NCC Report No. 1 - (IMD), Pune

EMR-II were based on the data of 1958-2000. The forecasts for the 2005 monsoonseason are shown in Table -10. As seen in the Table-10, the first stage forecasts byvarious models varied from 101 to 103 and the second stage forecasts varied from102 to 107.Various components of the Indian monsoon exhibit significant inter-decadalvariability (see the references given in Goswami, 2005). Modulation of inter-annualvariability by the inter-decadal variability influences predictability of the seasonalmean monsoon (Goswami 2005). A recent study by Goswami (2004) revealed thatpotential predictability of monthly mean summer monsoon climate has decreased byalmost a factor of two during the recent decades (1980s and 1990s) compared to thedecades of 1950s and 1960s associated with the major inter-decadal transition ofclimate in mid 1970s. Therefore, to generate forecasts for 2005 monsoon using thelatest data, say after mid 1970s, we have done yet another experiment. Wegenerated the first and second stage forecasts for the year 2005 using the followingsteps. i) Best models were identified by Jacknife method using predictor series oflatest 23 years (1982-2004) and ii) the ensemble forecast was computed as thesimple average of the predictions using the selected 5 models. We found that theselected 5 models were entirely different from the best five models shown in theTables-4a and 4b. The first stage forecast for the year 2005 using new EMR-I was100% and that for the second stage forecast using new EMR-II was 103% of LPA.For the PPR model, corresponding forecasts were 98% and 102% of LPArespectively.Preliminary forecasts from these experimental models were included in theofficial press releases made by IMD on the long range forecasts for the 2005southwest monsoon rainfall (http://www.imd.ernet.in).AcknowledgementsWe are thankful to Prof. V. S. Ramamurthy, Secretary, DST, Shri. B. Lal,LACD DGM, Shri. S R. Kalsi, ADGM(S) and Dr.(Mrs) N. Jayanthi, LACD ADGM(R)for encouragements and kind support given to us. Some of these results were26