Downburst
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A downburst is a column of sinking air that is capable of producing damaging straight-line winds over 100 mph, similar to, but distinguishable from tornadoes. Downburst damage will radiate from a central point, whereas tornado damage shows a pattern consistent with rotating winds.
Such columns of air usually occur during thunderstorms, but have been observed in situations where little or no rain has reached the ground.
The formation of a downburst starts with hail or large raindrops falling through dry air. Hailstones melt and raindrops evaporate -- this demands a lot of energy (in form of latent heat) so the air is cooled. Cold air has a higher density than warmer air around it, so it falls as a "cold air balloon" (compare to hot air balloon, which rises because hot air has a lower density than the surrounding air). As the cold air balloon hits the ground, it spreads out, and the front can be observed as a gust front.
Downbursts may cause damage over hundreds of square miles, or they may damage much smaller areas, in which case they are often called microbursts. A large event of this type is sometimes called a macroburst.
Downbursts are exceedingly dangerous to aircraft which are taking-off and landing. A number of fatal crashes have been attributed to downbursts.
See also: Tetsuya Theodore Fujita
External links
- What is a downburst? (http://www.weatherquestions.com/What_is_a_downburst.htm)
- Denton County, Texas - Downburst (http://dentoncounty.com/dept/main.asp?Parent=82&Link=84)de:Downburst