A dynamic weather system will approach the region with very powerful upper level winds energizing developing thunderstorms, which will also be fueled by a flow of moist unstable air from the Gulf of Mexico. Writes the National Weather Service Storm Prediction Center (SPC):
THE POSSIBILITY EXISTS FOR SEVERAL LONG-TRACK STRONG TORNADOES ASSOCIATED WITH ANY LONG-LIVED FAST-MOVING SUPERCELLS...ALONG WITH MORE WIDESPREAD DAMAGING WINDS ALONG THE MOST INTENSE PARTS OF THE BOWING QUASI-LINEAR CONVECTIVE SYSTEM
SPC has posted a moderate risk outlook for severe weather from west central Louisiana to west central Alabama - highly unusual for this time of year. It also highlights a somewhat broader region as having the potential for “significant” severe weather - as indicated by the hatched area in the above graphic. It defines “significant” as “as F2 or greater tornadoes, damaging winds with speeds greater than 65 knots, or large hail 2” or greater in diameter”.
NWS says more than 1.1 million people live in the moderate risk zone and over 27.7 million reside in the much larger area having slight risk of severe thunderstorms.
By Wednesday, the focus of the thunderstorm threat shifts to the region from southeast Virginia to northern Florida. The Wednesday thunderstorm risk may not be as high or widespread, but residents in these locations should closely monitor statements from the National Weather Service and possible watches and warnings.
Here is historical perspective on Christmas Day severe weather from SPC:
Notable U.S. tornado events with at least one EF2 tornado occurring between Dec. 24 and Dec. 26:
Dec. 24-25, 1964: 14 tornadoes, AL, FL, GA, NC, SC, TN, WV (3 F3, 2 deaths (GA), ~30 total injuries).
Dec. 25, 1969: 12 tornadoes, FL, GA, LA (2 F3, 1 death (LA), 17 total injuries).
Dec. 25-26, 1973: 7 tornadoes, AL, FL, GA, OH, MO (2 F2, 0 deaths, 2 injuries).
Dec. 24, 1975: 3 tornadoes, TX, FL (1 F3 (TX), 0 deaths, 0 injuries).
Dec. 24-25, 1977: 3 tornadoes, MS, FL (1 F3 (MS), 0 deaths, 7 injuries).
Dec. 24-26, 1982: 29 tornadoes, OK, MO, AR, TN, MS (1 F4 (AR), 2 F3, 3 deaths (AR/MO), 32 total injuries).
Dec. 24, 1988; 1 tornado, TN (1 F4, 1 death, 7 injuries).
Dec. 24, 1997: 3 tornadoes, AL (1 F2, 0 deaths, 5 injuries).
Dec. 25, 2006: 6 tornadoes, GA, FL (4 F2, 0 deaths, 14 injuries).
Dec. 24, 2009: 22 tornadoes, TX, LA, MS (3 F2, 0 deaths, 4 injuries).
Other relevant statistics from SPC:
* AL, GA, LA, MS, and FL are the most likely states to experience tornado events around this time of year.
* The last time a number of tornadoes impacted the Gulf Coast area around Christmas Day was in 2009, when 22 tornadoes occurred during the morning hours of December 24th.
* In over 60 years there have been two EF4-rated tornadoes on Christmas Eve, one in 1982 in AR, the other in 1988 in TN.
* The last killer tornado around Christmas was a Christmas Eve EF4 in TN in 1988, killing one person and injuring 7.