In the United States tornadoes develop most often in the spring when warm moist unstable air accompanies strong fronts and fluctuating upper-air systems. There is a also a slight increase in tornado activity in late October and November. Tornadoes form least often in December and January so the tornadoes that occurred yesterday over the south-eastern United States were unusual. The TRMM satellite was flying over on December 10, 2012 at 1743 UTC (12:43 PM EST) and captured data showing tornado spawning thunderstorms within a frontal system moving through Louisiana, Mississippi, Alabama, Georgia and northern Florida. This image shows a rainfall analysis from data captured with TRMM's Microwave Imager (TMI) and Precipitation Radar (PR) instruments. TRMM's Precipitation Radar (PR) found rain falling at a rate of over 77 mm/hr (~3 inches) in a few of these powerful storms. The locations of some of the tornadoes reported are shown overlaid in red.

TRMM is a joint mission between NASA and the Japanese space agency JAXA.

Click here to see a simulated 3-D Flyby around this line of thunderstorms using data from TRMM's Precipitation Radar (PR) instrument.