Dear Tom,
The wind blows dust and leaves around helter-skelter, and yet it does not do the same thing to clouds. Please explain.
Bruce Ameismeier, Chicago
Dear Bruce,
Clouds retain their shapes as they move along because they exist in a smoothly-flowing wind field relatively free of the gustiness and turbulence that characterize our ground-level winds.
The extreme variability of our “ground winds” diminishes surprisingly quickly with increasing height–literally within several tens of feet aloft (or several tens of feet above “rough” surface features like trees). Winds above that level blow with a remarkable constancy.
The tiny water droplets and ice crystals of which clouds are composed move with that steady wind, and the clouds retain their shapes.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
