Classification and Conceptual Models for Heavy Snowfall Events over East Vancouver Island of British Columbia, Canada

Abstract

he East Vancouver Island region on the west coast of Canada is prone to heavy snow in winter due to its unique geographical setting, which involves complicated interactions among the atmosphere, ocean, and local topography. The challenge for operational meteorologists is to distinguish a weather system that produces extreme snow amounts from one that produces modest amounts in this region. In this study, subjective, objective, and hybrid classification techniques are used to analyze the characteristics of 81 snowstorms observed in this region over a 10-yr period (2000?09). It is demonstrated that there are four principal weather patterns (occluded front, lee low, warm advection, and convective storm) conducive to heavy snow in East Vancouver Island. The occluded front pattern is the most ubiquitous for producing snow events, while the lee low pattern is the most extreme snow producer that poses the biggest forecast challenge.Based on the identified weather patterns and a further investigation of five key weather ingredients, four conceptual models are developed to illustrate the meteorological processes leading to significant snowfalls in East Vancouver Island. These conceptual models have the potential to help meteorologists better understand and identify weather systems that would produce heavy snowfalls in this region and, therefore, improve forecasting and warning performance.