Monday, June 23, 2008

Tropical Waves

Well we have had some tropical weather over the last week or so and it appears to be hanging around. We have had a little rain and some nasty winds. Some of the winds have been reported in the forty plus mile an hour range. A couple of days ago a charter boat, (not one of CYOA's) in the BVI's sunk after getting caught is a rain squall that they were apparently ill prepared for. The same front turned over a 28 foot boat on its mooring in St Thomas and broke another boat loose from its mooring in St John and put it on the rocks.

Here is the definition of a tropical wave.

A tropical wave is normally preceded by an area of sinking, intensely dry air, oriented as a northeast wind. With the passage of the trough line, the wind veers to the southeast, the humidity abruptly rises, and the atmosphere destabilizes, producing widespread showers and thunderstorms, occasionally severe. As the wave moves off westward, the showers gradually diminish.
A notable exception to the general characteristic of widespread precipitation behind a tropical wave occurs in the Atlantic. Periodically, a surge of intensely dry air known as the Saharan Air Layer (SAL) is entrained behind a tropical wave, resulting in cloudless or nearly cloudless skies as convection is capped by the dry layer inversion. Additionally, any dust which may be present within the SAL reflects solar radiation, slightly cooling the atmosphere below it.

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