A tree sitting atop a vehicle offers free firewood in Falls Church, Va., Monday, July, 2, 2012, as cleanup continued after a derecho pummeled the area. (AP Photo/Matthew Barakat)
Derechos are referred to as land hurricanes due to the hurricanelike conditions that occur over land with this weather phenomenon.
This term refers to a type of thunderstorm complex that is at least 240 miles wide, according to the Storm Prediction Center (SPC). These violent severe thunderstorm clusters produce widespread and long-lived, straight-line wind damage.
Wind gusts of greater than 58 mph occur in derechos, but winds may exceed 100 mph, according to the SPC. A wind gust of 128 mph was measured in eastern Wisconsin from a derecho that tore across Wisconsin and Michigan on May 31, 1998. Gusts were estimated to reach as high as 130 mph in Lower Michigan.
Hail, flooding and isolated tornadoes can also occur with derechos.
These thunderstorm complexes often take on a bowing shape due to the strong rear inflow of wind.
Making them even more dangerous, derechos often occur at night. Fewer people may be aware of dangerous weather situations at night compared to during the daylight hours. In these situations, it is important to keep a weather radio nearby to keep aware of severe storm warnings.
On June 29, 2012, an infamous derecho slammed a 700-mile swath from the Midwest to the mid-Atlantic. Washington, D.C., was among the cities hit hard by the derecho. Millions of people were without power for a week or more after the derecho struck due to the widespread damaging wind gusts, which were higher than 80-90 mph in several communities.
The image above shows the widespread damaging winds that occurred from Iowa to the mid-Atlantic coast on June 29, 2012, and June 30, 2012. The storm reports map is from the San Diego NWS office.
A couple of years prior to the 2012 derecho, another destructive event slammed the Midwest on June 18, 2010. The Chicago area was slammed by the violent storms. There were 340 wind reports with widespread winds over 70 mph. A couple of tornadoes touched down, and hail up to the size of tennis balls fell from the strongest storms.
Story by AccuWeather Meteorologist Meghan Evans.
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