Sea Fog
Serenely beautiful in a quiet little harbor, but potentially deadly to the small mariner, sea fog is a chilling enigma..literally! Warm land air blowing over a large and cold body of water will get foggy if the dew point of the land air is higher than the water temperature. The cold water chills the land air to below the dew point, condensing shallow but dangerous fog. The water temperature in Lake Superior -- largest, deepest and northernmost of the Great Lakes -- stays cold year-round: in the 40s Fahrenheit below surface in mid-lake, 50s on open water surfaces, and in summer may warm to the 60s in shallow, protected bays and harbors. In summer, dew points in the surrounding air may rise to the 70s F. When that warm and moist air moves over the lake, very dense fog often results. Before the era of shipboard radar and highly accurate nautical charts, fog caused killer Superior shipwrecks in all seasons.
Grand Marais MN (27 Jul 99) Looking W
(GPS)
