derechoes

A derecho is a widespread, long-lived, straight-line windstorm associated with a fast-moving group of severe thunderstorms. The term "derecho" comes from the Spanish word for "straight," reflecting the characteristic damage pattern of these storms. To be classified as a derecho, a windstorm must extend more than 240 miles (about 400 kilometers) and have wind gusts of at least 58 mph (93 kph) or greater along most of its length, with several well-separated 75 mph (121 kph) or greater gusts.

Derechos typically occur during the warmer months, from spring through summer, and are most common in the central United States. They are formed by a complex interplay of atmospheric conditions, including an unstable atmosphere, sufficient moisture, and a strong lifting mechanism. A key feature is the development of a leading convective system, often an unusually strong cold front or outflow boundary, which drives the thunderstorms forward at high speeds.

The damage caused by derechos can be severe, often resembling that of an F1 or F2 tornado. Straight-line winds can flatten large swaths of trees, cause extensive damage to buildings, and lead to widespread power outages. Because the winds are directed in a relatively straight line, the damage pattern is often distinct from the rotational damage associated with tornadoes. Meteorologists use Doppler radar and other tools to track and forecast these powerful storms.