November 18 - 22, 2016, as forecast by the GFS model on Thursday, November 17. Shown are anomalies (departures from average) in degrees Fahrenheit (top of legend) and Celsius (bottom of legend). Image credit: ClimateReanalyzer.com, University of Maine.

The atmospheric circulation this autumn has favored southerly flow from the eastern Pacific into the Atlantic, which has pushed recurrent bouts of unusually warm air across North America and the North Atlantic into the Arctic. One focal point of the warmth has been the Kara and Barents Sea, north of Scandinavia and western Russia, where sea ice has seen little or no expansion for November thus far. Temperatures in Longyearben, Norway--Earth’s northernmost permanent settlement, at latitude 78°N--have varied between about 7°C and -4°C (45°F and 25°F) since October 22. The average high and low for November 15 are about 12°F and 0°F.


Figure 5. Temperatures in Svalbard, Norway (in degrees C) from October 2015 to October 2016, including daily highs and lows (spiky line) and a running average (smoothed line). Readings above freezing (0°C) are shown in red, with readings below freezing in blue. Only a couple of days in the entire past year have stayed below average (black curve), and only four days this autumn through November 17 have failed to get above freezing. Image credit: Norwegian Meteorological Service.


Figure 6. Daily air temperature (highs and lows averaged) at Vize Island, Russia, in the northern Kara Sea (latitude 79°N) have cooled very little since August. The temperature on November 15 was close to freezing (32°F), compared to an average for the date of around -1°F. The island is experiencing some of the most extreme coastal erosion on Earth, as permafrost melts and stronger winds and waves reach the area. Image credit: Richard James, World Climate Service, via Brian Brettschneider, @Climatologist49.


Unusual cold and snow in Eurasia
The only place in the middle and high latitudes of the Northern Hemisphere that’s been consistently cold and snowy this autumn is Eurasia (see Figure 4 above). It’s as if the hemisphere’s entire allotment of chilly, snowy weather has been rounded up and consigned to one area, albeit a big one. For this, we can credit or blame what’s called a “wave one” pattern, where the upper-level circulation around the North Pole is dominated by a single elongated loop, shunted in this case toward the Eurasian side. Although the cold in Eurasia hasn’t been enough to balance the warmth elsewhere, it’s been quite dramatic on its own terms. On November 9, Stockholm, Sweden, experienced its heaviest one-day November snowfall (39 cm or 15.4 inches) in records going back to 1904. Across Siberia, October produced what appears to be the greatest snow extent for the time of year since 1998, and some areas got record totals for so early in the season, according to a weather.com report. In central China’s Hubei province, hundreds of homes were damaged and thousands of power poles were brought down by heavy snow during the second week of November, according to Xinhua.

By comparison, the snows over North America have been paltry indeed. On November 15, only 0.2% of the entire contiguous U.S. was covered by snow, the lowest coverage for mid-November in at least 14 years.


Figure 7. A woman walks through a record-setting snowfall on November 9, 2016, in Sundbyberg, near Stockholm, Sweden. Image credit: Jonathan Nackstrand/AFP/Getty Images.

Autumn snow cover in the Northern Hemisphere: On the increase?
Overall, it appears there has been an increase in snow cover across the Northern Hemisphere during autumn in recent years. This tendency has been largely overshadowed by the much more distinct and dramatic loss of snow cover during the Northern Hemisphere spring, and there are some good reasons. For one, because there is so much more sunlight in spring versus autumn, the loss of spring snowcover would have a much bigger effect on Earth’s radiative balance than a corresponding gain in autumn snowcover. Still, the apparent autumn trend is worth noting, especially since it may be playing a role in winter weather across North America and Eurasia.


Figure 8. Monthly anomalies (departures from average) in snow cover extent across the Northern Hemisphere, in millions of square kilometers, for the months of (top to bottom) October, November, April, and May. Image credit: Rutgers Snow Lab.


The images at right paint the general picture. Based on NOAA satellite observations, snow cover has increased slightly across the Northern Hemisphere (NH) in autumn and decreased sharply during spring. For the period 1967 - 2012, the spring trends were statistically significant (March through June) whereas the autumn trends weren’t, according to the most recent assessment report (2013) from the Intergovernmental Panel on Climate Change. Since that report came out, autumn snow extent has continued to run high across the Northern Hemisphere. The value for October 2016 was the third highest in the 51-year database, and the four prior Octobers were all well above the 1981-2010 average.

“The flakes have sure been flying in recent Octobers,” said David Robinson, state climatologist for New Jersey and leader of the Rutgers Snow Lab project. However, Robinson and other snow researchers I consulted still aren’t quite ready to classify the autumn increase as a significant trend. “My initial reaction is one of patience before being confident that there is a trend to identify,” said Robinson. “How many years that might take is the question.”

Complicating the task, ironically, is the improvement in satellite-based snow sensing technology over the years since 1967. In a 2013 paper titled “Is Eurasian October snow cover extent increasing?” (Environmental Research Letters), two scientists from Environment Canada, Ross Brown and Chris Derksen, presented evidence that the NOAA dataset was inconsistent with other sources of snow cover data for the period from 1982 to 2005, apparently due to improvements that allowed more early-season snow cover to be detected. After adjusting for this, the NOAA dataset showed a declining trend in Eurasian October snow cover through 2011, consistent with other datasets. Subsequent work along these lines has been carried out by Paul Kushner and Lawrence Mudryk (University of Toronto). “My conclusion from this is that the trends aren’t clear over the 1980s to early 2010s. I have not investigated the last few years,” Kushner told me.

A number of studies have pointed to the increasingly large expanse of open Arctic waters during autumn as a potential factor in producing heavier and/or more extensive snow cover. In particular, the open sections of the Karents and Bara seas provide a convenient source of moisture for early-season snowfall in adjacent Siberia. This is one of the key variables used to predict winter conditions across North America in the seasonal forecasting technique developed by Judah Cohen (Atmospheric and Environmental Research) and colleagues, as we discussed in an October 20 post. Importantly, Cohen’s technique doesn’t hinge on the presence of an increasingly snowy Eurasia, as Brown and Derksen point out: “The conclusion that October [snow cover extent] has not experienced significant increases over Eurasia in recent years does not undermine the arguments presented in Cohen et al (2012) linking Arctic moistening, Eurasian snow anomalies and extratropical winter cooling. This process depends on snow cover anomalies (not trends) and the physical processes involved in generating a strong surface cooling anomaly (albedo and surface temperature) depend on the areal extent and the depth of snow cover.”

In his weekly forecast update published on November 14, Cohen maintained that the above-average extent of snow this past October over Siberia should favor eventual disruption of the polar vortex and an enhanced chance of cold intrusions across Eurasia, possibly extending into eastern North America as we head into December and beyond.

We’ll be keeping an eye this weekend on slow-to-develop Invest 90L in the southwest Caribbean and will post updates as needed. See our post from earlier this morning for more details. Next week we’ll be covering the new GOES-R satellite, which at last check was scheduled to be launched at 5:42 pm EST Saturday. Sky and Telescope has details on how to watch the launch in person or online.

Have a great weekend, everyone!

Bob Henson

Antarctic Arctic Sea Ice Winter Weather

Invest 90L Off the Coast of Nicaragua Less Organized

By: Jeff Masters , 2:05 PM GMT on November 18, 2016

An area of disturbed weather in the extreme southern Caribbean off the coast of Nicaragua (Invest 90L) is struggling to develop, but is still expected to become a tropical depression by early next week as it meanders erratically. Satellite loops on Friday morning showed that 90L had a modest amount of rotation, but heavy thunderstorm activity had decreased since Thursday and was sparse and disorganized. The disturbance had plenty of moisture to work with (about 70% relative humidity at mid-levels of the atmosphere), and water vapor satellite imagery showed no large-scale areas of dry air that 90L might have to contend with. Wind shear was marginally favorable for development, near 20 knots. Sea surface temperatures (SSTs) were very warm, near 29.5°C (85°F), which was about 1°C (1.8°F) above average.


Figure 1. Latest satellite image of 90L.

Track forecast: 90L a heavy rain threat to Central America
Steering currents are weak in the region, and 90L will not move much over the next five days. Heavy rains over Panama, Costa Rica and Nicaragua are a major concern from 90L, as even a weak tropical depression or tropical storm meandering in this area for multiple days could cause significant flooding and landslides.

Our three reliable models for prediction of tropical storm genesis—the European, GFS and UKMET models—continued to forecast in their 0Z Friday operational runs that 90L would develop into a tropical depression by early next week. About three-quarters of the 50 forecasts from the 0Z Friday European model ensemble predicted that 90L would eventually become Tropical Storm Otto. However, only 6% of these forecasts showed 90L becoming a hurricane. About 85% of the 20 GFS ensemble members from the 0Z Friday forecast produced a Tropical Storm Otto. In their 7 am EST Friday Tropical Weather Outlook, NHC gave 90L 2-day and 5-day development odds of 10% and 60%, respectively—a decrease of 10% from the odds given Thursday morning. The Hurricane Hunter mission scheduled for Friday afternoon has been canceled, and is scheduled to fly on Saturday afternoon, if necessary.

We’ll have a new post early this afternoon on some crazy happenings in the Arctic.

Jeff Masters

Hurricane

Near-Record Global Warmth Continued in October

By: Jeff Masters , 6:24 PM GMT on November 17, 2016

October 2016 tied with 2003 as Earth's third warmest October since record keeping began in 1880, said NOAA's National Centers for Environmental Information (NCEI) on Thursday. October 2016 was 0.73°C (1.31°F) warmer than the 20th-century October average; the only warmer Octobers were during the two previous years, 2015 and 2014. NASA reported that October 2016 was the second warmest October in its database, behind October 2015. October 2016 was Earth’s coolest month (relative to average) since November 2014, which was 0.69°C (1.24°F) above average. This October was also the first month since April 2015 that failed to set a global heat record in either the NASA or NOAA database.


