07 April 2006 :: Tornado Outbreak

GOES-12 visible image - Click to enlarge

GOES-12 visible image

(* 76-image QuickTime animation *)

GOES-12 IR image - Click to enlarge

GOES-12 IR image

(* 76-image QuickTime animation *)

A major outbreak of severe convection occurred across much of the Mississippi, Tennessee, and Ohio River Valley regions on 07 April 2006 (in the warm sector of a midlatitude cyclone that moved across the eastern US). This outbreak was part of the abnormally active early severe weather season in 2006. According to the SPC storm reports there were 87 tornadoes (including three F3 tornadoes north of Nashville TN), 565 hail reports (up to 4.25 inches in diameter in TN), and 215 damaging winds reports (including a measured 80 mph wind in TN); 12 fatalities resulted from these storms. NOAA GOES-12 visible and InfraRed (IR) imagery (above) shows the development of some of this convection (centered on Tennessee and Kentucky), which exhibited several distinct overshooting tops on the visible channel and multiple "enhanced-v" signatures on the IR channel (the enhanced-v IR signature is often an indicator of severe weather).


GOES + MODIS visible  image - Click to enlarge

17:10/17:12 UTC GOES/MODIS visible image

GOES + MODIS IR image - Click to enlarge

17:10/17:12 UTC GOES/MODIS IR image

(- Fade between 17:10/17:12 UTC GOES/MODIS visible and IR image comparisons -)

Note the improved enhanced-v signature detection capabilities using the 1-km resolution MODIS IR data (compared to the 4-km resolution GOES-12 IR channel). On the 17:10/17:12 UTC GOES-12 / Terra MODIS comparison (above), 5 separate enhanced-v signatures can be seen on the MODIS IR image (these images were near the time of 2.75 inch diameter hail in TN). The later 18:45/18:47 UTC GOES-12 / Aqua MODIS comparison (below) revealed a striking display of 6 enhanced-v signatures, near the time of 1.75 inch diameter hail in KY (and about 45 minutes prior to the F3 tornadoes that developed and moved north of Nashville TN). The improved enhanced-v detection capability is primarily due to the fact that the MODIS IR data reveals colder cloud top temperatures than GOES in the regions of the more intense overshooting tops (-70 C vs -62 C at 17:10/17:12 UTC, and -72 C vs -67 C at 18:45/18:47 UTC) -- the warmer cloud top temperatures in the "warm wake" portion of the signature are similar on GOES and MODIS. These -70 to -72 C MODIS IR cloud top temperatures were also several degrees colder than the tropopause temperature as indicated by the Nashville TN rawinsonde reports that day.

GOES + MODIS visible  image - Click to enlarge

18:45/18:47 UTC GOES/MODIS visible image

GOES + MODIS IR image - Click to enlarge

18:45/18:47 UTC GOES/MODIS IR image

(- Fade between 18:45/18:47 UTC GOES/MODIS visible and IR image comparisons -)


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