About Jeff Masters
Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
By: Dr. Jeff Masters , 3:51 PM GMT on April 16, 2011
Dozens of tornadoes and dangerous severe thunderstorms tore through the Southeast U.S. on Friday, bringing a second day of severe weather havoc to the nation. The death toll from the two-day severe blitz now stands at seventeen, with up to 100 people injured and tens of millions of dollars in property damage. NOAA's Storm Prediction Center logged 98 tornado reports yesterday, bringing the two-day total for the outbreak to 120 tornadoes. These preliminary reports are usually a 15% over-count of the actual number of tornadoes, which still means over 100 tornadoes have probably touched down during the past two days. The deadliest tornado of the outbreak hit near Prattville, Alabama at 10:55pm CDT last night, killing three people in a mobile home, and injuring four others. One of the most damaging tornadoes occurred just west of Jackson, Mississippi, when a tornado touched down just south of I-20, crossed the expressway, flipping cars and semis, then plowed through the town of Clinton. At least nine people were injured in Clinton, and extensive damage characteristic of an EF-2 tornado is apparent in damage photos.
Figure 1. Radar reflectivity image of the Clinton, Mississippi tornado at 10:57am CDT as the twister crossed I-20 and hit the town. Note the classic hook-shaped echo of the parent mesocyclone in the rotating severe thunderstorms that spawned the tornado.
Figure 2. Doppler radar velocity image of the Clinton, Mississippi tornado at 10:57am CDT.
On Thursday, tornadoes and deadly severe thunderstorms tore through Oklahoma and Arkansas, killing at least nine people. A EF-3 tornado hit the small town of Tushka, Oklahoma, population 350, ripping off the roof of the local high school and destroying dozens of buildings in Tushka. Two people were killed and 25 injured. The tornado moved over farmland and dissipated a short time later, but the squall line that spawned the tornado moved into Arkansas overnight, spawning severe thunderstorm winds that killed seven more people.
Virginia, North Carolina, and South Carolina under the gun today
The action shifts eastwards to southern Virgina and eastern North Carolina and South Carolina today, which NOAA's Storm Prediction Center have placed under its "moderate risk" region for severe weather. This is the same level of risk as we've seen for the past two days for this storm system, and it is very unusual for this portion of the U.S. to experience such a high severe weather risk. Tornado watches have already been posted for portions of Georgia, South Carolina, and North Carolina. You can follow today's severe weather using our severe weather page and interactive tornado map. This map now shows links to Youtube storm chaser videos of tornadoes, plus any wunderphotos taken of the storm.
Figure 3. Satellite image from 23:32 UTC (7:32pm CDT) April 15, 2011, showing the strong low pressure system over the middle of the country that brought yesterday's severe weather outbreak. Image credit: NASA/GSFC.
Figure 4. Water vapor satellite image from 23:15 UTC (7:15pm CDT) April 15, 2011, showing a dry, eye-like feature in the strong low pressure system over the middle of the country. This eye-like feature persisted for many hours, but was not visible on infrared or visible satellite images. According to an analysis done by Scott Bachmeier at the University of Wisconsin, the stratosphere, which has very dry air, sunk down to the 600 mb height at the center of the storm, and it is possible that dry air from the stratosphere is responsible for this eye-like feature. This is a different mechanism than how hurricanes develop eyes, and yesterday's storm had only a shallow area of low clouds with light rain near the center--nothing like an eyewall of a hurricane. Image credit: NOAA.
Figure 5. Storm chaser video from Reed Timmer of the Clinton, Mississippi tornado on April 15, 2011. Numerous transformers blow as the tornado wipes out power lines, creating bright blue-green flashes.
Figure 6. Storm chaser video from tornadovideos.net of a huge tornado in Oklahoma during Thursday's outbreak there.
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