Great pictures Thursday from space showing a classic lake breeze near Lake Superior.
Look at the photos below. You can see the areas over western Lake Superior and the surrounding land areas are largely cloud free, except for an area of fog on the lake near Grand Marais.
Looking inland you can see a distinct line of clouds. These are cumulus clouds forming along the lake breeze front. Images are courtesy of the University of Wisconsin Madison MODIS page.
1000 meter resolution MODIS view of Lake Superior Thursday shows cloud free areas near the west end of the lake.
(click on photos for bigger images)
Higher resolution (250 meter) MODIS view. Note the distinct line of cumulus inland paralleling the North Shore.
Arrows on the right show cool dry stable wind flow coming off Lake Superior.
Cumulus cannot develop in this stable air mass. These are the cloud free zones. Arrows from the left show wind flow from the other side. A “convergence zone” is created where the two air flows meet. This is the lake breeze front. Since the air has nowhere to go but up, cumulus clouds form as the air rises.
Lake breezes are caused by temperature differences over land and water. In this case, cool air over Lake Superior is dense and pushes inland during the day as the land heats up.
Thursday’s surface map shows the wind direction and temperature differences. Notice how stations near Lake Superior are in the 60s while areas inland are in the lower 80s, nearly 20 degrees warmer!
In Chicago we always forecast “cooler by the lake” on spring and summer days like today. Thursday you could feel it in the air and see the effects from space near Lake Superior.