Lake Effect: Tales of Large Lakes, Arctic Winds, and Recurrent Snows
Snowbelts form downwind from the Great Lakes, a prime source of moisture, and their boundaries can vary markedly from year to year. Air flow is generally from the north, the northwest, or the west. Topographic obstacles such as Tug Hill (east of Lake Ontario) and the Keewenaw Peninsula cause the moist air to rise, cool, and produce heavy amounts of snow.
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Lake-effect snow is deposited by narrow bands of clouds formed when cold, dry arctic air passes over a large, relatively warm inland lake. Snow bands attached to one of the Great Lakes, or even the Great Salt Lake or Hudson Bay, can produce an intense “white out” lasting from a couple of minutes to two days. Television meteorologists call this the “lake-effect snow machine” because a slight shift in wind direction can shut down the snow suddenly, like flicking a light switch. With perhaps only half the water content of regular snow, lake snow is typically light, fluffy, and relatively easy to shovel. And because long stretches of gray days with persistent flurries are the norm, shoveling is a near-daily activity in the snowbelts, where whimsical weather is notorious for disrupting transportation, closing schools, canceling events of all types, and occasionally collapsing old or poorly designed buildings. Intriguing stories of the lake effect’s quirky behavior and diverse impacts include widespread ignorance of the phenomenon in the nineteenth and early twentieth centuries, before a network of systematic observers had collected several decades of data worth mapping, and the advent of reliable short-term predictions based on satellites, Doppler radar, and computer models.
Satellite image shows how winds from the northwest control the formation and direction of snow bands formed on Lakes Superior (upper left) and Michigan (center). Notice the multi-lake snow bands crossing Lake Huron and Georgian Bay (lower right). Multi-lake snow originating on the upper lakes enhances lake-effect snow off the lower lakes.
I’ve written this book for two audiences: Great Lakes residents who want to understand the lake-effect phenomenon and its implications more fully and nonresidents misinformed by a media stereotype of ceaselessly brutal winters. What I intend as a comprehensive and engaging narrative fits nicely into seven chapters, each with a telling one-word title: Recipe (chapter 1) outlines the basic physics essential to understanding what follows, Discovery (chapter 2) explores the slow cartographic recognition of lake-effect snow as a distinctive meteorological phenomenon, Prediction (chapter 3) examines the evolution of forecasting strategies, Impacts (chapter 4) limns societal effects and coping strategies, Records (chapter 5) investigates the collection and use of snowfall data and questions the national obsession with extreme weather, Change (chapter 6) looks at historical trends in snowfall and the regional implications of global warming, and Place (chapter 7) identifies seasonality as a key component of local economies and regional culture.
Table of Contents
In 1894 Mark Harrington, chief of the U.S. Weather Bureau, published his Rainfall and Snow of the United States. An "atlas" supplement accompanied his 80 pages of text and tables. Only one of the supplement's 23 charts addresses snowfall, and it consists of eight small maps like this one, each covering one month, October through May. In 1896 a textbook by Frank Waldo included a map of average annual snowfall, presumably based on Harrington's maps or data. Its only snowbelt was in the U.P.
Brooks based his snowfall map on a network of 159 stations, all in the eastern United States and all with 15 years of continuous data from July 1895 through June 1910. Brooks was the first climatologist to discover the Great Lakes snowbelts. His other contributions include founding the American Meteorological Society.