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Abstract
The Pennsylvania State University–NCAR Mesoscale Model version 5 (MM5), running 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) centered 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 at Binghamton, New York. The simulated precipitation distribution agreed well 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 simulated snowbands lay along the south shore of Lake Ontario, the simulated snowfall at inland locations of Oswego County was less than observed. During this period, the simulated precipitation over Lake Ontario appeared to be excessive, although no radar data or ground truth was available to confirm this.
Two short-wave troughs interacted with the Lake Ontario snowband. The temporary weakening of the snowband after passage of the first trough was simulated 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 comparable resolution (80 km) in handling the passage of the second more vigorous short wave. Both the Eta and the 80-km MM5 were a few hours too early with the passage of this trough. The nested-grid version of MM5 was correct in simulating the rapid southward movement of the band to Oswego County just after 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 shift of the snowband.
Results on the 15-km grid indicated that moisture plumes from Lake Huron and Georgian Bay fed into the Lake Ontario band. In the lowest few hundred meters, these plumes were deflected around the Shelburne Plateau, which lies between Lake Huron and Lake Ontario. Future research will focus on interactions between circulations downwind of Lake Huron and snowbands that form over Lake Ontario.
The results of the 4–5 January 1995 simulation are sufficiently encouraging to suggest that MM5 may be used to make real-time forecasts of lake-effect snowstorms. The lead author is participating in a COMET cooperative project to provide lake-effect snow forecasts, in GEMPAK format, to the National Weather Service Forecast Offices at Buffalo and Binghamton using a 20-km nested grid over Lakes Huron, Erie, and Ontario. Despite relatively coarse resolution, MM5 has produced useful predictions of snowband location and movement during the 1996/97 and 1997/98 lake-effect snow seasons.
Abstract
The Pennsylvania State University–NCAR Mesoscale Model version 5 (MM5), running 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) centered 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 at Binghamton, New York. The simulated precipitation distribution agreed well 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 simulated snowbands lay along the south shore of Lake Ontario, the simulated snowfall at inland locations of Oswego County was less than observed. During this period, the simulated precipitation over Lake Ontario appeared to be excessive, although no radar data or ground truth was available to confirm this.
Two short-wave troughs interacted with the Lake Ontario snowband. The temporary weakening of the snowband after passage of the first trough was simulated 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 comparable resolution (80 km) in handling the passage of the second more vigorous short wave. Both the Eta and the 80-km MM5 were a few hours too early with the passage of this trough. The nested-grid version of MM5 was correct in simulating the rapid southward movement of the band to Oswego County just after 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 shift of the snowband.
Results on the 15-km grid indicated that moisture plumes from Lake Huron and Georgian Bay fed into the Lake Ontario band. In the lowest few hundred meters, these plumes were deflected around the Shelburne Plateau, which lies between Lake Huron and Lake Ontario. Future research will focus on interactions between circulations downwind of Lake Huron and snowbands that form over Lake Ontario.
The results of the 4–5 January 1995 simulation are sufficiently encouraging to suggest that MM5 may be used to make real-time forecasts of lake-effect snowstorms. The lead author is participating in a COMET cooperative project to provide lake-effect snow forecasts, in GEMPAK format, to the National Weather Service Forecast Offices at Buffalo and Binghamton using a 20-km nested grid over Lakes Huron, Erie, and Ontario. Despite relatively coarse resolution, MM5 has produced useful predictions of snowband location and movement during the 1996/97 and 1997/98 lake-effect snow seasons.
