Various type ofwinter storms occur over Canada and produce major impacts on society. Canada is subjected to extra-tropical cyclones with ail their embedded structures, as well as blizzards, mountain-induced storms, lake effect storms and polar lows. Many of thèse storms are accompanied by heavy précipitation in thé form of snow or freezing précipitation, bitterly cold conditions, strong winds, and blowing snow. The occurrence and nature of thèse storms are discussed in this review article. RÉSUMÉ On examine la présence et la nature des nombreux types de tempêtes d'hiver qui touchent le Canada et y occasionnent des impacts importants sur la société. Le pays est éprouvé par les cyclones extra-tropicaux et tous leurs éléments, ainsi que par les blizzards, les tempêtes de montagnes, les effets de lac et les dépressions polaires. Des précipitations abondantes, sous forme de neige ou de verglas, des froids cinglants, des vents forts et de la poudrerie élevée sont souvent associées à ces tempêtes.
ABSTUACTCoastally trapped stratus events involve the alongshore*propagation of a lowlevel mesoscale ridge of high pressure, and generally occur only during summer in British Columbia. During these events, a body of cool dense air overlain by stratus cloud propagates northwards in the marine layer. This situation results because Coriolis efsects trap the dense air against the coastal mountains and an inversion layer prevents vertical leakage of energy.Detailed analysis of a late summer event and comparison of the observations with available theory are presented. It is shown that the theoretical speeds for the event agree reasonably with observations except near major topographic variability. The theoretical trapping scale (internal Rossby radius) computed from the sounding data matches the observed width of the coastal stratus seen on satellite imagery. It is found that the properties of the event may be accounted for by the propagation in the marine layer of a coastally trapped intrusion with steep leading edge or shock. Attention is drawn to the role that the complex topography of Vancouver Island plays in influencing the propagation of the event, and some suggestions for forecasting these phenomena are made. RI%UMICLes cas de stratus &tiers pi&g&s sont dus h la propagation d'une c&e de pression de mesoechelle a bas niveau le long des c&es; en Colombie-Britannique, ils ne se presentent generalement que durant 1 'ttb La force de Coriolis, qui pibge l'air dense contre les montagnes c&&-es, et la couche d'inversion qui empeche la perte verticale d'energie, poussent une masse d'air, dense et frais, recouverte par une couche de stratus ir se d&placer vers le nord dans la couche marine.On presente 1 'analyse detaillee d 'un cas de fin d'ett! et la comparaison des observations aux theories disponibles. Sauf pres des principaux accidents topographiques, les vitesses 'Present affiliation:
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