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What Is A Derecho? Experts Warn Of Unusual Weather Event As Storms Threaten Mid-Atlantic

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As Mid-Atlantic states prepare for potentially severe thunderstorms Thursday, meteorologists have warned that there is a chance an unusual weather event known as a derecho may hit parts of the region.

A derecho, which is capable of causing destruction similar to that of tornadoes, is a "widespread, long-lived wind storm that is associated with a band of rapidly moving showers or thunderstorms," according to the National Oceanic and Atmospheric Administration (NOAA).

"It's a cluster of thunderstorms that congeal into a line, and that line will then start moving east or southeast, and as it progresses the winds increase and produce damage along that path," Jim Keeney, weather program manager at the National Weather Service's office in Kansas City, Mo., told CBS News.

Unlike tornados, which tend to be more isolated, a derecho can impact a broad area, Keeney warned. Indeed, derechos are known to span at least 240 miles.

"A tornado, when it does occur, may be on the magnitude of a mile or two wide; a derecho could go for hundreds of miles, producing significant damage ... [and] winds in excess of 75 miles or greater and could run for hundreds of miles," Keeney told CBS. "A lot of people can be impacted by derechos; tornadoes are ... smaller in scale."

The term "derecho" was coined in 1888, NOAA research meteorologist Ken Pryor told the Associated Press. The word is Spanish for "straight ahead" or "direct," he said.

Last June, a derecho swept through the Mid-Atlantic, causing widespread damage from Chicago to Virginia. Five million people lost power and 22 were killed.

A derecho warning was first issued earlier this week when storms threatened and then swept through the Upper Midwest. However, as of Thursday morning, it had yet to manifest.

As the storm system heads over the Mid-Atlantic states, a derecho event becomes less of a possibility "with each hour that goes by," Greg Carbin of the National Weather Service's Storm Prediction Center in Norman, Okla., told Weather.com.

Even if a derecho does not develop, an NOAA warning Wednesday indicated that Washington D.C., Delaware, and parts of Maryland, New Jersey, Pennsylvania and Virginia will likely be hit on Thursday with severe weather, including strong winds and flash floods. People in the region have been warned to seek shelter when necessary and to take care when traveling out of doors.

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