Forecasting Strong Winter Winds over Puerto Rico and the Virgin Islands

Wintertime synoptic situations leading to the occurrence of strong surface winds over coastal waters of the Dominican Republic, Puerto Rico, the Virgin Islands, and the northern Leeward Islands are discussed. Six-hourly average wind speeds for the oceanic areas adjacent to Puerto Rico are obtained from ship reports and related to the surface pressure gradient. The onset of surface winds of 20 knots or greater is found to follow the crossing of the east coast of the United States by a migratory anticyclone with above critical central pressure, or the occurrence of strong trade winds above the gradient level a t San Juan, P. R., as a nonmigratory anticyclone intensifies. These results are combined into objective forecasting rules for predicting the onset of strong winds 12 to 24 hours ahead.