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MILWAUKEE, Wis. (CIVIC MEDIA) – Yes, you read that right a meteotsunami raced from Wisconsin and flooded beaches in Michigan.
A series of major waves quickly raised lake levels by roughly two feet, flooding beaches in Michigan.
Meteotsunamis occur around the world and need two special ingredients for one to form on the Great Lakes: a spike in wind and a jump in pressure.
The waves that built earlier this week and hit Holland, Michigan were caused by the severe storms that swept through southeastern Wisconsin late Monday and into early Tuesday morning.
These massive sudden waves on the Great Lakes are usually caused by storms like derechos, bow echoes and squall lines racing across the open waters, between March and July. They are usually amplified in areas with a shallow continental shelf and inlet, bay, or other coastal feature.
These can be quite dangerous, a 2019 study that looked at 94 deaths and 298 rescues attributed to rip currents at Lake Michigan beaches found that over 15 years of data determined that 16% of the deaths and 12% of the rescues happened on the same day as a meteotsunami occurrence.
So are they actually tsunamis? Not really. A tsunami is a series of giant waves created by a large volume of water displaced. This is usually from a shift in plates causing an earthquake underwater or volcanic activity below. Meteotsunamis are caused by air pressure disturbances that occur above land, and after fast-moving weather system.
Tsunamis are also much larger and catastrophic, making national and international news because the waves travel far distances and make it further inland. While, meteotsunamis are regional occurrences and usually only effect smaller, local areas.
These wave events are often confused with seiches, which also happen in the Great Lakes. A seiche is a standing wave that moves back and forth. It’s similar to water sloshing in a bathtub, but in the Great Lakes it’s happening on a much larger scale, rising the water levels on some shores.
A seiche is largely driven by wind, while a meteotsunami is mostly triggered by a rapid pressure change. Both can happen at the same time. Seiches last hours and meteortsunamis take minutes to a few hours of high waters.
Around 100 meteotsunamis occur on the Great Lakes each year and have been observed to reach heights of 6 feet or more. The last major one was in April 2018 after a 71mph storm pushed an 8 foot wave into Ludington, Michigan damaging docks and covering break walls.
Because the jet stream moves from west to east, these waves typically happen on the eastern side of Lake Michigan.
But it has happened on the west shorelines when a 10 foot wave crashed into a pier in Chicago and knocked anglers off, killing eight.
Most of these in the Great Lakes though are too small to notice. But large ones can bring dangerous waves, flooding and rip currents that can hurt beachgoers and damage shorelines.
It’s best to avoid the shores when thunderstorms are around. You can check wave heights and conditions daily from the National Oceanic and Atmospheric Administration to stay weather ready and safe.
