Unprecedented Tornado Activity: A Momentous Month of Tornadoes (April) by NOAA

Posted for the Dot Earth blog of The New York Times, this video loop shows the extraordinary stirrings of the atmosphere through the month of April that generated the first big tornado outbreaks this spring. Joplin came later. Here's NOAA's description:

The U.S. experienced unprecedented tornado activity throughout the month of April 2011. The NOAA Storm Prediction Center received 875 tornado reports during that month alone; 625 have been confirmed as tornadoes, so far. Many of these storms were concentrated during 7 different major outbreaks, mostly in the Southern U.S. The largest of these outbreaks occurred during April 27-28, leaving over 300 people dead as over 180 storms were reported from Texas to Virginia.

This animation shows the GOES-East infrared imagery from April 1-30, along with the locations of each tornado that formed during the time (symbolized as red dots). Though tornadoes cannot actually be seen by GOES, these satellites are instrumental in being able to detect the conditions associated with their formation. As the resolution of GOES has increased with each successive satellite series, so have the warning times for tornadoes. The future GOES-R satellite will provide even higher resolution and storm prediction capability, especially with the use of the Geostationary Lightning Mapper sensor. The actual tornado locations are acquired from the Storm Prediction Center, which uses both NEXRAD radar and ground reports to generate a detailed database of tornadoes in the U.S.