Ernesto has made landfall in southwestern Cuba this morning as a generously classified 45-kt tropical storm (Figure 1). Looking at the latest reconnaissance observations, the fastest flight level winds found were still only 44 kts (which translates to about 37 kts or 43 mph). Now the question remains, where does Ernesto go from here?
The immediate problem to tackle is how long does Ernesto remain over Cuba. The official NHC track forecast keeps Ernesto over Cuba for about 12 hours or so (Figure 2). However, that would mean that Ernesto makes a turn to the west-northwest. At its current heading (through simple extrapolation), Ernesto would move off Cuba in 6-9 hours. Indeed, some of the models are predicting this (Figure 3). NHC appears to have taken the model consensus for their forecast. How long Ernesto remains over Cuba is important for two reasons: 1) It is a small storm, so it will not take a long time for the mountains of Cuba to tear it apart, possibly dissipating the storm before it can reach the Gulf of Mexico, and 2) the earlier Ernesto gets back over open water, the more time it will have to intensify before it reaches Florida.
Assuming that Ernesto makes it off the coast of Cuba, the next forecast issue will be rapid intensification (RI). As mentioned in a post yesterday, the waters surrounding Florida are extremely warm (>30C) and shear is expected to remain low, which increases the probability of RI. If RI were to take place, Ernesto could come ashore in Florida as high as a Category 3 hurricane. However, this is way outside the guidance envelope (Figure 4). The GFDL is the only model taking Ernesto higher than a Category 2 hurricane. Of course, this makes sense if you look at the track forecast in Figure 2. The GFDL is one of the easternmost models, taking Ernesto off Cuba much quicker than the official forecast suggests. Also note that the usually dependable DSHIPS model keeps Ernesto as a tropical storm.
Onto what I think is going to happen. The models have been trending to the east for the last 72 hours. What originally looked like a landfall in New Orleans is now getting closer to Miami. I am tending to believe the GFDL track run (again, this is east of the NHC official forecast), simply because of the trends of the last 72 hours. This would put Ernesto on shore around Homestead, FL. That said, the GFDL intensity forecast seems a little high to me. Something I noticed last season (although not yet this season, possibly because we have only been dealing with weak storms over less than ideal conditions) was that the GFDL had a tendency to turn every storm into a Category 4 or 5 as soon as shear got less than 10 kts. That is the case with Ernesto once it moves off the coast of Cuba. Putting the proverbial gun to my head, I would follow the GFDL track forecast and call it a borderline Category 2-3 (~100 kts or 110 mph) hurricane when it makes landfall. I'll try to be updating every few hours today, so stay tuned to the StormTrack for more.