Derecho

derecho

A widespread convectively induced straight-line windstorm.

Specifically, the term is defined as any family of particularly damaging downburst clusters produced by a mesoscale convective system. Such systems have sustained bow echoes with book-end vortices and/or rear-inflow jets and can generate considerable damage from straight-line winds. Damage must be incurred either continuously or intermittently over a swath of at least 650 km (~400 mi) and a width of approximately 100 km (~60 mi) or more.

The term derecho derives from a Spanish word that can be interpreted as "straight ahead" or "direct" and was chosen to discriminate between wind damage caused by tornadoes, which have rotating flow, from straight-line winds. More specific guidelines for identifying derechos are suggested in the references below. These guidelines are subject to change with improvements in observing systems, particularly with severe wind measuring and reporting capabilities.

Corfidi, S. F., M. C. Coniglio, A. E. Cohen, and C. M. Meade, 2016: A proposed revision to the definition of “derecho.” Bull. Amer. Meteror. Soc., 97, 935–949, doi:10.1175/BAMS-D-14-00254.1.

Johns, R. H., and W. D. Hirt, 1987: Derechos: Widespread convectively induced windstorms. Wea. Forecasting, 2, 32–49, doi:10.1175/1520-0434(1987)002<0032:DWCIW>2.0.CO;2.

Term updated 18 March 2019.

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