Photograph of cirrus clouds
Click on image for full size
Courtesy of Lisa Gardiner
Cirrus (weather symbol - Ci) clouds are the most common of the High Cloud (5000-13000m) group. They are
of ice and consist of long, thin, wispy streamers. They are commonly known as
"mare's tails" because of their appearance.
The reason for the long tails is primarily due to the wind. In the upper troposphere, the winds travel at
very high speeds from west to east (in the Northern Hemisphere). The winds are
so strong at these altitudes that they actually stretch the crystalline
structure of the
Cirrus cloud, creating a tail.
Cirrus clouds are usually white and predict fair weather.
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