UBC Theses and Dissertations
The climatology and meteorology of windstorms that affect southwest British Columbia, Canada, and associated tree-related damage to the power distribution grid Read, Wolf Anthony
High-wind generating extratropical cyclones routinely strike southwest British Columbia. Improved understanding of these storms could help mitigate damage to electrical and other infrastructure. All independent windstorms from 1964-2012 were determined using the Victoria, Vancouver and Abbotsford hourly surface observations. For all qualifying events 1994-2012, storm tracks and central pressure tendencies were determined using surface maps. Storms were classified by peak wind direction and track location. Detailed synoptic and mesoscale maps were made and analyzed for eight strong windstorms. BC Hydro Corporation distribution-system power outage data from October 2005 to August 2009 was used in an analysis of tree-related line faults within a 50 km radius of Vancouver. For events with peak speed >40 km h-¹, maximum wind, gust, wind direction, storm total precipitation and storm duration were used to predict line faults using linear and Poisson regression. Data from four strong windstorms was used in an hour-by-hour analysis of wind speed and line faults. There were two dominant categories of cyclonic windstorm in this region: westerly and southeasterly. Cyclone tracks had much variation. However, compared to westerly storms, southeasters tended to have a stronger northward component to their direction of motion and tended to pass closer to the study region. Most low-pressure centers weakened rapidly as they moved inland and, as a result, peak winds typically occurred at landfall. The exception is for westerly storms where the wind is dependent on an onshore pressure gradient behind the low. There was moderately strong linear relationship between peak two-min wind or five-s gust and the frequency of distribution line faults. Poisson regression models indicate the potential for widespread grid damage for wind speeds approaching the historic 12 Oct 1962 windstorm. On average, southeasters cause approximately 1.5-1.9 times more line faults than westerly windstorms. A few-hour lag in the occurrence of line faults relative to observed wind speed, perhaps due to reporting delays, was observed. This has not been reported before and could confound analyses that use daily data. The modeling done here could be expanded to forecast storm impacts to the power grid using numerical weather prediction model inputs.
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