WINTER 1994 WEATHER AND ICE CONDITIONS FOR THE LAURENTIAN GREAT-LAKES

The Laurentian Great Lakes developed their most extensive ice cover in over a decade during winter 1994 [December-February 1993/94 (DJF 94)] . Extensive midlake ice formation started the second half of January, about 2 weeks earlier than normal. Seasonal maximal ice extent occurre d in early February, again about ?, weeks earlier than normal. Winter 1994 maximum (normal) ice coverages on the Great Lakes are Lake Superi or 96% (75%), Lake Michigan 78% (45%), Lake Huron 95% (68%), Lake Erie 97% (90%), and Lake Ontario 67% (24%). Relative to the prior 31 winte rs (1963-93), the extent of seasonal maximal ice cover for winter 1994 for the Great Lakes taken as a unit is exceeded by only one other win ter (1979); however, other winters for individual Great Lakes had simi lar maximal ice covers. Anomalously strong anticyclonic circulation ov er the central North Pacific (extending to the North Pole) and an abno rmally strong polar vortex centered over northern Hudson Bay combined to produce a circulation pattern that brought frequent air masses of A rctic and polar origin to the eastern third of North America. New reco rds were set for minimum temperatures on 19 January 1994 at many locat ions in the Great Lakes region. A winter severity index consisting of the average November-February air temperatures averaged over four site s on the perimeter of the Great Lakes (Duluth, Minnesota; Sault Ste. M arie, Michigan; Detroit, Michigan; and Buffalo, New York) indicates th at winter 1994 was the 21st coldest since 1779. The unseasonably cold air temperatures produced much-above-normal ice cover over the Great L akes and created problems for lake shipping. Numerous fatalities and i njuries were attributed to the winter weather, which included several ice and snow storms. The much-below-normal air temperatures resulted i n enhanced lake-effect snowfall along downwind lake shores, particular ly during early to midwinter, prior to extensive ice formation in deep er lake areas. The low air temperatures were also responsible for reco rd 1-day electrical usage and multimillion dollar costs associated wit h snow removal, U.S. and Canadian Coast Guard operational assistance t o ships beset in ice, damage to ships by ice, damage to public and pri vate property by river ice jams and associated flooding, frozen underg round water pipes, and damage to fruit trees.