Figure 1. Departure of temperature from average by region for October 2016, the third warmest October for the globe since record keeping began in 1880. Record warmth was observed across parts of Mexico and the Caribbean, parts of west central Africa, sections of Iraq and southeastern Asia, and western Alaska extending to Far East Russia, where temperatures were more than 5°C (9°F) above their 1981–2010 averages. Cooler- and much-cooler-than-average conditions were observed across much of western Canada, most of eastern Europe, and a large swath extending across much of central Asia, where temperatures were more than 5°C (9°F) below their 1981–2010 averages in places. No land areas experienced record cold temperatures during October 2016. Africa as a whole observed its second warmest October on record, behind only 2015; North America had its seventh warmest; Asia had its 39th coolest October in the 107-year continental record. Image credit: NOAA National Centers for Environmental Information (NCEI).


As we blogged about on November 11, a weak La Niña event is now underway in the Eastern Pacific. The cool waters present in that region have helped cool the planet slightly below the record warm levels observed during the strong El Niño event of 2015 - 2016. The fact that October 2016 was still the 2nd to 3rd warmest October on record despite the presence of La Niña can mostly be attributed to the steady build-up of heat-trapping greenhouse gases due to human activities. NOAA’s global surface temperature for the year so far (January-October 2016) is an impressive 0.97°C (1.75°F) above the 20th-century average and 0.10°C (0.18°F) warmer than the previous January-to-October record, set in 2015 (see Figure 2 below). Remarkably, no land areas were cooler than average for the year-to-date. Barring an asteroid impact or the largest volcanic eruption in human history sometime in the next month, it is almost certain that 2016 will end up as the warmest year on record for the planet, giving us three consecutive warmest years on record.

Ocean-only, land-only, and lower atmosphere temperatures in October
Ocean-only temperatures this October were the second warmest on record, while land-only temperatures were the 16th warmest on record. (Since most of Earth’s surface is covered by ocean, the land-plus-ocean reading is dominated by the ocean-only temperatures, thus keeping October 2016 so warm globally.) Including 2016, the past five Octobers (2012–2016) have had the five highest October global ocean temperatures in the 137-year record. For the lowest 8 km of the atmosphere, global satellite-measured temperatures in October 2016 were the second warmest in the 38-year record, just behind October 2015, according to the University of Alabama in Huntsville (UAH). For the Jan - Oct year-to-date period, these temperatures have been the warmest on record.


Figure 2. Departure from the 20th-century average for the global January-through-October 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).

Arctic sea ice hits its lowest October extent on record
October 2016 Arctic sea ice extent was the lowest in the 38-year satellite record, according to the National Snow and Ice Data Center (NSIDC). The new record low was due, in large part, to high sea surface temperatures in open water areas and unusually high October air temperatures that extended from the surface through a considerable depth of the atmosphere. Amazingly, temperatures in the Arctic have spiked in mid-November to even higher values, and were 20°C (36°F) above average north of 80°N this week (see Figure 3). The unusual warmth in the Arctic has created an unusual amount of open water, which has provided high amounts of moisture to the atmosphere. As a result, widespread snows fell in regions where it was cold enough to snow; snow cover in the Northern Hemisphere in October was the third greatest on record.


Figure 3. Daily mean temperatures by Julian day over the Arctic north of 80°N, as compiled by the Danish Meteorological Institute (DMI). Temperatures for this year (red line) are compared to the long-term averages (green line.) This week’s heat spike to 20°C (36°F) above average is a greater deviation from average than any previous spike recorded at any time of year since DMI began tracking Arctic temperatures in 1956. Previous record: 17°C warmer than average, set in December 2002 and January 2006. Thanks go to WU member VibrantPlanet for pointing this out.

One billion-dollar weather disaster in October 2016: Hurricane Matthew
According to the October 2016 Catastrophe Report from insurance broker Aon Benfield, one billion-dollar weather-related disaster hit the planet in October: Hurricane Matthew, which tore through the Caribbean before pounding The Bahamas and the southeast United States. Matthew caused $5.5 billion in damage in the Caribbean and The Bahamas, and up to $10 billion in damage to the U.S. Two other tropical cyclones in October fell just short of being billion-dollar disasters: Super Typhoon Haima in the Philippines and China ($940 million in damage) and Super Typhoon Sarika in the Philippines and China ($890 million). From January through October 2016, there were 28 billion-dollar weather disasters globally. This is the fifth greatest number of such disasters in any year since 1990, with only 2013 (41), 2010 (40), 2011 (35) and 2014 (29) with more. For the U.S., Aon Benfield counted thirteen billion-dollar weather disasters during January - October 2016, which is the second highest number of such disasters on record since 1980 (the record: sixteen in 2011.)

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

1) Flooding, Yangtze Basin, China, 5/1 - 8/1, $28.0 billion, 475 killed
2) Hurricane Matthew, Caribbean, Bahamas, U.S., 9/28 - 10/10, $15 billion, 601 killed
3) Flooding, Louisiana U.S., 8/9 - 8/16, $10 - $15 Billion, 13 killed
4) Drought, China, 1/1 - 3/1, $6 billion, 0 killed
5) Flooding, Germany, France, Austria, Poland, 5/26 - 6/6, $5.5 billion, 17 killed
6) Drought, India, 1/1 - 6/30, $5.0 billion, 0 killed
7) Wildfire, Fort McMurray, Canada, 5/2- 6/1, $5.0 billion, 0 killed
8) Flooding, Northeast China 7/16 - 7/24, $4.7 billion, 289 killed
9) Severe Weather, Plains-Southeast U.S., 4/10 - 4/13, $4.3 billion, 1 killed
10) Severe Weather, Rockies-Plains-Southeast-Midwest U.S., 3/22 - 3/25, $2.5 billion, 0 killed
11) Super Typhoon Meranti, China, Taiwan, Philippines, 9/13 - 9/16, $2.5 billion, 44 killed
12) Flooding, China, 6/18 - 6/23, $2.3 billion, 68 killed
13) Flooding, Texas U.S., 4/15 - 4/19, $2.0 billion, 9 killed
14) Winter Weather, East Asia, 1/20 - 1/26, $2.0 billion, 116 killed
15) Severe Weather, Plains-Midwest U.S., 4/29 - 5/3, $1.8 billion, 6 killed
16) Tropical Cyclone Roanu, Sri Lanka, India, Bangladesh, Myanmar, China, 5/14 - 5/21, $1.8 billion, 135 killed
17) Severe Weather, Plains-Rockies U.S., 7/28 - 7/29, $1.6 billion, 0 killed
18) Drought, Zimbabwe, 6/1 - 8/10, $1.6 billion, 0 killed
19) Flooding and Severe Weather, Plains-Midwest-Southeast-Northeast U.S., 3/4 - 3/12, $1.5 billion, 6 killed
20) Super Typhoon Nepartak, Philippines, Taiwan, China, 7/8 - 7/9, $1.4 billion, 111 killed
21) Severe Weather, Plains-Southeast U.S., 3/17 - 3/18, $1.4 billion, 0 killed
22) Tropical Cyclone Winston, Fiji, 2/16 - 2/22, $1.4 billion, 44 killed
23) Flooding, Argentina and Uruguay, 4/4 - 4/10, $1.3 billion, 0 killed
24) Severe Weather, Plains-Midwest U.S., 5/21 - 5/28, $1.3 billion, 1 killed
25) Severe Weather, Plains-Midwest-Southeast-Northeast U.S., 2/22 - 2/25, $1.2 billion, 10 killed
26) Severe Weather, Netherlands, 6/23 - 6/24, $1.1 billion, 0 killed
27) Severe Weather, Plains-Midwest-Mississippi Valley U.S., 5/7 - 5/10, $1.0 billion, 2 killed
28) Winter Weather, Eastern U.S., 1/21 - 1/24, $1.0 billion, 58 killed

And here is the one billion-dollar disaster from October 2016 in more detail:


Disaster 1. Category 4 Hurricane Matthew devastated Haiti on October 4, killing 546, making it the Atlantic’s deadliest hurricane in 11 years. Damage in Haiti was estimated at $1.9 billion—a staggering 21% of the impoverished nation’s GDP, and by far Haiti’s costliest hurricane on record, according to the international disaster database, EM-DAT. The previous record was $400 million (1980 dollars) in damage wrought by Hurricane Allen. Matthew battered Cuba as a Category 4 storm, causing $2.6 billion in damage (3.2% of their GDP.) Matthew was Cuba’s second most expensive hurricane on record, behind Hurricane Georges of 1998 ($3 billion in damage in 2016 dollars, according to EM-DAT.) The Bahamas suffered $600 million in damage from Matthew (6.8% of GDP), making it their third most expensive hurricane on record behind Hurricane Frances of 2004 ($1.28 billion in losses, 2016 dollars) and Hurricane Jeanne of 2004 ($700 million in damage). Matthew grazed the coast of Florida and Georgia before making landfall in South Carolina on October 8 as a Category 1 hurricane with 75 mph winds. Matthew killed 49 people in the U.S., 28 of them in North Carolina. U.S. damage was estimated at up to $10 billion. This would make Matthew the 17th most expensive hurricane in U.S. history. Remnant moisture from Matthew also brought flooding rains and high winds to parts of the Maritime Provinces of Canada, causing tens of millions of dollars in damage. In this image, we see a small town along the southwestern coast of Haiti that suffered extreme storm surge damage from Hurricane Matthew. Image credit: United Nations Stabilization Mission in Haiti (MINUSTAH), via univision.com.

Notable global heat and cold marks set in October 2016
Hottest temperature in the Northern Hemisphere: 44.5°C (112.1°F) at Podor, Senegal, 9 October
Coldest temperature in the Northern Hemisphere: -41.4°C (-42.5°F) at Geo Summit, Greenland, 1 October
Hottest temperature in the Southern Hemisphere: 44.2°C (111.6°F) at Augrabies Falls, South Africa, 28 October
Coldest temperature in the Southern Hemisphere: -72.7°C (-98.9°F) at Vostok, Antarctica, 11 October
(Courtesy of Maximiliano Herrera.)

Major weather stations that set (not tied) new all-time heat or cold records in October 2016 (Courtesy of Maximiliano Herrera)
Macapa (Brazil) max. 36.6°C, 5 October
Bandarawela (Sri Lanka) max. 33.0°C, 11 October
Majuro (Marshall Islands) max. 34.0°C, 16 October
Taua (Brazil) max. 39.4°C, 19 October
Tshane (Botswana) max. 41.5°C, 31 October

Note: On 5 October Buffelsfontein Farm in South Africa recorded -10.5°C, which is the lowest temperature ever measured in Africa for the month of October.

