1. La Niña impacts on Pacific Northwest climate in spring: 2011 and the historical record Jim Johnstone JISAO-UW jajstone@uw.edu

2. Niño 3.4 index

3. SST anomalies January 3, 2011

4. Sea-level pressure (SLP) anomalies March 2011 SOI

5. Niño 3.4 index SOI

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

7. Lowest Apr-Jun Tmax in WA (to 1900)

8. Pac NW Precip Pac NW Tmax

9. Airport cloud ceilings (hours per day) SeaTac

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

11. US Tmax anomalies Apr-Jun 2011 Record values (back to 1951)

12. Texas drought

13. April tornadoes

14. 2011 monthly 500 mb anomalies (i.e. pressure) Feb Mar Apr May Jun Jul

15. April-Jun 500 mb anomalies

16. Strong La Niña that persisted into April Persistent and strong anomalies over the Pacific NW (and beyond) through June Cause and effect? Do Feb-Apr La Niña conditions occur with Apr-Jun anomalies over the Pacific NW?

17. Composite La Niña (Top 10) Dec-Feb 500 mb

18. Composite La Niña (Top 10) Dec-Feb 500 mb

19. Winter La Niña composites (Dec-Feb) Precip Tmax

20. La Nina winter composite 2011 Apr-Jun

21. Composite La Niña (Top 10) Feb-Apr 500 mb

22. Composite La Niña (Top 10) (Feb-Apr) Feb-Apr Mar-May Apr-Jun 500 mb

23. Tmax Apr-Jun 2011 Apr-Jun response to Feb-Apr La Niña

24. Composite La Niña (Top 10) (Feb-Apr) Feb-Apr Mar-May Apr-Jun Tmax

25. 500 mb anomalies Apr-Jun 2011

26. Conclusion: Apr-Jun climate patterns similar to a typical La Niña pattern (Trough PNW, Ridge SE) But historical data shows limited effects of La Niña in spring

27. La NiñaUS tornadoes Spring (MAM) Z500 composite anomalies (normalized)

33. Top 5 Tmax