Regional Verification of CPC’s Seasonal Outlooks Michael Halpert & Kenneth Pelman Climate...
-
Upload
madlyn-lamb -
Category
Documents
-
view
213 -
download
1
Transcript of Regional Verification of CPC’s Seasonal Outlooks Michael Halpert & Kenneth Pelman Climate...
Regional Verification of CPC’sSeasonal Outlooks
Michael Halpert
&
Kenneth Pelman
Climate Prediction Center
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.
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.
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
• 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
Verification
0.5 Month Lead Skill
Data
9+ years of seasonal forecastsJFM 1995 – AMJ 2004
112 Total Forecasts
Winter: NDJ – JFM (28)Spring: FMA – AMJ (30)Summer: MJJ – JAS (27)Fall: ASO – OND (27)
Temperature – All Seasons
Temperature – By SeasonWinter Spring
Summer Fall
Temperature – By Category (All)
Above Below
Temperature - Category DJF&MAM
Winter/Above Winter/Below
Spring/Above Spring/Below
Temperature - Category JJA&SON
Summer/Above Summer/Below
Fall/Above Fall/Below
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
Forecast Tools
1. Optimal Climate Normal (OCN)
2. Canoncial Correlation Analysis (CCA)
3. Coupled Model (CMP)
4. Screened Multiple Linear Regression (SMLR)
Temperature – OCN/CCA All
OCN CCA
Temperature – OCN/CCA By Category
OCN/Above OCN/Below
CCA/Above CCA/Below
Temperature – SMLR/CMP All
SMLRCMP
Temperature – SMLR/CMP By Category
SMLR/Above SMLR/Below
CMP/Above CMP/Below
Forecast Tools - DJF
OCN CCA
CMP SMT
Forecast Tools - MAM
OCN CCA
CMP SMT
Forecast Tools - JJA
OCN CCA
CMP SMT
Forecast Tools - SON
OCN CCA
CMP SMT
Precipitation – All Seasons
Precipitation – By Season
Winter Spring
Summer Fall
Precipitation – By Category (All)
Above Below
Precipitation - Category DJF&MAM
Winter/Above Winter/Below
Spring/Above Spring/Below
Precipitation - Category JJA&SON
Summer/Above Summer/Below
Fall/Above Fall/Below
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
Precipitation – OCN/CCA All
OCN CCA
Precipitation – OCN/CCA By Category
OCN/Above OCN/Below
CCA/Above CCA/Below
Precipitation – SMLR/CMP All
SMLRCMP
Precipitation – SMLR/CMP By Category
CMP/Above CMP/Below
SMLR/Above SMLR/Below
Forecast Tools - DJF
OCN CCA
CMP SMT
Forecast Tools - MAMOCN CCA
CMP SMT
Forecast Tools - JJA
OCN CCA
CMP SMT
Forecast Tools - SON
OCN CCA
CMP SMT
DJF 2004-2005 Outlook