Dear Tom,
What are “supercells”?
Alice Browning
Dear Alice,
“Supercells” are a special breed of thunderstorms–enormous, severe, rotating (in the sense that air in the 10-50 mile wind field in which supercells are embedded spirals inward, usually in a counterclockwise sense). Most uniquely, supercells persist for hours, whereas most thunderstorms move through a life cycle of an hour or less.
A thunderstorm consists of warm currents of rising air that deliver the storm’s energy and cool downdrafts in the rain area. Normally, downdraft air undercuts the inflow of warm air within an hour and the storm dies. In supercell thunderstorms, the updrafts and downdrafts are in unique balance, so the storm’s demise is delayed. The longer life, sometimes 24 hours, allows for greater intensification and severe-weather production.
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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.
