Abraham Anthony Chen Trevor Falloon And Michael Taylor

The core of the West Indies (figure 11.1) consists of the archipelago of islands that stretches southeast from the Yucatan and Florida peninsulas to Venezuela. Generally the term "West Indies" is synonymous with the "Antilles" and is therefore often used to refer to the islands that compose the Greater and Lesser Antilles. The islands of the Greater Antilles include Cuba, Hispaniola, Puerto Rico, and Jamaica—all located in the north Caribbean Sea—while the Lesser Antilles encompasses the smaller islands found to the south and east (figure 11.1). In total, the West Indies embraces about 25 island territories.

There are complex mountain ranges in the Greater Antilles, such as the Blue Mountains (2257 m) in central Jamaica and the Pico Duarte (3175 m) in the Dominican Republic, smaller volcanic peaks in the northeast island arc, and low-lying islands composing the remainder of the Lesser Antilles. The variation in local topography contributes significantly to the general rainfall pattern across the West Indian islands, as the windward sides of the larger and more mountainous islands are rainy and windswept, while the leeward sides are drier. In comparison, the low-lying eastern islands receive much less rainfall due to their lack of topographic relief and are much more dependent on seasonal rains.

It is, however, the location of the West Indian islands between the permanent high pressure zone of the subtropical north Atlantic (the Azores high) and the equatorial trough of low pressure that gives rise to the mean monthly West Indian rainfall depicted in figure 11.2.

Early in the year (December through March) and for a brief period in July, the Caribbean is dominated by subsidence from the inner zone of the Azores high and is at its driest. Rainfall during this period (barring July) is largely from the intrusion of fronts from North America. By the onset of the rainy season, however, the Azores high drifts farther north, resulting

Figure 11.1 Map of the West Indies.

in weakened trade winds. At the same time, the Caribbean Sea warms up. These weakened trades and warmer sea-surface temperatures favor the convective development of easterly waves (weak troughs of low pressure). The waves begin their regular (every 3-5 days) trek across the tropical Atlantic and through the region during mid-June. Later, the easterly waves produce a summer with maximum rainfall and are largely responsible for the tropical storms and hurricanes that frequent the region and augment rainfall totals during this period.

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