Hurricane Hanna Forecast

Currently Hanna is located in a high shear environment created by the outflow from Hurricane Gustav. Gustav has made landfall and should weaken substantially now, and is already down to 80 mph winds from 115 mph this morning. As this continues, the shear caused by Gustav will weaken, which the models also confirm. However, this shear will not weaken substantially for another 36 hours. Luckily for Hanna (or un-luckily for the southeast US), she will stay in the southern Bahamas for this time period as Gustav's strongest shear moves north. Thus, considering she has survived the near 20 knots of shear over her now, she should be able to hold her strength or strengthen over the next 36 hours.

After 36 hours, things begin to change substantially. Gustav's shear will be minimal to moderate over Hanna, closer to the 5-15 knot range, allowing her to develop further. Upper-level divergence should be established over the system and the storm will still be over warm sea surface temperatures. Thus, I wouldn't be surprised (if she can survive the shear for the next 36 hours and keep her strength) to see Hanna reach Category 2 strength.

At 36-48 hours, a building ridge should begin to slide from the central Atlantic towards Hanna. With clockwise rotation around a high, this should begin to push Hanna towards the north-northwest. The GFS and European produce a stronger ridge than the CMC model. Thus, they push Hanna a bit further to the west into the GA/SC border region, while the CMC tracks the storm into NC. Right now, considering the CMC completely bombs out the system (which is unrealistic), which is likely a reason the ridge isn't depicted as strong, I am thinking on leaning on the European and GFS models. This also happens to be the area of greatest clustering of the rest of the models as well. Thus, right now I predict a GA/SC border landfall as a Category 2 storm.

As the system moves north, shear should remain low until 24 hours before landfall. At that time the models want to increase shear slightly over the North Carolina area. Considering Hanna's ability to keep her strength (and strengthen!), and Gustav's ability to stay a Category 3 all the way to landfall in a high shear environment, I think she should stay together and make landfall as a Category 2 storm. The landfall location will be very important in regard to Savannah, GA. If it lands on the GA/SC border the city will be spared from the surge. If it makes landfall to the south, the city will be inundated. Savannah is a city that can easily be washed away because of its close proximity to the water. Add on a local mentality that storms always miss their area, and a disaster could be on our hands. Hopefully Hanna turns more than expected, and maybe even goes out to sea...but I don't see that right now.