Intensity forecast for Isaac
Isaac survived passage over Hispaniola relatively intact. It's large size aided this, and this will also help it survive passage over Cuba today and Sunday. By the time Isaac pops off the coast of Cuba into the Florida Straits on Sunday, it will likely be a 50 mph tropical storm with a large, intact circulation.
Isaac will be over very warm waters of 31°C (88°F) in the Florida Straits, wind shear will be light to moderate, and the upper-level wind pattern will feature an upper-level anticyclone over the storm, aiding its upper-level outflow. As I discussed in my previous post, Crossing Hispaniola and Cuba: a history, there have been five storms since 1900 with an intensity similar to Isaac, which crossed over both Haiti and Cuba, then emerged into the Florida Straits. These five storms strengthened by 5 - 20 mph in their first 24 hours after coming off the coast of Cuba.
Given the relatively intact structure of Isaac so far, and the favorable conditions for intensification, I expect Isaac will intensify by 15 - 20 mph in 24 hours once the center moves off of the north coast of Cuba. If Isaac spends a full two days over water after passing the Florida Keys, it is possible that it will have enough time to develop a full eyewall and undergo rapid intensification into a Category 2 or 3 hurricane.
The latest 06Z (2 am EDT) run of the GFDL model is calling for Isaac to intensify to Category 2 strength, then weaken to Category 1 at landfall in Mississippi on Tuesday. The 06Z HWRF run is calling for landfall in the Florida Panhandle near Fort Walton Beach as a borderline Category 2 or 3 hurricane.
The 5 am EDT NHC wind probability forecast gave Isaac a 19% chance of becoming a Category 2 or stronger hurricane in the Gulf. I expect these odds are too low, and that Isaac has a 40% chance of becoming a Category 2 or stronger hurricane in the Northern Gulf of Mexico. I doubt the storm has much of a chance of hitting Category 4 or 5 status, though. While the surface waters in the Gulf of Mexico are very warm, near 30 - 31°C, the total heat content of these waters is unusually low for this time of year.
We got lucky with the Gulf of Mexico Loop Current this summer, as it did not shed a big warm eddy during the height of hurricane season, like happened in 2005 (I discuss this in my Gulf of Mexico Loop Current Tutorial.) Without the type of super-high heat energy we had in 2005 in the Gulf of Mexico, Category 4 and 5 hurricanes in the Gulf of Mexico in 2012 will have difficulty forming.
Re: Masters’ forecast: that’s what Joe B. is suggesting right now on Fox: that it could be a 100-120mph storm at the keys with ‘explosive’ development tomorrow. Also could do ‘main’ landfall at least that strength.
Hi NautiNurse,This doesn’t sound good.Our newest son-in-law is a lineman.They are headed down to Florida right now.
Here is an ensemble model from wunderground whatever that is looks like a bunch of spaghettis. Just to show you how wacky these storms can get one spaghetti shows this thing going to just West of Perry,Fl. then hitting GA., SC maybe Wilmington, NC then doubling back hitting West Palm and back to the Keys.Unreal if it actually happened.
http://www.wunderground.com/tropical/tracking/at201209_ensmodel.html
The only thing I would disagree with Masters on is his assertion of 88 degree water. While there are pockets of it and even higher in Fla. Bay, Mollasses reef light right now is 84.6 with the highest in the last 24 hours 85. Still a few degrees above normal but not 88. The stream typically runs between 80 and 84 degrees. in the winter it can get into the high 70’s. There are warmer pockets but 88 is really up there. You might find some 88 degree water near the Cuban shore but even then when all this rain comes down and the wind blows water temps usually go the other way.