WunderBlog Archive » Category 6™
Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.Warm, Wet Year for U.S.; Record Heat in South Africa; Tropical Storm Pali Intensifies
Many Americans were throwing on T-shirts or rain gear instead of heavy coats last month, in what proved to be the nation’s mildest and wettest December in more than a century of record-keeping. On Thursday, NOAA’s National Centers for Environmental Information (NCEI) released initial data on December and for the year 2015. (A full report will be issued on January 13). As a whole, 2015 came in as the second warmest and second wettest year on record for the contiguous U.S.
It’s hard to overstate the striking character of December’s mildness. Millions of people along the Eastern Seaboard experienced it first hand, as all of the big cities (and many smaller ones) from Washington, D.C., to Portland, Maine, smashed their previous records for December warmth. New York City’s Central Park went through the entire month of December without dipping down to freezing, whereas all prior Decembers back to 1871 had reached 32°F at least six times. As shown in Figure 1, each state east of the Mississippi--plus Minnesota, Iowa, and Missouri--saw its warmest December on record, and even the coolest states were close to their long-term December average. All told, close to 12,000 daily records (warm highs and warm lows) were set across the nation in December, as noted by weather.com. There was plenty of moisture to be had as well: 40 states came in above average on precipitation, with Iowa and Wisconsin getting their wettest December on record and Minnesota, Missouri and Illinois coming in at second-wettest. These rains contributed to the exceptional flood crest now moving along the lower Mississippi River.
Figure 1. Temperature and precipitation rankings by state for December 2015. Higher numbers indicate warmer and wetter conditions. States labeled 121 (dark red and dark green) experienced the warmest or wettest Decembers in 121 years of national recordkeeping. Image credit: NOAA/NCEI.
For the year as a whole, the warmth and moisture were widely distributed across the contiguous U.S. There were more than twice as many daily record highs as record lows for the year, but as noted by Climate Central, a brutally cold February over the eastern U.S. was the main factor keeping 2015 from being the nation’s warmest year. The northwest and southeast corners of the 48 states, Washington and Florida, both had their warmest year on record, as did Oregon and Montana. All 48 contiguous states saw at least a top-25 warmest year. Only five were notably drier than average in 2015--California, Montana, Connecticut, Rhode Island, and Massachusetts--while many central states had a top-10 wettest year, with Texas and Oklahoma notching their wettest on record. (During the first week of 2016, moisture has also returned to California in a big way, thanks to a parade of soggy Pacific storm systems; more on that in a future post.)
Figure 2. Temperature and precipitation rankings by state, as in Figure 1, but for the entire year of 2015 (January – December). Higher numbers indicate warmer and wetter conditions. States labeled 121 (dark red and dark green) experienced the warmest or wettest year in 121 years of national recordkeeping. Image credit: NOAA/NCEI.
How did the U.S. stay so mild and moist at the same time?
The combination of unusual warmth and unusual moisture is a standout in itself. Heavy, persistent precipitation often means lots of sun-blocking clouds that cut down on heating. Very warm months are typically the driest ones. That was the case in June 1933 and May 1934, two Dust Bowl months that still reign as the warmest and driest May and June in U.S. history (thanks to Nick Wiltgen at weather.com for this find). What made the difference last month, and last year, was the record-warm sea surface temperatures over the tropical Pacific and Atlantic, a function of El Niño and other short-term oceanic patterns as well as long-term warming related to human-produced climate change. These warm SSTs allowed vast amounts of moisture to evaporate into air masses flowing toward the lower 48 states. In turn, this led to countless records for precipitable water (the amount of water vapor in the air above a given measuring site). Near the surface, the moisture helped to keep nighttime temperatures consistently high in many locations.
Here’s just one example: During the nine-day period from December 23 to 31, the lowest temperature observed in Key West, Florida, was 78°F. This happens to be the previous record-warm minimum for the entire month of December, going back to 1871! This is the first time I’ve heard of any U.S. location with more than a century of weather-observing history that managed to tie or set a monthly record on so many consecutive days. Key West’s daily lows were an astounding 79°F on December 25, 27, 28, 29, and 31. Finally, on January 3, the mercury dropped below 69°F, for the first time since April 1--making it the longest such streak at or above 69°F (277 days) in Key West history.
