On the Nature of the Winter Season Rainfall in the Dominican Republic

Abstract

The winter season rainfall data for the Dominican Republic for the years 1960?67 are examined in detail. Frontal zones dissipating over the area are found to he the primary rain-producing mechanism during the winter months. A relatively small number of fronts produce a large share of the total rainfall. Rainfall producing fronts are most pronounced in November and least evident in February. Mountains are seen to play a crucial role in the intensity and distribution of precipitation throughout the country. The interactive effects of synoptic-scale frontal zones with the local terrain seem to account for the large peak of precipitation observed along the north coast of the country during November. Synoptic-scale conditions that seem to favor enhanced frontal precipitation include the establishment of strong ridging north of the Greater Antilles, with a corresponding strengthening of the trades over the area. Upper level westerlies in the vicinity of the Greater Antilles also tend to become more pronounced during heavy rain occurrences. The use of a nonlinear diagnostic balance model in a detailed case study suggests that synoptic-scale warm advection and diabatic heating (primarily latent) are the dominant forcing functions producing ascent in the Dominican Republic region. Terrain influence is a very important modifying factor.