Pileus Cloud Over Northern Georgia

August 19, 2012

GeorgiaPileusCloud (2)

: Thomas Faber
Summary Author: Thomas Faber

This photo shows a building cumulonimbus cloud just north of Alpharetta, Georgia on the afternoon of July 12, 2012. The thunderstorm is displaying a prominent pileus cloud above it -- the smooth cloud with the fuzzy edges. Pileus clouds are accessory type clouds that form when a layer of humid air is pushed upward by strong updrafts in growing storms. This prominent pileus developed very quickly. When I first saw it, about a minute before this photo was taken, it exhibited only a single layer. But over the next minute or two, several additional layers became obvious. Note the faint iridescence about the lower left portion of the pileus cloud. A less conspicuous pileus is also visible just above the tree canopy at far left. Photo taken at 5:04 p.m.

Photo details: Camera Maker: Canon; Camera Model: Canon PowerShot SX100 IS; Focal Length: 42.5mm; Aperture: f/4.0; Exposure Time: 0.0010 s (1/1000); ISO equiv: 80; Exposure Bias: none; Metering Mode: Matrix; White Balance: Auto; Flash Fired: No (enforced); Orientation: Normal; manually focused at infinity, optical zoom 7X; Color Space: sRGB.