A
derecho (
/dəˈreɪtʃoʊ/, from
Spanish:
derecho[deˈɾetʃo], "straight") is a widespread, long-lived,
straight-line wind storm that is associated with a land-based, fast-moving group of
severe thunderstorms.
[1] Derechos can cause hurricane force winds, tornadoes, heavy rains, and flash floods. Winds
convection-induced take on a
bow echo (backward "C") form of
squall line, forming in an area of wind divergence in upper levels of the
troposphere, within a region of low-level
warm air advection and rich low-level moisture. They travel quickly in the direction of movement of their associated storms, similar to an
outflow boundary (gust front), except that the wind is
sustained and increases in strength behind the front, generally exceeding
hurricane-force. A warm-weather phenomenon, derechos occur mostly in summer, especially during June, July, and August in the Northern Hemisphere, within areas of moderately strong
instability and moderately strong vertical
wind shear. They may occur at any time of the year and occur as frequently at night as during the daylight hours.
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