[UPDATE, 2:00 AM: Now Dean is at 150 mph, with 930 mb of pressure. Will it be a Category 5 by the time I wake up in the morning? I wouldn’t be at all surprised.]

As of 11:00 PM, Hurricane Dean has maximum sustained winds of 145 mph, and a minimum central pressure of 937 mb — and he’s not done strengthening. The headline on the public advisory is “CATEGORY FOUR DEAN INTENSIFYING OVER THE EASTERN CARIBBEAN,” and the discussion predicts that Dean will reach 155 mph (1 mph short of Cat. 5 status) in 24 hours.

Personally, I’d bet even money that Dean will become a Cat. 5 sometime tomorrow. Keep in mind, it has increased from 100 mph to 145 mph today, so jumping another 11 mph tomorrow (or 15, really, since they always round to the nearest multiple of five) isn’t exactly a huge stretch. Nor would it be surprising if the NHC’s current forecast is slightly downplaying the potential for further intensification. Because of the difficulty inherent in forecasting the internal dynamics of intense hurricanes, the NHC tends to be rather conservative in its intensity forecasts at this stage of a storm’s life. So just because the forecast has Dean hitting Jamaica in roughly 42 hours with “only” 155 mph sustained winds, it doesn’t necessarily follow that that’s the most likely scenario. I’d wager on 165 mph, myself, but as always, I’m just a layman and that’s just a guess.

The forecast track has shifted ever-so-slightly to the left, and now calls for the eye to rake the south shore of Jamaica instead of crossing the middle of the island from east tip to west tip. Of course, the whole island is easily within the “cone of uncertainty,” and the possibility of small but crucial last-minute “wobbles” means it will probably be impossible to predict Dean’s precise course vis a vis Jamaica until very close to landfall.

What seems fairly certain is this: Jamaica is going to be hit, and hit hard. A direct hit is distinctly possible — and if it’s a direct hit from a Category Five, that would be a first in the island’s history, according to Wikipedia — but even a “glancing blow” from a Cat. 4-5 hurricane would be quite bad. Much like the monster hurricanes of 2005, Dean is growing geographically larger, its wind field expanding as it intensifies. Still, Jamaica’s best hope at this point is for the storm’s eye to track far enough south of the island (or north, but south seems more likely) that the eyewall, or at least the inner portion of the eyewall, doesn’t come ashore. Otherwise, Drudge is right: it will indeed be a “HISTORIC HELL STORM.”

Dean’s exact intensity between now and landfall in Jamaica will depend mostly on eyewall replacement cycles, the dynamics of which meteorologists really don’t fully understand and can’t reliably predict. So another thing to hope for, if Dean does hit land, is a well-timed cycle right before landfall that brings the eyewall ashore during a weakening phase.

Alas, however, there is reason to fear that Dean might come ashore during a strengthening phase. Take a look at the Tropical Cyclone Heat Potential map of the waters surrounding Jamaica:

That white-hot color on either side of the island represents the most dangerously warm waters in the whole Atlantic basin, and just as the Gulf Stream and the Loop Current tend to supercharge hurricanes that pass over them, I fear Dean could get a final, deadly burst of energy from the patch of pink and white just off the eastern shore. That would be a very bad thing, because major hurricanes are worse when they are strengthening than when they’re stable or weakening; the greater instability of the intensification cycle leads to higher wind gusts and such. In other words, the only thing worse than a Category 5 hurricane making landfall is a strengthening Category 5 hurricane making landfall.

It’s probably too late to get the hell out of Jamaica now; I’m told all outbound flights are booked through Sunday afternoon, at which point the storm will be hitting. But if there’s any way to get out, do it, as Alan Sullivan says:

If you are a tourist on Jamaica, get off the island tomorrow — even if you have to go to Cancun. You’ll have a extra day to get out of there. Seriously, you don’t want to be trapped in a hurricane-ravaged Third World country. There will be no utilities, no untainted water or food, scarcely even a secure place to sleep, in areas exposed to the full force of a category four or five storm. Do whatever you have to do, pay whatever it costs, and get out. Jamaica residents should of course rush all preparations to completion. They live there. One hopes they know what to do for their own security.

For those who can’t leave, Jamaican residents and tourists alike, now is the time to make prudent preparations (like filling bathtubs with water) and get ready to hunker down for the storm… then ride out the aftermath. And it’s also a good time for the rest of us to keep them in our thoughts, and pray for them if we’re so inclined. It’s going to be a very rough few days in paradise.

After Jamaica? The computer models continue to disagree about where Dean will go, and there will be plenty more time to talk about that over the weekend. For now, the only thing I want to say about the storm’s post-Jamaica future is that Dean’s path over the island could be quite significant to the long-term intensity forecast. The more interaction between the hurricane and the mountains, the more likely it is to weaken. Conversely, the further offshore it stays, the better for Jamaicans but the worse, potentially, for residents of the Yucatan Peninsula, who would then be more likely to bear the full brunt themselves. Ultimately, though, it may not matter, since the waters between Jamaica and the Yucatan are plenty warm, and Dean will have plenty of time to get its act back together even if it does weaken over Jamaica. Two Cat. 5 landfalls are certainly not out of the question. In fact, the NHC, which is holding Dean to a high Cat. 4 in its predicted Jamaica landfall (and not specifically predicting any weakening from land interaction), is forecasting it to reach minimal Cat. 5 status in 72 hours, and make landfall as such near Cozumel late Monday or early Tuesday.

And with that, I’m going to bed. I’ll try my best to keep posting storm updates through the weekend, though I also continue to have a ton of errands and housework I desperately need to get done, and it seems like this hurricane-blogging thing very quickly becomes all-consuming. :) As soon as I’m done with one lengthy post, something else happens and I feel the urge to start a new one! And, as I told Becky earlier, all this extra web traffic is like a drug: it makes me want to blog more and more! After all, if lots of people are visiting my blog, I want to give them good, timely information, and not leave them disappointed with what’s here! So I blog and blog and blog. And blog. … Anyway, I’ll do my best to balance the blogging with my other responsibilities over the next few days, so that I can keep giving y’all updates without totally screwing the pooch on everything else (like cleaning our massively untidy house for our houseguest who is arriving in less than a week… AAAHH!!!).

Anyway, g’nite all. Pray for Jamaica. I leave with you with another scary satellite image, from a few hours ago:

P.S. Interesting aside: a blogger in Jamaica notes that the island nation has an general election scheduled for August 27. All campaigning has stopped as the storm approaches, and it is possible the election may need to be postponed, depending on the extent of the damage.