Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
By: Dr. Jeff Masters , 3:25 PM GMT on April 23, 2011
A violent EF-4 tornado ripped through St. Louis near 8pm local time Friday night, severely damaging Lambert International Airport. The airport, the world's 30th busiest, may be closed for several days. The tornado ripped off the roof from Concourse C, blew out more than half of the windows in the main terminal, and moved an aircraft that was parked at a gate twenty feet. So far, only minor injuries due to flying glass have been reported from the tornado. The tornado also passed over nearby residential areas, causing severe damage. The National Weather Service office in St. Louis has rated the damage from the St. Louis tornado EF-4, making the twister the first violent EF-4 tornado of the year. Softball-sized hail also pelted three towns in Missouri--Hermann, Big Spring, and Warrenton--during Friday night's severe weather outbreak. NOAA's Storm Prediction Center logged 24 tornado reports Friday in Oklahoma, Arkansas, Missouri, Illinois, and Kentucky. The cold front responsible for triggering last night's severe weather will remain draped over the nation's mid-section for the next three days, and a slight risk of severe weather is predicted along a swath from Texas to Ohio both Saturday and Sunday. A more substantial risk of severe weather is likely on Tuesday through Wednesday, as a new, more powerful spring storm system gathers strength over the Midwest.
Figure 1. Radar reflectivity image of the EF-4 St. Louis tornado taken near 8pm local time on Friday, April 22, 2010. This image is from the high-resolution Terminal Doppler Radar (TDR) at the St. Louis Airport, and shows very fine details of the tornado, which displays a classic hook echo here.
Figure 2. Radar Doppler velocity image of the St. Louis tornado taken near 8pm local time on Friday, April 22, 2010. This image is from the high-resolution Terminal Doppler Radar (TDR) at the St. Louis Airport, located at the "+" sign on the image. Green colors denote areas where precipitation is moving towards the radar, and red and yellow colors show where precipitation is moving away from the radar. Pink colors are bad data regions. The small couplet of greens right next to reds is where the tornado was, since the tight vortex had winds moving towards the radar and away from the radar. The area marked "RFD" shows where a Rear-Flank Downdraft (RFD) was occurring behind the tornado. The downdraft hit the ground to the west of the radar site and spread out in all directions, creating a diverging area of winds moving both towards and away from the radar. An area of air flowing into the tornado on the SE side is marked "Inflow." Thanks go to Dr. Rob Carver, wunderground's tornado expert, for annotating this image.
Remarkable video from a security camera at the St. Louis airport showing the roof being torn off Concourse C.
Figure 4. Severe damage characteristic of at least a strong EF-2 tornado is apparent from this helicopter view of residential St. Louis neighborhoods taken by KMOV.
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