PICTURE OF THE MONTH: Satellite View of a Lake-Effect Snowstorm

Abstract

The lake effect on snowfall has been of great interest to meteorologists for many years. Earlier work by Sheridan (1941) and Wiggin (1950) showed that cold arctic air flowing across relatively warm open water such as Lakes Erie and Ontario picks up vast amounts of moisture and heat. This is most pronounced during the early winter months when there is a large air-lake temperature difference. Heating of the lowest layer of arctic air produces convection that can result in heavy snowfall to the lee of the lakes.Later, a group of scientists under the direction of Dr. George McVehil made a study (McVehil et al. 1967) on the lake effect and agreed with these earlier ideas, but further concluded that initial air mass stability, height, and strength of air inversions and large-scale vorticity are important factors in determining the extent of lake-induced snow. Lavoie (1968) tested several of these ideas in his model of mesoscale lake-effect storms, found good agreement with earlier results, and observed that the most intense band of convergence was created when the average wind direction below 850 mb was 250°-280" with little shear but with large vertical gradient. He did, however, have diaculty explaining the strong vertical motions associated with the most severe storms of this type. Jiusto et al. (1970) made an extensive investigation of this type of snowstorm, with strong emphasis on determining what mechanism controlled the intensity and amount of snowfall to the lee of lakes. Conclusions drawn from this study supported earlier work, but added a t least one important new idea. Jiusto found that a severe snowstorm occurred when there was an upper level shortwave trough located west of the heavy snow area. This shortwave trough was so positioned that there was positive vorticity advection (on an isentropic surface) east of the trough over the lake area where other criteria had been met and conditions were ripe for heavy snowfall.The satellite pictures in figures 1A and 1B show the band of clouds, @ to @, associated with a severe snowstorm to the lee of Lake Erie on Nov. 23, 1970. The cloud band appears to form near the central portion of the lake. The winds were moderately strong from the west-southwest as cold arctic air moved across the relatively warm lake. A rapidly moving front passed Buffalo, N.Y., during the evening of November 22 and was located just off the east coast ( fig. 2) by the time the satellite picture was taken at 0941 EST on November 23. The clouds associated with a portion of this front extend northeast from point @ in figure 1A. At 0700 EST on November 23, the National Meteorological Center (NMC) FIGURE 1.-(A) ESSA 8 APT photograph at 0941 EST on Nov. 23, 1970; (B) an enlargement of the area enclosed by the dashed line in (A).over Lake Michigan with positive vorticity advection (on a constant pressure surface) extending from just east of the trough northeastward across Lake Erie. These conditions meet many of the aforementioned requirements for a severe lake-induced snowstorm. The following is a...

Comparison of Observations with Idealized Model Results for a Method to Resolve Winter Lake-Effect Mesoscale Morphology

“…These studies described 18 MV events that occurred over Lakes Superior, Huron, and Michigan. Studies of SB events include Sykes (1966), Peace and Sykes (1966), Ferguson (1971), Holroyd (1971), Passarelli and Braham (1981), Braham and Kelly (1982), Ballentine (1982), Niziol (1982), Braham (1983), Schoenberger (1986a,b), Elsner et al (1989), Byrd et al (1991), Burrows (1991), Wagenmaker et al (1997), Ballentine et al (1998), and Laird et al (2003a). Information was collected from these studies for 31 SB events occurring within the entire Great Lakes region.…”

Meteorological satellite accomplishments

“…Heavy snow showers can occur in the lee of the Great Lakes when cold air passes over the relatively warm water. Ferguson (1971) showed that ESSA 8 photographs were useful for depicting the position of the clouds associated with these showers as well as for locating clouds that indicated positive vorticity advection which can enhance shower intensity.…”