National Weather Service confirms December 15th’s severe weather event as a derecho
A line of severe thunderstorms that swept through the Upper Midwest December 15th, 2021 has been declared as a “Serial Derecho”. This is the first ever December derecho on record to occur within the United States.
WAUSAU, Wis. (WSAW) - The National Weather Service and Storm Prediction Center have officially classified the December 15th, 2021 Upper Midwest severe weather event as a “serial derecho”. This is the first known December derecho on record to occur within the United States.
A derecho is known as a widespread, long-lived wind storm associated with a band of showers and thunderstorms. But, to be officially classified as a derecho, the wind damage associated with the event must extend more than 240 miles with wind gusts of at least 58 mph or greater for most of its path. Additionally, must also include several, isolated 75 mph or greater wind gusts.
December 15th’s severe weather event meets the criteria and will be categorized as a “serial derecho”, which is mostly driven by a strong area of low-pressure and powerful atmospheric winds. In addition to the criteria above, a serial derecho is produced by several bow echoes within a squall line, which moves across a large area.
The total number of tornadoes that occurred in Wisconsin stands at 5, but the number may be revised as additional storm surveys conducted by the National Weather Service are ongoing.
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