No all-time national heat records set or tied in October 2016
No nations or territories set all-time heat or cold records in October 2016. From January through October 31, 2016, a total of 21 nations or territories tied or set all-time records for their hottest temperature in recorded history. This breaks the record of eighteen all-time heat records in 2010 for the greatest number of such records set in one year. Also, one all-time cold temperature record has been set so far in 2016 (in Hong Kong.) For a detailed list of these all-time records, see our September global climate summary post.

We'll be back with our next post on Friday. See our earlier post today for more on Invest 90L, in the southwest Caribbean, which has changed little since Wednesday.

Jeff Masters

Climate Summaries

Little Change to 90L Off the Coast of Nicaragua

By: Jeff Masters , 2:28 PM GMT on November 17, 2016

An area of disturbed weather in the extreme southern Caribbean off the coast of Nicaragua (Invest 90L) has changed little since Wednesday, but is still expected to develop into a tropical depression by early next week as it meanders erratically. Satellite loops on Thursday morning showed that 90L had a modest amount of rotation, but heavy thunderstorm activity was sparse and not showing any increase. The disturbance had plenty of moisture to work with (about 70% relative humidity at mid-levels of the atmosphere), and water vapor satellite imagery showed no large-scale areas of dry air that 90L might have to contend with. Wind shear was marginally favorable for development, near 20 knots. Sea surface temperatures (SSTs) were very warm, near 29.5°C (85°F), which was about 1°C (1.8°F) above average.


Figure 1. Latest satellite image of 90L.

Track forecast: 90L a heavy rain threat to Central America
Steering currents are weak in the region, and 90L will not move much over the next five days. Heavy rains over Panama, Costa Rica and Nicaragua are a major concern from 90L, as even a weak tropical depression or tropical storm parked in this area for multiple days could cause significant flooding and landslides. For example, Tropical Storm Gamma of 2005, with top winds of just 50 mph, stalled just north of Nicaragua on November 18 - 20, causing at least 37 fatalities in Honduras and Belize.

Our three reliable models for prediction of tropical storm genesis—the European, GFS and UKMET models—continued to forecast in their 0Z Thursday operational runs that 90L would develop into a tropical depression by early next week. About half of the 50 forecasts from the 0Z Thursday European model ensemble predicted that 90L would eventually become Tropical Storm Otto. However, only 4% of these forecasts showed 90L becoming a hurricane. About 85% of the 20 GFS ensemble members from the 0Z Thursday forecast produced a Tropical Storm Otto. In their 7 am EST Thursday Tropical Weather Outlook, NHC gave 90L 2-day and 5-day development odds of 20% and 70%, respectively—a decrease of 10% from the odds given Wednesday morning. The Hurricane Hunters are on call to potentially investigate 90L on Friday afternoon.

We’ll have a new post early this afternoon on the NOAA global climate summary for October.

Jeff Masters

Hurricane

A Slowly Unfolding Saga: 90L Takes Its Time Developing

By: Jeff Masters and Bob Henson , 4:49 PM GMT on November 16, 2016

An area of disturbed weather in the extreme southern Caribbean off the coast of Nicaragua (Invest 90L) is likely to develop into a tropical depression by this weekend as it moves little. Satellite loops on Wednesday morning showed that 90L had developed a modest amount of rotation, and heavy thunderstorm activity was sparse but on the increase. The disturbance has plenty of moisture to work with (about 70% relative humidity at mid-levels of the atmosphere), and water vapor satellite imagery showed no large-scale areas of dry air that 90L might have to contend with. Wind shear was favorable for development, a moderate 10 - 15 knots. Sea surface temperatures (SSTs) were very warm, near 29.5°C (85°F), which was about 1°C (1.8°F) above average.


Figure 1. Visible satellite image of 90L as of 1445Z (9:45 am EST) Wednesday, November 16, 2016. 90L is drawing on moisture from the Caribbean as well as from the Pacific Ocean south of Panama. Image credit: NASA/MSFC Earth Science Office.


Figure 2. Sea surface temperatures that are now even higher than the average readings for September in the Caribbean (about 2.5 standard deviations above the mean) will help support development of 90L. Michael Lowry (The Weather Channel) tweeted on Tuesday: “Caribbean waters are *supposed* to cool down by this point in the season but then again what’s “normal” nowadays?” According to Lowry, SSTs in the Caribbean are running just behind those in 2005 as the warmest on record for November. Image credit: @MichaelRLowry.

Track forecast: 90L a heavy rain threat to Central America
Steering currents are weak in the region, and 90L will not move much over the next five days. Heavy rains over Panama, Costa Rica and Nicaragua are a major concern from 90L. Even a weak cyclone parked in this area could cause significant flooding and landslides. During the hyperactive season of 2005—when we’d already run through the alphabetic list of Atlantic names by mid-November—the slow-developing Tropical Storm Gamma stalled just north of Nicaragua on November 18 - 20, causing at least 37 fatalities in Honduras and Belize.

In their 7 am EST Wednesday Tropical Weather Outlook, NHC gave 90L 2-day and 5-day development odds of 30% and 80%, respectively. The Hurricane Hunters are on call to potentially investigate 90L on Friday afternoon. The next name on the Atlantic list of storms is Otto. Ensemble model guidance from 00Z Wednesday supports the idea that 90L could become Otto. About two-thirds of the European model ensemble members develop Otto into at least a tropical storm by Sunday, including three of the four highest-probability members. About three-quarters of the GFS ensemble members produce a Tropical Storm Otto by this weekend. The ensemble guidance suggests only a slim chance that Otto could go on to become a hurricane. Any movement of 90L away from the extreme southwest Caribbean is likely to be at least a week from now.

The heat goes on
At last count, the U.S. had set 2820 record highs and 23 record lows for the month of November thus far, and this ratio is sure to become even more lopsided as the month rolls on. Dozens of record highs are likely to fall on Wednesday and Thursday from the Rockies to the East Coast, ahead of a sharp cold front plowing across the nation late this week. A blizzard watch was in effect for Thursday and Friday for parts of the eastern Dakotas and western Minnesota, with winter storm watches extending from the Northern Rockies to the Upper Midwest. This week’s front will bring temperatures down to near or slightly below average in many areas. However, it now appears that temperatures will surge back well above average for at least the western and central U.S. during most of Thanksgiving week, while the East Coast states are in line for seasonably cool conditions. It’s quite possible that a number of U.S. locations will end up with their warmest November on record, including Lincoln, NE (see embedded tweet below from Ken Dewey at the University of Nebraska-Lincoln).

We’ll be posting regularly on 90L as well as other topics over the next few days.

Jeff Masters and Bob Henson


Figure 3. Temperature anomalies (departures from average, in degrees C) at 18Z (1:00 pm EST) Thursday, November 17, 2016, as projected by the 12Z Wednesday run of the GFS model. Readings will be 15°F to 25°F above average on Thursday from the Central and Southern Plains to the Midwest and South, while temperatures will run below average over most of the intermountain West on Thursday behind a sharp cold front. Image credit: tropicaltidbits.com.




Hurricane Heat

Trump’s Proposals: Dangerous to our Climate’s Future

By: Jeff Masters and Bob Henson , 4:18 PM GMT on November 15, 2016

The greatest environmental challenge of our lifetimes will play out in a strikingly new and uncertain context with the election of Donald Trump as the 45th U.S. president. Trump has made it abundantly clear he disagrees that humans are changing Earth’s climate, and he has questioned whether our climate is changing at all. This places him at odds with the leaders of virtually every other nation on Earth, according to a Sierra Club compilation of statements from world leaders released in July. Among Trump’s campaign pledges, as summarized in Vox, are:

--scrap the Clean Power Plan, put forth by President Barack Obama to regulate greenhouse emissions from power plants
--dismantle most or all of the Environmental Protection Agency (EPA)
--abolish federal spending related to climate change, which could end or disrupt the work of thousands of scientists and engineers
--“cancel” the hard-fought global Paris Agreement on climate change mitigation, which was years in the making and finalized only last year.

The roster of potential members of the Trump administration includes several fossil-fuel executives, and a post-election organization chart confirmed that economist Myron Ebell (Competitive Enterprise Institute) will be heading up Trump’s transition team at EPA. Ebell has long been one of the nation’s most prominent voices fostering doubt about climate change and its risks. In 2007, Ebell told Vanity Fair: “…whether it's caused by human beings or not, it's nothing to worry about."


Figure 1. American students take part in a protest outside the COP22 international climate conference in Marrakesh, Morocco, on Wednesday, November 9, 2016, following the U.S. presidential election. Image credit: Fadel Senna/AFP/Getty Images.

Trump has railed against established climate science for years, most famously with his tweeted claim of November 6, 2012: “The concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive.” At the three 2016 presidential debates, the topic of climate change was never raised by moderators, even though one unasked question--”What are the steps you will take to address climate change?”--placed #4 among 30 potential questions for the second debate as ranked by participants in an online poll. Likewise, climate change was not addressed in the wide-ranging “60 Minutes” interview with Trump and family members on Sunday, November 13.

Commentary
Trump’s election to the presidency of the most powerful nation on Earth is a serious blow to our hopes of preserving a livable climate for our children. In order to keep global warming below the dangerous threshold of 2°C above pre-industrial levels, we needed strong American leadership and a near-WWII-level effort to move the U.S. and global economy away from fossil fuels. Instead, Trump has promised to strongly oppose that transition. While Trump’s actions cannot stop the ongoing shift of our energy economy away from fossil fuels, they could still do a tremendous amount of damage, because there remains far more fossil fuel on Earth than we can safely burn while still avoiding dangerous risks to our climate. As climate science writer and former energy researcher Joe Romm wrote on Wednesday at thinkprogress.org: “The clean energy revolution is unstoppable because of underlying global market, policy, and technological trends. President Trump can’t reverse those trends even if he appoints oil executives to run both the Departments of Energy and Interior. He can’t stop the inevitable triumph of solar, wind, efficiency (such as LED light bulbs), advanced batteries, and electric vehicles. But, as I’ve written, he could probably slow it enough to destroy the modest chance we had to keep total warming ‘well below 2°C’ as the world committed to in Paris.”

