Wall cloud
From Free net encyclopedia
Image:Wallcloudwithtailcloud.jpg A wall cloud is a cloud formation. It is a lowering beneath the rain-free portion of a thunderstorm, and indicates the area of maximum updraft. In the special case of a supercell thunderstorm, the wall cloud will often be seen to be rotating. It is the area of the thunderstorm which is most likely to produce tornadoes.
They can extend from a being a fraction of a mile wide to over five miles across, and typically form at the south or southwest end of a supercell mesocyclone.
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