The summer monsoon rainfall forecast proceeds with the projection of the antecedent multi-season SST anomalies on the recurrent modes of spatiotemporal variability of seasonal SSTs in the 20th century (1900-2015); the modes were obtained from an extended-EOF analysis (following Guan and Nigam 2008) of global SSTs. As the multi-season SST anomaly is centered several seasons prior to the forecast period (summer season), the obtained SST principal components are multiplied by their multi-season-lagged seasonal rainfall regressions, generating the summer (June-September) monsoon rainfall forecast. We show that focusing on the multi-season SST structure leads to a discriminating analysis and facilitates forecast of the monsoon rainfall distribution.
The prediction is based on the influence of global SSTs on the South-Southeast Asian monsoon. The skill of the SST-based statistical forecast establishes the bar – an evaluative benchmark – for the dynamical prediction of summer monsoon rainfall.