Figure 3. Average temperatures for the period September-December since 1895 for the contiguous U.S. This past Sep-Dec was more than 1°F warmer than the previous record-holder, 1998. Image credit: NOAA/NCEI.
The big wet
Two states saw their wettest months on record in May 2015: Texas (8.81”) and Oklahoma (14.40”). South Carolina didn’t manage that feat during its extreme October deluge, but the state did end up with its wettest autumn on record (23.62”, more than 5” above the previous record). Hand in hand with these large-scale dousings, there were some particularly hefty year-long accumulations at individual sites, including these wettest local years on record:
St. Louis, MO: 61.24” (old record 57.96” in 2008)
Fort Smith, AR: 73.93” (old record 71.81” in 1945)
Dallas-Fort Worth, TX: 61.61” (old record 53.54” in 1991)
Figure 4. A Japanese camellia (japonica) in bloom at Danville, Virginia, on December 25, 2015. Image credit: wunderphotographer WeatherWise.
A Christmas warm wave for the ages
December culminated in a memorable week-plus period of record warmth that swaddled most of the nation east of the Rockies. On Christmas Eve and Christmas Day, a total of 847 U.S. stations tied or broke record daily highs, according to preliminary data on NOAA’s U.S. Records website. Dozens of those previous marks were bested by at least 10°F. In Hanover, New Hampshire, it was 67°F on Christmas Day--a full 17°F warmer than any other Christmas in 122 years of recordkeeping. Just after noon on Christmas Eve, the heat index in Virginia Beach, VA, reached an absurdly unseasonable 86°F! Not to be outdone, the northwestern Alaska town of Kotzebue basked in the relative warmth of 37°F--tying its record monthly high--on the evening of December 30.
Chilly weather has returned to much of the central and eastern U.S. for early January. Although the cold is a bracing experience for those who got accustomed to extreme autumn mildness, it’s merely garden-variety chill by climatological standards. We are unlikely to see many record lows or record-cold highs in the foreseeable future, whereas a day of near-record warmth is once again possible in the mid-Atlantic and southern New England on Sunday. Still, one of the coldest pro football games in recent decades is on tap for Sunday, when the Minnesota Vikings will host the Seattle Seahawks in a wild-card playoff. Though probably well above record levels, temperatures at the 12:05 pm kickoff at the non-domed TCF Bank Stadium in Minneapolis are expected to be near or just below 0°F, with a wind chill as cold as –20°F possible. According to the Weather Channel’s Michael Butler, the Seahawks have never played in temperatures any colder than 16°F (Dec. 3, 2006, in Denver). The Vikings, who are temporarily based at TCF Bank Stadium while awaiting a new roofed stadium, have kicked off only once before in subzero weather: on Dec. 3, 1972, with a temperature of -2°F.
All-time record heat in southern Africa
A heat wave in the midst of an already scorching summer has baked southern Africa this week, producing the hottest readings ever observed in a number of locations. According to weather records researcher Maximiliano Herrera, Botswana set the world’s first all-time national high temperature of 2016 on Wednesday, January 6, then exceeded it on Thursday, January 7, as the city of Maun hit at least 43.8°C or 110.8°F (officially rounded upward to 44°C). Herrera, one of the world's top climatologists, maintains a comprehensive list of extreme temperature records for every nation in the world on his website, which lists dozens of all-time local record highs set since the first of this year across South Africa, Botswana, and Zimbabwe. South Africa’s capital city, Pretoria, soared to 42.7°C (108.9°F) on Thursday--the most recent in a string of several all-time record highs there over the last few weeks. In the nation’s largest city, Johannesburg, an all-time record of 36.5°C set only last November has been topped several times, most recently on Thursday with a high of 38.9°C (102.0°F). The heat across South Africa has also toppled many all-time world temperature records for any location at altitudes between 1000 and 1600 meters (3280 - 5250 feet), according to Herrera.
