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Posted at 10:45 AM ET, 05/02/2011

Alabama tornado outbreak visuals: jaw-dropping radar and satellite imagery


Radar sequence of tornado supercell thunderstorms that tracked from western Mississippi into southwest North Carolina. (Brian Tang)

This post contains some of the most extraordinary imagery from Wednesday’s deadly and historic tornado outbreak in the South. The latest reports indicate fatalies from the outbreak now exceed 342 people, surpassing the number of deaths from the 1974 Super Outbreak. It is the most people killed by tornadoes in a two-day period since April 5-6, 1936 when 454 people died.

Of the many images I’ve seen since this horrible outbreak last Wednesday, the image above, created by Brian Tang, a postdoctoral research fellow at the National Center for Atmospheric Research, seemed the most incredible. Here’s how Tang describes the image:

“Radar montage of the most impressive supercell from [Wednesday’s] massive tornado outbreak. This cell traveled about 450 miles and lasted over 8 hours! It also was responsible for the large, violent tornado that caused the destruction in Tuscaloosa, [the north] side of Birmingham, and a number of other cities.”

The National Weather Service reported this morning that the tornado spawned by this supercell from Tuscaloosa to Birmingham was on the ground for 80 miles and reached high-end EF-4 intensity (winds to 190 mph).

Almost all of the radar echoes for this storm display the tell-tale hook shape, indicative of intense rotation and tornado production.

Keep reading for more imagery and videos....


Vertical cross section of radar when tornado was in the vicinity of Tuscaloosa, Alabam on April 27. (@iwitnessweather and The Weather Channel via Twitter )

The above three-dimensional radar image shows not only the hook echo across the horizontal plane but also see the “debris” generated by the tornado right as it’s in the vicinity of Tuscaloosa. The debris is depicted by the “ball” of pink (indicating the high reflectivity) at the point of the hook echo. In the vertical, you can see the radar’s reflection of the actual funnel.


Rotation tracks from the thundderstorms on April 27, 2011. Bright reds, oranges and yellows show tracks of where rotation was strongest as detected by NWS Doppler radars (NOAA)

The incredible geographic scale of the spin the atmosphere on April 27 is evident in the above image. All of the lines painted in yellow, orange and red indicate rotating thunderstorm tracks on that date. Bright reds and yellows depict the most intense circulations. More information about how this image was generated can be found on NOAA’s blog.

The height and extent of the rain columns associated with the thunderstorms that spawned the 4/27 tornadoes are seen in the animation above from NASA. Amazingly, the cloud top heights reached almost 10.6 miles (17 km) or 55,000 feet into the atmosphere. The animation was generated using imagery from the Tropical Rainfall Measuring Mission (TRMM) satellite.


Tracks of three tornadoes captured by NASA’s Aqua satellite. Contrast of this image was enhanced slightly to better highlight the three tracks. (NASA Earth Observatory)

The tracks of three of the tornadoes in the vicinity of Tuscaloosa were captured by NASA’s Aqua satellite using the MODIS sensor. NASA describes the image accordingly: “The tracks are pale brown trails where green trees and plants have been uprooted, leaving disturbed ground. Though faint, the center track runs from southwest of Tuscaloosa, through the gray city, and extends northeast towards Birmingham. Two other tracks run parallel to the center track.”

A satellite loop of the entire outbreak, spanning April 26 through April 28, can be seen in the animation above, also created by NASA. Here’s the description of the loop, from NASA’s excellent Earth Observatory website:

The animation starts on April 26 and runs through the morning of April 28. The ingredients for severe weather are evident in the cloud patterns. A relatively stable mass of cold air—visible as a swirl of more-or-less continuous clouds—rotates in the north along the top of the image. Meanwhile, moist air pushes north and west from the Atlantic Ocean and Gulf of Mexico. The warm air contains small low clouds.

The collision between two such air masses is enough to generate severe weather, but the weather also was amplified by the jet stream on April 27. Though not directly visible in the image, the narrow band of fast-moving wind blew north and east between the two air masses. With surface winds blowing from the south and east, and the jet stream blowing from the west, powerful smaller-scale circulation patterns generated lines of intense thunderstorms.

The thunderstorms shown in this image began to rise over Louisiana midway through the day on April 27—around 16:00 UTC or 11:00 a.m. local time—and moved across Mississippi and Alabama through the afternoon. Forming along and ahead of the turbulent boundary between the air masses, the storms move east and north with the jet stream. The bright white spots within the clouds are very active storms, quite probably the systems that generated tornadoes.

Throughout the day, many such storms arose over the South. The slow eastward progression of the upper-level system permitted successive storms to affect the same region for a much longer time span than usual. According to the National Weather Service, more than 150 tornadoes were reported throughout the day.

As of yesterday, the National Weather Service has increased the estimated number of tornadoes to 226 (from 8 a.m. 4/27 to 8 a.m. 4/28).

By  |  10:45 AM ET, 05/02/2011

Categories:  Thunderstorms, U.S. Weather, Latest

 
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