Water vapor satellite imagery from this morning showing Dorian becoming cut off from the moisture feed flowing in from the south (pink arrows) as more and more of the circulation is getting surrounded by dry air (yellow arrows). This interruption in moisture return from the south is likely contributing to the weakening we’ve seen since last night.
In addition, differences in the environmental flow driving Dorian are creating a less-than-favorable upper air environment for the system. The low-level center is slipping out in front of the thunderstorms, and this process tends to lead to a progressively less-organized system. The big question today is whether or not Dorian can survive this process, which should continue for another 48 hours before the upper winds become less hostile. If it does, there’s a chance some land mass will ultimately have to deal with Dorian. If not, it will be more evidence in the books as to why July is such a hostile month for tropical systems in the Atlantic.