here’s my theory on lake st clair thermals:

unlike sandy areas like for instance tawas, thermals at metro & blue lagoon dont depend too much on the sun, thermals go off cloudy or sunny, colder or warmer weather.

so my theory is this, that if you have 2 or more days of west winds followed by a day of south wind, that wind will turn into a thermal.

If you look at the shipping lane for lake st clair it goes from the flats down to the detroit river bisecting the lake. Now the thing about this shipping lane is that it is full of very cold lake huron water.

So what the 2 days of western winds do is push the top of the water over to canada, and then the water has to go somewhere so it then folds under, and at metro this means that the water is upwelling from the bottom of the lake.

But you need a bit of time for this upwelling to set in so that the cold lake huron water can get all the way to metro.

If this does happen, then you’ll have a nice thermal. But also notice that because the wind shifted from west to south, you aren’t going to have another thermal, so normally when you get a thermal at metro it is only for a day.

so it takes about 2 days to “recharge” this cold water so a thermal can happen and then if the wind shifts south, boom, thermal.

I was thinking about thermals all last year, because for one they do not show up on the wind gauges (the thermal is pretty narrow, and right next to shore).

So that’s my theory. Eastern winds the day before turn off thermals, south winds use up the cold water powering the thermals while western winds recharge thermals.

part of this theory is that while you can get nice north winds at the blue lagoon you never get a thermal because it’s too far from the shipping lane, by the time the lake huron water gets there, it’s all warmed up.