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CPC Seasonal Forecasts ASO 2005-JAS 2006
Edward O’Lenic
Michael Halpert, David Unger
NOAA-NWS-CPC
31st Climate Diagnostics and Prediction WorkshopBoulder, Colorado
Monday, October 23, 2006
OverviewDuring 2005-06 CPC implemented an objective forecast tools
consolidation (CON), combining OCN, CCA, SMLR and CFS into a single CON tool. In retrospective forecasts over 1995-2004 CON improved on official (OFF) temperature (T) and precipitation (P) forecasts by ~18% and ~130%, respectively. We don’t have cross-validated scores yet for this technique and, therefore, don’t know how CON performs on independent data. However, Dave Unger has cross-validated this technique on SST forecasts and found no significant difference in skill between dependent and independent data sets.
I will discuss the performance of the 12 ASO2005-JAS2006 ½-month lead T, P forecasts in the context of OFF real-time and CON retrospective forecasts from 1995-2006.
%100)(
)(
et
ecs
)(
)3
(
et
ecec
s
randomoverforecastsofficialoftimprovemens .....%.
Non-EC All=Non-EC and EC
47 48 12-month mean skill
TNon-EC
12 612-month mean skill
PNon-EC
47 48 12 612-month mean skill
T P
47 48 12 612-month mean skill
13 2236 37 1995-2006 standard deviation
T P
47 48 12 612-month mean skill
13 2236 37 1995-2006 standard deviation
1995-2006 corr. Skill vs % coverage (non-EC) 0 6-1 -2
T P
47 48 12 612-month mean skill
13 2236 37 1995-2006 standard deviation
1995-2006 corr. Skill vs % coverage (non-EC) 0 6-1 -2
T P
1995-2006 corr. Skill vs % coverage (ALL) 13 2126 16
47 48 12 612-month mean skill
13 2236 37 1995-2006 standard deviation
1995-2006 corr. Skill vs % coverage (non-EC)
1995-2006 corr. Skill vs % coverage (ALL)
0 613 21
-1 -226 16
T P
•It was a very good year for both T and P OFF forecasts.•OFF followed CON closely for T, mediocre guidance for P.•SD is large for T, CON P, implying big swings in skill.•There is no relationship between skill and % coverage for non-EC forecasts•Area-weighted, all stations skill is more meaningful than non-EC
OFF VER CON
01 ASO
T4531
skill
OFF VER CON
01 ASO
P-2132
skill
OFF VER CON
01 ASO
T P4531
skill skill
-2132
OFF VER CON
02 SON
T1240
skill
OFF VER CON
02 SON
Pskill
-2312
OFF VER CON
02 SON
T P1240
skill skill
-2312
OFF VER CON
03 OND
T5555
skill
OFF VER CON
03 OND
Pskill
-13-3
OFF VER CON
03 OND
T P5555
skill skill
-13-3
OFF VER CON
04 NDJ
T8485
skill
OFF VER CON
04 NDJ
Pskill
23-18
OFF VER CON
04 NDJ
T P8485
skill skill
23-18
OFF VER CON
05 DJF
T7771
skill
OFF VER CON
05 DJF
P7771
skill
-4-18
OFF VER CON
05 DJF
T P7771
skill skill
-4-18
OFF VER CON
06 JFM
T6468
skill
OFF VER CON
06 JFM
Pskill
558
OFF VER CON
06 JFM
T P6468
skill skill
558
OFF VER CON
07 FMA
T3138
skill
OFF VER CON
07 FMA
Pskill
15-8
OFF VER CON
07 FMA
T P3138
skill skill
15-8
OFF VER CON
08 MAM
T3827
skill
OFF VER CON
08 MAM
Pskill
328
OFF VER CON
08 MAM
T P3827
skill skill
328
OFF VER CON
09 AMJ
T4843
skill
OFF VER CON
09 AMJ
Pskill
4033
OFF VER CON
09 AMJ
T P4843
skill skill
4033
OFF VER CON
10 MJJ
T3936
skill
OFF VER CON
10 MJJ
Pskill
23-6
OFF VER CON
10 MJJ
T P3936
skill skill
23-6
OFF VER CON
11 JJA
T6058
skill
OFF VER CON
11 JJA
Pskill
-96
OFF VER CON
11 JJA
T P6058
skill skill
-96
OFF VER CON
12 JAS
T1220
skill
OFF VER CON
12 JAS
Pskill
2719
OFF VER CON
12 JAS
T P1220
skill skill
2719
Summary• CPC’s objective consolidation (CON) of OCN, CCA, SMLR, CFS improves
upon official (OFF), ½-month lead T forecasts (FMA1995-JFM2005) by about 18% and about 130% for P (non-EC).
• CPC began using CON for T in fall, 2005, and for P in mid- 2006.• It was a very good year for both T and P OFF forecasts, with T skill
continuously above zero.• SD is large for T, CON P, implying big swings in skill.• CON was good guidance for T, poor guidance for P for these 12 forecasts. • There is no relationship between skill and % coverage for non-EC forecasts.• There is a weak skill-%coverage relationship for all stations skill.• Subjective deviations from CON P succeeded perhaps because CON
predictions cover smaller contiguous areas than OFF. • CON predicts much larger area coverage for T than OFF, especially in the
eastern U.S.• Forecasts appear to change much more than the OBS from lead-to-lead.
OFF VER CON
01 ASO
T P4531
skill skill
-2132
OFF VER CON
02 SON
T P1240
skill skill
-2312
OFF VER CON
03 OND
T P5555
skill skill
-13-3
OFF VER CON
04 NDJ
T P8485
skill skill
23-18
OFF VER CON
05 DJF
T P7771
skill skill
-4-18
OFF VER CON
06 JFM
T P6468
skill skill
558
OFF VER CON
07 FMA
T P3138
skill skill
15-8
OFF VER CON
08 MAM
T P3827
skill skill
328
OFF VER CON
09 AMJ
T P4843
skill skill
4033
OFF VER CON
10 MJJ
T P3936
skill skill
23-6
OFF VER CON
11 JJA
T P6058
skill skill
-96
OFF VER CON
12 JAS
T P1220
skill skill
2719