derecho [key], a long-lived windstorm over a wide expanse that is associated with a line of rapidly moving thunderstorms or showers. The winds in a derecho generally exceed 57 mph (92 kph) and may reach 100 mph (161 kph) or more; derecho winds are produced by clusters of downbursts, with stronger winds being produced by microbursts within downbursts. The line of storms associated with a derecho typically takes on a broadly curved or bowed shape, known as a bow echo from its appearance on radar. A serial derecho, usually associated with a strong, moving low pressure system, contains multiple bow echoes within a squall line that usually is hundreds of miles long and traverses an extensive area. A progressive derecho is typically associated with a weak surface low pressure area and with a line of thunderstorms less than 250 mi (400 km) long; the squall line usually remains relatively narrow as it progresses and may contain only a single bow echo. Hybrid derechos have characteristics of both serial and progressive derechos. Derechos typically cause so-called straight-line wind damage, in which the destruction is aligned in one general direction. Derecho winds can topple trees and power lines, overturn high-profile trucks and other vehicles, and even overturn mobile homes; the sudden, widespread destruction they cause can lead to prolonged power outages.
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