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Lake Breeze Weather - Page 2

© Keith C. Heidorn

If you are standing near the shoreline of a large lake such as Lake Michigan, you should be able to feel the lake breeze front pass you. The air becomes notably cooler (and often perceptibly moister), the wind direction shifts, and a gusty breeze arises from the direction of the lake.

The lake breeze frontal zone is quite narrow (1-2 km wide) and often moves slowly enough that you can walk back and forth across it from the warm land air to the cool lake air, a most interesting experience. How far the lake breeze front penetrates inland depends on the temperature contrast between the land air temperature and that over the lake. Meteorologists have recorded inland penetration as far as 40 kilometres (25 miles), but 16 km (10 miles) is more typical.

At the upper levels of the lake breeze front, cumulus clouds often form and, when the conditions are right, thunderstorms can pop up along the frontal zone.

Lake Breeze Thunderstorms

Thunderstorms are triggered by a wide variety of atmospheric interactions, including those along the lake breeze front. The development of thunderstorms requires quantities of low-level moisture, deep layers of conditional atmospheric instability which when triggered allow the development of towering cumulonimbus clouds, and significant upward vertical motion which provides the trigger. A hot, humid summer day can usually provide the first two ingredients, but the third ingredient is often missing. This can be provided by the lake breeze front. Rising air motions at the frontal boundary induce the lift required to initiate thunderstorm development

The region of southwestern Ontario along a line from Detroit to Toronto is bounded by Lake Huron to the north and Lake Erie to the south. Lake breeze fronts often move in from both lakes and approach each other. The two frontal advances push the warm, humid land air into a narrow, and often stationary, convergence zone, forcing it to rise upward. This convergence first forms bands of cumulus clouds, some of which can grow into lake breeze thunderstorms when conditions are ripe.

Recently, scientists in Ontario, Canada documented a severe thunderstorm triggered by lake breezes flowing off Lakes Erie and Huron and converging over southwestern Ontario.

During the field research study, named ELBOW, into lake breeze thunderstorms, meteorologists observed a thunderstorm born between the converging lake breeze fronts quickly grow into a severe storm in about 20 minutes. A spotter team experienced heavy rain, downed trees and flooded roads and fields from the storm. Local radar estimated that 200 mm (8 inches) of rain fell at the small crossroads community of Punkeydoodle Corners over a five-hour period from this stationary thunderstorm storm cell.

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