A severe multi-year drought in and near South Africa has drained reservoirs, devastated farming, and parched the landscape, allowing the summer sun to heat the land and air more efficiently (the same process that fostered record heat in California over the last several years). Making things worse, El Niño tends to produce drier-than-average conditions over southern Africa. Record-warm temperatures over the Indian Ocean are also playing a role, according to researchers. “The warming of the Indian Ocean is contributing to the stable air mass over the interior,” said Mary Scholes (University of the Witwatersrand) in an email. As global temperatures continue to climb this century due to human-produced greenhouse gases, Africa is expected to warm more quickly than the global average. Particularly high warming rates are expected over southwestern South Africa, Botswana, and Namibia, according to the chapter on Africa (PDF) in the 2014 Fifth Assessment Report (Working Group II) of the Intergovernmental Panel on Climate Change (IPCC). “Africa as a whole is one of the most vulnerable continents [to climate change] due to its high exposure and low adaptive capacity,” notes the report.
Figure 6. Infrared image of Tropical Storm Pali at 17Z (12 pm EST) Friday, January 8, 2015. Image credit: NOAA/NESDIS.
Tropical Storm Pali gathers strength in Central Pacific
The tropical depression located about 1400 miles southwest of Hawaii became Tropical Storm Pali on Thursday. Pali is the earliest tropical storm on record to develop between the International Date Line and the Americas (though one could argue the record-smashing 2015 tropical season in the Central Pacific has sloshed into 2016). As of 15Z (10 am EST) Friday, January 8, Pali’s top sustained winds had reached 55 knots (65 mph). Pali is embedded in a low-level trough between a westerly wind burst south of the equator and strong trade winds north of the storm, with easterly wind shear evident in satellite imagery. Pali’s northwestward motion is expected to slow to a crawl this weekend, after which the storm may bend back toward the south. The strong vertical wind shear (20 - 30 knots) and interactions with the surface trough are expected to gradually weaken Pali over the next several days.
In the Northwest Atlantic, a powerful nontropical low is stirring up the ocean west of Bermuda with a large area of strong winds, some as high as 65 mph. Models continue to move this system toward the east and southeast by early next week, which could put it in a more favorable environment for subtropical development. On Friday morning, the National Hurricane Center gave this system a 30% chance of subtropical or tropical development over the next five days.
Have a great weekend, everyone!
Bob Henson
It’s hard to overstate the striking character of December’s mildness. Millions of people along the Eastern Seaboard experienced it first hand, as all of the big cities (and many smaller ones) from Washington, D.C., to Portland, Maine, smashed their previous records for December warmth. New York City’s Central Park went through the entire month of December without dipping down to freezing, whereas all prior Decembers back to 1871 had reached 32°F at least six times. As shown in Figure 1, each state east of the Mississippi--plus Minnesota, Iowa, and Missouri--saw its warmest December on record, and even the coolest states were close to their long-term December average. All told, close to 12,000 daily records (warm highs and warm lows) were set across the nation in December, as noted by weather.com. There was plenty of moisture to be had as well: 40 states came in above average on precipitation, with Iowa and Wisconsin getting their wettest December on record and Minnesota, Missouri and Illinois coming in at second-wettest. These rains contributed to the exceptional flood crest now moving along the lower Mississippi River.
Figure 1. Temperature and precipitation rankings by state for December 2015. Higher numbers indicate warmer and wetter conditions. States labeled 121 (dark red and dark green) experienced the warmest or wettest Decembers in 121 years of national recordkeeping. Image credit: NOAA/NCEI.
For the year as a whole, the warmth and moisture were widely distributed across the contiguous U.S. There were more than twice as many daily record highs as record lows for the year, but as noted by Climate Central, a brutally cold February over the eastern U.S. was the main factor keeping 2015 from being the nation’s warmest year. The northwest and southeast corners of the 48 states, Washington and Florida, both had their warmest year on record, as did Oregon and Montana. All 48 contiguous states saw at least a top-25 warmest year. Only five were notably drier than average in 2015--California, Montana, Connecticut, Rhode Island, and Massachusetts--while many central states had a top-10 wettest year, with Texas and Oklahoma notching their wettest on record. (During the first week of 2016, moisture has also returned to California in a big way, thanks to a parade of soggy Pacific storm systems; more on that in a future post.)
