1. Winter Outlook for the Pacific Northwest: Winter 06/07 14 November 2006 Kirby Cook. NOAA/National Weather Service Acknowledgement: Climate Prediction Center / NCEP

2. Overview This looks like a winter that is going to be controlled by the tropical pacific ocean – El Nino. El Niño conditions are in place in the tropical Pacific Ocean. Tropical Sea Surface Temperature (SST) anomalies are between +1.0C and +1.4C in all of the Niño regions. Based on recent trends, and a majority of our forecast models, the El Niño conditions should intensify over the next three months and will likely continue through April- June 2007.

3. Taking a look back…temperature Forecast from 9/05Observed DJF Departure from Normal

4. What about the last two years for Seattle? 2004/20052005/2006

5. Taking a look back…precipitation Forecast from 9/05Observed DJF Percent of Normal Precipitation

6. What about the last two years for Seattle? 2004/20052005/2006

7. Natural cycles or patterns El Niño and La Niña (ENSO) Arctic Oscillation (AO) North Atlantic Oscillation (NAO) Madden Julian Oscillation (MJO) Long-term trends (human caused and natural) Trend tools (statistical approaches) Seasonal Forecasting Tools

8. Long Term Trend

9. El Niño / La Nina (ENSO) Most prominent phenomenon affecting inter-annual variability Impacts are nearly global in extent North American impacts are well understood Favorable timescale to add skill to seasonal forecast

10. El Niño, La Niña, and “ENSO-neutral”

11. Systematic differences in the large-scale circulation and jetstreams associated with each phase of ENSO lead to distinct temperature and precipitation anomaly patterns as well as regional changes in the number of weather extremes.

12. More Jetstreams…

13. Warm Episode Relationships By studying past events, we can derive anomaly patterns consistent with El Niño events.

14. Niño Indices: Recent Evolution The recent atmospheric circulation and precipitation patterns indicate moderate El Niño conditions in the tropical Pacific Ocean. SST anomalies are around 1.0C, or higher, in all of the Niño regions. Animation

15. Current Conditions in Tropical Pacific Winter 2004/05 was a weak El Nino. Winter 2005/06 was an ENSO neutral year. This winter will likely be a moderate El Nino.

16. Summary of Predictors Moderate El Nino conditions to persist through winter season Long term trends continue to indicate warmth in the West; little signal in precipitation

17. U. S. Seasonal Outlook December 2006-February 2007 TemperaturePrecipitation Outlook combines long-term trends and soil-moisture effects, with typical ENSO cycle impacts, when appropriate. (More)(More)

18. Northwest Average Temperatures

19. Northwest Average Precipitation

20. April 1 Snow Water Equivalent

21. Snowdepth at Snoqualmie Pass

22. SeaTac Airport DJF Forecast (More)

23. weather.gov/seattle Nationwide - weather.gov

24. In Summary Moderate El Niño conditions are occurring and are expected to intensify through this winter. Winter in the northwest (on average): –Better than normal odds (60% to 40%) that it will be warmer than the long-term average. –Just a slight tipping of the scale toward drier than the long-term average. –Snow Average snow level will be higher than normal. It is likely there will be less mountain snowpack than last year. The threat of lowland snow is much reduced. –Reduced odds on significant damaging storms. Intraseasonal fluctuations are likely.