Indeed, any U.S. action to halt or slow down climate change mitigation and adaption will run up against powerful worldwide momentum, including the global recognition of climate change threats and the enormous growth of wind and solar energy. What appears almost certain now is that U.S. emission cuts will fail to meet the national pledge submitted as part of the Paris Agreement (a 26 - 28% reduction in U.S. greenhouse emissions by 2025 compared to 2005). This agreement was intended to grow stronger in subsequent years, with each country raising its voluntary goals, but in this case the U.S. would be moving backward. Even if other nations remain on board, the extra greenhouse emissions from the United States will raise the odds of truly serious consequences for many years to come. This year to date is the warmest in global records, and carbon dioxide concentrations have risen above 400 ppm for good, ensuring even more warming to come. The atmosphere is not waiting for U.S. leaders to decide whether human-produced climate change is real or not.


Figure 2. A man walks on dunes on October 26, 2016 near Morocco's southeastern oasis town of Erfoud, north of Er-Rissani in the Sahara Desert. The oasis of Tafilalet near Er-Rissane is at risk of disappearing as the area is plagued by long-term drought and desertification. Image credit: Fadel Senna/AFP/Getty Images.

Based on every signal we have now, a Trump presidency would abandon any U.S. leadership role in global climate policy. It remains to be seen how Trump’s proposals will translate into firmer plans and actions, and how other nations might be influenced. For the sake of this discussion, let’s assume that the Trump administration’s plans and their repercussions worldwide could end up producing an additional 0.5°C increase in Earth's temperature before it eventually stabilizes. This difference may not seem like much, but it would make a huge difference in some regions. For example, research published last month in Science stated that the impact on ecosystems of a 1.5°C warming is not unknown for Mediterranean societies, but it warned that a 2°C warming would make the warm forests of southern Spain and North Africa likely to be taken over by desert by the end of the century, making living there difficult. Even before Trump’s election, holding global warming to 2°C above pre-industrial levels was looking unlikely. Now, a 3°C warming is looking more probable, raising the specter that the children of today voting during the U.S. election of 2056 will be grappling with whether or not we should attempt desperate geo-engineering efforts to intentionally modify the climate in order to avoid massive disruption and damage to our ecosystems and societies.

Trump’s proposals thus far on climate change would put short-term profits ahead of the long-term well-being of ourselves and the children of future generations, and they need to be strongly resisted and protested. If we want to preserve our best chances for a livable climate, we must protect environmental regulations, push for divestment from fossil fuel stocks, invest in renewable energy, join action groups, organize ballot initiatives, and work with state and local governments. Hunter Cutting of climatesignals.org has a more in-depth analysis on how the climate action movement can move forward. In his address to the nation after the election, Trump said he wanted to be a president for all Americans. Let’s hold him to that promise.

Jeff Masters and Bob Henson
Note: Our views are our own and not necessarily representative of The Weather Company or IBM.

Additional reading

China may leave the U.S. behind on climate change due to Trump
Andrew Freedman, Mashable

What Trump can--and can’t--do all by himself on climate
Paul Voosen, Science

Climate Trumps Everything, No Matter Who Is President
Michael E. Mann and Susan Joy Hassol, Scientific American

Climate Change Politics

November 2016: Plenty of Smoke, Not Enough Rain and Snow

By: Bob Henson , 4:22 PM GMT on November 14, 2016

The atmospheric spigots have been turned off across most of the United States over the last several weeks. According to the weekly U.S. Drought Monitor report from Thursday, November 10, more than 27% of the contiguous U.S. has been enveloped by at least moderate drought (categories D1 through D4). This is the largest percentage value in more than a year, since late October 2015. The upward trend of the last month is worrisome given the outlook for the coming winter: drier-than-average conditions are projected by NOAA across the southern half of the contiguous U.S., a frequent outcome during La Niña winters.


Figure 1. U.S. Drought Monitor released on November 10, 2016, valid for the week ending November 8. Image credit: National Drought Mitigation Center.

Where’s the Western snow?
It’s common for parts of the mountainous U.S. West to take until late autumn or early winter to build up a proper snowpack, but such a delay seldom extends to the entire region. This month, nearly all of the high country of the western U.S. is running far below the seasonal average for the amount of water held in snowpack. Ski areas are feeling the pain, especially since temperatures have rarely been cold enough this autumn for snowmaking to supplement nature. Several of Colorado’s major resorts have already postponed their opening dates, including Keystone, Breckenridge, and Copper Mountain.

The paltry snowpack is especially striking in the Pacific Northwest, which just experienced its wettest October on record. Most of that precipitation came in the form of rain, leaving all but the highest mountains snow-free. “Still early in winter but snowpack is terrible,” tweeted Brad Udall, senior water and climate scientist at the Colorado Water Institute. Outside the Pacific Northwest, precipitation has been scanty and temperatures have been consistently warmer than average.


Figure 2. The amount of water held in western U.S. snowpack (snow water equivalent) as of November 13, 2016, shown as a percentage of average for this date relative to the 1981-2010 median. Values are well below 50 percent over most areas. Image credit: USDA/NCRS National Water and Climate Center, courtesy @bradudall.


Figure 3. Temperatures are running well above average over nearly all the United States (as well as Canada and the Arctic, not shown here) for the first 12 days of November 2016. Shown here are the departures from average (anomalies) in degrees Fahrenheit. As of Monday morning, November 14, NOAA reported a total of 2713 daily record highs and 18 daily record lows for the month thus far. Image credit: NOAA/NWS Climate Prediction Center.


East of the mountains, the Plains and Midwest have been especially mild this month (see Figure 3 above). The Minneapolis-St. Paul International Airport has yet to see a temperature below freezing, breaking the city’s all-time latest-freeze record of November 7, 1900. La Crosse, WI, and Peoria, IL, have also broken their latest-first-freeze records as they wait to dip to 32°F. All three locations should finally get a freeze this weekend in the wake of a potent storm system swinging across the central U.S. The storm will bring high winds and widespread snow to the northern Great Plains and Upper Midwest--perhaps a foot or more in parts of the Dakotas. The Central Plains could see an inch or so of rain, but prospects for rain further to the south and east are looking dim.

Weeks on end without a big Southeast rain
It’s been more than a month since parts of the Southeast have seen a drop of measurable rain. Birmingham, AL, is on a record dry streak: 56 consecutive days without measurable rain as of Sunday, beating the previous record of 52 days set in 1924. “Nine minutes of sprinkles Nov. 4 and another bout of sprinkles on Oct. 16 has been the entirety of Birmingham's rainfall so far this fall,” observed Jon Erdman in a weather.com roundup on Sunday. The most widespread rain since Hurricane Matthew in early October fell from eastern Georgia across northern South Carolina and southern North Carolina on Sunday, with widespread 0.5” - 1.0” amounts (Wilmington, NC, picked up 1.77”). However, nearly all of the significant rain fell east of the drought-stricken areas. Assuming no major rainmakers arrive over the next couple of weeks--and none are on the horizon right now--large parts of the Southeast have a shot at their driest autumn on record (September - November).

In a region where rain is usually plentiful and frequent, a drought this prolonged has major consequences. In northwest Georgia, “our dirt is like talcum powder,” ranger Denise Croker (Georgia Forestry Commission) told Insurance Journal last week. Smoke from wildfires across the southern and central Appalachians has poured across the Southeast, especially where inversions have kept the smoke confined near the surface, as explained by Marshall Shepherd (University of Georgia) in Forbes.


Figure 4. Streamers of smoke can be seen blowing northwestward from wildfires across the southern and central Appalachians on November 7, 2016. Image credit: NASA Earth Observatory.


Figure 5. Enhanced infrared satellite image of Tropical Storm Tina at 1430Z (9:30 am EST) Monday, November 14, 2016, just before Tina was downgraded to a tropical depression. Image credit: NOAA/NESDIS.

Tropical Storm Tina pops up and fades out in the East Pacific
A cluster of showers and thunderstorms gained just enough organization over warm waters (above 30°C) off Mexico’s Pacific coast to become Tropical Storm Tina on Sunday night. Tina was the 21st named storm of this year’s busy East Pacific hurricane season. Located about 200 miles west of Manzanillo, MX, Tina didn’t last long as a tropical storm. Christened at 10 pm EST Sunday with top sustained winds of just 40 mph, Tina was downgraded to a tropical depression at 10 am EST Monday. High wind shear will continue to degrade Tina’s circulation as it decays into a remnant low by Tuesday, remaining well west of the Mexican coast.

Potential late-season tropical cyclone in the Caribbean
Long-range computer models have suggested for several days that a broad circulation over the far southwest Caribbean east of Nicaragua might evolve into a tropical cyclone over the next week or two. Sea surface temperatures remain very warm in the region: around 29 - 30°C, about 1°C above average for this time of year. In its latest Tropical Weather Outlook, issued at 7:00 am EST Monday, the National Hurricane Center gives a near-zero chance of a tropical depression forming in this area by Wednesday morning, but a 60% chance by Saturday. Ensemble model runs from 00Z Monday provide support for the idea of very gradual development, with low odds of formation on any particular day but higher collective odds over a multi-day period. About a third of members of the ECMWF ensemble produce a tropical cyclone in the 3-5 day period (Wednesday to Friday night) and about half do so in the 6-10 day period. The GFS is more bullish, with nearly all of its ensemble members developing at least a tropical depression by the coming weekend. Steering currents will be extremely weak for some time, so any tropical cyclone that does develop could pose a threat for heavy rain if it lingers near the east coast of Central America.

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

Bob Henson


Figure 6. Enhanced infrared satellite image of an area of disturbed weather in the southwest Caribbean Sea at 1515Z (10:15 am EST) Monday, November 14, 2016. Image credit: NASA/MSFC Earth Science Office.

Drought Winter Weather Heat Hurricane

Weak La Niña Expected to Persist into 2017

By: Bob Henson , 5:06 PM GMT on November 11, 2016

After a few months of on-again, off-again prospects for a La Niña in 2016-17, NOAA pulled the trigger on Thursday. In its monthly El Niño/Southern Oscillation (ENSO) Diagnostic Discussion issued on Thursday, NOAA placed its alert system into La Niña Advisory mode. A La Niña Advisory means that La Niña conditions are now present and expected to continue--in this case, through winter 2016-17.

