Simple Thunderstorm Hazards

Downbursts and Gust Fronts

• downburst: violent downdraft   * caused by thunderstorms “exhaust” (cool and dry descending air)
• when a downburst hits the ground, it moves laterally as a gust front
• if over loose sediment (like sand, silt) they become sandstorms or haboobs   * haboob: dust cloud within a gust front

Hail

• layered balls of ice
• formed by updrafts and rapid condensation (desublimation) inside thunderstorms
• require:

     1. large thunderstorms with buoyant, warm, moist air   2. mid- and upper-level freezing cold air (maximum temperature contrast) which results in…

           1. strong updrafts to keep hail suspended in cloud while adding coatings of ice

• occurs in largest storms with the greatest temperature variation   * largest variation makes strong updrafts that keep hail aloft and more layers are added   * leads to baseball/grapefruit-sized hail

Heavy Rain/Flash-floods

• thunderstorms occur in dry areas
• heavy rains overload local drainage systems
• cause flash floods

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