Seiche on Lake Michigan With Today's Storms

Courtesy: NOAA

The more than 100-mile wide swath of 60 to 80 mph winds that hit northern Illinois and southern Wisconsin this morning were so powerful they changed the level of Lake Michigan this morning! Admittedly, the change was temporary, but still an impressive display of this storm complex's power. The graph at left (the upper image specifically) shows the water level at Calumet Harbor south of Chicago. Notice the red marks centered on the morning of July 11th indicate a nearly 2-foot change in water level at this location!

One will also notice the water level oscillates from high to low several times before "settling" back to normal. Such a phenomenon is called a "seiche." A seiche is caused by powerful winds along a lake that force water to pile-up along the opposing shore (in this case, Indiana and southwest Michigan). When the winds leave the area, this water sloshes back and forth for a period of time (sometimes several hours) from one shore of the lake to the other. This sloshing water can damage watercraft, knock people off of piers and breakwaters, and pull swimmers away from shore.