The various computer models predicting Isabel’s future movements are beginning to “cluster” around the forecast track, which is usually a sign of increased confidence that the forecast will be correct, or close to correct. The models have stopped “trending” to the right, and a Weather Channel forecaster said this morning that, as they get a better handle on the movements of the high pressure system to Isabel’s east, it looks less and less likely that the monster hurricane will miss the East Coast altogether. So my prediction of yesterday appears to be quite a bit less likely to come true than it did 16 hours ago. (And, I must admit, it was always rather dubious.) As the Hurricane Center puts it:

Unfortunately…the models are now in excellent agreement with Isabel making landfall along the central U.S. East coast in about 4 days. There is still uncertainty on where the exact landfall could occur since the developing central U.S. trough could deepen and dig southward more than is forecast by the global models…which could lead a more northward motion and landfall farther up the east coast than what is currently forecast. Unfortunately…all of the model guidance agree on a large and strong north-south oriented ridge remaining east of Isabel…which should prevent the powerful hurricane from recurving out to sea. Landfall along the U.S mid-Atlantic coast somewhere between North Carolina and New Jersey between 4 or 5 days is appearing more and more likely.

As stated above, there is still a great deal of uncertainty about where exactly Isabel’s most devastating impact will be — not so much because of inherent forecasting difficulties, but because of the angle at which it will be approaching the coast, getting closer and closer to parallel the further north it goes. Looking at the predicted Wednesday position and comparing it to possible landfall locations, there is only about a 30-degree difference, angle-wise, between a Cape Hatteras landfall and a central Long Island landfall.

In other words, very slight changes in Isabel’s path could shift the target zone hundred of miles north or south. Unless the track uncertainties decrease greatly in the next 24-36 hours, I suspect we will be seeing a very large Hurricane Watch area when the NHC first sounds the alarm, which will probably happen late Monday or (more likely) Tuesday. I wouldn’t be surprised if the watch zone stretches all the way from southern North Carolina to somewhere along the Jersey Shore, with a Tropical Storm Watch reaching out onto Long Island.

Hopefully, Isabel will weaken substantially before it hits anywhere, and there is a decent chance of that. The NHC brings it down to 125 miles-per-hour before landfall — that’s a medium-strength Category Three. It would nice to see it get down to 110 or 115 mph (still no walk in the park by any means, but not capable of the utter devastation that a landfall at Isabel’s current strength would cause).

But if she doesn’t weaken drastically, and if the out-to-sea track is indeed ruled out, there is no “good” forecast, no “good” track for Isabel to take. (The best-case scenario might be a Long Island landfall, since that would give the hurricane more time to weaken, especially since it would have to spend some time over cooler waters before hitting. But what’s “best-case” in the grand scheme of things would still be very bad news for Long Island and Connecticut.) There are, however, plenty of “bad” tracks. Indeed, if Isabel remains at least a Category Four, or even a strong Category Three, it raises the possibility of several nightmare scenarios that hurricane experts have long been concerned about.

One of those nightmares is a landfall just to the west of Cheasapeake Bay; in that scenario, the hurricane’s “right-front quadrant,” always the strongest portion because the forward motion is aligned with the counterclockwise circulation, would bring an enormous storm surge and devastating flooding all up and down the bay. The current official forecast raises that spectre in a big way:

A tiny bit further to the left, and that storm surge could come directly up the Potomac River, toward D.C. A little further to the right, and a similar flooding disaster could happen in Delaware Bay. And then there’s another nightmare scenario: a landfall, dare I say it, just to the west of New York City. It is not hard to imagine the devastation that a 30-foot storm surge would cause in Lower Manhattan.

I’ll put it this way: If Isabel and its storm surge are heading my way come Thursday or Friday, I won’t be going to work. My apartment in Washington Heights — note the key word there, “heights” — is going to be a lot safer than Tribeca, near the island’s flat southern tip. I suggest that any of my readers who are located between the Carolinas and Long Island start thinking along similar lines: where will you go, what will you do, how will you prepare, if this monster storm heads your way? (This means you, Dane!) The time for disaster preparation is now. (Now might also be a good time to buy a few canned goods and batteries. Beat the rush, as they say.)

