Straight Line Wind Damage on the Morning of April 27, 2011

Radar Reflectivity

Radar Velocity

This is the line of thunderstorms that marched through Central Alabama on the morning of April 27th.  These particular images were when the line went through Tuscaloosa and Walker Counties. EF-3 tornado  damage occurred in both Coaling and Cordova. Click the image for a radar loop of the event. 

 

A line of thunderstorms, known as a quasi-linear convective system or QLCS, moved into Central Alabama around 4 am.  Often times, a QLCS will create small spinups, or rotational areas,  on the front edge of the line. These spinups typically result in an EF-0 or EF-1 tornado.  With this particular system, the spinups were much more robust.  These spinups actually generated 3 EF-3 tornadoes and 5 EF-2 tornadoes. Not only were there 11 total tornadoes on the morning of April 27th, but there were also numerous areas that received heavy straight line wind damage.  Here are some of the the damage accounts: 

 
Pell City/Riverside 

National Weather Service Meteorologists surveyed storm damage locations in and around Pell City and Riverside in St. Clair County.  There was a diffuse and intermittent, yet discernible swath of wind damage that extended from just west of the St. Clair County Courthouse, northeastward across Pell City, Industrial Park Drive, Interstate 20 and through Riverside.  Additional storm damage reports and surveys indicated a fairly widespread area of isolated wind damage to the south and east of this main damage swath.  The most significant damage was several large trees that were uprooted, which caused damage to homes and structures.  One fatality was caused when a large oak tree was uprooted and fell on a manufactured home.  Two metal building structures received direct damage from the winds, however the damage with both of these buildings appears to have been associated with the failure of large doors.  Dozens of homes in the area received minor roof damage as well.  Based on the analysis of the damage, as well as eye-witness reports and detailed post-analysis of radar signatures, it appears this damage was the result of straight line winds on the order of 80 to 100 mph.  Radar analysis indicated these winds were associated with rear inflow jets behind the bow echo as it moved across the area at 60 to 70 mph between 615 am and 625 am on the morning of April 27th. 

 
Moody 

National Weather Service Meteorologists surveyed storm damage in and around the city of Moody.  It was found to be consistent with straight-line winds, with peak wind gusts estimated between 80 and 100 mph.  There were two main areas of enhanced damage. The first was right along US-411 in the main business district of the city of Moody.  In this area numerous trees were blown down and snapped.  Several units of an apartment complex and several nearby homes received roof damage directly from the wind.  A metal-sided garage type building had one half of its roof and siding structure lifted and peeled off, which left just the supporting steel beams standing. The other area of enhanced damage was in a broad swath in a largely wooded area about 3 to 4 miles east of first location, a couple miles northeast of the Brompton Community.  In this area, numerous trees were snapped off and uprooted.  One tree fell onto a mobile home, which fatally injured one of its occupants. In both areas, numerous other buildings received varying degrees of damage, both directly from the wind and as a result of trees being blown on top of them.  Virtually all damage in both of these areas was in a northeasterly direction, with no sign of convergence or any other evidence that would suggest it was caused by a tornado. 

 
 
 
 
 

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