Ducktown Hole Punch
July 02, 2007
The photo above shows a "fall-streak hole" (also referred to a hole punch cloud) over Ducktown, Tennessee. Ducktown was the site of the Atlanta Astronomy Club's annual star party -- held last year on October 18. Shortly before sunset, altocumulus clouds began to roll in from the southwest. While taking several pictures of these clouds, I noticed that a hole was forming (this image was taken at 6:23 p.m. Eastern Daylight Time). Holes such as this result from ice crystals falling through a shallow layer of clouds. When this occurs, supercooled droplets freeze and release their heat of fusion, which warms the air and evaporates the surrounding cloud. The fibrous ice falling from the clouds are called fall-streaks. See also tomorrow's Earth Science Picture of the Day.