A widespread, long-lived windstorm produced by a fast-moving band of thunderstorms, defined by damaging straight-line winds extending more than about 400 miles along its path. Unlike a tornado's rotating winds, a derecho's damage runs in one predominant direction, often felling trees and power lines across an entire region within a matter of hours. The term, Spanish for "straight," was coined in the 1880s to distinguish this damage pattern from a tornado's twisted debris.
Facts
PeriodicityDerechos in North America form predominantly from April to August, peaking in frequency from May into July, and are a warm-weather phenomenon most common in June, July and August in the Northern Hemisphere. 1 ScaleA derecho-producing convective system may remain active for many hours, occasionally even for several days, with straight-line winds, sometimes enhanced by embedded downburst clusters, that may exceed 45 m/s (85 kn) and reach 60 m/s (115 kn). 1 First DescribedThe word derecho was first used in the 1888 American Meteorological Journal by Gustavus Detlef Hinrichs, in a paper describing the phenomenon and based on a significant derecho event that crossed Iowa on 31 July 1877. 1 Identification
Distinguishing AppearanceClassic derechos occur with squall lines that contain bow- or spearhead-shaped features as seen by weather radar, known as bow echoes or spearhead echoes, producing widespread straight-line wind damage rather than the rotating damage pattern of a tornado. 1 Connections
Associated With
A derecho is defined as a widespread, long-lived windstorm produced by a family of downburst-producing thunderstorm clusters; the downbursts are the derecho's own constituent wind-damage mechanism.
The damaging straight-line winds of a derecho are produced by clusters of microbursts embedded in its parent convective system, the smaller-scale downdraft events that combine into the storm's wider damage swath.
Demonstrated By
Source National Oceanic and Atmospheric Administration
Sources
1. Derecho (Wikipedia)
Wikimedia FoundationDevelopment section
Classic derechos occur with squall lines that contain bow- or spearhead-shaped features as seen by weather radar that are known as bow echoes or spearhead echoes.
Etymology section
The word was first used in the 1888 American Meteorological Journal by Gustavus Detlef Hinrichs in a paper describing the phenomenon and based on a significant derecho event that crossed Iowa on 31 July 1877.
Location section
Derechos in North America form predominantly from April to August, peaking in frequency from May into July.
Characteristics section
Winds in a derecho can be enhanced by downburst clusters embedded inside the storm. These straight-line winds may exceed 45 m/s (85 kn), reaching 60 m/s (115 kn)
View the Source National Oceanic and Atmospheric Administration
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