AS

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