What is a derecho?
http://www.myfoxdc.com/story/18932317/what-is-a-derecho#ixzz1zUSQ5LtL
WASHINGTON - The storms that hit the Washington, D.C., Maryland and Virginia areas Friday evening were a meteorological phenomenon known as a derecho.
According to the National Oceanic and Atmospheric Administration (NOAA) Storm Prediction Center, a derecho (deh-REY-cho) is a widespread wind storm that is associated with a band of rapidly moving showers or thunderstorms. Although a derecho can produce destruction similar to that of tornadoes, the damage typically is directed in one direction along a relatively straight swath.
The term ‘straight-line wind damage' is used to describe derecho damage.
By definition, if the wind damage swath extends more than 240 miles and includes wind gusts of at least 58 mph (93 km/h) or greater along most of its length, then the event may be classified as a derecho.
Unlike a hurricane which can often be tracked days ahead of impact, Friday's storm offered no warning.
Power crews from as far away as Florida and Oklahoma were on their way to the mid-Atlantic region to help get the power back on after mass outages.
Attachments: