Shelf Cloud Near Olds Airport in Alberta, Canada

February 16, 2009


Photographer: Mark Firmin and Patrick King
Summary Author: Patrick King

Thunderstorms occur frequently in the foothills of the Canadian Rockies during midsummer. On occasion, towering cumulonimbus clouds can produce damaging hail. In July of 2008, the Unstable Project was specifically set up to study the initiation of such storms. The image above is stitched from two photos (taken at the Olds Airport in Alberta, Canada) and shows a classic shelf cloud and a 'beaver tail' (rain burst) associated with a particularly nasty storm on July 13, 2008. Shelf clouds (or arcus clouds) are wedge-shaped clouds, attached to the base of cumulonimbus clouds, formed by strong downdrafts.