A localized, intense downdraft of air that plunges from a thunderstorm and spreads out violently upon striking the ground, producing damaging straight-line winds within an area typically less than two and a half miles across. A microburst can generate wind speeds rivaling a strong tornado for a brief period and has been implicated in numerous aircraft accidents during landing and takeoff. Dry microbursts, common in arid climates, can occur with little or no rain reaching the ground at all.
Facts
ScaleA microburst affects an area 4 km (2.5 miles) in diameter or less, the threshold distinguishing it from the larger macroburst, and downbursts of this kind may last only seconds to minutes while producing straight-line winds of over 240 km/h (150 mph) in strong cases. 1 First DescribedTed Fujita identified microbursts while studying the starburst-like damage patterns of the 1974 Super Outbreak, then coined the term while investigating the 1975 crash of an Eastern Air Lines flight at JFK Airport, an accident later attributed to a downburst. 2 Open Questions
PeriodicityNo stated annual or seasonal frequency count in the source consulted.
The source describes downburst-type straight-line wind events in general as most common in the United States spring but gives no microburst-specific occurrence rate; recorded as unknown pending a dedicated microburst climatology source. Identification
Distinguishing AppearanceA microburst is a downburst affecting an area 4 km (2.5 miles) in diameter or less; like other downbursts its damage radiates outward from a central point where the descending column spreads out on hitting the surface, rather than the convergent, rotating damage pattern left by a tornado. 1 Connections
Associated With
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
Desert, Biomes Source National Oceanic and Atmospheric Administration
Sources
1. Downburst (Wikipedia)
Wikimedia FoundationDefinition section (Downburst article, covering microburst)Quote, Definition section (Downburst article, covering microburst)
Most downbursts are less than 4 km (2.5 mi) in extent: these are called microbursts.
2. How Ted Fujita Revolutionized Tornado Science (Weather.com)
The Weather Company, 20201974 Super Outbreak discovery passageQuote, 1974 Super Outbreak discovery passage
Fujita returned to the downdraft concept after he noticed starburst-like damage patterns from the 1974 Super Outbreak.
National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric AdministrationDemonstrated By: DesertView the Source Reader Challenges (0)
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