Seasonal Outlook for 2010 Southwest Monsoon Rainfall D. S. Pai Director, Long Range Forecasting South Asian Climate Outlook Forum (SASCOF -1) April 2010, Pune

14 April, 2010 Long range Forecast Schedule:2010  APRIL The first Long Range Forecast of South- west Monsoon season (June – Sept) rainfall over the country as a whole.  May Forecast for monsoon onset over Kerala  June Seasonal forecast Update Forecast for July & August rainfall for the country as a whole Forecasts for season (June-Sept) rainfall for 4 broad geographical regions of India, viz. –NW India, NE India, Central India, South Peninsula

14 April, 2010 Predictors used for April Forecast for the seasonal rainfall over the country as a whole:2010 S.NoPredictorPeriodF/U/N 1North Atlantic Sea Surface Temperature December +January Favorable 2Equatorial SE Indian Ocean Sea Surface Temperature February + March Favorable 3East Asia Mean Sea Level Pressure February + March Neutral 4NW Europe Land Surface Air Temperatures JanuaryUnfavorable 5Equatorial Pacific Warm Water Volume February +March Neutral

14 April, 2010 PREDICTORS (5) MR MODEL PPR MODEL ENSEMBLE AVERAGE OF BEST MODELS MEAN FORECAST ALL POSSIBLE MODELS (31) ALL POSSIBLE MODELS (31) Statistical Ensemble Forecasting System for Seasonal Rainfall over Country as a whole: The average of the ensemble forecasts from best out of all possible MR (multiple regression) models and that from PPR (projection pursuit regression) models gives the final forecast. MR Models PPR Models

14 April, 2010 Geographical Regions of the Predictors

14 April, 2010 Performance of the April Ensemble Forecasting System: RMSE = 6 % of LPA

14 April, 2010 Probabilistic Forecast Category Climatological Probability (%) Drought Less than 90% 16 Below Normal90-96% 17 Near Normal96%-104% 33 Above Normal104%-110% 16 Excess more than 110% 17 There is 92% probability for 2010 All India Seasonal Rainfall to be below to near normal (90% to 104%)

14 April, 2010 IMD’S DYNAMICAL FORECASTING SYSTEM FOR EXPERIMENTAL LRF  The Seasonal Forecast Model (SFM) of Experimental Climate Prediction Center (ECPC) is used for this purpose  The model showed some useful skill during hindcast mode ( ).  The dynamical model needs more testing and refinement.

14 April, 2010 IMD SFM Forecast: Persistent Method March SST Persisted – 10 Initial Conditions (21 – 30 March 2010) Forecasts suggest Below normal rainfall over most parts of the country. Country as a whole: 68% of LPA

14 April, 2010 IMD SFM Forecast: Using CFS SST Forecast (April) Forced by CFS Forecasted SST 10 Initial Conditions (21 – 30 March 2010) Forecast suggest above normal rainfall over most parts of the country Country as a whole :158% of LPA

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2010 Rainfall Predictions by Various Climate Prediction Centres Based on Multi- Model Ensemble Methods

14 April, Models were used for prepareing the multi- model ensemble: ECHAMp5 CCM3v6 NCEP NSIPP-1 COLA ECPC GFDL IRI, US: Multi-Model Probability Forecast: June to August, 2010 JJA: Climatological probabilities for entire country. JAS: Over Peninsula, Highest Probability for above normal rainfall

14 April, Models: ECMWF UKMO Meteo-France Over Peninsula the rainfall is most likely to be above normal EUROSIP forecast

14 April, 2010 APCC JJA 2010: Issued March 2010

14 April, 2010 Status of Other Important Factors that Having Influence on Monsoon

14 April, 2010 ENSO Conditions over Pacific and Prediction oEl Nino conditions are prevailing. oEl Niño is expected to continue at least through the Northern Hemisphere spring oENSO Neutral Conditions likely to prevail during monsoon 2010.

14 April, 2010 El Nino Vs Monsoon El Nino Year (Y) Rainfall (% Dep) Y+1Rainfall (% Dep) El Nino Years (Y)ISMRYEAR (Y+1)ISMR EXC (>+10)0 2 NOR (±10)10NOR (±10)14 DEF (<-10)7 1 Total Years17Total Years17

14 April, 2010 Indian Ocean Dipole IOD forecast: Basin-wide warming in the tropical Indian Ocean in following spring and summer. There is a tendency of a negative IOD to happen in Sep-Nov 2010 associated with the La Nina development. FRCGC, Japan: March, 2010

14 April, 2010 Monthly Snow Cover Area Departure from normal March February January Data source: RUTGERS UNIVERSITY

14 April, 2010 Epochal Variation of ISMR

14 April, 2010 Conclusions  IMD probability model forecast for 2010 SW Monsoon Season (June to September) Rainfall over the Country as a Whole indicate the highest probability for below normal to near normal categories.  IMD SFM model:  Below Normal: Persistent Method  Above Normal: CFS SST  MME Forecast From Various Centers indicate above normal rainfall over Peninsula  Analysis of various factors having influence on monsoon indicate normal rainfall  The Combined Outlook: Near Normal Rainfall

14 April, 2010 Thank you

14 April, 2010 METHODOLOGY OF GENETIC ALGORITHMS BASED MONSOON RAINFALL PREDICTION FROM SAC AHMEDABAD In GA method, annual monsoon is treated as a time-series whose evolution can be expressed as a combination of a number of periodic processes. The predictors of the annual monsoon are time-series of monsoon rainfall over different homogeneous zones of India during previous years. Original GA model was developed during the year 2003, but is updated each year with the availability of new observations of rainfall. The “prediction” shown in the diagram indicates the “hindcast skill” of the “latest” GA model, and may be different from the actual prediction made by GA model during previous years. The standard error of the current model is 4%.

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S.NoPredictorUsed for forecasts in 1North Atlantic Sea Surface Temperature (December +January) April and June 2Equatorial SE Indian Ocean Sea Surface Temperature (February + March) April and June 3East Asia Mean Sea Level Pressure (February + March) April and June 4NW Europe Land Surface Air Temperatures (January) April 5Equatorial Pacific Warm Water Volume (February +March) April 6Central Pacific (Nino 3.4) Sea Surface Temperature Tendency (Mar+Apr+May) – (Dec+Jan+Feb) June 7North Atlantic Mean Sea Level Pressure (May) June 8North Central Pacific wind at 1.5 Km above sea level (May) June

14 April, 2010