[NOTE: A lengthier “get the hell out” advisory to folks in Jamaica can be found here.]
I’m breaking my Dean-silence 80 minutes early to report that the storm is now a Category 2 hurricane, with 100 mph winds, rapidly approaching the Lesser Antilles. Indeed, the outer bands are already affecting the islands, and the eye will pass through overnight tonight and tomorrow morning. A new advisory is due out within the next few minutes, and I’ll post an update after it’s released.
UPDATE: Dean is still at 100 mph as of 11:00 PM. According to Dr. Jeff Masters, the storm’s strengthening has stalled because “dry air on the storm’s northwest side…is getting wrapped into the storm. This dry air will persist through at least Friday, and should act to prevent Dean from undergoing rapid intensification until it clears the Lesser Antilles Islands.”
Once Dean gets into the Caribbean, however, it’ll be a different story. “Dean is steadily moistening the environment around it, and may be able to overcome the dry air on Friday and put on a burst of rapid intensification,” Masters writes. “I expect Dean will become a large and extremely dangerous major hurricane by Saturday.” And by Monday night, when it’s expected to reach the Yucatan Peninsula, “The GFDL and HWRF intensity forecasts both project Dean will be a Category 5 hurricane.” In fact, according to Eric Berger, the GFDL predicts that Dean will have 180 mph winds by Monday. Berger thinks “that’s almost certainly too high,” but I’m not sure why — as Dr. Masters noted earlier today, the Western Caribbean’s “ocean heat content is near the record levels observed during 2005.” Frankly, I’ll be surprised if Dean doesn’t reach at least 165 mph at some point between now and Monday night. It’ll probably take an unexpectedly severe run-in with either wind shear or dry air to prevent such an eventuality. (The NHC’s 11pm discussion provides a glimmer of hope on that front: “THE UPPER FLOW COULD BE A LITTLE LESS FAVORABLE IN THE WESTERN CARIBBEAN…PARTICULARLY IF THE UPPER LOW LAGS A BIT.”)
As for Dean’s future track, Berger says the latest model runs show “some hints that Dean might skirt the Yucatan peninsula and come into the Gulf between there and Cuba,” which would be the “worst-case scenario” that I diagrammed yesterday. But that’s four days away yet, and anyway most models still show the storm hitting the Yucatan.
After that? The current consensus is a final landfall somewhere between the Mexico-Belize border and the Texas-Louisiana border. Dr. Masters said earlier today that he’d “be surprised to see Dean make a turn northwards in the Gulf of Mexico towards Louisiana or points further east, as there are no strong troughs of low pressure coming across the U.S. until late next week.” That statement still appears to hold, for the most part, although the GFDL is now taking Dean toward western Louisiana.
In any event, rather than dissecting the current model runs too closely, the best course of action is probably to take a deep breath and wait until tomorrow morning. As Dr. Masters points out, “Tonight marks the first flight of the NOAA jet, and we’ll have a much more reliable set of model runs Friday morning. Hopefully, this will narrow down the uncertainty of what will happen when Dean reaches the Gulf of Mexico.” Berger agrees, saying it will be “more prudent to seriously consider the models tomorrow morning, when they have aircraft data for the first time and hopefully a better handle on the atmospheric dynamics that will guide Dean early next week.”
So keep an eye out for those 12Z (8:00 AM) model runs. The more “clustered” they look, the more confidence we can have in their predictions (though, as always, don’t make life-or-death decisions purely on the basis of computer models). When they’re available, you’ll be able to see them here and here and here and here.
P.S. If anybody in Jamaica or the Yucatan Peninsula is reading this, now would be a good time to, ahem, get the hell out. Or at least start making plans to get the hell out soon, because Dr. Masters believes the airports in Jamaica will close on Sunday, and the ones in the Yucatan will follow suit on Monday. And personally, I wouldn’t want to be in the path of Gilbert, the sequel if I could avoid it.
As for the U.S. Gulf Coast, it’s far too early to think about evacuating, but definitely keep an eye on this thing through the weekend. That goes doubly for Texas. Hard decisions may await early next week.
Oh, and the latest specs and track speculation on Dean can be found here.