Extreme Weather of the Pacific Northwest Cliff Mass University of Washington

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

3. 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. 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. John Meares, 1788, off of Cape Flattery of the Olympics Peninsula

5. Extreme Northwest Precipitation

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

7. Largest Precipitation Differences Annual Precipitation

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

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

10. Our region has extreme differences in annual precipitation

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

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

14. 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

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

16. Mount Rainier National Park18 inches in 36 hr (Nov 8, 2006)

17. Extreme Winds

18. The region’s most extreme winds are associated with large low pressure areas from off the Pacific Inauguration Day Storm January 29, 1993 1993 Inauguration Day Storm

19. Northwest Cyclones • Our strong low-pressure storms are midlatitude cyclones…areas of intense low pressure that derive their energy from the the north-south variation of temperature in the midlatitudes. • In contrast: tropical cyclones…like hurricanes… get their energy from the warm sea surface of the tropics.

20. 1000 miles 1000 miles Hurricane Ivan Our storms are bigger than theirs!

21. Trees—our force multiplier

22. Compared to their wimpy tropical palms

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

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

25. Columbus Day 1962: At Cape Blanco there were 150 mph with gusts to 179. Strongest winds on bluffs and windward slopes of coastal orography

26. Extreme Local Winds

27. February 13 1979: The Hood Canal Storm Winds over 110 mph destroyed the Hood Canal Bridge Cost to replace: over 100 million dollars

29. The Hood Canal Storm

30. February 13 1979: The Hood Canal Storm

32. But there is another strong wind situation for the San Juans: the Fraser River Gap Winds

33. Fraser River Gap Windstorms December 28, 1990

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

36. Is Our Weather Getting More Extreme?

37. There has been a lot discussion in the media and the scientific literature suggesting that western U.S. extreme precipitation events have already increased in intensityor will soon increase under anthropogenic global warming

39. Press Advisory National Wildlife Federation November 17, 2009 Contacts: XXXX (name removed) YYYY (you know her!) Senior Environmental Policy Specialist Climate Scientist National Wildlife Federation, Pacific Region National Wildlife Federation … Global warming is exacerbating extremely heavy rainfall events, and recent climate change modeling suggests that these pineapple express storms are no exception. “Heavier rainfall events combined with significant snowmelt in midwinter is just what the Pacific Northwest should expect from global warming,” said Dr. YYYY, climate scientist, National Wildlife Federation. …. Recent data[1] suggests that as a result of climate change, the largest storms (i.e., those that are most likely to cause flooding) will trend toward producing increasingly larger quantities of precipitation.

40. Other Claims • Recent big storms are just signs of natural variability. • Global warming is an unproven theory we don’t have to worry about, and recent more extreme weather events don’t have anything to do with it.

41. The Truth is More Complex

42. Are there trends in major precipitation events? • Trends in top 60 two-day precipitation events at stations along the coast for 1950-2008. • Not uniform.

43. When it Rains it Pours Used the Kunkel Approach for 1-day rainfall (1948-2006) • More over Wa, LESS over Oregon, little trend, N. CA.

44. West Coast Windstorms Are Following the Same Pattern • Increasing number of major windstorms from northern Oregon into southern BC • Decreasing numbers to the south.

45. Why Simple Arguments Could Fail • A number of theoretical, modeling, and observational studies have suggested that the jet stream may move northward under global warming. • Strong storms and heavy rainfall (pineapple express situations) tend to follow the jet stream. • It is possible that the “action” could move north of us under GW, with less major storms.

46. Bottom Line • Global warming will substantially change northwest climate in the latter half of this century--particularly bringing higher temperatures and lesser snowpack. • Except for temperature, the atmospheric sciences community is not yet sure whether global warming will produce a change in extreme weather frequency or intensity over the Northwest. • This is an area of active research and we should know a lot more in five years. • Until then, be wary of simplistic, dire predictions.

47. The End Mercer Island: Hanukah Eve Storm