We’ve all heard of tsunamis and the one that struck Indonesia in 2004 was a particularly deadly one killing over 250,000 people and wiping whole towns off the map. I wrote an article published March 3, 2014 explaining tsunamis. Here is a link to that article:
A recent article written by Keith Matheny of the Detroit Free Press that was posted on the WKYC-TV web page sparked my interest in the fact that tsunamis actually occur on the Great Lakes. Who knew that they could happen 106 times per year on the Great Lakes? They even have a special name for them “meteotsunamis.” The term describes a tsunami with a meteorological (weather-related cause) rather than a geological cause for the typical tsunami.
According to the National Weather Service webpage nws.weather.gov “Meteotsunamis have characteristics similar to earthquake-generated tsunamis, but they are caused by air pressure disturbances often associated with fast moving weather systems such as squall lines. These disturbances can generate waves in the ocean that travel at the same speed as the overhead weather system. Development of a meteotsunami depends on several factors such as the intensity, direction, and speed of the disturbance as it travels over a water body with a depth that enhances wave magnification.”
Let’s take a look at 5 meteotsunamis events and how dangerous they were. Here are three events quoted from WKYC-TV:
- On July 4, 1929, a 20-foot wave that scientists now believe was caused by a meteotsunami crashed over holiday beach-goers on a pier in Grand Haven. Ten people were pulled out into Lake Michigan and drowned.
- On June 26, 1954, a 10-foot meteotsunami-caused wave swept fisherman off a pier on the shores of Lake Michigan in Chicago. Seven were killed.
- On July 4, 2003, seven swimmers drowned on Lake Michigan near Sawyer in Berrien County. According to media reports at the time, the drownings occurred within a 3-hour span after a powerful thunderstorm plowed through the area that morning, producing wind gusts of 50 m.p.h.
Back to nws.weather.gov for two more incidents:
- October 28, 2008 – Booth Bay Harbor, Maine: A series of waves up to 12 feet high emptied and flooded the harbor three times over 15 minutes, damaging boats and shoreline infrastructure.
- May 27, 2012 – Lake Erie: A seven-foot wave hit the shoreline near Cleveland, Ohio, sweeping beachgoers off their feet and swamping boats in harbors.
We need to take a closer look at exactly how meteotsunamis function. The disturbance on the surface of the water can be caused by a sudden atmospheric pressure change or very strong downdraft winds both of which suddenly force the surface water downward producing the kind of wave increase as the geological tsunami but, causing the disturbance on a smaller body of water such as a lake or harbor.
One last statement from nws.weather.gov about meteotsunamis. “A meteotsunami should not be confused with storm surge associated with tropical storms and other large coastal storms. Storm surge is a wind-driven effect that occurs when strong winds push water onshore, causing water levels to steady reserver the course of several hours. Recent research has shown that meteotsunamis are more common than previously thought and suggests that some past events may have been mistaken for other types of coastal floods, such as storm surges or seiches, which also tend to wind-driven.”
That statement brought up another relatively unknown term seiche. The National Ocean Service of The National Oceanic and Atmospheric Administration (NOAA) defines seiche as ” a standing wave oscillating in a body of water.” They are usually caused by strong winds and rapid changes in air pressure that push water from one end of a body of water to another. When the wind subsides the water retreats back to its original side of the body of water. I know you were anxious to know that difference.
After digesting all of this information it should be obvious that you should always check weather forecasts when planing to be on a lake. Even a small-scale meteotsunami can swamp a boat putting the occupants in danger.
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