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Extreme Weather of the Pacific Northwest
Cliff Mass University of Washington
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The extreme side of Northwest weather
The strongest non-tropical cyclones in the nation, with the wind speeds of some equivalent to category 1 or 2 hurricanes. The greatest annual rainfall in the continental U.S. World-record snowfalls in our mountains Billion dollar floods The greatest avalanche losses in the continental U.S. Localized hurricane-force winds and many more … The extreme side of Northwest weather
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John Meares, 1788, off of Cape Flattery of the Olympics Peninsula The force of southerly storms was evident to every eye; large and extensive woods being laid flat by their power, the branches forming one long line to the North West, intermingled with the roots of innumerable trees, which have been torn from their beds and helped to mark the furious course of their tempests.
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Extreme Northwest Precipitation
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Greatest Annual Precipitation in the Continental U.S.
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Largest Precipitation Differences
Annual Precipitation
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SW Olympic Slopes-Hoh Rain Forest: 150-170 inches yr-1
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Sequim: Haven for Retirees
15 inches a year—similar to LA!
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The NW region has extreme differences in annual
precipitation
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Why such extremely dry summers?
Few thunderstorms Fewer thunderstorms!
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Greatest Annual Snowfall Totals in the World!
The Mt. Baker Ski Area in northwestern Washington State reported 1,140 inches of snowfall for the snowfall season
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The most costly extreme weather of the Northwest:
Flooding
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Most are associated with the “Pineapple Express”
A relatively narrow current of warm, moist air from the subtropics…often starting near or just north of Hawaii. a.k.a. Atmospheric rivers
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A Devastating Pineapple Express: November 6-7, 2006
Dark Green: about 20 inches
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Mount Rainier National Park 18 inches in 36 hr (Nov 8, 2006)
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The results: massive landslides and river flooding
Dec. 3, inches in two days over coastal terrain of SW Washington The results: massive landslides and river flooding
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Sometimes damaging NW rains are very localized Thunderstorms and narrow valleys
Heppner, Oregon June 14, 1903
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Extreme Winds
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The region’s most extreme winds are associated with strong Pacific Cyclones
Inauguration Day Storm January 29, 1993 1993 Inauguration Day Storm
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Trees—our force multiplier
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Much more damaging than wimpy tropical palms
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The Most Extreme Northwest Windstorm: The Columbus Day Windstorm of 12 October 1962
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Max Winds (mph) Columbus Day Storm 1962 Probably the most intense non-tropical cyclone to hit the continental U.S. in a century
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Columbus Day 1962: At Cape Blanco there were 150 mph with gusts to 179
Columbus Day 1962: At Cape Blanco there were 150 mph with gusts to Strongest winds on bluffs and windward slopes of coastal orography
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The Great Coastal Gale of December 3-4, 2007
A very unusual windstorm Hurricane-force winds sustained for nearly 24-h Flooding over the coastal mountains
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Near Route 26 in Oregon
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Extreme Local Winds
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Winds over 110 mph destroyed the Hood Canal Bridge
February 13 1979: The Hood Canal Storm Winds over 110 mph destroyed the Hood Canal Bridge Cost to replace: over 100 million dollars
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The Hood Canal Storm
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February 13 1979: The Hood Canal Storm
Intense pressure gradient led to strong winds
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Extreme Winds are Also Observed Downstream of Gaps Example: Fraser River Gap Winds
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Fraser River Gap Windstorms
December 28, 1990
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Fraser River NE Gap Flow
Max Winds, 28 Dec. 1990 Fraser River NE Gap Flow Gusts above 90 mph December 28, 1990
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Enumclaw and nearby foothills locations can experience severe windstorms…while calm winds occur a dozen miles away Winds over 118 mph December 24, 1983
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December 24, 1983
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Why Enumclaw?
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Enumclaw Windstorm Pressure Pattern
December 28, 1990 December 24, 1983
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Extreme Avalanches The greatest loss of life from an avalanche occurred in Washington State Wellington WA disaster, March 1, 1910 96 people killed in a train going across Stevens Pass Heavy snow followed by heavy rain *
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Even today, avalanches are major problems in our region
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And didn’t even mention many other extreme weather effects of the region!
Extreme freezing rain in and downstream of the Columbia Gorge and eastern Washington Massive wildfires in certain meteorological conditions The greatest rain-caused slope failure in US history.
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But don’t be afraid Most of you will survive your career at the UW
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The End
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