Influence of Environmental Winds on Land–Sea-Breeze Afternoon Thunderstorms over Western Puerto Rico

Land and sea breeze circulations are induced by large temperature contrasts along coastlines. In Puerto Rico, a relatively small Caribbean island with a prolonged mountain range and completely surrounded by water, sea breezes are often present. This phenomenon—along with terrain and other factors—affects thunderstorm formation on the island. For this reason, this study focuses on the direct consequence of the confluence of the land-sea breeze phenomenon and the upstream winds on thunderstorm location and intensity over the western side of the island. The research aims to improve the precise prediction and understanding of these convective storms, which still remains a challenge. The data used for analyzing upstream winds were gathered from the San Juan National Weather Service soundings, and the ones used to determine sea breeze days were obtained from the Mayagüez Harbor station. A climatological wind analysis determined winds predominantly come from the east, in addition to some southeasterlies and northeasterlies, and their direction depend on the subtropical high location and intensity during the sea breeze days. Radar data and numerical simulations with the Weather Research and Forecasting (WRF) model were examined to test the hypothesis that upstream wind conditions affect the location and intensity of thunderstorms associated with sea breeze. The results conclude that our hypotheses on rainfall location were correct at the time the convection started, but as time passed, thunderstorms moved and expanded due to the sea breeze duration and intensity, amongst other factors.