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Friday, September 11, 2020

What is a derecho? An atmospheric scientist explains these rare but dangerous storm systems

Thunderstorms are common across North America, especially in warm weather months. About 10% of them become severe, meaning they produce hail 1 inch or greater in diameter, winds gusting in excess of 50 knots (57.5 miles per hour), or a tornado.

The U.S. recently has experienced two rarer events: organized lines of thunderstorms with widespread damaging winds, known as derechos.

Derechos occur mainly across the central and eastern U.S., where many locations are affected one to two times per year on average. They can produce significant damage to structures and sometimes cause “blowdowns” of millions of trees. Pennsylvania and New Jersey received the brunt of a derecho on June 3, 2020, that killed four people and left nearly a million without power across the mid-Atlantic region.
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-Gary