As of 09z, 5 am this morning the storm has run up against an mid level vorticity that is lingering over the Florida Straits between Cuba and the Upper Keys. This has also brought the track forecast a little to the left and keeps the core off the northern Cuban coast.
With this in mind the storm would have a better chance to gain some "juice" as it moves northwest, and therefore NHC is going to intensify the forecast to category 1 hurricane by the 36 hour forecast period.
This will force a hurricane warning for the entire Florida Keys and Southwest Florida Coast.
I will have to bow to the GFS model in so much as it keep banging on the forecast with little deviation, even if the reason was totally unclear as to why.
There are still some issues with the intensity forecast in my eye, the vorticity to the northwest of Issac, and there are some terrain issues yet to be worked out for the next 24 hours or so.
Issac is forecast to remain in the cat one range of intensity from 36 hours through 96 hours as it crosses the northern Gulf Coast near Mobile Alabama Thursday. On the current track even though it would be necessary to issue a tropical storm warning for Sarasota southward, but the good news is that mort of the winds will be offshore before the storm weakens and moves inland.
I will try to update later, but this boy needs some sleep after I get the morning forecast out at 6am.
Be prepared and be safe.