GRAND RAPIDS, Mich. (WOOD) — If you’ve lived in Michigan for a while, you already know that the Great Lakes can have a profound impact on the weather — lake effect snow, for example.
But there’s another phenomenon that you might not be familiar with — the severe weather buffer the Great Lakes provide.
During the spring when lake temperatures are still very cold, the Great Lakes can knock down the strength of thunderstorms and sometimes eliminate them altogether.
To understand this phenomenon, you need to understand the three key elements a thunderstorm needs: moisture, instability and a lifting mechanism, like a cold front or lake breeze.
Thunderstorms are giant masses of water that can reach heights twice as tall as Mount Everest. The “fuel” for thunderstorms is warm, moist air, but the heat that is needed gets broken down when a strong to severe thunderstorm crosses the cold Great Lakes.
Thunderstorms that form in Wisconsin and Illinois during spring may mature in temperatures that are in the 70s, 80s and even 90s. But when they cross Lake Michigan, the difference between the air temperature that they formed in and the water temperature can be as much as 30 to 40 degrees. As the thunderstorms ingest the colder air over the 60 to 90-mile width of Lake Michigan, they weaken and possibly dissipate.
This year, Lake Michigan’s average surface water temperature is running approximately 8 degrees colder than last year, making Lake Michigan a stronger buffer for severe storms.
The effect is evident when looking at severe weather reports of hail, wind and tornadoes for 2017 so far.
Michigan has only received 54 reports of severe weather, as of June 1. None of those happened in May.
We are nearly half-way through the year, and the National Weather Service in Grand Rapids has issued only nine severe weather/tornado warnings. Surrounding states have reported four to eight times more severe weather incidents.
The Great Lakes buffer doesn’t work in every situation.
It will break down as surface water temperatures naturally warm up during late spring to summer.
Sometimes thunderstorms are not surface-based storms; they generate their instability at a higher level in the troposphere. We call these thunderstorms “elevated” since their fuel source is a layer above the planetary boundary layer. An example of this is with warm fronts, where the warmer air first arrives aloft, forming an elevated layer of instability.
Also, some systems can be so dynamically strong that Lake Michigan has no effect whatsoever. That was the case during the deadly May 31, 1998 derecho that devastated communities from North Dakota to the East Coast.
The effect of the Great Lakes on weather is a case-by-case environmental challenge for forecasters — that’s where Storm Team 8’s experience comes in to play.
The team’s expertise will be tested again this weekend when a cold front and area of low pressure skirts across the Great Lakes Saturday and Sunday. Tune into Storm Team 8 as we track the storms that will likely develop in Wisconsin into Michigan Saturday evening.
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