Formation
The formation of a downburst starts with hail or large raindrops falling through drier air. Hailstones melt and raindrops evaporate—this is an endothermic process that demands a lot of energy (in the form of latent heat) so the air is cooled. Cooler air has a higher density than the warmer air around it, so it falls as a "cold air balloon" (compare to a 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 a mesoscale front can be observed as a gust front. Areas under and immediately adjacent to the downburst are the areas which receive the highest winds and rainfall, if any is present. Also, because the rain-cooled air is descending from the middle troposphere, a significant drop in temperatures is noticed. Due to interaction with the ground, the downburst quickly loses strength as it fans out and forms the distinctive "curl shape" that is commonly seen at the periphery of the microburst (see image). Downbursts usually last only a few minutes and then dissipate, except in the case of squall lines and derecho events. However, despite their short lifespan, microbursts are a serious hazard to aviation and property and can result in substantial damage to the area.
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