Earlier today, the Weather Channel showed an animated high-seas forecast map showing an “orange” zone of 20- to 25-foot waves engulfing much of the East Coast by Wednesday and Thursday. So this is not going to be a good beach week for anybody. Another thing to consider is this: wherever Isabel goes, there will probably be strong winds all up and down the coast throughout the latter part of this week, because of the tight pressure gradient between the high pressure system to the north and Isabel to the south. I’m not talking about hurricane-force winds, but the sort of high winds and wind gusts that you might expect on a very blustery winter day.

Well, anyway. I need to stop posting now, and pack for my return trip to New York, having spent this weekend in Connecticut. I’ve been working on this post for almost two hours!! :) But rest assured, there will be plenty of updates on this hurricane in the days ahead. Maybe even some live, on-the-scene updates. We shall see.

I neglected to include a satellite image of Isabel in my last post — a glaring omission, given the extraordinary appearance of this extraordinary hurricane. Not only is Isabel intense, tightly wound, and very symmetrical, but it is also a geographically small hurricane with a geographically huge eye, 50 miles across. Check it out:

The latest official forecast track for Hurricane Isabel shows it aiming directly at the Delmarva Peninsula of Virginia, Maryland, and Delaware, about five days from now.

In its discussion, the National Hurricane Center says, “Note that the 5 day forecast position is rather close to the mid-Atlantic U.S. Coast.” As if anyone would have failed to notice.

It’s worth remembering, however, that this is the first year the Hurricane Center has even done a five-day forecast; they used to predict only 72 hours (three days) into the future. The technology has improved enough that they can now attempt a 120-hour forecast, but that doesn’t mean it can be expected to have pinpoint accuracy. Hence the wide forecast “cone” in the graphic above (a cone which, it’s worth noting, now includes New York and Connecticut). In other words, it’s simply way too soon to say what’s going to happen.

I’m going to go out on a limb, however, and make a prediction: I bet this hurricane misses land altogether and floats harmlessly out to sea (or, at the worst, hits Nova Scotia and/or Newfoundland as it weakens). I base this not on the current forecast, but on the trend of the last couple of days’ forecasts and computer tracks. A consistent forecast trend, I have observed, is sometimes a better predictor than any one forecast or computer-model run. And in this case, the models keep budging their predictions further and further to the right, and the NHC keeps following suit — and I bet that trend continues.

I think something is happening in the atmospheric dynamics — “wind is changing,” as Ghan-Buri-Ghan said in the Lord of the Rings — and the computers are slowly adjusting to it. Two or three days from now, I bet the official forecast will be calling for a near miss offshore of Cape Cod; and in the end, I bet it won’t even be very close.

That’s barely more than a hunch, and it’s going against all the conventional wisdom at the moment, but it’s my best guess based on watching these things — and watching the Hurricane Center deal with these things — for the last 14 years or so. Isabel reminds me a lot of Hurricane Hortense in 1996, which, at this point in its track, looked almost inevitably bound for the mid-Atlantic or Northeast because it was wedged between a high pressure system offshore and a trough onshore, just like Isabel is. But things changed, and Hortense ended up missing the coast by a wide margin, and I bet Isabel will, too.

On the other hand, the latest set of computer models includes one, the GFDL, that looks like a classic Long Island-Connecticut landfall track:

“All of you from Florida all the way to Maine should keep an eye on this system,” a Weather Channel forecaster just said.

We will just have to wait and see. My “prediction” is really just the marginally educated guesswork of an amateur. So who knows? I’ve said it before and I’ll say it again: Stay tuned.

Updates: UConn lost. Notre Dame is losing badly. USC is winning comfortably. Isabel is back up to 160 mph, Cat. 5, and the latest computer models suggest a sharper right turn than previously expected. Meanwhile, here are Sara, Jen, and Krista on carousel.

Hurricane Isabel is down to “only” 150 mph, a very strong Category Four, but having now completed an eyewall replacement cycle, “some slight strengthening is possible during the next 24 hours.”

As for the track, this comment in the latest discussion is very interesting: “All of the global and regional models have had a distinct right-of-track bias by as much as 10 degrees…and each model run has been a little farther west and slower.” I have often found, in observing hurricanes and hurricane forecasting, that the trend of Hurricane Center forecasts can be more important than any one forecast track. If Isabel is trending to the left of the forecasts, the Carolinas had better watch out.

