Friday's Destructive Wind Storm ExplainedWhat's a derecho? And why is it so unusual?
As the millions of people still without power today will attest, that was no ordinary wind storm on Friday.
An event that reportedly happens about once every four years, a fast and furious thunderstorm formed west of Chicago at about 11 a.m. and then raced at speeds upwards of 60 mph in a straight line across Illinois, Indiana, Ohio, Virginia, Maryland, and Washington, D.C. and out over the Atlantic Ocean by midnight, according to news reports.
Meteorologists call this kind of straight-lined fast moving thunderstorm a derecho. And this Friday's derecho already has its own wiki page.
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Like other thunderstoms, derechos generate power from convective wind gusts formed between pressure systems. But unlike other storms, derechos maintain a forward motion, basically feeding off the interface between the systems in a race that moves the storm at upwards of 50 mph for distances of hundreds of miles.
"Derechos often form along the northern boundary of a hot-air mass, right along or just south of the jet stream, where upper-level winds zip along at high speeds," reported the Seattle Times.
The record-setting temperatures on Friday clashed with the weather systems over Chicago and the storms that emerged grew in power forming a derecho that the upper-level winds continued push forward as the storm chewed its way through the heat wave.