Hail Stones in the French Alps

May 22, 2006

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Provided and copyright by: Diane Ryckebusch
Summary authors & editors: Diane Ryckebusch

The above photo was taken in July, 2005, in the French Alps, and shows a collection of marble-sized hailstones in the aftermath of a severe summer storm. This unexpected storm caught everyone by surprise and destroyed many vineyards, crops and greenhouses in the Geneva/Veigy Foncenex region of the Alps. Hailstones consist of irregular lumps of ice that are often characterized by concentric internal layering, resembling the structure of an onion. Hail usually develops in intense thunderstorms having vigorous updrafts and an abundance of supercooled water droplets. Frozen water particles are repeatedly coated with supercooled droplets as they're carried aloft in the storm's updrafts. Eventually, the individual hail stones become too heavy to be supported by the vertical air currents and fall toward the surface.

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