U.S. Has its Warmest Winter on Record; Major Deluge Coming to TX, AR, LA

By: Jeff Masters , 5:31PM GMT on March 8,2016




 

The contiguous U.S. just experienced its warmest winter on record, said NOAA's National Centers for Environmental Information on Tuesday, with the three-month meteorological winter period of December 2015 through February 2016 coming in tops for the 121-year period of record that began in 1895. Every state had above-average temperatures, and 36 states had a top-ten warmest winter on record. The most notable warmth was in the Northeast, where all of New England had their warmest winter on record. The record-warm U.S. winter was made possible by very warm conditions in December and February: December 2015 was the warmest December on record for the contiguous U.S., and February 2016 was the 6th warmest February. January 2016 was a bit cooler, ranking as the 33rd warmest January. NOAA will release its winter temperature rankings for the entire globe on March 17. I expect that we will see Earth set a new record for warmest winter on record globally, since December 2015 and January 2016 were the two warmest months in recorded history (expressed as a departure from average.) The record warmth is due to the steady accumulation of heat-trapping gases in Earth's atmosphere due to human activities, plus an extra approximately 10% bump in temperatures due to the slowly waning record-strength El Niño event in the Eastern Pacific.


Figure 1. State-by-state temperature rankings for the winter period December 2015 through February 2016. Every state had above-average temperatures, and 36 states had a top-ten warmest winter on record. The most notable warmth was in the Northeast, where all of New England had their warmest winter in the 121-year period of record. Image credit: NOAA/NCEI.


Figure 2. State-by-state precipitation rankings for the winter period December 2015 through February 2016. Only two states had below-average precipitation, and ten states had a top-ten wettest winter on record. One state--Iowa--had their wettest winter on record. Image credit: NOAA/NCEI.

Major deluge headed for Arkansas, Louisiana, and East Texas
A large low pressure system (a "cut-off" low) has separated from the jet stream, and will stay parked over the U.S./Mexico border region during much of the week. The counter-clockwise flow of air around this low will bring up plenty of warm, moisture-laden air from the tropics along the east side of the low, resulting in an extended period of very heavy rains over Arkansas, Louisiana, and East Texas this week. With rainfall amounts in excess of 7" expected over this region, flash flooding will be the main concern this week. By this weekend, when all of this rain has had time to flow into area rivers, expect to see several rivers crest at near-record flood levels. Sea Surface Temperatures (SSTs) are near average over the Gulf of Mexico, which will keep the amount of moisture available to this week's storms lower than would be the case if SSTs were unusually warm. However, the cut-off low has tapped into a moisture source in the deep tropics over the Eastern Pacific where SSTs are record warm. An "atmospheric river" of water vapor can be seen on satellite images extending from the record-warm waters south of Mexico directly into the Southern U.S. (Figure 3.) This warm, moist air will be very unstable, helping contribute to severe thunderstorms with a few tornadoes over the Southern U.S. today through Thursday. As of noon EST Tuesday, one tornado had been reported in Texas, along with fourteen reports of severe thunderstorm winds.


Figure 3. Satellite-derived Integrated Water Vapor (the total amount of rain, in centimeters, that would result from condensing all water vapor in a column of air) as of 8:55 am EST March 8, 2016. Two "atmospheric rivers" of water vapor are seen affecting the U.S.--one from the Eastern Pacific flowing across Mexico into the Southern U.S., and one extending from the tropics past Hawaii towards the coast of California. Image credit: NOAA/ESRL.


Figure 4. Predicted precipitation for the 3-day period ending 7 am EST Friday, March 11, 2016. Image credit: National Weather Service.

Jeff Masters