Thursday, November 4, 2010

Lake Michigan enhanced convection last night

I wanted to quickly point out some interesting occurrences over Lake Michigan last night. As a blast of cold air came down out of Canada and chilled surface temperatures into the 30s across surrounding coastal areas of Lake Michigan, the water surface temperatures remain in the middle 50s. This warmer surface temperature, coupled with much colder air blasting down aloft created an area of enhanced low level instability over the lake, very similar to what we would see in a lake effect snow event. You take that cold air mass aloft and lift it over the already cold 35F temperatures of the land surface and your temperature change with height as you go up is negligible when it comes to achieving any kind of instability, and unable to support convection. However, take that same cold air mass and move it over the water surface, which is about 20F degrees warmer than the land, and suddenly your low level lapse rates increase rapidly.

A few convective cells were able to tap into this area of enhanced low level juice and maintain themselves for quite some time as they passed SSE across the lake, even producing lightning at time, and showing the possibility of some small hail production.

I archived a couple meso-analysis maps, as well as a radar image of one of the more intense cells occurring a little before midnight.

Radar image of the storm over SE Lake Michigan. The green triangle indicated the potential for some small hail in the updraft.

Low level lapse rates bullseyed over southern Lake Michigan at 8 degrees C/km.

And then the lifted index maxima over the same area.

RUC analysis also indicated the possibility of surface based cape of 300-400 j/kg in the same area.

The storm quickly vanished as it moved ashore into the colder surface temperatures where instability was null.

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