Weather Nerd

Dolly strengthening rapidly; 100+ mph winds likely

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[UPDATE: Welcome, InstaPundit readers! Alas, this post is now out-of-date; hurricane information becomes obsolete faster than Apple computers and iPods! For the very latest, please go to the Weather Nerd homepage.]

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Hurricane Dolly is now strengthening rapidly, and is likely to come ashore as a Category 2 hurricane. As of 9:00 AM EDT, Dolly’s maximum sustained winds are up to 95 mph — just 1 mph short of Cat. 2 status. [UPDATE: At 9:33 AM EDT, FLhurricane.com reports: “From recon reports, it appears that Dolly is now a mid range Category 2 Hurricane.” This is not yet officially confirmed by the NHC.] . . . [UPDATE 2: It’s now official, as of 11:00 AM EDT. Dolly is a Category 2 hurricane with 100 mph winds. “SOME ADDITIONAL STRENGTHENING IS POSSIBLE BEFORE LANDFALL.”]

The storm’s minimum central pressure is down to 964 millibars as of 9:17 AM. That’s an 18-millibar pressure drop since 2:00 AM, more than 2 millibars per hour. If Dolly were to keep up this pace, it would qualify as rapid deepening. Luckily, she’s going to run out of water very soon. The eye is just 40 miles east of Brownsville, and landfall is expected in the next few hours. If Dolly had a few more hours over water, she would very likely become a major hurricane.

Even without reaching major-hurricane status, Dolly’s wind damage may be somewhat more severe than expected. Strengthening hurricanes tend to do more damage, all other things being equal, than stable or weakening hurricanes. The environment is more unstable and dynamic, resulting in higher wind gusts relative to the sustained wind speeds. That is likely to be the case here, as Dolly’s winds will be catching up with her recent pressure drop while she makes landfall:

It takes a while for the winds of a hurricane to respond to a rapid pressure fall, and Dolly’s winds do not yet reflect the recent big drop in pressure. … Dolly’s winds should rise above 100 mph in the next few hours.

That quote is from Dr. Jeff Masters, who predicts “considerable wind damage from Dolly, exceeding $100 million.” On the bright side, storm-surge damage will be quite limited, and inland flooding may be less severe than previously expected, according to Eric Berger.

Here is a constantly-updating live radar image of Dolly making landfall, courtesy of the National Weather Service in Brownsville:

UPDATE, 9:56 AM: In the last few minutes, radar has shown the north side of Dolly’s eyewall seemingly falling apart. This is reminiscent of what happened with Katrina’s western eyewall a few hours before landfall in Louisiana, but it’s very strange in this case because a) Katrina was in a weakening mode, whereas Dolly otherwise appears to be in a strengthening mode; and b) the portion of Katrina that weakened was the usually-weaker “left front quadrant,” which is more susceptible to dry air being sucked in; the portion that’s seemingly weakening here is the usually-stronger “right front quadrant,” which should be relatively immune from dry air, given the direction of the storm’s circulation. Regardless, this is good news, if the trend keeps up. The left front quadrant may actually be the strongest part of Dolly — from the landfall spot on southward. Folks north of the landfall point may be spared the brunt of the storm’s wrath, if the current radar image is any indication.

ON THE OTHER HAND: Infrared, visible and water vapor satellite loops show no hint of the northern eyewall erosion. So, maybe it’s just an artifact of the radar being unable to penetrate the storm’s core. Or something. I honestly don’t know. (For what it’s worth, Corpus Christi radar shows the same thing.)

Anyway, again, here are some live views of Dolly: