Isaac is still fighting off some drier air to the north as well as some light to moderate shear just ahead of it. This combo should keep it as a tropical storm over the next 24 hours.
High pressure will continue to push it due west through the end of the week, then by the weekend most models indicate a turn to the north/northwest. This turn puts South Florida in the cone of concern.
While the track is coming more into focus, the question of how strong it will be, is still a mystery. If Isaac tracks over the Islands, specially Hispaniola, high terrain here (the highest in all of the Caribbean. Pico Duarte in Dom. Rep. is over 10,000 feet high) could shred it apart. This may sound good, but that process could dump allot of rain over Dominican Republic and Haiti leading to flooding, land and mudslides.
If Isaac misses the islands and stays over the warm waters of the Caribbean, there is plenty of hot water here that it could use as fuel for growth.
This what NHC is saying:
THE INTENSITY FORECAST
IS COMPLICATED BY HOW MUCH THE CORE OF THE SYSTEM INTERACTS WITH
THE MOUNTAINOUS LAND MASSES OF HISPANIOLA AND EASTERN CUBA. THE
OFFICIAL WIND SPEED FORECAST IS FAIRLY CLOSE TO THE STATISTICAL-
DYNAMICAL GUIDANCE FOR THE FIRST 48 HOURS AND THEN TRIES TO TAKE
INTO ACCOUNT THE LAND INTERACTION. NEEDLESS TO SAY...THERE IS
CONSIDERABLE UNCERTAINTY IN THE INTENSITY OF ISAAC IN THE 3 TO 5
DAY TIME FRAME.
Because of this UNCERTAINTY, everyone throughout the Caribbean and South Florida should continue to monitor the track of Isaac. Another recon mission is set for today to get a better handle on Isaac and where it may eventually end up.