MyFoxHurricane.com blog

Tropics unusually dry

Posted by Andy Johnson under Daily updates

Three tropical waves continue to move westward in the Atlantic basin. The westernmost wave is in western Gulf of Mexico and is being sheared by the TUTT low further west in Texas. Scattered convection has continued to move onshore over much of coastal Texas and Louisiana today but with no organization. Another upper level low is evident centered near Jamaica and is causing moderate shear in the central Caribbean. The combination of shear and a large amount of dry air on either side of the second wave near Trinidad and Tobago is inhibiting development. The third wave west of the Cape Verde Islands has the most concentrated convection but shows no signs of large scale organization. The wave is also moving into a large area of relatively dry air, especially for this time of year.

The water vapor channel satellite image below shows a large expanse of dry air (shown in red) extending from the Azores all the way to the Virgin Islands with another tendril extending into the eastern Atlantic ahead of the third tropical wave. Another large area of dry is located in the central Caribbean in associated with an upper circulation. More dry air extends from NE Florida into the Alantic.  

The image below shows a moderate area of shear in the Caribbean being caused by the upper low there. Shear is very low ahead of the third tropical wave in the eastern Atlantic but that wave is also moving into a much drier environment.

The image below is the 72-hour forecast value of shear overlaid on surface streamline wind flow. By then the wave just entering the Caribbean will have moved to the western Caribbean and Atlatic wave will be approaching the Lesser Antilles. Overall, the tropics are pretty quiet for this time of year. Remember, though, that 90% of tropical storms occur in August, September and October.