Figure 2. Temperature and precipitation rankings by state, as in Figure 1, but for the entire year of 2015 (January – December). Higher numbers indicate warmer and wetter conditions. States labeled 121 (dark red and dark green) experienced the warmest or wettest year in 121 years of national recordkeeping. Image credit: NOAA/NCEI.
How did the U.S. stay so mild and moist at the same time?
The combination of unusual warmth and unusual moisture is a standout in itself. Heavy, persistent precipitation often means lots of sun-blocking clouds that cut down on heating. Very warm months are typically the driest ones. That was the case in June 1933 and May 1934, two Dust Bowl months that still reign as the warmest and driest May and June in U.S. history (thanks to Nick Wiltgen at weather.com for this find). What made the difference last month, and last year, was the record-warm sea surface temperatures over the tropical Pacific and Atlantic, a function of El Niño and other short-term oceanic patterns as well as long-term warming related to human-produced climate change. These warm SSTs allowed vast amounts of moisture to evaporate into air masses flowing toward the lower 48 states. In turn, this led to countless records for precipitable water (the amount of water vapor in the air above a given measuring site). Near the surface, the moisture helped to keep nighttime temperatures consistently high in many locations.
Here’s just one example: During the nine-day period from December 23 to 31, the lowest temperature observed in Key West, Florida, was 78°F. This happens to be the previous record-warm minimum for the entire month of December, going back to 1871! This is the first time I’ve heard of any U.S. location with more than a century of weather-observing history that managed to tie or set a monthly record on so many consecutive days. Key West’s daily lows were an astounding 79°F on December 25, 27, 28, 29, and 31. Finally, on January 3, the mercury dropped below 69°F, for the first time since April 1--making it the longest such streak at or above 69°F (277 days) in Key West history.
Figure 3. Average temperatures for the period September-December since 1895 for the contiguous U.S. This past Sep-Dec was more than 1°F warmer than the previous record-holder, 1998. Image credit: NOAA/NCEI.
The big wet
Two states saw their wettest months on record in May 2015: Texas (8.81”) and Oklahoma (14.40”). South Carolina didn’t manage that feat during its extreme October deluge, but the state did end up with its wettest autumn on record (23.62”, more than 5” above the previous record). Hand in hand with these large-scale dousings, there were some particularly hefty year-long accumulations at individual sites, including these wettest local years on record:
St. Louis, MO: 61.24” (old record 57.96” in 2008)
Fort Smith, AR: 73.93” (old record 71.81” in 1945)
Dallas-Fort Worth, TX: 61.61” (old record 53.54” in 1991)
Figure 4. A Japanese camellia (japonica) in bloom at Danville, Virginia, on December 25, 2015. Image credit: wunderphotographer WeatherWise.
A Christmas warm wave for the ages
December culminated in a memorable week-plus period of record warmth that swaddled most of the nation east of the Rockies. On Christmas Eve and Christmas Day, a total of 847 U.S. stations tied or broke record daily highs, according to preliminary data on NOAA’s U.S. Records website. Dozens of those previous marks were bested by at least 10°F. In Hanover, New Hampshire, it was 67°F on Christmas Day--a full 17°F warmer than any other Christmas in 122 years of recordkeeping. Just after noon on Christmas Eve, the heat index in Virginia Beach, VA, reached an absurdly unseasonable 86°F! Not to be outdone, the northwestern Alaska town of Kotzebue basked in the relative warmth of 37°F--tying its record monthly high--on the evening of December 30.
Chilly weather has returned to much of the central and eastern U.S. for early January. Although the cold is a bracing experience for those who got accustomed to extreme autumn mildness, it’s merely garden-variety chill by climatological standards. We are unlikely to see many record lows or record-cold highs in the foreseeable future, whereas a day of near-record warmth is once again possible in the mid-Atlantic and southern New England on Sunday. Still, one of the coldest pro football games in recent decades is on tap for Sunday, when the Minnesota Vikings will host the Seattle Seahawks in a wild-card playoff. Though probably well above record levels, temperatures at the 12:05 pm kickoff at the non-domed TCF Bank Stadium in Minneapolis are expected to be near or just below 0°F, with a wind chill as cold as –20°F possible. According to the Weather Channel’s Michael Butler, the Seahawks have never played in temperatures any colder than 16°F (Dec. 3, 2006, in Denver). The Vikings, who are temporarily based at TCF Bank Stadium while awaiting a new roofed stadium, have kicked off only once before in subzero weather: on Dec. 3, 1972, with a temperature of -2°F.
