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2011 Pacific Northwest Climate Recap Jim Johnstone JISAO – University of Washington

2011 Pacific Northwest Climate Recap Jim Johnstone JISAO – University of Washington jajstone@uw.edu. 1. Review of ENSO conditions (record La Niña) 2. Review of Pacific NW climate 2011 (Unusual spring conditions) 3. Re-development of La Niña in late 2011 4. La Niña and Pacific NW Climate.

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2011 Pacific Northwest Climate Recap Jim Johnstone JISAO – University of Washington

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  1. 2011 Pacific Northwest Climate Recap Jim Johnstone JISAO – University of Washington jajstone@uw.edu

  2. 1. Review of ENSO conditions (record La Niña) 2. Review of Pacific NW climate 2011 (Unusual spring conditions) 3. Re-development of La Niña in late 2011 4. La Niña and Pacific NW Climate

  3. Niño 3.4 index El Niño La Niña

  4. Niño 3.4 index SST anomalies January 3, 2011 El Niño La Niña

  5. Southern Oscillation Index (SOI) Sea-level pressure (SLP) anomalies March 2011 La Niña El Niño

  6. Feb-Apr SOI Strongest spring La Niña on record (to 1866)

  7. Niño 3.4 index SOI El Niño La Niña La Niña El Niño

  8. Current SST anomalies

  9. ENSO summary: 2011 Strong La Niña from summer 2010 to spring 2011 Record positive SOI in early spring (Feb-Apr) SST anomalies not as extreme Decay to neutral conditions in May-June Re-emergence of weak-moderate La Niña by July-August

  10. Precipitation anomalies: Oct-Dec 2010 Jan-Mar 2011

  11. US Precip anomalies Apr-Jun 2011

  12. Pacific NW Climate: 2011 (Washington, Oregon, Idaho) Pac NW Precipitation

  13. Snow water content Stevens Pass, WA Mt Hood, OR Hemlock Butte, ID

  14. April-Jun 500 mb anomalies (i.e. pressure)

  15. US Tmax anomalies Apr-Jun 2011 Record values (back to 1900)

  16. Texas drought

  17. Pacific NW Tmax (persistently cool Feb-July)

  18. Lowest Apr-Jun Tmax in Washington history (to 1900)

  19. Airport cloud ceilings (hours per day) SeaTac Portland

  20. Pacific NW Climate summary: 2011 • Unusually wet, cloudy, cool conditions in late spring (April-July) • Late snowfall into April-May • Anomalous June snow pack (~2-5x normal) • Trough over Pacific NW, Ridge over SW North America • Cool, wet PNW / hot, dry Texas • Did a strong early spring La Niña generate late spring cool/wet conditions over the Pacific NW?

  21. Tmax Apr-Jun 2011 Top 5 early spring La Niñas 1971 1974 2008 2000 1989

  22. Precip Apr-Jun 2011 Top 5 early spring La Niñas 1971 1974 2008 2000 1989

  23. Did a strong early spring La Niña generate late spring cool/wet conditions over the Pacific NW? Probably not – La Niña forcing of PNW climate not strong in late spring What about the coming winter?

  24. Winter La Niña composites (Dec-Feb) Tmean Strong events Moderate events

  25. Winter La Niña composites (Dec-Feb) 500 mb heights Strong events Moderate events

  26. Winter La Niña composites (Dec-Feb) Precipitation Strong events Moderate events

  27. Developing La Niña conditions portend a cool, wet winter. Precipitation response is more consistent for stronger events.

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