The NOAA advisory follows a cooling trend that’s persisted for months across the central and eastern equatorial Pacific, including the Niño3.4 region. The core definition of La Niña is a cooling of sea surface temperatures (SSTs) over the Niño3.4 area to at least 0.5°C below the seasonal average. To be considered full-fledged La Niña conditions, the SST shift must be accompanied by La Niña-supportive trends in the overlying atmosphere, such as a strengthening of Pacific trade winds and increased shower and thunderstorm activity in the western Pacific. SSTs entered La Niña territory back in July, but the atmospheric cofactors were less consistent and more ambiguous until the last month or so. The nagging uncertainty, which was backed up by less-than-enthusiastic computer model runs, led to NOAA’s issuing a La Niña Watch in April, implementing a La Niña Advisory in July, reverting to a La Niña Watch in August, cancelling that watch in September, and reissuing it in October. In a NOAA ENSO Blog posted Thursday, Emily Becker outlines the step-by-step process guiding NOAA’s decision-making on La Niña. According to Becker, “The atmospheric response overall is fairly weak, going along with the borderline cooler sea surface temperatures of this La Niña…but it’s been consistent for a few months, meaning that we are seeing a change on seasonal timescales, and it’s time to formally welcome La Niña conditions!”

Australia’s Bureau of Meteorology (BOM) issued a La Niña Watch in April and has stuck with it ever since, including its November 8 update. The agency uses a more stringent definition than NOAA for La Niña: SSTs in the Niño3.4 region must be at least 0.8°C below average, together with other cofactors. An interesting retrospective analysis from BOM points up how uncertain this year’s picture has been: if advisories had been issued by the agency starting in 1980, this year’s La Niña Watch would be the most protracted La Niña or El Niño Watch of the entire period, based on the conditions that unfolded.


Figure 1. Sea surface height anomalies (departures from average) during the northern-autumn phase of the last four La Niña events, including the one now beginning. Higher sea surface heights (red and white areas) are associated with warmer upper-ocean temperatures. Image credit: NASA imagery, compilation courtesy Jan Null, @ggweather, Golden Gate Weather Services.

La Niña competes with a warming Pacific
El Niño and La Niña events are playing out in a Pacific Ocean that’s warming up, in line with the planet-wide warming associated with human-produced greenhouse gases. During the “super” 2015-16 El Niño event, we saw SSTs jump to record- or near-record levels over a vast part of the northern and eastern Pacific, well beyond the equatorial region where El Niño is focused. Now we’re seeing a narrow ribbon of La Niña cooling squeezed by a continuation of warm SSTs on either side (see Figures 1 and 2). Traditional indices of El Niño and La Niña don’t consider SSTs poleward of 5°N and 5°S, except right off the coast of South America, so the Niño3.4 values for La Niña don’t incorporate the very warm conditions elsewhere in the tropical and subtropical Pacific. However, the NOAA indices do take into account long-term warming within the immediate Niño3.4 region, since they are calculated against 30-year averages that are updated every 5 years.


Figure 2. The Niño3.4 region is one of the few parts of the Pacific Ocean where temperatures in early November 2016 have been below average. Image credit: NOAA/CPC and climate.gov.

The outlook into next year
La Niña 2016-17 isn’t looking like a spectacular event. Model runs released this week from the North American Multi-Model Ensemble (see Figure 3 below) are in general agreement that this should bottom out as a weak La Niña event over the next several months, with SSTs gradually returning to the neutral range by late winter or early spring. In their joint predictions from early November, forecasters at NOAA and the International Research Institute for Climate and Society (IRI) call for neutral conditions to be the most likely state by the first quarter of 2017 (see Figure 4 below). Hints of a possible return to El Niño in 2017-18 are already showing up in the longest-range model runs. The NOAA/IRI outlook gives odds twice as high for El Niño (about 30%) as for La Niña (about 15%) by summer 2017, although neutral conditions remain the most likely outcome.


Figure 3. Predicted departures from average sea-surface temperature in the Niño3.4 region of the tropical Pacific, based on various models in the North American Multi-Model Ensemble. The NMME website includes more details on the various models that make up the NMME. Image credit: NOAA/CPC.


Figure 4. The likelihood of La Niña (blue), El Niño (red), or neutral (green) conditions for overlapping three-month periods into mid-2017, as determined by forecasters at NOAA’s Climate Prediction Center and the International Research Institute for Climate and Society. Image credit: IRI.

Will warmth win out over northern La Niña chill?
During northern winter, La Niña tends to favor relatively dry, mild weather over the southern U.S. and northern Mexico, with relatively cool conditions across the far northern U.S. and western Canada and wetter-than-average winter for the U.S. Pacific Northwest. Many of these favored conditions have already popped up, with October producing record-high precipitation over the Pacific Northwest and extreme drought over the Southeast. What you wouldn’t expect from La Niña is unusual warmth encompassing virtually all of North America, as we’ve seen in recent weeks. As always, La Niña and El Niño intersect with other factors. This is the warmest year in global recordkeeping, and warmth has been sharply focused over North America this autumn. Meanwhile, it’s been quite cold and snowy across northern Eurasia (more on that in a future post). It remains to be seen when or even if the high-latitude circulation will shift to bring some of this intense cold toward North America. Most of the NMME model runs from early November suggest that temperatures could end up above average for the entire winter across much or most of North America. For at least the next few days, the continent’s autumn warm wave should stay remarkably widespread, with especially dramatic mildness persisting over the Arctic and unusually sharp cold centered over Russia (see Figure 5 below).


Figure 5. Departures from average temperature for the five-day period from Friday, November 11, 2016 to Wednesday, November 16, as projected by the GFS model. Image credit: ClimateReanalyzer.org, University of Maine.

Supermoon!
The dry, mild pattern across much of North America will provide optimal conditions for viewing the moon’s closest encounter with Earth in almost 70 years. This “supermoon” will peak on Sunday and Monday nights, as the moon’s closest approach will be at 6:15 am EST Monday. The moon will appear about 14 percent larger and up to 30 percent brighter than it does at its furthest distance from Earth. EarthSky has excellent background on the event. A supermoon of this caliber is about as rare as the Chicago Cubs making it to the World Series, as the last one was in January 1948 (though less dramatic supermoons are fairly common). The next Earth-Moon encounter this close won’t be until November 2034, so if the weather cooperates where you are, be sure to take advantage of the chance to appreciate nature at its finest.

Have a great weekend, everyone!

Bob Henson


Figure 6. This image approximates the look of the Nov. 14, 2016, full moon with data from NASA's Lunar Reconnaissance Orbiter. Credit: NASA/GSFC Scientific Visualization Studio.

Third Warmest October in U.S. Weather Records

By: Bob Henson , 6:13 PM GMT on November 08, 2016

Unusual autumn warmth was spread generously across the United States--but rainfall was hogged by the periphery of the nation--during October 2016, according to the monthly U.S. summary released by NOAA’s National Centers for Environmental Information (NCEI) on Tuesday. For the 48 contiguous U.S. states, October came in as the third warmest of the 122 Octobers in data extending back to 1895. This means that three of the six warmest Octobers on record have occurred in the last three years: 2014 (#6), 2015 (#5) and 2016 (#3). Still on top of the list for October warmth are 1963 (#1) and 1947 (#2).

On a statewide level, this year produced the warmest October on record for New Mexico, and 22 other states had a top-ten warmest October. Only one of the 48 contiguous states ended up cooler than average. That was Oregon, in large part because of the soggy, sun-blocking pattern that prevailed across the Pacific Northwest.


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

Stark contrasts in wetness and dryness
The contiguous U.S. had its 49th wettest out of the last 122 Octobers, but much more telling details emerge as we shift to the state and local scales. A relentless stream of storms swept across the Pacific Northwest and into the northern Rockies during October, giving large swaths of the region their heaviest precipitation for any October. The states of Washington, Idaho, and Montana all had their wettest October on record, and both Oregon and California placed in the top five (the latter mainly because of rains in the northern half of the state). Spokane, WA, saw its wettest month in 135 years of recordkeeping, with a total of 6.23”. Across the Southeast, the extreme rains from Hurricane Matthew over eastern North and South Carolina were enough to give SC a top-ten wettest October. Although the same wasn’t true for NC, plenty of local rainfall records were set, and the state’s inland flooding was severe, affecting an estimated 100,000 structures. Heavier-than-average rains also prevailed across the Upper Midwest, Great Lakes, Northeast, and New England, including areas struggling with drought for much of this year.

Meanwhile, a belt of less-than-average precipitation extended across the nation’s Sunbelt from Arizona to the southern Appalachians. The states of Alabama, Colorado, Louisiana, Mississippi, Tennessee, and Texas all had top-ten driest Octobers. Georgia was truly a divided state, as reflected in the percentile maps below. Little or no rain fell in parts of northwest Georgia--Atlanta received only 0.16”, less than 5% of its average rainfall for October--while Matthew brought phenomenal totals to parts of the southeast Georgia coast, including 17.49” at Savannah’s Hunter Army Air Field. NOAA’s winter outlook calls for drier-than-average conditions to prevail across the southern tier of the nation through the next few months.


Figure 3. Temperature and precipitation percentiles for the contiguous U.S. for October 2016. Produced by mapping U.S. data onto a grid with 5-kilometer-wide cells, these maps allow for finer-scale regional analysis. Pockets of record heat are most evident over New Mexico and western Texas, with record dryness over parts of far western Florida and Alabama. Image credit: NOAA/NCEI.


Figure 4. Chris Moore walks down Martin Luther King Blvd. on October 12, 2016 in Lumberton, NC, one of the areas hardest hit by inland flooding associated with Hurricane Matthew. Image credit: Sean Rayford/Getty Images.


Figure 5. Temperatures for the period from January through October for the contiguous U.S., 1895 - 2016. Image credit: NOAA/NCEI.


For the year to date (January - October), 2016 is running just behind 2012 for the title of warmest year in U.S. record-keeping history (see Figure 5 above). In order to come out on top, this year would have to generate the nation’s warmest November and December on record--and then some--so a #2 finish appears much more likely. The planet as a whole remains on track for its warmest year on record, a topic we’ll cover in more depth in our October global climate summary next week. The United States only represents about 2% of Earth’s surface area, so we wouldn’t expect U.S. temperatures to rise and fall in lockstep with the globe’s overall warming trend. When this does occur, it’s often in association with a year that begins with a strong El Niño in place, as was the case this year. Another good example is 1998, when both the United States and the planet as a whole had their warmest years on record (up to that point) in the wake of the record-setting 1997-98 El Niño.

