Dear Tom,
Recently a news broadcast showed an Oklahoma TV news team filming a tornado that was rotating in a clockwise direction. Isn’t this unusual?
Vic Mazylewski, Shorewood, Ill.
Dear Vic,
The great majority of Northern Hemisphere tornadoes possess winds that spiral inward and upward in a counterclockwise sense, but Dr. Joe Golden, a senior scientist with NOAA, tells us that, “A few percent (up to 10 percent) of tornadoes rotate clockwise, or anticyclonically.”
Tornadoes are spawned in relatively large-scale low-pressure wind circulations, 10 to 50 miles in diameter, that respond to the Coriolis force (the force that causes counterclockwise rotation in low pressure systems). However, Coriolis is so weak in smaller circulations that they can sometimes rotate in a clockwise sense, as do the tornadoes they trigger.
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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.
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or asktomwhy@wgntv.com (Mail volume precludes personal response.)
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
