Adjustment of a VARMA model for precipitation anomalies in Central Americaand indices of the Pacific Ocean and the Tropical Atlantic

Several studies had shown that the anomalies of the sea surface temperature of the Tropical Atlantic and Pacific Oceans, are related to variations in the duration and timing of the rainy season in Central America. Cluster ana lysis was used to identify common patterns of 72 rain gauge stations of the region, with their anomaly time series as grouping variables, five cluster s where identified through this process. A Vector Auto Regressive-Moving Av erage (VARMA) model was fitted to the data to quantify the ocean-atmosphere interaction between the oceanic indices of the Tropical North and South At lantic, the Tropical Eastern Pacific and the first EOF's of the regional ra infall clusters. This model shows that the Tropical North Atlantic has the largest influence over the region when compared with the influence of the o ther indices, having positive correlation with all the rainfall EOF's. The Nino 3, instead, was found to have lower correlation with the rainfall of t he region, influencing only the Pacific related clusters. This work shows t hat the variability of the Tropical North Atlantic sea surface temperature anomaly (SSTA) presents stronger associations with the Central America rain fall, than the Tropical Eastern Pacific SSTA. The Tropical North Atlantic S STA is mainly related to the degree of development of the Tropical Upper Tr opospheric Through (TUTT) and the SSTA of the Nino 3 region with the meridi an position of the Intertropical Convergence Zone (ITCZ).