When it comes to climate extremes, 2016 is making its mark nationally. NCEI’s U.S. Climate Extremes Index for the year to date (Jan - Oct) shows that 44.4% of the contiguous U.S. has experienced at least one of the five primary heat- or precipitation-related extremes that make up the index. This puts 2016 in third place behind 2012 and 1934 for the largest areal coverage of extreme conditions. When tropical cyclones are factored in, 1998 nudges into second place, pushing 2016 into fourth place. Not surprisingly, the main reason why 2016 ranks so high on the list is this year’s record-warm minimum temperatures, a topic we explored in depth in late October.

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

Bob Henson

Climate Summaries

A Mild, Tranquil Election Day on Tap

By: Bob Henson , 5:22 PM GMT on November 07, 2016

The weather will be doing its part to keep the mood positive when Americans go to the polls on U.S. Election Day, Tuesday, November 8. Temperatures should be near or above normal over nearly all of the contiguous 48 U.S. states, continuing a string of mildness that’s lasted for weeks in many locations. Freezing temperatures will be largely absent on Tuesday morning outside of the higher terrain of the Rockies and New England (plus most of Alaska, of course). Afternoon readings from the 40s to 60s Fahrenheit will prevail over most of the nation, quite reasonable for early November. The only precipitation of note will be some mostly light rains ahead of a fairly weak upper-level trough extending from Michigan to the Gulf Coast.

It doesn’t look like Tuesday’s weather will have a major impact on the national-level outcome. However, there are cases where inclement weather may have actually swung U.S. presidential races, according to a WU news article by freelance contributor Sami Grover. The rapid spread of early voting in many U.S. states is likely blunting the effect of weather on Election Day turnout, noted Grover.


Figure 1. Precipitation forecast for the six hours from 7:00 am to 1:00 pm EST Tuesday, November 8, 2016, as projected by the 12Z Monday run of the GFS model. Image credit: tropicaltidbits.com.

Warmth by the numbers
As detailed by weather.com, a number of Midwestern locations could experience their latest first freeze of any year on record this year, including Minneapolis (Nov. 7), Des Moines (Nov. 13), and Detroit (Nov. 15). Here’s another telling illustration of how consistently mild the nation has been over the past several weeks: The preliminary total of U.S. daily record highs either tied or broken for the one-week period ending on November 4 was 887, while the corresponding number of daily record lows was a mere 1. Referring to the 887-to-1 ratio, independent meteorologist Guy Walton said: “Since cataloging record counts starting on 1/1/2000, this is the highest weekly ratio of daily highs to daily lows I have ever seen!” The numbers were almost as lopsided for the week ending November 7 (see Figure 2). Preliminary numbers typically grow a bit larger as late-reporting stations come in.


Figure 2. Preliminary data on U.S. records for the week ending November 7, 2016. The month to date has seen 1324 daily record highs set or tied, but only 7 daily record lows set or tied. Image credit: NOAA/NCEI.

As we discussed in a post last week, the biggest story of U.S. temperatures in 2016 is not the large number of daily record highs but the phenomenally small number of daily record lows--less than half as many as for any year on record since the 1920s, when enough data had accumulated to make such comparisons.

The absurdly consistent warmth has been especially evident across the South. As noted by weather.com’s Jonathan Erdman (@wxjerdman), a remarkable eight-day string of consecutive daily record highs began in Meridian, Mississippi, on October 28 and ended on November 4. The streak included a new all-time November high of 89°F on the 1st. Records in Meridian began in 1889. At the opposite end of the United States--Alaska--you’ll also find incredible mildness (relatively speaking). Readings on the Arctic Ocean coast at Barrow have been above average every day since September 15. The typical high and low in Barrow on November 7 are 9°F and -2°F, but as of Monday morning, Barrow had yet to dip below 13°F this entire autumn. We’ll have more on this fall’s amazing Arctic mildness later in the week.

Nationwide, at least 272 U.S. stations set or tied all-time monthly highs for November during the first seven days of the month. That’s a large chunk of the 860 monthly highs set or tied during the entire year up to November 7.

Will autumn arrive before winter?
Over the last several days, long-range computer model guidance has become increasingly insistent that a switch to much chillier weather could occur over the bulk of North America in about 10 to 15 days, perhaps kicked off with a very blustery Midwestern storm. This is at the outer edge of confidence in major pattern shifts, so we’ll have to see if the apparent trend holds water over the next few days. I wouldn’t hold my breath waiting for widespread record lows, but at this point even a shift toward near-normal temperatures would feel bracing.

Two killed as large tornado strikes near Rome, Italy
A massive, highly visible tornado injured dozens of people and startled many more in central Italy on Sunday evening (see embedded photo below). The twister struck around 6 pm local time near the coastal town of Ladispoli, about 20 miles west of central Rome and only about 10 miles northwest of the city’s international airport. Weather.com reported that one man was killed in Ladispoli by a cornice falling from a building, while another in Cesano, about 10 miles northeast of Ladispoli, was crushed by a falling tree. Dramatic video of the tornado can be found on the Facebook page Severe Weather Europe. Weaker tornadoes were reported on Sunday on the Canary Islands and the island of Sardinia.


Figure 3. Severe weather outlook for Monday, November 7, 2016. Image credit: European Storm Forecast Experiment (ESTOFEX).

The ESTOFEX project (European Storm Forecast Experiment) warned that more severe weather was possible Monday afternoon and evening across southern Italy east to Albania ahead of a strong, slow-moving upper-level trough. Ahead of the trough, jet-stream level winds of more than 100 mph were juxtaposed above relatively warm, moist air over the Tyrrhenian Sea. ESTOFEX noted the presence of very strong vertical wind shear resulting in storm-relative helicity (rotation) values of 400 to 1000 m2/s2, “which favors strong mesocyclones that can easily produce a (violent) tornado as well as large hail.” The juxtaposition of moist air from the Mediterranean and dry air from Africa is also a key factor in producing severe weather over the region, according to The Weather Guys (CIMMS/SSEC/University of Wisconsin-Madison). “Because these circumstances are most likely to get organized in the late fall, the limited tornado season that does occur in Italy occurs in October and November,” they write. “It would be interesting to know how many merchant vessels in the long history of Venice have gone down in such autumn storms.”

Tornadoes and other localized forms of wild weather are the focus of the American Meteorological Society’s 28th biennial Conference on Severe Local Storms, which kicked off Monday in Portland, OR. You can follow news from the meeting at the Twitter hashtags #SLS2016 and #SLS16. The agenda is online, with links to abstracts.

We’ll be back with a new post by Tuesday afternoon.

Bob Henson



Heat Tornado

Paris Agreement Becomes Official As Climate Change Hits U.S. State Ballots

By: Bob Henson , 5:29 PM GMT on November 04, 2016

The first truly global agreement to reduce human-produced greenhouse gas emissions--a huge milestone in the effort to address climate change--went into effect on Friday, November 4, 2016. The Paris Agreement was forged at the 21st annual United Nations Conference of Parties meeting (COP 21) in December 2015. In order to become official, the agreement needed to be ratified by 55 nations representing 55% of human-produced greenhouse gas emissions. That goal was met in October when the European Union ratified the plan.

The Paris Agreement is weaker than the preceding Kyoto Protocol in that it doesn’t mandate emission cuts by international law. Instead, think of it more like a pot-luck dinner: each nation determines its own contribution and submits its plan in the form of an “intended nationally determined contribution” (INDC). The idea is that regular scrutiny of the plans, and the progress in meeting them, will provide enough international peer pressure to make the agreement work. Moreover, having virtually every country on board is a marked change from the Kyoto Protocol, which was not ratified by the United States and which mandated no reductions from China and India, thus leaving more than half of the world’s greenhouse emissions unchecked. Global carbon dioxide emissions from fossil fuel use have more than doubled since the early 1970s.


Figure 1. The Eiffel Tower was illuminated in green light on November 30, 2015, on the first day of the COP 21 meeting in Paris. The tower and the Arc de Triomphe were scheduled to be lit in green on Friday night, November 4, 2016, in honor of the Paris Agreement going into force. Image credit: Stephane de Sakutin/AFP/Getty Images.

As stated by the UN Framework Convention on Climate Change, the Paris Agreement’s central aim is “to strengthen the global response to the threat of climate change by keeping a global temperature rise this century well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5°C.” The goals seem more ambitious than ever in light of the stunning global temperature jump of the last three years. For the period January through September, NOAA data show that temperatures have risen about 1.2°C in the last 100 years. In 2016 alone, we’re running a full 1°C above readings that prevailed in the 1940s to 1960s, and every year is boosting the atmosphere’s temperature-goosing storehouse of carbon dioxide. The weekly average of atmospheric carbon dioxide measured at Hawaii’s Mauna Loa Observatory dropped below 400 parts per million in late August 2016. It’s virtually certain to be the last weekly value below 400 ppm in any of our lifetimes.

Where do the national pledges stand?
The independent organization Climate Action Tracker is carrying out detailed analyses of each nation’s INDCs. Thus far, they’ve analyzed the INDCs from more than 30 countries representing about 70% of the world’s population and about 80% of global emissions. Their work suggests that the plans submitted thus far will cut global emissions, but not by enough to meet the ambitious Paris targets. The group has rated the INDCs of 5 nations as “sufficient” in helping the world meet the 1.5°C goal of the Paris Agreement. However, the INDCs from 11 other nations and the European Union were rated “medium,” while those from 14 countries were deemed “inadequate”.

Sufficient: Bhutan, Costa Rica, Ethiopia, The Gambia, Morocco
Medium: Brazil, China, European Union, India, Indonesia, Kazakhstan, Mexico, Norway, Peru, Philippines, Switzerland, United States
Inadequate: Argentina, Australia, Canada, Chile, Japan, New Zealand, Russian Federation, Saudi Arabia, Singapore, South Africa, South Korea, Turkey, Ukraine, United Arab Emirates
Not rated: Nepal, Gabon

Climate Action Tracker has a page with capsule summaries that link to the full analyses for each country, including details on how each analysis was carried out. The group takes into account how much each nation’s plan is likely to cut emissions, as well as “whether a government is doing its ‘fair share’ compared with others toward the global effort to limit warming below 2°C.” Because each nation has leeway to forge its own plan, the assumptions and techniques in each plan vary from country to country, making it a challenge to compare apples with apples as well as oranges, cantaloupes, strawberries, and everything else.

