Weather Nerd

Hurricane Watches issued for Texas, Mexico coast

Hot off the presses, the 11:00 AM EDT advisory is out, and it declares most of the Texas coast to be under either a Hurricane Watch or a Tropical Storm Watch:

dolly-track-mon-am.gif

The Tropical Storm Watches extend all the way to San Luis Pass, at the western edge of Galveston Island. The Hurricane Watch area includes Corpus Christi and points north, all the way to Port O’Connor.

If you live in the watch areas, it’s time to start your preparations in earnest. Folks in Houston and Galveston might want to dust off their hurricane plans, too, just in case; the dynamics affecting Dolly’s track are somewhat in flux, and an unexpected northward turn isn’t totally out of the question.

Dolly’s circulation center has, as anticipated last night, reformed somewhat to the north of the previous track, increasing the threat to Texas. It may take some time for the computer models to adjust to this new reality, and meanwhile the atmospheric trends steering Dolly continue to evolve, so I won’t feel confident in the track forecast for another 12-18 hours or so. For what it’s worth, however, here is what the 11:00 AM discussion says about Dolly’s track:

DOLLY IS STILL MOVING RATHER QUICKLY…300/16…TO THE SOUTH OF A MID-LEVEL RIDGE OVER THE SOUTHEASTERN UNITED STATES. ALL OF THE DYNAMICAL MODELS FORECAST THIS RIDGE TO GRADUALLY WEAKEN DURING THE NEXT FEW DAYS…RESULTING IN TRACK GUIDANCE SHOWING A SIGNIFICANT SLOWING OF THE FORWARD MOTION AS THE CYCLONE PROCEEDS INTO THE WESTERN GULF. MOST OF THE GUIDANCE HAS SHIFTED A LITTLE NORTHWARD OVER THE WESTERN GULF…AND SO HAS THE OFFICIAL FORECAST…WHICH REMAINS DOWN THE MIDDLE OF THE GUIDANCE ENVELOPE. THERE ARE VERY RELIABLE MODELS ON BOTH SIDES OF THE OFFICIAL TRACK…SO IT IS IMPORTANT NOT TO FOCUS ON THE EXACT LOCATION OF LANDFALL IMPLIED BY THE OFFICIAL TRACK.

Here is Dr. Jeff Masters‘s take on Dolly’s track, published just before the 11:00 AM advisory came out:

The models are pretty united in forecasting a track towards the Texas/Mexico border over the next two days, with a decrease in forward speed. Some significant uncertainty creeps into the forecast for Wednesday, when steering currents weaken and the models have differing solutions on the orientation and strength of the ridge of high pressure steering Dolly. The latest GFDL and HWRF models runs from 2 am EDT this morning have shifted significantly north, bringing Dolly ashore near Corpus Christi, Texas. The GFDL shows a very large borderline Category 1/2 hurricane, with tropical storm force winds extending from Galveston to Brownsville at landfall. Dolly will probably grow quite large and affect a 200-mile stretch of coast with tropical storm-force winds. Like her namesake, actress Dolly Parton, Dolly the tropical cyclone appears destined to become a media star.

Equally uncertain is how strong Dolly will get. Again quoting Dr. Masters, he threw some cold water (figuratively speaking) on the alarmist “perfect conditions for rapid intensification” talk, writing:

Dolly will be over waters of 28-29°C. These SSTs are slightly below average for this time of year, but plenty warm enough to support Dolly intensifying into a hurricane before landfall. These warm waters extend to a moderate depth, with a Tropical Cyclone Heat Potential of about 40 kJ/cm**2. This is below the value of 80 usually associated with rapid intensification, but still high enough to allow Dolly to strengthen into a major hurricane, if it has enough time to do so. Our skill in making intensity forecasts is poor, but it currently appears that Dolly only has enough time to intensify into a Category 1 or 2 hurricane. I give a 10% chance that Dolly will go through a burst of rapid intensification shortly before landfall and achieve major hurricane status at landfall.

The NHC writes that “STRENGTHENING APPEARS LIKELY…BUT GIVEN THE CURRENT SPRAWLING NATURE OF THE CIRCULATION…THE RATE OF INTENSIFICATION IS DIFFICULT TO FORECAST…SINCE IT IS UNCERTAIN HOW LONG IT WILL TAKE FOR A TRUE INNER CORE TO DEVELOP.

I’ll be incommunicado for the next several hours, but I’ll post another update in the late afternoon or early evening EDT. In the mean time, you can use the links at right to follow the latest developments.