Isaac remains a tropical storm this morning, and though he has restrengthened some since yesterday, his proximity to Cuba has filled his large circulation with lots of dry air, and the inner core remains rather ragged on satellite and radar imagery. Due to Isaac’s large size it will take a while to mix out all of this dry air, but once he does, significant strengthening may be possible over the open waters of the Gulf of Mexico. Radar is showing spiral bands with tropical storm force winds already moving into the Florida keys and the southern Florida peninsula. The forecast intensifies Isaac into a hurricane tonight, and a category 2 hurricane over the central Gulf of Mexico. Currently an upper-end Cat 2 is forecasted at landfall on the gulf coast, but if Isaac mixes out the dry air and establishes an inner core more quickly, he could easily strengthen more than forecast, and it is not out of the question that Isaac becomes a major hurricane before landfall.
The track forecast has been a wreck over the last few days, and everyone is having to shift westward with the models, which now take Isaac into Louisiana or Mississippi. This is the path I called highly improbable, but it looks like it may happen. Isaac has hit the “sweet spot” between the trough over the eastern seaboard and the ridge over the Rockies, a situation similar to what we had with Debby earlier this year, where my forecast also had to flip. When a storm is in this kind of a position, it is very hard to predict whether the storm will get recurved by the trough or brought westward by the ridge. This is the time when we are very glad to have computer models that can catch on to which path the storm will ultimately take at least 2-3 days in advance of landfall. The track forecast now calls for a landfall on the Mississippi coastline, very close to the 11am NHC track, though it should be noted that the cone of uncertainty fans out considerably near the gulf coast, and it is still possible that Isaac could deviate significantly to the right or the left, and everyone on the north gulf coast should be prepared for a hurricane hit. The NHC has expressed the abnormally high uncertainty with this track forecast as well.
We shall see what happens!