Embedded Files
Southwest Michigan AMS/NWA
25 April 2019
West Michigan Aviation Academy
5363 44th St
Grand Rapids, MI 49512
Vice President Cort Scholten called the meeting to order at 7PM. A total of 16 people were in attendance. All of the board members were present.
President Warren Wheeler asked for a show of hands to approve asking Dr. Maria Molina, currently from Central Michigan University, to speak to our group over the
summer about her recent expedition to Antarctica. The members present approved the idea. More information will be coming soon about when this can be scheduled.
Treasurer William Marino gave the treasurer’s report. As of April 25, the club has funds of $1037.11 and 15 paid members.
Our speaker for the evening was Bob Dukesherer, lead forecaster and marine program leader with the local National Weather Service Office. His talk was about a fairly recently studied
phenomena called a meteotsunami. A meteotsunami is a tsunami type of wave in a large lake that is generated by a meteorological event instead of a seismic event. It differs from a seiche in that it is a wave that propagates through a lake and can cause very rapid water level changes in a short period of time. A seiche is a sloshing of water back and forth in a lake basin with much slower changes in water level. The image below represents the difference.
The following photo is of the meteotsunami at Ludington, MI on April 13, 2018. In this photo, the water level dropped 8 feet and then rose 7 feet above the previous level in
about 5 minutes. You can see how anyone on the pier would be in serious trouble.
Much additional research will be needed before we can forecast the actual occurrence of a meteotsunami, however, there are some general conditions that can alert
forecasters to the possibility of such an event.
Springtime events occur in March, April and May. They occur north of a warm or stationary front and often occur out ahead of strong upper level troughs emerging from
the Rockies. The convection that produces them forms in the Plains states overnight and usually reaches Lake Michigan early in the morning to near midday. Summer
events usually occur with strong squall lines.
The thunderstorms, and an accompanying atmospheric pressure jump of at least 3 to 5 millibars in one minute, need to be moving at between 58 and 75 mph forward speed
across Lake Michigan to set up a resonance between the atmosphere and the lake, which creates the fast moving, long lasting wave. Slower thunderstorm movement or a
weaker pressure jump will not create a meteotsunami on Lake Michigan.
Since such an event cannot be well forecast, it is crucial for swimmers and boaters to pay very close attention to all NWS marine warnings and advisories, even if skies are
clear at the time.
The meeting was adjourned at 8:20PM. The next meeting will likely be on Thursday May 30. More information forthcoming soon.
Respectfully submitted
Craig James Woods
Secretary
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