In this study large-scale ocean-atmosphere patterns are examined for their influence on the interannual variability of Caribbean rainfall. We examine patterns in (i) sea surface temperatures of the tropical and equatorial Atlantic and Pacific, and (ii) vertical shear patterns over the tropical north Atlantic (TNA), given the importance and known influence of each on the development of traveling convective centers (particularly easterly waves) which provide the Caribbean with most of its annual rain. After stratifying the Caribbean rainfall season into two-month periods, canonical correlation analysis (CCA) is employed to identify the large-scale patterns of both variables that best explain simultaneous patterns in interannual rainfall variability. An attempt is then made to link these patterns to known global interannual fluctuations such as ENSO.

The Caribbean rainfall season spans May through November, with peaks in both June and October. We find evidence of strong tropical north Atlantic (TNA) modulation in the early part of the rainfall season, with the TNA SST anomalies also related to an altered vertical shear environment. We however find an inter-basin response to predominate in the latter part of the rainfall season with strong links between the vertical shear during this period and the SSTs of the equatorial Pacific.