Eric Berger

Hurricane Dorian reaches Category 5, as pressures continue to fall

This post concerns Hurricane Dorian, which presents no threat to Texas, but which we are covering due to general public interest. For Houston, for the foreseeable future, we can expect hot days, low rain chances, and no taste of fall.

Crossing over very warm seas and not having to battle much in the way of wind shear, Hurricane Dorian‘s maximum winds increased to 180mph on Sunday morning. As central pressures continued to fall, further intensification seems to be possible today. Unfortunately, as it is reaching peak intensity, Dorian is now beginning to cross over the northern Bahamas. Its crawling westward movement will prolong exposure on these islands to wind gusts of up to 200mph, very high seas, and heavy rainfall. Areas such as Freeport in the Bahamas will very likely see extreme levels of damage.

Hurricane Dorian official forecast track at 10am CT Sunday. (National Hurricane Center)

Beyond Monday, we still expect Dorian to make a northern turn as a trough of low pressure currently over the upper Midwest sweeps down and pulls the tropical system north. The ultimate track will depend on the timing of this trough, as well as any wobbles in Dorian’s path over the next couple of days. These two factors will determine whether the coastal regions of Florida, Georgia, and the Carolinas escape with a near miss on catastrophic conditions—which seems more likely at present—or face the brunt of Dorian’s intensity.

European ensemble model forecast for Dorian. (Weathernerds.org/Space City Weather)

Dorian probably will maintain its Category-4 and Category-5 intensity for the next couple of days as it undergoes a period of eyewall replacement cycles, when the inner eyewall weakens and then re-forms. By Tuesday or so, as it begins to pull north and at least its outer bands begin to interact with the continental United States, it should begin a weakening trend.

Yes, there’s a chance Hurricane Dorian will miss Florida

In Thursday afternoon’s post on Hurricane Dorian, we called attention to the high uncertainty in the track for the storm—and that remains the case this afternoon. Before discussing this, let’s just note that Dorian has reached Category-3 status, and will likely be a major hurricane at a Category 3, 4, or potentially even 5 level as it approaches Florida on Monday.

The problem for trying to determine where Dorian goes is that steering currents fall apart over the weekend, and so Dorian’s forward speed is likely to slow to a few miles per hour. This means that it could stall, or wobble offshore, before finally getting pulled in some more definitive direction. At some point it will find the western edge of a high pressure system and get pulled north, but the big question is whether that happens 50 or 100 miles off the Florida coast, along the Florida coast, or inland. Here’s the official track forecast as of 4pm CT—they’re basically splitting the difference.

That is a very large cone of uncertainty. (National Hurricane Center)

This afternoon’s ensemble output from the European model suggests that, more likely than not, Dorian’s center will remain off the Florida coast. But we will want to see this model trend continue for another 12- to 24-hours before having too much confidence in such an outcome. Nevertheless, what we are seeing now is a good trend.

More than two-thirds of the ensemble members of the European forecast model now keep the center of Dorian offshore. (Weathernerds.org)

In terms of impacts, obviously it’s much better if the storm stays offshore. But unfortunately, given all of the uncertainty, most of the Florida peninsula, as well as Georgia and the Carolinas need to be prepared for the possibility of high winds and heavy rainfall early next week. Hopefully as the track gets better defined, we’ll be able to clear some areas of significant threats.

Afternoon Hurricane Dorian update—uncertainty abounds for Florida

We’ve had a lot of requests from out-of-state readers to continue providing our perspective on Hurricane Dorian—which threatens to make landfall in Florida as a major hurricane in three or four days time. To be clear, there is absolutely no threat to Houston or Texas.

As of 4pm CT on Thursday, Dorian had maximum sustained winds of 85mph, but based upon its satellite appearance it appears likely to undergo a bout of intensification soon. It will likely become a major hurricane within 24 hour, and then should experience more or less favorable atmospheric conditions for further intensification for several days as it passes north of the Bahamas and turns west toward Florida.

In looking at this afternoon’s weather model data, what is particular striking to me is the high degree of uncertainty about where Dorian is going to go by Sunday or Monday. There is, in fact, no guarantee it will even hit Florida. There is a non-zero chance it goes south of Miami, or turns north before reaching the Florida peninsula. A little while ago, I wrote a story for Ars Technica about this uncertainty, which is highlighted in this afternoon’s ensemble output from the European forecast model:

Five-day ensemble forecasts for Hurricane Dorian’s track. (Weathernerds.org)

If you click the image above to enlarge it, the following explanation will probably be more clear. In any case, this plot shows the track of Dorian out to 120 hours, so that means its position as of Tuesday at 7am CT. Notice that there is a remarkable variance in the location of the “center” of Dorian in these roughly four dozen ensemble members. Yes, a reasonable amount of the ensemble members bring Dorian to the coast between Sunday and Tuesday, but some are far, far away. In some scenarios, Dorian turns north before even reaching Florida. This is reflective of the fact that steering currents for the storm are likely to become extremely weak by Saturday or so.

The 4pm CT Thursday track forecast from the National Hurricane Center captures this ambiguity. It encompasses the entire Florida peninsula within the five-day cone of uncertainty.

4pm CT Thursday track forecast from the National Hurricane Center.

This is singularly unhelpful to the residents of the Sunshine State, who are staring down at the possibility of a major hurricane making landfall somewhere along the peninsula in three to four days. The time for preparations and evacuations is now, but it is hard to offer much in the way of specificity about where the worst storm surge, damaging winds, and inland rainfall will occur. Certainly a slow-moving storm will make the latter variable, rainfall, worse.

Matt and I will continue coverage of the storm through the Labor Day Weekend.

Summer rambles on for Texas, Dorian coming for Florida

On Wednesday, for Houston’s now-daily game of rainfall roulette, the Inner Loop area of the city generally “won” the contest with 2 to 3 inches of rainfall. Meanwhile, most of the suburbs were dry, or saw only a few raindrops. This pattern will likely continue through the work week, although the intensity of storms today and Friday hopefully won’t be quite so high.

Thursday

Today will be hot and mostly sunny, with high temperatures in the mid-90s. We’ll see our usual ramp up in storm activity this afternoon, but high-resolution models indicate that storms won’t be as widespread or as intense as Wednesday. As usual, storms should wane with the loss of daytime heating, and nighttime temperatures probably won’t fall much below 80.

Rain chances on Thursday will be a little better along the coast. (Pivotal Weather)

Friday

Another day like Thursday, although rain chances may take another step backward, with perhaps only 20 percent coverage during the afternoon and early evening hours.

Saturday and Sunday

Drier air from a dying front should make for a pretty nice—all things considered—Labor Day Weekend. Expect high temperatures in the mid-90s, with mostly sunny skies. Lows at night may get into the mid-70s for central and northern parts of the metro area, so mornings and evenings may be a smidge more pleasant than we’ve seen. Finally, rain chances will be very low.

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