1A.7 Major windstorms of the Pacific Northwest interior

Tuesday, 26 June 2007: 9:30 AM
Summit A (The Yarrow Resort Hotel and Conference Center)
Bri Dotson, University of Washingon, Seattle, WA; and C. Mass

Major windstorms in the Pacific Northwestern United States have been key events in the region's history due to their high impact on people and infrastructure. For example, one of the most memorable and destructive of these events produced wind gusts exceeding 100 mph in the Willamette Valley of Oregon on 12 October 1962. The storm, colloquially referred to as the Columbus Day Storm, resulted in about $250 billion (in 1962 dollars) in damages, over 11 billion boardfeet of felled timber, and at least 31 deaths in Oregon and Washington. Other known major storm dates include 14 November 1981, which produced wind gusts exceeding 70 mph in the Willamette Valley, 20 January 1993, which produced wind gusts exceeding 60 mph in the Puget Sound region of Washington, and 12 December 1995, which produced wind gusts exceeding 70 mph along the Pacific Northwest interior corridor.

This paper presents an objective method for identifying major southerly wind events in the Pacific Northwest interior and examines the synoptic characteristics of these events via compositing. Ten Pacific Northwest interior weather stations with lengthy and reliable histories are utilized to identify windstorm events based on the National Weather Service (NWS) criteria for high wind warnings and watches. The majority of events display regional signatures, and thus the Pacific Northwest is divided into four regions of influence for major windstorm events. Composites of pertinent meteorological variables from the National Center for Environmental Prediction (NCEP) – National Center for Atmospheric Research (NCAR) Reanalysis Project (NNRP) grids reveal the synoptic characteristics and evolution of these events as a class of storms.

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