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Long Range Forecast Update for the 2009 Southwest Monsoon Rainfall

Long Range Forecast Update for the 2009 Southwest Monsoon Rainfall. India Meteorological Department Presents. Long range Forecast Schedule. 1 st Stage Forecast. All India June – September Rainfall. April. Update for All India June – September Rainfall. 2 nd Stage Forecast.

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Long Range Forecast Update for the 2009 Southwest Monsoon Rainfall

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  1. Long Range Forecast Update for the 2009 Southwest Monsoon Rainfall India Meteorological Department Presents

  2. Long range Forecast Schedule 1st Stage Forecast All India June – September Rainfall April Update for All India June – September Rainfall 2nd Stage Forecast All India Monthly (July & August) Rainfall June June – September Rainfall for Four Homogeneous Regions In addition, Forecast for Date of Monsoon Onset over Kerala in May

  3. Long Range Forecast of 2009 South-west Monsoon Season (June-September) Rainfall issued on 17th April, 2009 IMD’s operational Long Range Forecast for the 2009 South-west Monsoon season (June-September) is that the rainfall for the country as a whole is likely to be Near Normal. Quantitatively, monsoon season rainfall is likely to be 96% of the Long Period average (LPA) with a model error of ± 5 %.

  4. Predictors Used in the Ensemble Forecasting System for the Seasonal Rainfall over the Country as a Whole

  5. Geographical Locations of the 8 Predictors Rajeevan et al. ( 2006), Climate Dynamics

  6. Second Stage Forecasts: Method • Forecast update for the southwest monsoon season (June-September) rainfall over the country as a whole using a 6-parameter ensemble statistical model with a model error of ± 4%. • Forecast for the monthly rainfall over the country as a whole for the months of July & August using separate principle component regression models with a model error of ± 9%. c)     Forecasts for the southwest monsoon season (June-September) rainfall for the following four broad geographical regions of India using separate multiple linear regression models with a model error of ± 8%.

  7. MR MODEL ALL POSSIBLE MODELS (31/63) ENSEMBLE AVERAGE OF BEST MODELS PREDICTORS (5/6) MEAN FORECAST PPR MODEL ALL POSSIBLE MODELS (31/63) ENSEMBLE AVERAGE OF BEST MODELS Ensemble Forecasting System for Seasonal Rainfall over Country as a whole: Linear Models Non-Linear Models The average of the ensemble forecasts from best out all possible MR (multiple regression) models and that from PPR (projection pursuit regression) models gives the final forecast.

  8. Definitions of Rainfall Categoriesbased on 1901-2005 data • Excess : Above 110% of LPA (16% Prob) • Above Normal: 104-110% of LPA (17% Prob) • Near Normal: 96-104% of LPA (33% Prob) • Below Normal: 90-96% of LPA (16% Prob) • Deficient: Below 90% of LPA (17% Prob)

  9. 2nd Stage Forecasts

  10. IMD’ s Experimental Dynamical Model Forecasts May SST Persisted 10 Initial Conditions 21 – 30 May 2009 Forecasts suggest positive rainfall anomalies over most parts of the country, except along some part of west coast where the anomalies are positive. For the country as a whole, the ensemble dynamical forecast suggests normal monsoon season rainfall (104% of LPA).

  11. 2009 Rainfall Predictions from Various Institutes • IMD has also taken into account the experimental forecasts prepared by the national institutes like Indian Institute of Tropical Meteorology (IITM), Pune, Indian Institute of Science (IISc), Bangalore, Space Applications Centre (SAC), Ahmedabad, National Aerospace Laboratories (NAL), Bangalore, Centre for Mathematical Modelling and Computer Simulation (CMMACS), Bangalore, National Centre for Medium Range Weather Forecasting (NCMRWF), Noidaand Centre for Development of Advanced Computing (C-DAC), Pune and • Operational/experimental forecasts prepared by international institutes like World Meteorological Organization (WMO)’s Lead Centre for Long Range Forecasting - Multi-Model Ensemble (LRFMME), the National Centers for Environmental Prediction (NCEP), USA, International Research Institute for Climate and Society (IRI), USA, Meteorological Office, UK, the European Center for Medium Range Weather Forecasts (ECMWF), UK , the Experimental Climate Prediction Center (ECPC), USA, and Asian-Pacific Economic Cooperation (APEC) Climate Centre, Korea.

  12. IRI, US: Multi-Model Probability Forecast: July to August, 2009 7 Models were used for prepareing the multi-model ensemble: ECHAMp5 CCM3v6 NCEP NSIPP-1 COLA ECPC GFDL Below normal rainfall over most parts of the country.

  13. 3 Models: ECMWF UKMO Meteo-France Below normal rainfall over the north and northwestern parts of the coutnry. Normal to above normal rainfall over all other areas.

  14. Models: From 10 GPCs, Beijing ECMWF Exeter Melbourne Montreal Moscow Seoul Tokyo Toulouse Washington WMO Lead Center for LRF-MME: JAS Below normal rainfall over North and northwestern parts of the country. Normal rainfall over south Peninsula and northeast.

  15. 2009 Rainfall Predictions from Various Institutes • In general, the experimental forecasts based on statistical models suggest below normal monsoon season rainfall over the country as whole and that based on the dynamical models suggest normal to above normal rainfall.

  16. La Nina Conditions over Pacific and Prediction 1st stage forecast • Currently Atmospheric and oceanic conditions reflect neutral ENSO conditions.

  17. Latest ENSO Forecast • Forecasts from both dynamical and statistical models suggest high probability (about 60%) for El Nino conditions to prevail during the monsoon season • About 40% probability for ENSO neutral conditions. • La Niña is ruled out.

  18. Indian Ocean Dipole FRCGC, Japan: June, 2009 IOD forecast: weak positive IOD during the monsoon season

  19. Second Stage Long Range Forecast for 2009 South-west Monsoon Season(June –September ) Rainfall25th June, 2009

  20. Summary of the Update Forecasts for 2009 Southwest Monsoon Rainfall i) South-West Monsoon Season Rainfall IMD’s long range forecast update for the 2009 south-west monsoon season (June to September) is that the rainfall is likely to be below normal. Quantitatively, monsoon season rainfall for the country as a whole is likely to be 93% of the long period average with a model error of ±4%. The Long period average rainfall over the country as a whole for the period 1941-1990 is 89 cm. ii) Monthly (July & August) Rainfall Rainfall over the country as a whole in the month of July 2009 is likely to be 93% of its LPA and that in the month of August is likely to be 101% of LPA both with a model error of ± 9 %.

  21. Summary of the Update Forecasts for 2009 Southwest Monsoon Rainfall iiI) Rainfall over Broad Geographical Regions Over the four broad geographical regions of the country, rainfall for the 2009 South-West Monsoon Season is likely to be 81% of its LPA over North-West India, 92% of its LPA over North-East India, 99% of its LPA over Central India and 93% of its LPA over South Peninsula, all with a model error of ± 8 %.

  22. Thank you

  23. Epochal Variation of ISMR

  24. Verification of 2008 Operational Forecasts The forecast for onset over Kerala was29th May. The actual monsoon onset over Kerala was31st May.

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