Regional Verification of CPC’s Seasonal Outlooks

1. Regional Verification of CPC’sSeasonal Outlooks Michael Halpert & Kenneth Pelman Climate Prediction Center

2. Seasonal Outlook Schedule/Leads • Each month, near mid-month CPC prepares a set of 13 outlooks for 3-month “seasons” (any set of 3 adjacent months) for lead times ranging from ½ month, 1 ½ months, 2 ½ months, 3 ½ months, …, 12 ½ months. • The outlook for each successive/prior lead time overlaps the prior/successive one by 2 months. This overlap makes for a smooth variation from one map to the next.

3. Outlook Categories and Probabilities • Seasonal outlooks are prepared for average temperature and total accumulated precipitation category • Three categories are used (terciles). These are BELOW-,NEAR- and ABOVE-normal (median), for temperature (precipitation). • Regions where the likelihoods of the three categories are the same (33.33…% each) are designated as “EC”, for equal chances. • In non-EC regions the labels on the contours give the total probability of the dominant category.

4. Verification • Heidke Skill Score • H=[ ( NC – CH)/(NT – CH) ] * 100 • H=Heidke Skill Score • NC = total number of correct forecasts by station • NT = total number of forecasts made by station • CH = number of correct forecasts, by chance • In 3 class system, scores range from -50 to +100

5. Verification • Examples • a. 99 stations, 50 correct forecasts • H = [(50-33)/(99-33)] *100 = 25.8 • b. 51 stations, 12 correct • H = [(12-17)/(51-17)]*100 = -14.7 • c. 45 stations, 35 correct • H=[(35-15)/(45-15)*100 = 66.7

6. 0.5 Month Lead Skill

7. Data 9+ years of seasonal forecasts JFM 1995 – AMJ 2004 112 Total Forecasts Winter: NDJ – JFM (28) Spring: FMA – AMJ (30) Summer: MJJ – JAS (27) Fall: ASO – OND (27)

8. Temperature – All Seasons

9. Temperature – By Season Spring Winter Summer Fall

10. Temperature – By Category (All) Below Above

11. Temperature - Category DJF&MAM Winter/Below Winter/Above Spring/Above Spring/Below

12. Temperature - Category JJA&SON Summer/Below Summer/Above Fall/Above Fall/Below

13. Temperature Summary (Official) • Good skill from the Pacific NW, peaking in the SW and extending through the South. • No skill in N. Plains, Great Lakes, NE • Winter forecasts best, Fall poorest • No skill in NE, always skill in SW • All skill comes from above normal; negative skill everywhere for below

14. Forecast Tools • Optimal Climate Normal (OCN) • Canoncial Correlation Analysis (CCA) • Coupled Model (CMP) • Screened Multiple Linear Regression (SMLR)

15. Temperature – OCN/CCA All CCA OCN

16. Temperature – OCN/CCA By Category OCN/Above OCN/Below CCA/Above CCA/Below

17. Temperature – SMLR/CMP All CMP SMLR

18. Temperature – SMLR/CMP By Category SMLR/Above SMLR/Below CMP/Above CMP/Below

19. Forecast Tools - DJF CCA OCN SMT CMP

20. Forecast Tools - MAM CCA OCN SMT CMP

21. Forecast Tools - JJA CCA OCN SMT CMP

22. Forecast Tools - SON CCA OCN SMT CMP

23. Precipitation – All Seasons

24. Precipitation – By Season Spring Winter Summer Fall

25. Precipitation – By Category (All) Below Above

26. Precipitation - Category DJF&MAM Winter/Below Winter/Above Spring/Above Spring/Below

27. Precipitation - Category JJA&SON Summer/Below Summer/Above Fall/Above Fall/Below

28. Precipitation Summary (Official) • Skill in West, South and NE (few cases) • Skillful regions vary by season • Skill in all seasons in NW, except Spring • Skillful forecasts for both above and below in the SW and along Gulf Coast, FL • Skill for winter/spring forecasts for below in South, only along Gulf Coast for above

29. Precipitation – OCN/CCA All OCN CCA

30. Precipitation – OCN/CCA By Category OCN/Above OCN/Below CCA/Above CCA/Below

31. Precipitation – SMLR/CMP All CMP SMLR

32. Precipitation – SMLR/CMP By Category CMP/Above CMP/Below SMLR/Above SMLR/Below

33. Forecast Tools - DJF CCA OCN SMT CMP

34. Forecast Tools - MAM CCA OCN SMT CMP

35. Forecast Tools - JJA CCA OCN SMT CMP

36. Forecast Tools - SON CCA OCN SMT CMP

37. DJF 2004-2005 Outlook