1. Extreme Weather of the Pacific Northwest
Cliff Mass
University of Washington

3. 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

4. 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.

5. Extreme Northwest Precipitation

6. Greatest Annual Precipitation in the Continental U.S.

7. Largest Precipitation Differences
Annual Precipitation

9. SW Olympic Slopes-Hoh Rain Forest: 150-170 inches yr-1

10. Sequim: Haven for Retirees
15 inches a year—similar to LA!

11. The NW region has extreme differences in annual
precipitation

12. Why such extremely dry summers?
Few thunderstorms
Fewer thunderstorms!

13. 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

14. The most costly extreme weather of the Northwest:
Flooding

16. 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

17. A Devastating Pineapple Express: November 6-7, 2006
Dark Green: about 20 inches

18. Mount Rainier National Park 18 inches in 36 hr (Nov 8, 2006)

19. 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

20. Sometimes damaging NW rains are very localized Thunderstorms and narrow valleys
Heppner, Oregon
June 14, 1903

22. Extreme Winds

23. The region’s most extreme winds are associated with strong Pacific Cyclones
Inauguration
Day
Storm
January 29,
1993
1993 Inauguration Day Storm

24. Trees—our force multiplier

25. Much more damaging than wimpy tropical palms

26. The Most Extreme Northwest Windstorm: The Columbus Day Windstorm of 12 October 1962

27. Max Winds (mph)
Columbus Day Storm 1962
Probably the most intense non-tropical cyclone to hit the continental U.S. in a century

28. 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

29. 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

31. Near Route 26 in Oregon

32. Extreme Local Winds

33. 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

35. The Hood Canal Storm

36. February 13 1979: The Hood Canal Storm
Intense pressure gradient led to strong winds

38. Extreme Winds are Also Observed Downstream of Gaps Example: Fraser River Gap Winds

39. Fraser River Gap Windstorms
December 28, 1990

40. Fraser River NE Gap Flow
Max Winds, 28 Dec. 1990
Fraser River NE Gap Flow
Gusts above 90 mph
December 28, 1990

42. Enumclaw and nearby foothills locations can experience severe windstorms…while calm winds occur a dozen miles away
Winds over 118 mph
December 24, 1983

43. December 24, 1983

44. Why Enumclaw?

45. Enumclaw Windstorm Pressure Pattern
December 28, 1990
December 24, 1983

46. 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 *

48. Even today, avalanches are major problems in our region

49. 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.

51. But don’t be afraid Most of you will survive your career at the UW

52. The End