Could you please explain the seiche phenomenon?
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, Ill.
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 great danger to people at the lakeshore.
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 lakeshore,initiating a sudden,
temporary rise in the lake level.