GRAND RAPIDS, Mich. — It's a bright summer day in West Michigan. Temperatures are in the 70s, but we have had plenty of 80 and 90 degree days over the past few weeks. Sounds like it's time to enjoy the lake on a day where the sand won't be so scolding hot.
You get to the beach, pick the perfect spot, and now you're set to head in for a dip.
YIKES!
Instead of a warm relaxing swim, you are greeted by 40 to 50 degree waters that send a chill through your entire being!
You run back to your spot on the sand, and bury yourself in its warm embrace.
What happened?
Let's explain!
The Forecast:
While it has been a hot summer in West Michigan, and the lakes have been very warm as a result, all of that changed earlier this week. Strong and persistent winds from the north began blowing over Lake Michigan. You may think this pulled down cooler water from the north, but this unusually cold water actually came from deep within the lake's depths.
The winds from the north are the cause, but the how is slightly more complex.
How It Happens:
While common sense would lead you to think winds from the north will cause water to flow to the south, this isn't actually how things work. When you are looking at a body of water as large as Lake Michigan over the 300+ miles of north to south distance something else comes into play, the Coriolis Effect.
This is an effect on moving objects created by the rotation of the earth. Over long distances it causes a force to the right of the direction of travel for an object in the northern hemisphere. This force is to the left of the direction of travel in the southern hemisphere.
What this means for waters on Lake Michigan is that a persistent north wind will actually send waters off to the west. This process is called the Ekman spiral.
As the flow across the lake is now heading toward the west, the warm surface water gets replaced by water from below in a process known as upwelling. While waters at the surface of Lake Michigan can be in the 70s and 80s, waters deeper in the lake are commonly in the 40s and 50s. Through upwelling this chilly water will eventually make it to the surface, replacing the warmer water that has moved toward the west.
The good news for anyone looking to head to the beach in the coming weeks is that this process has now backed off since winds from the north are no longer in play. Additionally, temperatures over the weekend will rise back to the mid to upper 80s, and water temperatures along the lake are expected to rise.
In fact, water temperatures in the 70s are already starting to return, but still many spots remain in the 50s.
If you ever have a question about the weather around the world or here in West Michigan you can always ask by emailing me at: MBehrens@13OnYourSide.com.
You can also ask on social media via Facebook at Meteorologist Michael Behrens, Instagram @MikeBehrensWX, or Twitter @MikeBehrensWX.
Get ready to enjoy the lake again as things warm up this weekend, just make sure to remember your social distancing!
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