On the other hand, there is still disagreement among the computer models. The GFDL continues to call for a track that could easily bring the storm up the coast toward New England. “The official forecast was adjusted slightly to the left of and slower than the previous forecast… However…it is still too early to determine when or where Isabel will make landfall.” (Notice they’re not saying “if.”)

Technically speaking, Hurricane Isabel is still a Category Five hurricane at this hour, with winds of 160 miles per hour, tying it for third all-time among the longest-lasting Cat. 5 storms ever recorded in the Atlantic (at 30 hours). But really, the National Hurricane Center is cheating here. “I very much doubt that Isabel still has winds of [160 mph],” the NHC says in its 11:00 PM advisory.

The Hurricane Center notes that satellite intensity estimates are way down, and dry air appears to be infiltrating the system. “But since another aircraft will be in the hurricane in just three hours…we will wait for confirmation of this apparent weakening trend,” the discussion says. In other words, expect Isabel to “suddenly” weaken when the 5:00 AM advisory comes out.

Nevertheless, this is a very intense and, if it hits shore, a very dangerous hurricane. Which, of course, leads us to the obvious question: Where is it going? It seems the NHC’s computer models disagree. The UKMET model takes Isabel on a track that would seem likely to result in a landfall in the Carolinas; the GFS and NOGAPS models suggest a course that could take Isabel directly toward New York and New England; and the GFDL turns it north sharply enough that it might go out to sea.

The major players in this drama are a trough of low pressure offshore of the Carolinas and an upper-level high pressure system off New England. The low pressure system will tend to block Isabel from moving too far west, while the high pressure system will tend to keep it from going too far east. Both will push it north. This is just the sort of situation where that rare hurricane track scenario — a northward up-the-coast move directly toward New England — could quite plausibly happen. Indeed, I would venture that Isabel has the best chance of hitting New England of any major hurricane since Edouard and Hortense in 1996. (Those storms both missed, but the meteorological conditions were very close.)

But it’s way too soon to say for sure. It will all depend on the exact timing of the motions of those upper-level systems. The NHC explains: “The GFS and NOGAPS models are very similar in holding [the low-pressure trough off the Carolinas] in place almost a day longer than the UKMET…with the result that the former two models turn Isabel much more sharply northward than the UKMET.” If the GFS and NOGAPS are right, I might be photo-blogging images of hurricane-force winds in about a week. If the UKMET is right, look out, Carolinas. Which one will be right? We’ll just have to wait and see.

Wherever Isabel hits, it will very likely be weaker then that it is now. Hopefully, it will be considerably weaker.

By the way, the Hurricane Center said earlier today that it now believes Isabel may actually have been stronger yesterday than 160 mph. I’m guessing maybe 170 or 175? Wow.

The National Hurricane Center says Hurricane Isabel, now approaching Category Five status with 150 mile-per-hour sustained winds, “has a textbook appearance on visible and infrared satellite images.” They’re right. Check this action out:

This storm could be a serious problem for someplace along the East Coast late next week. Stay tuned, as they say.

They don’t call September 10 the peak day of the Atlantic hurricane season for nothing. Hurricane Isabel was upgraded to 145 mile-per-hour winds at 11:00 PM. About a week from now, it could be threat to anyplace along the U.S. East Coast, from Miami to Hatteras and perhaps further north. Stay tuned.

Hurricane Isabel has 125 mile-per-hour winds as of 5:00 PM, and is forecast to strengthen further tomorrow.

Isabel will probably become Category Four soon (maybe in a few minutes, when the 11:00 advisory comes out!), and could eventually get stronger than Fabian ever did. The forecast brings it up to 145 miles per hour in 24 hours — and the Hurricane Center admits, “the intensity forecast could easily be too low given that the outflow pattern is expected to continue to improve…the vertical shear is forecast to remain less than 10 kt…and Isabel will be moving over 28c and warmer [sea surface temperatures].”

(UPDATE: Yup, it became Category Four at 11:00 PM. Now it’s up to 135 mph.)

Even more importantly, Isabel, unlike Fabian, could impact the northern Caribbean islands — though it’s too soon to say for sure — and if so, that would put it on a course that’s more likely to eventually impact the U.S. East Coast than Fabian ever was. So, stay tuned.

Meanwhile, a new system, Tropical Depression 14, has formed off the African coast, and it’s forecast to be a hurricane within three days. Hey, they don’t call the first two weeks in September the peak of the hurricane season for nothing!

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