1. Seasonal prediction of South Asian summer monsoon 2010: Met Office
Michael Vellinga and many colleagues at the Met Office Hadley Centre and ECMWF

2. Probabilistic seasonal forecasts with dynamical models
Nino 3.4 forecasts
Forecast probabilities for South Asian region for:
JJA rainfall
sea surface air temperature
AMJ surface air temperature
Results from:
Met Office’s GloSea4 system: anomalies relative to hindcasts
ECMWF’s System3: anoms. relative to

3. Nino3.4

4. GloSea4: Nino3.4 Jan f/c

5. GloSea4 Nino3.4: Feb f/c

6. GloSea4 Nino3.4: March f/c

7. ECMWF: Nino3.4 Jan f/c

8. ECMWF Nino3.4: Feb f/c

9. ECMWF Nino3.4: March f/c

10. Nino3.4 March f/c

11. June-July-August Precipitation

12. Precipitation June-July-August
normal or above-normal rainfall
more likely, below normal less likely for
most of region
Opposite signal SE of the region
(Myanmar/Thailand/Indochina)
All categories equally likely over most
of Pakistan

13. Precipitation GloSea4 ROC scores June-July-August
Limited skill of Glosea4 for Asian summer monsoon rainfall tercile anomalies months 4-6

14. ECMWF JJA precipitation
Above average rainfall:
ECMWF JJA precipitation
‘wet signal’ (above-average precipitation more likely, and below-average precipitation less likely) similar as GloSea4 less restricted to north, south and west of region and over Himalayas
equal probabilities for all categories for C India
Average rainfall:
Below average rainfall

15. Forecasts for June (from MAJ forecasts from WMO-LCMME)

16. April-May-June temperature

17. Temperature most of region: Increased
probability of warmer than normal,
reduced probability of colder than
normal.
Increased probability of well-above
normal temperature

18. Temperature

19. Temperature ECMWF
Similar as GloSea4, but weaker signal for central and eastern India, Bangladesh

20. JJA 2m temperature No clear signal for most of region
For NE India, Bangladesh, Himalayas: Increased probability of above-normal temperatures, reduced probability of below-normal temperatures

21. June-July-August SST

22. Sea surface temperature
Indian Ocean: Increased probabilities of above-average SST in, reduced probability of normal or below-normal SST
in E Pacific: Increased probabilities of normal to below-normal SST, reduced probability of above-normal SST

23. Summary: based on GloSea4 seasonal forecasts
Indications that ENSO/Nino3.4 SST will move from current warm phase to neutral or La Nina phase by June 2010
Warm SST in Indian Ocean June-July-August more likely
Increased probability for normal to above-normal precipitation in June-July-August for most of S Asia. Regional variations!
Increased probability for normal to warmer than normal temperatures in May-April-June for most of region
Lasting into June-July-August for NE and Maldives for, no clear signal elsewhere)

24. the end

26. Ensemble-mean SST anomalies