Weather Nerd

By Brendan Loy

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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 Alas, this post is now out-of-date; hurricane information becomes obsolete faster than Apple computers and iPods!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:

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5 Comments, 5 Threads

  1. 1. PMH

    Isn’t the eyewall’s falling apart simply dry air that was sucked in hours ago, and on earlier revolutions?

  2. 2. Brendan Loy

    I’m honestly not sure what’s going on with the eyewall, PMH. I’m looking around, asking around and trying to figure it out. This is one of those times when not actually being a meteorologist is rough. :)

    Anyway, let the record show that I just removed this paragraph from my post:

    The National Hurricane Center says “SOME INCREASE IN STRENGTH IS EXPECTED…AND DOLLY COULD APPROACH CATEGORY TWO INTENSITY WHEN IT REACHES THE COASTLINE LATER TODAY.” This is a somewhat strangely worded statement, since any increase in strength would result in Dolly not just “approaching,” but attaining, Category 2 intensity. The NHC is hedging is bets rhetorically, but I’d say the smart money is on Dolly coming ashore as a Category 2.

    For clarity and ease of understanding, I took this out and added the “UPDATE” (indicating the Dolly is now officially a Cat. 2) to the earlier paragraph. I think the article flows better that way. But I wanted to quote the original paragraph here, to be faithful to the historical record of what originally appeared in this post.

  3. 3. KEVIN STERN

    Brenden, thanks so much for this blog. You are doing a great job . I have been waiting for someone sensible to pull all the sources and analysis together for some time. Thanks you.

  4. 4. anon in tx

    The Brownsville airport only saw 48 mph winds. A private wx station in Brownsville saw 60 mph winds. I suspect NHC have their amps turned up to 11.

  5. 5. Brendan Loy

    The eyewall didn’t go over Brownsville, so it’s not hugely surprising that the winds weren’t hurricane-force there. As for the NHC, I’m not sure what you’re suggesting. It isn’t like this was some sort of made-up hurricane. The reconnaissance planes that repeatedly found hurricane-force winds and barometric pressures weren’t lying. Nor was the satellite… or the radar…