Dear Tom,
Why do winds move from west to east. Why not east to west?
Garrett Ariana, Western Springs, Ill.
Dear Garrett,
ItM-9s a complex question requiring a technical answer.
Planet-wide, the warmest air resides in the tropics and the coldest air at the poles. At any given elevation aloft, say 30 thousand feet, air pressure is higher in warm air than in cold air (because warm air is expanded relative to cold air). Air always tries to move from higher air pressure (in the tropics) to lower pressure (at the poles). Because the Earth is spinning, a deflection (Coriolis) causes northward moving air aloft to turn toward the right, thereby establishing prevailing westerly winds aloft, especially in the Earth’s middle latitudes. That steers weather systems from west to east.
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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.
