The High-Wind Climatology of Vancouver and Abbotsford A Exploration of Contrasts Over a Small Spatial Scale, and Some Possible Regional Trends in Windstorm Frequency Wolf Read MSc Candidate in Forest Science University of British Columbia Overview Lower Mainland, BC, High-Wind Storms • Annual Frequency of windstorms at Vancouver and Abbotsford and the Pacific Decadal Oscillation (PDO) • Westerly windstorms at Vancouver compared to Abbotsford • Trends in Fraser River Valley outflow events (“Arctic outbreaks”) Definitions • Minimum High-Wind Criteria Storm: • 64 km/h (35-knot) 1-min wind* • 93 km/h (50-knot) 1-sec to 3-sec gust • Minimum Catastrophic High-Wind Storm: • 80 km/h (43-knot) 1-min wind • 113 km/h (61-knot) 1-sec to 3-sec gust • To be high-wind criteria, either wind or gust must meet the minimum value. Both are not required. * 63 km/h wind included due to conversion factors: 34-kt = 39.10 mph = 63 km/h 35-kt = 40.15 mph = 65 km/h Methods • Wind speed and direction data from Environment Canada, obtained from “Climate Data Online”. • Observation period: Jan 1955 - Jan 2008. • This sorting filter applied: • All events with a 74 km/h or higher peak gust noted • Interesting events with 69 - 73 km/h peak included • Filter likely captures: • All events with a 93 km/h or higher peak gust • Most events with 63 km/h or higher 1-minute wind • All Fraser outflow events with 74 km/h or higher gust Annual Frequency of High Wind Events at Vancouver International Airport Influenced by the Pacific Decadal Oscillation? Timing of recent PDO cold-phase onset is somewhat contested among climate researchers Annual Frequency of High Wind Events at the Abbotsford Airport Fraser Timing of recent PDO cold-phase onset is somewhat contested among climate researchers High-Wind Events at Vancouver and Abbotsford: Annual Frequency Note: Standard deviation is large for all values, with considerable overlap among and between bins Westerly High-Wind Storms That Struck Both Vancouver and Abbotsford Westerly High-Wind Storms That Struck Both Vancouver and Abbotsford • Vancouver has long over-water fetch from a westerly direction • Abbotsford is further inland, with long over-ground fetch Abbotsford: Fraser River Outflow Events Fraser Abbotsford: Fraser River Outflow Events Fraser Abbotsford: Fraser River Outflow Events Fraser Abbotsford: Fraser River Outflow Events Fraser Abbotsford: Fraser River Outflow Events Fraser Fraser Arctic Outbreaks: Synoptic Setup Fraser Arctic Outbreaks: Synoptic Setup Fraser Arctic Outbreaks: Synoptic Setup Fraser Arctic Outbreaks: Synoptic Setup Fraser Arctic Outbreaks: Synoptic Setup In Summary • Frequency of high-wind storms, as measured at Vancouver and Abbotsford, my be influenced by the PDO • Vancouver International, with a strong overwater fetch to the west, is particularly prone to high westerly winds when compared to an inland station like Abbotsford • Frequency of strong Fraser Valley outflow events, as measured at Abbotsford, appear to be decreasing 1955-2007 • Change in frequency of strong Fraser outflow events may be related to the great 1976-77 transition of the PDO • Wind speed and the coldness of Fraser outflow events appear unchanged during same period 1955-2007 Questions & Comments Wolf Read University of British Columbia Forest Sciences 3401-2424 Main Mall Vancouver, BC V6T 1Z4 [email protected] Boeing Field AWOS, Seattle, WA, 27 Jan 2008 .