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A 'Ring of Fire': Just What Were the Deadly Thunderstorms That Tore Through the Eastern U.S.?

A fallen tree blocks the sidewalk and damages a park vehicle in the Dupont Circle neighborhood of Washington, Saturday, June 30, 2012. Violent evening storms following a day of triple-digit temperatures wiped out power to more than 2 million people across the eastern United States. (AP Photo/Pablo Martinez Monsivais)

D.C. derecho

The explosive line of thunderstorms that ripped through the mid-Atlantic region on Friday wasn't any regular weather event: turns out it was a special kind of storm system called a derecho -- a widespread, long-lasting band of windstorms capable of producing tornado-like damage.

The Washington Post's Capital Weather Gang has more:

They 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.

During summer, the jet stream atop a sprawling heat dome is sometimes called a “ring of fire” due to the tendency for explosive thunderstorms to form along this weather front separating hot, humid air to the south and cooler, drier air to the north.

According to the Post, Friday's line of storms raced across the country at speeds of more than 60 mph. They formed west of Chicago in the late morning, approaching the Atlantic ocean by midnight. According to the Associated Press, at least 13 people were killed and two million still without power Saturday evening as the region sweltered in a triple-digit heat wave.

Watch a timelapse of the derecho's movement across the country from Davenport, Iowa to Richmond, Va. over 14 hours:

The Post has the peak wind gusts for the Washington, D.C. region:

71 mph near Dulles Airport

70 mph in Damascus, Md.

79 mph in Reston, Va.

65 mph in Rockville, Md.

70 mph at Reagan National Airport

76 mph in Seat Pleasant, Md. (Prince George’s co.)

77 mph in Swan Point, Md. (Charles co.)

70 mph in Ashburn, Va.

69 mph in Leesburg, Va.

Were you affected by the derecho? Tell us about your experience below in the comments.

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