Seiches
Seiches are periodic oscillations of water level set in motion by some atmospheric disturbance passing over a Great Lake. The disturbances that cause seiches include the rapid changes in atmospheric pressure with the passage of low or high pressure weather systems, rapidly-moving weather fronts, and major shifts in the directions of strong winds. Seiches exist on the Great Lakes, other large, confined water bodies, and on partially-enclosed arms of the sea.
The intervals (or periods) between seiche peaks on the Great Lakes range from minutes to more than eight hours. One or more seiches following a storm surge may cause repeated flooding of low-lying property. Small seiches (less than a foot high) are an everyday occurrence on the Great Lakes.
Hi guys ! A small bit of info I found at the University of Wisconson Coastal Hazard page.