Upwelling causes Lake Michigan water temps to tumble

GRAND RAPIDS, Mich. (WOOD) — Brisk north to northeast winds have caused water temperatures to tumble along the Lake Michigan coast in West Michigan.

The graph above shows the water temperature at Ludington, Michigan. If you look at the raw data, the water temperature fell from 58.5 degrees at 5:30 p.m. Tuesday to 41.9 degrees Wednesday at 7:40 a.m. That's a drop of 16.6 degrees in 14 hours and 10 minutes.

Warm, dry weather prevalent in first half of October for Grand Rapids

This occurs through a process called "upwelling." The northeast wind pushes the warmer surface water away from the shore toward the middle of Lake Michigan. Colder water then rises to the surface. Here's another classic case of upwelling at Lake Michigan .

Above is a graph of the water temperature in Chicago. The scale is a bit different on the left side. The cool air mass has caused the surface water to cool, but not to the degree it has on the Michigan shore. Here in Chicago the water temperature fell from 65.3 degrees on Oct. 11 at 8 p.m. to 60.4 degrees Wednesday. That's a drop of 4.9 degrees in four days and 15 hours.

Storm Team 8 Forecast

With winds turning back to the southwest Thursday, the relatively warmer water should return to the Michigan shore.