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- Title
Synoptic-Scale Environments Conducive to Orographic Impacts on Cold-Season Surface Wind Regimes at Montreal, Quebec.
- Authors
Razy, Alissa; Milrad, Shawn M.; Atallah, Eyad H.; Gyakum, John R.
- Abstract
Orographic wind channeling, defined as dynamically and thermally induced processes that force wind to blow along the axis of a valley, is a common occurrence along the St. Lawrence River Valley (SLRV) in Quebec, Canada, and produces substantial observed weather impacts at stations along the valley, including Montreal (CYUL). Cold-season observed north-northeast ( n == 55) and south-southeast ( n == 16) surface wind events at CYUL are identified from 1979 to 2002. The authors partition the north-northeast wind events into four groups using manual synoptic typing. Types A and D ('inland cyclone' and 'northwestern cyclone') are associated with strong lower-tropospheric geostrophic warm-air advection and near-surface pressure-driven channeling of cold air from the north-northeast, along the axis of the SLRV. Type C ('anticyclone') shows no evidence of a surface cyclone and thus is the least associated with inclement weather at CYUL, whereas type B ('coastal cyclone') is associated with predominantly forced wind channeling along the SLRV. Type D of the north-northeast wind events and all south-southeast wind events exhibit similar sea level pressure patterns. The respective magnitudes of the pressure gradients in the Lake Champlain Valley south of CYUL and the SLRV play a large role in determining the favored wind direction. Soundings of the various event types illustrate substantial differences in temperature structure, with a large near-surface temperature inversion particularly prevalent in north-northeast events. The results of this study may provide guidance in forecasting winds, temperatures, and observed weather in and around the SLRV, given certain synoptic-scale regimes.
- Subjects
MONTREAL (Quebec); QUEBEC (Province); WIND forecasting; WIND measurement -- Statistical methods; WIND speed measurement; OROGRAPHIC clouds
- Publication
Journal of Applied Meteorology & Climatology, 2012, Vol 51, Issue 3, p598
- ISSN
1558-8424
- Publication type
Article
- DOI
10.1175/JAMC-D-11-0142.1