Weather Nerd

Disorganized Dolly confuses forecasters; Texans should begin to prepare

The National Hurricane Center’s 5:00 AM EDT discussion states that Dolly’s “MID-LEVEL CENTER [HAS] REFORMED TO THE NORTH OF THE PREVIOUS TRACK.” The discussion acknowledges, however, that Dolly still probably doesn’t have a circulation center at the surface, which makes forecasting incredibly difficult because so much depends, as I wrote last night, on exactly where and when the surface center re-forms.

There is some disagreement among weatherbloggers this morning about what to make of these developments. For instance, Alan Sullivan writes:

[Dolly] is a large and strong system, but disorganized at the surface. Most of the heavy weather is passing through Yucatan Channel, and when the [surface] center does reform, it will probably be well north of previous positioning. Dolly is definitely a threat to Texas. I thought yesterday it would take a course to the right of guidance, in response to the jut of land, and the nice opening afforded by Yucatan Channel. A younger, weaker storm is more likely to bounce off land in that way. Having gained latitude, Dolly will present a much greater threat to Galveston.

The Gulf is warmer than usual, the warmth runs deep, and upper winds are getting more favorable. Dolly could near major hurricane status in the last hours before landfall. It is potentially quite a dangerous storm, and people along the coast should rush their preparations. At the same time, however, I must note that some intensity models do not agree that Dolly will even become a hurricane. An upper low has been distorting the storm for the past few days. Tracking in tandem with Dolly, that system is still having some effect. If it refuses to dissipate, Dolly will not strengthen. Tropical cyclones are very fickle.

The Houston Chronicle‘s Eric Berger echoes these concerns, in a post titled “A strong hurricane may strike Texas this week“:

The center of Tropical Storm Dolly appears to have jogged northward over night in the process of reforming, and that means two things: 1) the threat to Southern Texas has gone up since yesterday, and 2) as the storm should now spend less time over the Yucatan Peninsula it will weaken less during this brief encounter with land. …

At this point, areas from Victoria to northern Mexico appear at the highest risk, but all of Texas should keep an eye on a system that could reach the Texas coast late Wednesday or early Thursday.

And how strong would such a system be?

Unfortunately, we cannot rule out rapid intensification of Dolly, which presently has 50 mph winds, once the storm reaches the Gulf of Mexico. This is not only because of the warm water, but also because of favorable atmospheric conditions. …

The official forecast still calls for an 85 mph hurricane, but my guess is that this will be raised during the next update [at 11:00 AM EDT] to reflect Dolly’s northward jog.

Texas may well be struck by a goodly sized hurricane later this week. Houston, though an unlikely target, is not yet out of the woods.

On the other hand, Michael Cornelius at thinks the treat to Texas may be diminishing:

Tropical Storm Dolly is highly questionable this morning. This system has been very resistant to tropical development for a week now, and even as a named system it seems to be missing a low level circulation. And without a Low-Level Circulation the argument that it is not a Tropical Cyclone could be made. …

From analyzing it this morning, it seems the forecast track may have to be adjusted to the left (south, more into Mexico) if the current trend continues. The ridge to the north and the fact that it remains very weak and not so organized is suggesting that it will likely keep the more westerly track.

Northern Mexico probably has the best chance of seeing a landfall. [But] [s]ince the [current] center may be more at the Mid-Levels (again a questionable tropical cyclone) it’s very possible the system could reform its center again. Aircraft Recon is out checking out dolly now to help determine this. …

The lack of a good circulation center will keep the entire cone watching, from South Texas to Mexico (more likely Northern Mexico). Intensity wise, it’s even harder to say. Following persistent trends suggest it may stay weak, but the Gulf of Mexico is known to change things. …

[But] keep watch, especially through the afternoon. Although the westerly track is more likely, if Dolly does get organized and gains strength then northerly is definitely possible as well. … Everyone in that forecast cone needs to be watching this system.

Cornelius’s focus on “current trends” is interesting. Often, at the risk of horribly anthropomorphizing, it seems as if tropical storms have certain intrinsic character traits. Bertha, for instance, was stubborn and a bit wacky, and those traits repeatedly reared their head throughout the storm’s life. Dolly’s most obvious trait thus far, going back to her days as a tropical wave, is an inability to get her act together, even when the conditions are such that it seems like she should be able to do so. Her inability to settle on a surface center, even now, is another example of this. The forecasts calling for surface reformation and rapid strengthening assume that Dolly will finally get her act together over the Gulf. But maybe she won’t! She certainly never has been able to up till now.

On the other hand, the convection over the Gulf does appear to be getting stronger over the last hour or two — and it almost looks like it’s starting to wrap around a broad center:

In any case, folks in Texas should assume that Berger and Sullivan are correct, and prepare accordingly. At the very least, it is definitely possible that a major hurricane will be bearing down in Texas — most likely south Texas — in three days. It’s already time to dust off those preparations and take whatever preliminary steps you need to take. If Dolly does follow the Berger/Sullivan path, evacuations will most likely begin tomorrow, and landfall would be overnight Wednesday night into Thursday.

Things are going to happen fast now. It’s time to get prepared.

P.S. If it seems like I’ve been ignoring Tropical Storm Cristobal on these last couple of updates… well, I have, because there isn’t much to say about it, and Dolly is the much bigger threat. But Cristobal did brush the Outer Banks of North Carolina yesterday, with minimal effects. Here’s how the WRAL weatherblog in Raleigh/Durham/Fayetteville summarizes things:

Cristobal … had minimal wind impacts along the coast, as the core of the tropical storm strength winds remained well southeast of the center and principally affected offshore waters. Most southern and central coast reporting station logged sustained winds in the 10-25 mph range through the weekend, with some gusts as high as 30-40 mph fairly common, and one 45 mph gust reported at Johnny Mercer pier in Wrightsville beach. As is often the case with tropical systems that parallel the coast, rainfall was mostly confined to areas near the coast and even there variety prevailed, with many areas receiving storm total rainfall on the order of one quarter to three-quarters of an inch (New River MCAS got .30″ while Frisco picked up .56″ for example), while some small pockets and streaks were much more heavily hit, with 2 [stations receiving] nearly 5 inches over the weekend (3.46″ at the Wilmington airport and 4.96″ near Ogden, both in New Hanover County). Cristobal is accelerating away from the state today and should have little additional influence on the state.

Now Cristobal is headed for Canada, the CBC reports:

A tropical storm that formed off the east coast of the United States over the weekend is expected to drench much of Canada’s Atlantic region in rain over the next few days.

Tropical storm Cristobal, which formed off the coast of the Carolinas and was spiralling there early Monday morning, is on a tack for southern Nova Scotia, Cape Breton and Newfoundland.

With sustained winds of up to 83 kilometres an hour, Cristobal is forecast to bring rain, at times heavy, to southern New Brunswick on Monday and Tuesday and to most of Nova Scotia until Thursday.

“It is continuing to race northeast, and by Wednesday or Thursday pretty much making a beeline for Nova Scotia,” said CBC News: Morning’s Colleen Jones. She said the storm is “going to dump a lot of rain” on Nova Scotia, “probably somewhere in that 60-millimetre range.”

I’ll let you all do the math on that. :) Anyway, here’s the forecast track. Cristobal’s center is actually expected to remain just offshore.