Investigating the link between early season Caribbean rainfall and the El Nino plus 1 year

The Caribbean rainfall season is best characterized by its bimodal nature, with an initial peak in May-June and a second more prominent one in September-October. This allows for a convenient division into an early and a late rainfall season. In this study we examine the rainfall patterns of the early rainfall season (mid April to July) for links with El Nino-Southern Oscillation (ENSO) events. Whereas traditionally ENSO events have been identified with dry conditions during the later Caribbean rainfall season, recent research suggests a second signal that manifests itself as a wet early rainfall season of the year of ENSO decline (the El Nino+l year). Two leading empirical orthogonal function modes of early season Caribbean rainfall are examined for evidence of this. Strong correlations are shown to exist between the first mode and wintertime equatorial Pacific anomalies. The first mode explains nearly half of the early season variability. The idea that the wintertime Pacific anomalies alter the early Caribbean rainfall season via the warm spring sea surface temperature anomalies they induce in the north tropical Atlantic is also investigated. An atmospheric general circulation model is also used to show that, when warm/cold anomalies exist across the north tropical Atlantic, this results in a large-scale atmospheric circulation that is more/less favourable to rainfall production over the Caribbean. Copyright (C) 2002 Royal Meteorological Society.