Inflow and outflow through the Sea-to-Sky Corridor in February 2010: lessons learned from SNOW-V10

Southerly inflow and northerly outflow through the Sea-to-Sky Corridor in southern British Columbia not only affect the surface winds, but also precipitation and visibility in the areas of Howe Sound and Whistler. The Science and Nowcasting of Olympic Weather for Vancouver 2010 (SNOW-V10) project provided a unique opportunity for improving our understanding and ability to forecast these orographic winds. In this study, we analyzed the flow structures and evolutions through February 2010, using data from intensive observations and numerical weather prediction (NWP) models of all scales available through SNOW-V10. We focused on a few atypical episodes during the study period: a) a strong prefrontal southeasterly wind event in Howe Sound that began at 0700 UTC of 12 February, which could be predicted based on marine forecasters' rules of thumb, but was not obvious from the observed and model-predicted synoptic pressure pattern; b) an inflow event on 16 February, which was predicted by the NWP models, but was delayed to reach the surface by the precipitation-induced down-valley drainage flow; c) a low level jet that developed during 17-20 February, which had a clear diurnal cycle and an interesting semi-diurnal cycle. Physical mechanisms behind these phenomena are explored through further analyses. New conceptual models are proposed to improve the accuracy of operational forecasts.