1. Cliff Mass Department of Atmospheric Sciences University of Washington
Winter Outlook
Cliff Mass
Department of Atmospheric Sciences
University of Washington

2. Last Year: No Major Cyclone Wind Damage
Sustained Winds

3. Gusts

4. November 13th

5. Gusts mph

7. City Light Had Far Fewer Outages than PSE

8. February 17, 2018

11. 2017-2018 Was a Relatively Boring Storm Season

12. What About ?

13. The Big Story for this Winter: A Weak to Moderate El Nino Should be in Place

14. El Nino 101
Neutral
La Nina
Three Phases

15. Neutral

16. La Nina

18. Why do we care? The Answer: Teleconnections

19. Moderate to strong El Nino Patterns

20. Latest Status and Forecast from The NOAA Climate Prediction Center

21. Niño Region SST Departures from Normal (oC)
Last Year We had weak La Nina
Now we are slightly above normal…neutral
Niño 4
0.4ºC
Niño 3.4
0.3ºC
Niño 3
0.4ºC
Niño 1+2
0.2ºC

22. Defining El Nino
Weak (with a 0.5 to 0.9C SST anomaly from normal in Nino 3.4 area),
Moderate (1.0 to 1.4 C),
Strong (1.5 to 1.9 C)
Very Strong (≥ 2.0 C) events.  

23. Tropical Pacific Ocean Has Warmed Considerably
Central and Eastern Pacific Upper-Ocean (0-300 m) Weekly Average Temperature Anomalies
Tropical Pacific Ocean Has Warmed Considerably

24. NOAA Forecast
ENSO-neutral is favored through August-October 2018, with El Niño favored thereafter. Chances for El Niño are 65-70% during Northern Hemisphere winter

25. Weak El Nino

26. What does a weak to moderate El Nino Imply for the Winter

27. El Nino Correlation with Our Winter
El Nino years (moderate or greater) tend to be warmer and drier in NW. Fewer big storms.
Not as much lowland snow.
Less than normal snowpack in the mountains.
Less windstorms

28. El Nino, La Nina, La Nada and Major Windstorms
Major windstorms appear to avoid El Nino and La Nino years
They like neutral winters.

29. Snow? A bit less in fall

30. More of a wash after New Years

31. Latest Climate Prediction Center Forecast for the Upcoming Winter

32. October through December

34. January through March

36. Skill: The El Nino Correlation with Our Weather is Not Perfect: Think of it as weighting some dice

37. Bottom Line
Will probably be in a weak to moderate El Nino near winter.
If moderate or stronger, good chance we will be warmer than normal, with less snow or fewer windstorms.
Less chance of big snowpack year or major windstorm.
If the El Nino is weak—then anything can happen…including big events.

38. Remember WindWatch: Very useful guidance for the short-term (https://atmos.washington.edu/SCL/)

39. WindWatch State of the art short-term wind forecasts
This year a major new capability: uncertainty information based on ensembles of many forecasts.

40. The End