http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2142
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Violent severe thunderstorms swept through Eastern North Carolina Sunday afternoon and evening, killing three people--one in a collapsed building, and two due to a falling tree. The deadly thunderstorms were fueled by the extreme heat affecting the Southeast, coupled with unusually high levels of moisture. The extraordinary heat and moisture caused high levels of atmospheric instability rarely seen. For those of you familiar with atmospheric stability indicies, the Convective Available Potential Energy (CAPE) in Eastern North Carolina and South Carolina at 2 pm EDT Sunday was 5000 - 6000, with a lifted index of -14. The Morehead City NWS office analyzed CAPE levels in excess of 7000 in the region, which is a truly rare occurrence. Fortunately, there was very little wind shear Sunday, so the upper-level winds were not able to induce the kind of twisting force needed to generate tornadoes. Sunday's powerful storms brought more power outages and damage to a region still suffering the impacts of Friday's rare derecho event, which killed 14 people and left power outages that still affect at least 2 million people. According to insurance broker Aon Benfield, the storm initially knocked out power to 2.5 million people in Virginia, the largest non-hurricane related power outage in state history. A derecho is a fast-moving, long-lived, violent thunderstorm complex that usually develops along the northern edge of a very hot air mass, in conjunction with an active jet stream. Friday's derecho was one of the largest and most destructive in U.S. history, and compares to the May 8, 2009 derecho that swept across the nation from Kansas to Kentucky, killing six and causing $500 million in damage.
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