For example, in the large, heavily forested United States, the longstanding difficulty in assessing how much net carbon is taken up by vegetation and soil makes a big difference. A recent change in methodology has increased the amount of carbon dioxide projected to be taken up by forests and land-use changes by the year 2025 from 33% to 50%. This, in turn, reduces the amount of emission cuts required to meet U.S. targets by more than 4%. Carbon emissions from the U.S. have already dropped by a few percent in the last decade. Some big factors in the mix include a flattening of vehicle miles driven, a large-scale shift from coal to natural gas for electricity generation, and the growth of energy-efficient technologies such as cars that get better gas mileage and LED light bulbs. As shown in Figure 2, further progress will hinge in large part on whether the Clean Power Plan is implemented. That plan, put forth by the Environmental Protection Agency in 2014 to limit carbon pollution from power plants, was put on hold by the U.S. Supreme Court in February 2016, pending judicial review. (Needless to say, there are major differences in where the U.S. presidential candidates stand on climate change policy.)


Figure 2. The United States’ carbon emissions since 1990 (black line at left) and the projected emissions through 2030 based on current policy (blue extension], which assumes that the U.S. Clean Power Plan and at least some parts of the U.S. Climate Action Plan will be implemented. Also shown are the projected emissions if the Clean Power Plan is not implemented (black dashed line) and if the plan and all major parts of the preexisting Climate Action Plan are fully implemented (blue dashed line). Image credit: Climate Action Tracker.


Climate-related items on U.S. state ballots
There are two especially noteworthy items relevant to climate change on the state-level ballots in next week’s U.S. general election. In Washington, voters will consider a Carbon Emission Tax and Sales Tax Reduction Initiative. If it passes, this will be the first-ever carbon tax in a U.S. state. The idea behind such a tax--implemented thus far in only a handful of nations and provinces around the world--is to prod emission reductions by putting a cost on the act of adding carbon dioxide to the atmosphere through fossil fuel use. The proposed tax in Washington is based on an influential carbon tax implemented in neighboring British Columbia in 2008. It’s crafted as a revenue-neutral approach, where revenue brought in through the carbon tax is returned to taxpayers in the form of personal and business tax cuts and credits (as has been the case in British Columbia), including a sales tax reduction.

The Washington carbon tax has drawn support from dozens of earth, atmospheric, ocean, and space-science faculty at the University of Washington, as well as the eminent former NASA scientist James Hansen, a longtime proponent of putting a price on carbon. In a Seattle Times op-ed, Hansen said: “Washington [state] has a singular opportunity, with approval of Initiative 732, to address the threat of climate change and alter the ineffectual course of national climate policies. As if that isn’t enough, Washington voters also would be sending a broader message to our nation’s capital: The public demands an alternative to putrid politics-as-usual and is taking action.” The initiative is opposed by a number of industry groups and labor organizations, as well as by several environmental groups that would prefer to see revenue from any carbon tax used more specifically to advance clean-energy and climate-justice efforts.

At the other end of the nation, residents of the Sunshine State will vote on the Florida Solar Energy Subsidies and Personal Solar Use, Amendment 1. This is the latest skirmish in a heated debate playing out in states nationwide on how ever-growing residential solar power should be accommodated by the nation’s energy grid. In many states, “net metering” allows homeowners with solar panels to sell unused power back to their electric utility, typically at retail rates. This happens most often on hot, sunny summer days, when the utilities can use the extra power to combat spikes in power demand from air conditioning, so in many ways it’s a win-win arrangement. However, in some areas, homeowners sell back enough power to reduce their electric bills to little or nothing (or even pocket a small dividend at times). This has prompted claims that such users aren’t paying their fair share to keep the overall grid functioning. More broadly, the growth of rooftop solar is shifting the balance of energy production away from large utilities.


Figure 3. Logos for Consumers for Smart Solar (left), which supports the solar power amendment in Florida, and Floridians for Solar Choice (right), which opposes the amendment.

The Florida amendment is a cleverly constructed two-parter. The official ballot summary opens with a carrot to fans of solar power: “This amendment establishes a right under Florida's constitution for consumers to own or lease solar equipment installed on their property to generate electricity for their own use.” The second part takes a different tack: “State and local governments shall retain their abilities to protect consumer rights and public health, safety and welfare, and to ensure that consumers who do not choose to install solar are not required to subsidize the costs of backup power and electric grid access to those who do.”

The main coalition supporting the amendment, the grass-rootsy-sounding Consumers for Smart Solar, has spent more than $21 million, with more than $19 million of that total provided by four utilities. The main opposition group, Floridians for Solar Choice, is vastly underfunded by comparison. However, virtually every newspaper in Florida that’s weighed in on the amendment has come out against it.

Ballotpedia has extensive background on both the proposed Washington initiative and the proposed Florida amendment. Utilitydive.com has an excellent summary of various solar-related state legislative developments as of early 2016.

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

Bob Henson


Figure 4. SolarCraft workers Craig Powell (left) and Edwin Neal install solar panels on the roof of a home in San Rafael, California, on February 26, 2015. According to a survey report by the Solar Foundation in 2015, the solar industry employs more workers than coal mining, with nearly 174,000 people working in solar compared to close to 80,000 mining coal. Image credit: Justin Sullivan/Getty Images.

Climate Change Politics

Another Quirky Medicane Hits the Eastern Mediterranean

By: Bob Henson and Jeff Masters , 7:27 PM GMT on November 02, 2016

When the Atlantic hurricane season begins to quiet down in late October and November, it’s time to cast an eye toward the Mediterranean Sea for “medicanes”--a nickname for storms that develop tropical characteristics just off the coast of southern Europe. Medicanes aren’t considered full-fledged tropical systems, since the waters of the Mediterranean aren’t extensive or warm enough to sustain a true hurricane. However, it’s quite possible for an existing center of low pressure in the Mediterranean to briefly take on tropical characteristics, including a symmetric structure and a small core of warm air. Such was the case with a low that intensified last weekend while traveling from near Malta (south of Italy) toward the Greek island of Crete. As it pushed east, this medicane sent high surf west toward Malta and east toward Israel.

The storm swept across Crete on Monday with high winds and heavy rain. On Crete’s northwest coast, the city of Chania (Souda Air Base) recorded 3.07 inches of rain and peak wind gusts of 60 mph on Monday, October 31. Sustained winds topped out at just 35 mph. Crete’s largest city, Heraklion, on the island’s northeast coast, got 0.71 inches of rain, with top wind gusts of 46 mph. On Friday, a ship reported a wind gust to 57 mph, noted Capital Weather Gang. The system probably hit its peak intensity while over the open Mediterranean west of Crete during the weekend. As reported by weather.com, sea surface temperatures in the region were only about 22 - 24°C (72 - 75°F). That’s as much as 2°C above average for this time of year, but well below the usual 26°C benchmark for tropical development. Still, it appears the system briefly took on the symmetric warm-core features typical of a tropical storm.


Figure 1. MODIS satellite image of the medicane approaching Crete taken on Sunday afternoon, October 30, 2016. John Knaff (CIRA/RAMMB/Colorado State University) produced this large-scale black-and-white satellite loop. Image credit: NASA.


Figure 2. Image from a color-enhanced infrared satellite loop of the medicane centered just south of Greece’s Peloponnese peninsula at 0345Z (05:45 a.m. local time) Monday, October 31, 2016. Image credit: Scott Bachmeier, CIMMS/SSEC/University of Wisconsin-Madison.

Where to watch for medicanes
This week’s storm occurred in one of two “hot spots” where medicanes are most likely to develop, according to a long-term climatology published in 2014 in Climate Dynamics. Interpolating from long-term atmospheric data for the period 1948-2011, the authors estimated that medicanes occur once or twice per year, on average, but with much year-to-year variability. None of the world’s meteorological agencies are tasked with monitoring medicanes, so countless such storms have no doubt gone unrecognized, especially before routine satellite monitoring began. The most favored area for development is in the western Mediterranean, especially between Spain and the islands of Sardinia and Corsica. The other hot spot is the Ionian Sea, especially just southeast of Malta and the Italian peninsula, where this week’s storm cranked up. In both areas, medicanes become more likely in autumn, peak in winter, and decrease in spring, according to the study, although the western area has a broader “season.”

Since the waters of the Mediterranean aren’t warm enough to support conventional hurricane development, medicanes rely on colder air aloft, typically brought in as part of an upper-level low that decays over the Mediterranean. Wind shear relaxes as the upper low decays, and the contrast between the cold air aloft and the relatively warm sea surface temperatures can stimulate the formation of showers and thunderstorms. These, in turn, may congeal around a weak surface low and help give it a symmetric, warm-core structure--and sometimes even a cloud-free, eye-like feature. Often a medicane’s warm core will be enveloped within broader cold-core features, which makes it more akin to a hybrid or subtropical storm than a tropical storm.

The last Mediterranean storm to get this much notice occurred in the first week of November 2014. It was dubbed Qendresa by the Free University of Berlin, whose vortex-naming practices have become the default choice for medicanes. Qendresa produced wind gusts as high as 96 mph on the north coast of Malta. Winds at the Luqa, Malta, airport looked suspiciously like what one would observe with a tropical storm passing overhead--a double peak with a near-calm in between, with the pressure falling to 984 mb during the calm. Wunderground member Zivipotty, a meteorology student in Hungary who has analyzed Qendresa, believes it was primarily subtropical in nature, as it weakened rapidly once it became detached from its parent frontal system. In early November 2011, another noteworthy storm named Rolf took shape in the western Mediterranean. Rolf was the only medicane to be officially monitored by NOAA, whose Satellite Analysis Branch named it 01M and tracked it for two days. Zivipotty found Rolf to be more tropical in nature than Qendresa at its peak.


Figure 3. Winds at the 250-mb level (about 34,000 feet above sea level) were very weak (less than 20 knots on the legend at right, or 23 mph) above the medicane, which is shown here as a 1013-millibar low southwest of Greece at 12Z (2:00 pm local time) Sunday, October 30, 2016. Image credit: tropicaltidbits.com.


Figure 4. Near-surface winds derived from the space-borne European Advanced Scatterometer (ASCAT) show speeds topping 50 knots (58 mph) around the center of the medicane as it approached Crete on Monday, October 31. Image credit: ASCAT and NOAA/NESDIS.

