Dear Tom,
Years ago, I remember hearing seiche (pronounced saysh) warnings mentioned for Chicago’s lakefront. Could you please explain that phenomenon?
— Royse Cramton, Oak Park
Dear Royse,
In the Great Lakes region, any sudden rise in the water level in a harbor or on the shore of one of the Great Lakes is known as a seiche. In extreme cases, the rise, occurring within a minute or less, can be several feet. Such dramatic events obviously present a great danger to people along the shore.
The Chicago seiche situation is unique. In rare cases, an air-pressure jump in advance of southeastward-moving thunderstorms can push a low surge of water from Chicago across Lake Michigan. Upon striking the Michigan/Indiana shore, the surge reflects back to, and focuses upon, Chicago’s lake shore, initiating a sudden, temporary rise in the lake level.
———-
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or: asktomwhy@wgntv.com
Weather Report is prepared by the WGN-TV Weather Center, where Tom Skilling is chief meteorologist. His forecasts can be seen Monday through Friday on WGN News at noon, 5:55 p.m. and 9 p.m.
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
IN THE WEB EDITION: For updated weather news, forecasts by ZIP code and local radar images, go to chicagotribune.com/weather or wgntv.com
