The scientific community has been putting in continuous efforts to improve long-range forecast of Indian summer monsoon rainfall (ISMR). In this study we try to search for new predictors which may improve the prediction of ISMR. The shared nearest neighbour technique has been applied to surface temperature (ST) and sea-level pressure (SLP) to obtain the clusters in pre-monsoon months (January through May) and seasons (winter, spring). The powers of time series averaged over the clusters are used as parameters for predicting ISMR. Instead of a single prediction equation, two separate equations are developed based on the positive and negative phase of effective strength index (ESI) tendency. Simple multiple regression equations are developed using these cluster parameters for predicting ISMR during the contrasting phases of ESI tendency. During positive (negative) phase of ESI tendency, the SLP (ST) cluster parameters can predict ISMR. The prediction of ISMR is improved if we use the prediction equation depending upon the phase of ESI tendency
