A SPECTACULAR case of upwelling has occurred on Lake Michigan! The above graph is the water temperature at the Ludington buoy. The water temperature at the buoy was 65° at 4:40 pm yesterday (9 22 21) Just 3 hours and 10 minutes later, the water temperature was 42°. As I write this Thu. PM – the water temp. at the buoy is 40° – that’s just 8° above freezing! And it’s not just at Ludington…
Here’s the graph of the water temp. at the Port Sheldon Buoy near Holland MI – here the water temp. fell from 69° at 3:40 pm on 9/22. Twelve hours later, the water temp. was down to 47° and as I write this Thu. PM, it’s down to 43°.
Lake Michigan is a deep lake (923 feet at its deepest point NW of Manistee). While surface water warms in the summer, the bottom of the lake remains at at temperature of around 40°. When we get a strong and or prolonged offshore wind, it can blow the warmer surface water out toward the middle of the lake. Colder water then rises to the surface. Water temperatures will warm back up with the wind turns back onshore.
Same story at the South Haven buoy (see graph above).
This is a satellite pic. taken Fri. AM. The lighter colored water near the Michigan shore is the cold surface water that has come up from the bottom of the lake. There has not been any upwelling at the mid-Lake Michigan buoy, where water is darker. The water temperature at the mid-lakebuoy is still 67°.
Wave height peaked at 14.8 feet at the Michigan City IN buoy at 8:50 pm Wed. Waves there were still at 9.2 feet at mid-afternoon Thursday. At the buoy, the wind was steady at about 30 mph for 24 hours with a peak gust of 45 mph.