Seasonal atmospheric transitions in the Caribbean basin and Central America

摘要: The dates of the transition between winter and summer (W2S) (S2W) regional-scale atmospheric regimes have been defined using daily weather types above around Caribbean basin from 1979 to 2017. uncertainties due either use two different reanalyses (i.e., NCEP-DOE ERA-Interim) or parametrization used for definition typically a small impact on interannual variability seasonal transitions. When both are considered together, average W2S date occurs, average, May 13 (with standard deviation 9 days) while S2W October 26 12 days). characteristics associated with transitions reveal asymmetries in annual cycle. is rather abrupt near-synchronous sharp increase rainfall, propagating Central America NE basin, weakening Low Level Jet. also not preceded by any significant sea surface temperature (SST) anomalies tropical North Atlantic Eastern Pacific. On other hand, overall smoother, anomalously warm (cold) SST over Sea Gulf Mexico (Eastern Pacific) during boreal usually related delayed (and vice versa). variations mostly independent each other. potential real-time predictability explored subseasonal-to-seasonal prediction ensemble (11 runs 1998 2017) ECMWF model. Its skill close zero lead time longer than 15–20 days, confirming weak antecedent upon transition. suddenly increases late April, 2–3 weeks only before mean date. It suggests that some forcing, operating synoptic intra-seasonal scale, plays role, but it seems barely occurrence, sequence, specific types.