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Dry slot in the tropics

Posted by Andy Johnson under Daily updates

There are 3 tropical waves we are following in the Atlantic basin. One is west of the Cape Verde Islands and is showing signs of some spin near the surface on its northern edge. Another tropical wave associated with a wind surge is northeast of Venezuela moving fairly rapidly westward. The first two waves are moving into a large slot of dry air that covers much of the tropical Atlantic. The third wave extends from the Central Gulf of Mexico southward into the western Atlantic. An upper level low west of the Gulf wave is causing shear over the wave. The combination of shear to the west and the landmass of Mexico and Central America should prevent this tropical wave from developing. The situation reminds me of Bonnie a few days ago, when there was an upper low to the west of Bonnie and dry was being entrained from the east.

The enhanced IR satelitte image below shows large convective clusters with the wave affecting Belize, Hoduras and the Yucatan Peninsula as it moves westward.

The water vapor image below shows an unusual amount of relatively dry air for this time of year in the Atlantic basin. The tropical wave approaching Trinidad and Tobago is basically surrounded by the dry air and the slightly more organized wave west of the Cape Verde Islands is moving into a drier environment, as well. The large area of dry air should inhibit tropical development over a large portion of the basin for the next few days, at least.

The streamline analysis shown below shows a slight circulation associated with the eastern Atlantic tropical wave. However, the wave is moving into an unfavorable area for  development due to drier air even though wind shear is light to the west of the system.  

The image below is the forecast streamline and shear analysis. The tropica wave east of the Lesser Antilles will move into an area of moderate shear over the next few days. Shear will remain light near the eastern Atlantic tropical wave. However, the streamline analysis below shows an open wave in a few days with no closed circulation.f