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The Great Lakes: Storm Breeding Ground

© Keith C. Heidorn

The Anglo-Saxons called the eleventh month of the year: the winde-monath. In much of North America, particularly along the Canada-US border, the name is appropriate as well, for in November, many blustery storms follow a track southward from polar lands into eastern North America.

As autumn slips slowly into winter, the North American continent becomes besieged with storminess. In the northwest, the Aleutian Low anchors into its winter position in the Gulf of Alaska and sends wave upon stormy wave of wind and rain against the Pacific Coast. Across the continent, powerful Nor'easters form off the northern Atlantic Coast that lash the coast with a fierceness equal to hurricanes.

But our weather eye this month focuses on the Great Lakes region. Over the world's largest fresh water bodies, two storm tracks converge in November. One brings storms southward from Alberta. The second track pushes storms from the lee of the central Rockies north toward the Great Lakes. When cyclonic systems reach the region, the jet stream above and the warm Great Lakes waters below often induce an even more deadly spin in these storms.

Two major storm tracks cross the Great Lakes Basin in November

The Lake Mothers Superior, Michigan, and Huron in particular have given birth to many great November storms, and their toll on Great Lakes shipping has long been the subject of story and song. In The Wreck of the Edmund Fitzgerald, folksinger Gordon Lightfoot warned of the "bones to be chewed when the gales of November blow early." Although storms can sweep the Great Lakes during any month, November has been the most deadly. At least 25 killer November storms have struck the five Lakes since 1847. What then is the reason for this infamy?

The Great Lakes play a major role in determining the weather and climate around their basin. The main source for their large influence lies in their waters. Water, you see, gains or losses heat much slower than air or land surfaces. Thus, the large volumes of water filling the Great Lakes cool so slowly that the open near-surface water temperatures are out of step with the seasons by several months (shallow Erie cools fastest; deep Superior, the slowest). As autumn progresses, the lake waters therefore still retain much of their summer warmth, and during November those temperature contrasts are at their greatest.

In Autumn, the clash between the cold, dry air moving down from the Canadian North and the warm, moist air flowing up from the Gulf of Mexico forms great storm systems where they meet in the middle of the

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