Tropics Watch: The Latest on Isaac

Tropical Storm Isaac continues tracking west across the northern Caribbean Wednesday afternoon. As of 5PM AST, max winds remained at 45 mph and the system's motion was west at 22 mph. Numerous tropical weather watches and warnings remain in effect:

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...
 
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* MARTINIQUE
* DOMINICA
* GUADELOUPE AND THE SURROUNDING ISLANDS...AND ST. MARTIN
* ST. KITTS...NEVIS...ANTIGUA...BARBUDA...MONTSERRAT...AND ANGUILLA
* SABA...ST. EUSTATIUS...AND ST. MAARTEN
* BRITISH VIRGIN ISLANDS
* PUERTO RICO...VIEQUES...CULEBRA...AND THE U.S. VIRGIN ISLANDS
 
A HURRICANE WATCH IS IN EFFECT FOR...
* PUERTO RICO...VIEQUES...CULEBRA...AND THE U.S. AND BRITISH VIRGIN
ISLANDS
* SOUTH COAST OF DOMINICAN REPUBLIC FROM ISLA SAONA WESTWARD TO THE
HAITI-DOMINICAN REPUBLIC SOUTHERN BORDER
 
A TROPICAL STORM WATCH IS IN EFFECT FOR...
* NORTH COAST OF DOMINICAN REPUBLIC FROM THE HAITI-DOMINICAN
REPUBLIC NORTHERN BORDER EASTWARD TO NORTH OF ISLA SAONA

Isaac's track still remains very uncertain as the global dynamic models and the tropical models all show differing solutions, especially in the period beyond the next 4-5 days. If the European solution is correct, this would have the biggest impact on our forecast, as this model brings Isaac into the Gulf and ashore along the central Gulf Coast as a major hurricane. At this time, the Euro is the outlier among all the models, but cannot be totally ignored. Here is what the European is forecasting for NEXT Thursday morning, Aug 30th:

Most opposite to the Euro's solution is the NAM, which keeps Isaac in the Atlantic through the next 84 hours, east of Florida. Here is the NAM's output, valid Saturday evening at 7 pm: 

The GFS and Canadian's solutions basically split the difference between the NAM and Euro, and target the Florida peninsula then the eastern seaboard.

Isaac's evolution of intensity is also in question due to the rugged terrain of the Caribbean Islands it will be crossing in the coming days. Isaac is expected to cross right over the Island of Hispañola and the eastern part of Cuba. The mountainous terrain of this area will really tear Isaac apart and the extent to which any re-strengthening will occur remains to be seen. 

Dry air to the north of the cyclone is also being entrained towards the center, preventing rapid strengthening. The storms structure is not nearly as compact as it has been, as it has become more elongated in nature and overall, appears to be disorganized:

Here is the official NHC track:

As far as the model spread, the majority have shifted slightly west with time, bringing Isaac up the west coast of the Florida peninsula:

It is still WAY too early to make a call as far as ultimate destination. Stay tuned for further updates...