Mesoscale model simulation of the 4-5 January 1995 lake-effect snowstorm

The Pennsylvania State University-NCAR Mesoscale Model version 5 (MM5), run ning on a triply nested grid, was used to simulate the intense lake-effect snowstorm of 4-5 January 1995. On the finest grid (5-km resolution) centere d over Lake Ontario, MM5 produced a snowband in the correct location having a size and orientation similar to the band observed by the WSR-88D radar a t Binghamton, New York. The simulated precipitation distribution agreed wel l with the observed snowfall during the first 18 h during the time when the snowband was in its midlake position extending into the Tug Hill plateau. During the last 12 h of the simulation, when both the observed and simulate d snowbands lay along the south shore of Lake Ontario, the simulated snowfa ll at inland locations of Oswego County was less than observed. During this period, the simulated precipitation over Lake Ontario appeared to be exces sive, although no radar data or ground truth was available to confirm this. Two short-wave troughs interacted with the Lake Ontario snowband. The tempo rary weakening of the snowband after passage of the first trough was simula ted well in the triply nested MM5 simulation. A comparison was made between the operational Eta Model run and an MM5 simulation on a grid of comparabl e resolution (80 km) in handling the passage of the second more vigorous sh ort wave. Both the Eta and the 80-km MM5 were a few hours too early with th e passage of this trough. The nested-grid version of MM5 was correct in sim ulating the rapid southward movement of the band to Oswego County just afte r the second trough moved east of the lake. However, because of the timing error with the trough, MM5 was premature by a few hours in the southward sh ift of the snowband. Results on the 15-km grid indicated that moisture plumes from Lake Huron an d Georgian Bay fed into the Lake Ontario band. In the lowest few hundred me ters, these plumes were deflected around the Shelburne Plateau, which lies between Lake Huron and Lake Ontario. Future research will focus on interact ions between circulations downwind of Lake Huron and snowbands that form ov er Lake Ontario. The results of the 4-5 January 1995 simulation are sufficiently encouraging to suggest that MMS may be used to make real-time forecasts of lake-effect snowstorms. The lead author is participating in a COMET cooperative projec t to provide lake-effect snow forecasts, in GEMPAK format, to the National Weather Service Forecast Offices at Buffalo and Binghamton using a 20-km ne sted grid over Lakes Huron, Erie, and Ontario. Despite relatively coarse re solution, MM5 has produced useful predictions of snowband location and move ment during the 1996/97 and 1997/98 lake-effect snow seasons.