Could bona fide hurricanes develop in the Mediterranean later this century?
According to research published in 2007, an increase in ocean temperatures of 3°C (5.4°F) in the Mediterranean by the end of the century could lead to hurricanes forming there. Miguel Angel Gaertner of the University of Castilla-La Mancha in Toledo, Spain, ran 9 different climate models with resolutions of about 50 km and found that some (but not all) of the models simulated hurricanes in the Mediterranean in September by the end of the century, when sea surface temperatures there could reach 30°C (86°F). Though the Mediterranean could start seeing hurricanes by the end of the century, these storms should be rare and relatively short-lived for three reasons:

1) The Mediterranean is quite far north and is subject to strong wind shear from jet stream activity.

2) The waters are shallow, and have relatively low heat content. There is no deep warm water current like the Gulf Stream.

3) The Mediterranean has a lot of large islands and peninsulas poking into it, increasing the chances that a tropical storm would weaken when it encountered land.

Wikipedia has an excellent page on Mediterranean tropical-like cyclones (medicanes).


Figure 5. Infrared image from Japan’s Himawari-8 satellite of Invest 90W and invest 99W in the Northwest Pacific at 1630Z (12:30 pm EDT) Wednesday, November 2, 2016. Image credit: CIMMS/SSEC/University of Wisconsin-Madison.

A potential tropical threat to the Philippines next week
Two large but loosely organized tropical waves in the Northwest Pacific are expected to gather strength, and one of them may pose a significant threat to the Philippines in a week or so. The westernmost of the two waves, Invest 90W, will have supportive conditions for growth as it moves west over the next few days: very warm sea surface temperatures of 29 - 30°C, a very moist atmosphere (mid-level relative humidities around 80%), and fairly light wind shear of around 10 - 15 knots. By early next week, the GFS, European, and UKMET models all project Invest 90W to reach typhoon strength. On its westward track, 90W could be approaching the Philippines by the middle of next week, perhaps still strengthening. The other wave, Invest 99W, should track further northwest, possibly gaining typhoon strength while over the open Northwest Pacific.

Meanwhile, the National Hurricane Center is keeping an eye on two systems with limited potential for development. A nontropical low well northeast of the Lesser Antilles may take on subtropical characteristics late this week as it heads toward the central North Atlantic, while a disturbance west of Costa Rica could become a tropical cyclone as it heads toward the northeast Pacific. NHC gives both systems a 20% chance of development over the next five days.

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

Bob Henson and Jeff Masters



Hurricane

September in November: Mild Autumn Continues for Much of U.S.

By: Bob Henson , 4:52 PM GMT on November 01, 2016

The tenacious pattern that’s delayed the first frosts and freezes this autumn as far north as the Upper Midwest remains in place for much of the U.S. as we kick off November. Most of the Mid-Atlantic and Northeast has had a few quick shots of cold weather (Baltimore had its first freeze on October 26, a few days earlier than average), but many other parts of the nation have been uncommonly free of autumn’s frosty grasp. Denver has yet to see its first snowflake, making this second autumn in a row it has gotten to October 31 without any snow. This is also the first time the city has experienced three snowless Octobers in a row in records going back to 1872 (although there was a trace of snow in September 2014). There was plenty of snow in Minneapolis 25 years ago today, when the city was still in the throes of its infamous Halloween Blizzard of 1991 (here’s a nice photo gallery from the Minneapolis Star-Tribune). On November 4, 1991, the airport low reached –3°F, the earliest below-zero reading in city history. The contrast with this year couldn’t be much more stark. The Twin Cities have yet to dip below 36°F anytime this fall, and readings there should stay near or above 40°F for at least the next week. The latest freeze on record for Minneapolis occurred on Nov. 7, 1900.

Monday was the warmest Halloween on record for a wide swath of U.S. cities, as noted by weather.com’s Chris Dolce, including Atlanta, GA (86°F); Huntsville, AL (88°F); Amarillo, TX (87°F); and Colorado Springs, CO (80°F). A number of locations across the South and Midwest could set all-time heat records for November on Tuesday and/or Wednesday. For example, Louisville, KY, has a shot on both days at matching or beating its all-time November high of 84°F (set Nov. 17, 1958). Records in Louisville go back to 1872.

This past month has a shot of beating 1963 for the warmest October in U.S. recordkeeping, though it’ll be a few days before we know for sure.


Figure 1. Temperature anomalies (departures from average) for October 1 - 30, 2016. Virtually the entire nation was above average for the month, except for the soggy Pacific Coast from northern California through most of Washington. Image credit: NOAA/NWS Climate Prediction Center.

Still wet to to the northwest, dry to the southeast
October delivered a bountiful crop of moisture to the United States, but that water was distributed very unevenly. From Washington to northern California, the U.S. Pacific Coast was slammed by a series of powerful Pacific storms that gave two state capitals (Olympia, WA, and Salem, OR) their wettest Octobers on record. The relentlessly strong Pacific jet pushed enough moisture to eastern Washington and western Idaho to produce even more impressive records there. Spokane saw not only its wettest October but its wettest single month on record, with 6.23” beating the 5.85” notched in November 1897. The city saw 22 days with measurable precipitation, besting the monthly record of 20 days recorded in October 1947, plus 4 more days with a trace of rainfall. At higher altitudes, the strong Pacific flow led to record-high monthly precipitation at dozens of mountain stations (see Figure 2). Further southeast, a few high-altitude spots in Utah, Wyoming, and Colorado reported their lowest October totals on record.

All-time wettest Octobers
Seattle, WA: 10.05” (old record 8.96”, 2003; records began in 1894)
Spokane, WA: 6.23” (old record 5.41”, 1947; records began in 1881)
Olympia, WA: 12.43” (old record 10.72”, 2003; records began in 1948)
Vancouver, WA: 8.22” (old record 7.37”, 1997; records began in 1892)
Priest River, ID: 9.26” (old record 8.31”, 1947; records began in 1898)
Salem, OR: 11.25” (old record 11.17”, 1947; records began in 1892)



Figure 2. Mountain precipitation for the water year to date (October 1-31, 2016) shows the wettest totals on record for stations in dark blue, with the driest totals on record for stations in dark red. Periods of record vary by location but are typically several decades long. Image credit: USDA/NRCS National Water and Climate Center.


Figure 3. The weekly U.S. Drought Monitor report that tracked conditions through October 25, 2016, showed patches of D4 drought (exceptional), the most dire category, over parts of northeast Alabama, northwest Georgia, and far southeast Tennessee. Much of the South is now experiencing both short- and long-term drought impacts (black circle). Image credit: National Drought Mitigation Center


Message from the Southeast: please send water
While heavy rains and snows plastered the Northwest, drought conditions intensified across the Southeast. Much of Alabama and Georgia was lucky to see even 0.25” of rain, and many locations got far less. According to the weekly U.S. Drought Monitor issued on October 27, two of Georgia’s nine climate divisions and one of Alabama’s eight divisions saw their driest 60-day periods on record.

All-time driest Octobers, or extremely close
Tuscaloosa, AL: 0.00” (old record a trace, 1904; records began in 1900)
Rome, GA: trace (tied with 1938 and 1963; records began in 1893)
Birmingham, AL: trace (record remains 0.00”, 1924; records began in 1895)

There is a glimmer of hope in the medium-range forecast for the Southeast, as part of an upper-level trough may break off and dip into the region to bring rain next week. However, that scenario could easily change. In the longer term, NOAA’s Seasonal Drought Outlook is calling for drought to persist (and possibly worsen) through January 31, 2017, from the Arkatex region across to western North Carolina, including most of Mississippi and Alabama. With a weak La Niña expected, NOAA is projecting drier-than-average conditions over the Southeast through the upcoming winter and into spring 2017. La Niña tends to favor an active storm track across the northern U.S. with drier conditions across the Sunbelt.


Figure 4. In this Wednesday, Oct. 26, 2016 photo, an abandoned boat sits in the remains of a dried-out pond in Dawson, Alabama. Some of the South’s most beautiful mountains and valleys are filling with desperation as a worsening drought kills crops, threatens cattle, and sinks lakes to their lowest levels in years. The very worst conditions are in the mountains of northern Alabama and Georgia. Image credit: AP Photo/Brynn Anderson.

An ecological and political crisis deepens
On October 18, Alabama’s Office of Water Resources placed roughly the northeast half of the state under a drought emergency, which urges large users of water to implement conservation plans. Streamflows across northern Alabama are at or near record lows. Despite the drought’s severity, there are no state restrictions on water usage. “There’s a complete lack of a water plan in Alabama, and if you look at the history of water management in state, we always freak out in droughts,” Mitch Reid, director of the nonprofit Alabama Rivers Alliance, told the Huffington Post. One report issued in September found that Alabama was the weakest of the Southeastern states in its water management practices.

The current situation is the latest in an escalating series of drought-related crises affecting the Southeast, where rising populations have come up against an increasingly uncertain water supply. While the average amount of summer rainfall across the Southeast hasn’t changed in recent decades, the year-to-year variability has significantly increased. The comprehensive global modeling (CMIP5) associated with the most recent Intergovernmental Panel on Climate Change assessment shows that this variability in Southeast summer rainfall is likely to increase even further as this century unfolds, according to a 2013 study in Geophysical Research Letters led by Laifang Li (Duke University). “Overall, the ensemble of CMIP5 models suggest that the increase in [greenhouse gas] concentrations will likely enhance SE U.S. summer precipitation variability and result in more frequent occurrence of both dry and wet extremes in the future,” wrote Li and colleagues.

Recent droughts have also intensified the stakes in courtrooms, where the seemingly endless “tri-state water dispute” has pitted Georgia, Alabama, and Florida against each other since an initial lawsuit was filed back in 1990. In a nutshell, Florida is accusing metropolitan Atlanta and the state of Georgia of taking more than its fair share of southward-flowing water from the Chattahoochee and Flint rivers. Alabama is siding with Florida in the latest salvo, a trial that began on Monday at a federal courthouse in (of all places) Portland, Maine. Observers are calling this trial a potential milestone in the ongoing battle. This article from the Gainesville (FL) Times has a handy chronology of the 26-year-old saga.

We’ll be back with a new post by Wednesday afternoon.

Bob Henson

Climate Summaries


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