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Isaac Gets Organized, Moves into Haiti

August 24th, 2012 - 10:32 pm

I am beginning to suspect that, even if Tampa is largely bypassed, the Republican Party will end up needing to compress its convention, or at least the “made for TV” portion thereof, into Wednesday and Thursday. This is largely based on a “Gustav precedent,” when they cancelled Day 1 of a convention in Minnesota because of the perceived optics of throwing a big party while a hurricane was hitting the Gulf. Imagine those same optics if the hurricane was just a couple hundred miles, or less, away. So yeah, I think the GOP convention will end up basically starting Wednesday, after Isaac is inland. But I’m just speculating that; I don’t know.

Back to the intensity forecast for a moment: the good news, as Dr. Jeff Masters noted earlier today, is that the Gulf waters aren’t as conducive for rapid intensification as we’ve seen in years past. Here’s a map to demonstrate this:

isaac_tchp_aug24

Dr. Masters explains:

For tropical cyclones in favorable environmental conditions for intensification (i.e., vertical wind shear less than 15 kt, mid-level relative humidity >50 %, and warm SSTs [i.e., >28.5C]) and with intensities less than 80kt, values of ocean heat content greater than 50 kJ/cm^2 (yellow and warmer colors) have been shown to promote greater rates of intensity change. Isaac will be in such a region when it is over water between its current location and the Florida Keys. Once Isaac goes beyond the Keys, total ocean heat content will fall to levels not as conducive for rapid intensification. …

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, I doubt we can get a Category 5 hurricane in the Gulf in 2012.

And thank goodness for that. The possibility of Isaac becoming a Category 2 or 3 hurricane, though, remains very much alive. We shall see. A big factor will be, not how much the wind speed per se weakens over Haiti and Cuba, but how much of the storm’s newly developed inner core structure is maintained over the islands. If the mountains of Cuba just basically rip the storm’s core apart, it will take longer for Isaac regain its strength, and intensificaiton to a major hurricane is unlikely. So, root for those mountains to do their thing, I guess.

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