Timeline of derecho that hit Friday

WTOP's Dave Dildine created this wind speed map using data from the Storm Prediction Center. (WTOP/Dave Dildine)
derecho 2012 On the National Mall, tents at the Smithsonian Folklife Festival collasped during the storm. (WTOP/Dave Dildine)
(Courtesy National Weather Service)
(Courtesy NWS)

Dave Dildine, wtop.com
Megan Cloherty, wtop.com

WASHINGTON – The ferocious storm that blew through the Washington-area Friday night is a weather system known as a derecho.

It is not only an unusual weather event for the region, but the circumstances surrounding the storm changed its pattern characteristics, according to ABC 7 Meterologist Mike Stinneford.

Derecho is a Spanish word that means “straight.” It is in reference to the storm’s powerful straight-line winds.

Derechos typically form along the top of a hot air mass and can move an average of 70 miles per hour. That wind speed is normally associated with a Category 1 hurricane.

WTOP Traffic Reporter Dave Dildine is also a weather research analyst. He compiled this chronology of the derecho’s movements Friday.

Timeline of Friday’s derecho forecast

8:53 a.m. eastern time

The Storm Prediction Center places the Mid-Atlantic, including the Washington, D.C metro area, under a slight risk for severe weather. They note “considerable variability in storm evolution” but point to the possibility of “damaging winds spreading south-eastward” through the evening.

10:35 a.m.

The National Weather Service in Sterling, Va., introduces increased chances for thunderstorms for the Washington area, stating that they “expect storms to continue to roll east

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