Southeast US Tornado Outbreak, Northcentral US Blizzard

March 2nd, 2007 |

AWIPS water vapor image

A very large and very intense mid-latitude cyclone was responsible for a major tornado outbreak in the southeastern US, as well as widespread blizzard conditions across the northcentral US on 01 March 2007. AWIPS images of the GOES water vapor channel (above; 48-image QuickTime animation) and the GOES 10.7 µm InfraRed (IR) channel (below; 48-image QuickTime animation) show the unusually large size of the storm during the 01-02 March period. Widespread reports of tornadoes, hail, and damaging winds were noted over much of the southeastern quarter of the US, including several fatal tornadoes (Caulfield, Missouri; Enterprise, Alabama; and Americus, Georgia — all rated EF3). A total of 31 tornadoes were reported, with 20 fatalities; hail was as large as 2.5 inches in diameter in parts of Missouri and Arkansas. The Storm Prediction Center issued a rare “High Risk” Convective Outlook early in the day, and eventually issued 3 Severe Thunderstorm Watches and 13 Tornado Watches during the prolonged severe weather event. Meanwhile, in the northcentral US, blizzard conditions were common across parts of North and South Dakota, Nebraska, Minnesota, and Iowa (US watches, warnings, and advisories) — several locations in that region reported snowfall totals of 15-21 inches, and many schools and highways across the region were closed due to the blowing and drifting snow.
AWIPS IR image

A closer look at the GOES-12 10.7 µm IR imagery (below; 100-image QuickTime animation) shows the cloud top temperature structure from 12:15 UTC on 01 March to 03:40 UTC on 02 March — GOES-12 was in Rapid Scan Operations, so images were available at 5-10 minute intervals during much of the period. There were no well-defined “enhanced-v” signatures evident on the IR images, but cold cloud top temperatures in the -60º to -70º C range (orange to red enhancement) were common; the coldest cloud top temperature noted on the GOES-12 IR imagery was -76 C at 19:15 UTC (green enhancement), which was around the time of the Enterprise, Alabama tornado (which caused 8 fatalities when it struck a high school). Radar images of the Enterprise tornado can be seen on the NWS Tallahasse site and the  Weather Underground WunderBlog. Vertical wind shear was enhanced over the southeastern US by strong winds in the middle to upper troposphere associated with an approaching jet streak — this helped to create an environment favorable for the development of rotating updrafts and supercell thunderstorms.
GOES-12 10.7µm IR image