All-time record heat in southern Africa
A heat wave in the midst of an already scorching summer has baked southern Africa this week, producing the hottest readings ever observed in a number of locations. According to weather records researcher Maximiliano Herrera, Botswana set the world’s first all-time national high temperature of 2016 on Wednesday, January 6, then exceeded it on Thursday, January 7, as the city of Maun hit at least 43.8°C or 110.8°F (officially rounded upward to 44°C). Herrera, one of the world's top climatologists, maintains a comprehensive list of extreme temperature records for every nation in the world on his website, which lists dozens of all-time local record highs set since the first of this year across South Africa, Botswana, and Zimbabwe. South Africa’s capital city, Pretoria, soared to 42.7°C (108.9°F) on Thursday--the most recent in a string of several all-time record highs there over the last few weeks. In the nation’s largest city, Johannesburg, an all-time record of 36.5°C set only last November has been topped several times, most recently on Thursday with a high of 38.9°C (102.0°F). The heat across South Africa has also toppled many all-time world temperature records for any location at altitudes between 1000 and 1600 meters (3280 - 5250 feet), according to Herrera.
A severe multi-year drought in and near South Africa has drained reservoirs, devastated farming, and parched the landscape, allowing the summer sun to heat the land and air more efficiently (the same process that fostered record heat in California over the last several years). Making things worse, El Niño tends to produce drier-than-average conditions over southern Africa. Record-warm temperatures over the Indian Ocean are also playing a role, according to researchers. “The warming of the Indian Ocean is contributing to the stable air mass over the interior,” said Mary Scholes (University of the Witwatersrand) in an email. As global temperatures continue to climb this century due to human-produced greenhouse gases, Africa is expected to warm more quickly than the global average. Particularly high warming rates are expected over southwestern South Africa, Botswana, and Namibia, according to the chapter on Africa (PDF) in the 2014 Fifth Assessment Report (Working Group II) of the Intergovernmental Panel on Climate Change (IPCC). “Africa as a whole is one of the most vulnerable continents [to climate change] due to its high exposure and low adaptive capacity,” notes the report.
Figure 6. Infrared image of Tropical Storm Pali at 17Z (12 pm EST) Friday, January 8, 2015. Image credit: NOAA/NESDIS.
Tropical Storm Pali gathers strength in Central Pacific
The tropical depression located about 1400 miles southwest of Hawaii became Tropical Storm Pali on Thursday. Pali is the earliest tropical storm on record to develop between the International Date Line and the Americas (though one could argue the record-smashing 2015 tropical season in the Central Pacific has sloshed into 2016). As of 15Z (10 am EST) Friday, January 8, Pali’s top sustained winds had reached 55 knots (65 mph). Pali is embedded in a low-level trough between a westerly wind burst south of the equator and strong trade winds north of the storm, with easterly wind shear evident in satellite imagery. Pali’s northwestward motion is expected to slow to a crawl this weekend, after which the storm may bend back toward the south. The strong vertical wind shear (20 - 30 knots) and interactions with the surface trough are expected to gradually weaken Pali over the next several days.
In the Northwest Atlantic, a powerful nontropical low is stirring up the ocean west of Bermuda with a large area of strong winds, some as high as 65 mph. Models continue to move this system toward the east and southeast by early next week, which could put it in a more favorable environment for subtropical development. On Friday morning, the National Hurricane Center gave this system a 30% chance of subtropical or tropical development over the next five days.
Have a great weekend, everyone!
Bob Henson
Map from @SERCC is truly incredible. All the "1s" are locations setting a record warm December. Many others top 3. pic.twitter.com/3bF73eQHrd
— Jonathan Erdman (@wxjerdman) January 1, 2016Climate Summaries Climate Change Hurricane Extreme Weather
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.