Looking at a number of sat images including Caribbean & GoM WV loops and the Isaac floater, it sure appears that he is gulping dry air on the western side. That appears to be killing convection on the far west and south sides. At the same time, it appears that convection is increasing around a much tighter and better defined core that is just past the southern tip of Hispaniola and bearing down on the south edge of Hati. With Hispaniola to the north and dry air coming in from the west, I suspect that Isaac may weaken and get shaky for the next 24 hours, but may develop a tighter and better defined core as it does so.