July 2, 2008

Seiche Warning Prompts Lake Swim Ban: Waves Expected to Hit Chicago Area Around 6 P.M.

By Chicago Tribune

Jul. 2--The Chicago Park District issued a swim ban Wednesday afternoon in response to a National Weather Service seiche warning, officials said.

The warning was issued after a massive storm front currently over the lower peninsula of Michigan crossed Lake Michigan in the early afternoon Wednesday and piled the water toward the Michigan shore as it traveled east.

Water flooded the harbor in St. Joseph, Mich., and crept more than 15 feet across the sand there, said NWS meteorologist Nathan Marsili. When weather service meteorologists looked at lake levels on the Illinois side, they found they had also dropped by several inches.

That water is expected to slosh back to the Illinois shore--in Chicago and on beaches north of the city--between 6 and 7 p.m., Marsili said. When it subsides overnight and early Thursday morning, it may also cause dangerous rip currents, he said.

In response, Chicago Park District spokeswoman Marta Juaniza said a swim ban was issued for all Chicago beaches as of 4 p.m.

Boat crews put out red flags and began calling people out of the water, Juaniza said.

"There will be no more swimming today," she said.

Conditions will be monitored Thursday to determine when beaches can reopen for swimming.

Seiches occur when lake levels gyrate rapidly in short periods of time, and they are produced when fast-moving squall lines push domes of water into the Michigan shoreline.

Rich Brumer, another National Weather Service meteorologist, said storms over Sheboygan, Wis., a lakefront town between Milwaukee and Green Bay, caused water levels in southern parts of Lake Michigan to drop by about 2 feet.

He said the water levels between Chicago and St. Joseph should continue to rise and fall suddenly until later tonight. "The water levels will go back and forth like in a bathtub," Brumer said.

In addition to the lakeshore flood warning, the weather service has issued a severe thunderstorm watch until 10 p.m. for the entire Chicago area.

Ray Quintanilla, Jason Meisner and James Janega, Tribune reporters


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