Examining Tropical Cyclone Development in the Southwest Caribbean Sea

Tropical cyclones (TCs) that develop in the southwest Caribbean Sea commonly make landfall due to their relatively close proximity to land masses, bringing flooding rains, high winds, and destructive storm surge to the impacted areas. Despite the dangers posed by southwest Caribbean TCs, there are relatively few studies in the refereed literature that examine the TC genesis climatology and pre-TC development synoptic-scale flow environment in this region. The aim of this study was to use the National Hurricane Center best track database and gridded atmospheric reanalysis data to construct a climatology of TC formation, determine the origin of the low-level precursor disturbance, and diagnose the synoptic-scale flow pattern in which TC genesis occurs in the southwest Caribbean Sea from 1990–2014. Results are presented from the synoptic climatology, composite, and case study perspectives.

The results show that TC formation in the southwest Caribbean Sea occurs preferentially in October and November, later in the season compared to the North Atlantic basin as a whole. Of the 45 TCs identified, 28 occurred in a baroclinic environment on the southeast flank of an upper-tropospheric trough. The upper-level trough results most frequently from downstream energy propagation via a Rossby wave train initiated in the western North Pacific. Preliminary findings suggest that the upper-level trough and attendant baroclinicity provide a focus for enhanced synoptic-scale ascent, which aids in moistening, destabilization, and maintenance of convection. Results from this study may provide aid in medium-range forecasting of southwest Caribbean TCs through awareness of synoptic precursors and their effects.