Weather Nerd

Gustav a Cat. 3 in name only; eastern core disappears

Three years ago, as Hurricane Katrina was approaching the Louisiana and Mississippi coasts, the storm’s western eyewall — which was poised to track over, or very near, New Orleans — suddenly weakened drastically, sparing the Crescent City a much more severe blow.

This morning, as Hurricane Gustav nears Louisiana, its eastern eyewall — normally the fiercest part of a hurricane — has vanished, along with much of the rest of the storm’s eastern and southern core. This is, again, the portion of the storm that will come closest to New Orleans. You can see this on radar here and here:


Live NWS radar loop. This image should stay current all morning.

New Orleans lucks out again! The 5:00 AM EDT discussion explains:

OBSERVATIONS FROM AN AIR FORCE HURRICANE HUNTER AIRCRAFT INDICATE THAT GUSTAV IS NOT STRENGTHENING. THE CENTRAL PRESSURE HAS RISEN SLIGHTLY AND…BASED ON RECENT FLIGHT-LEVEL AND SFMR SURFACE WIND MEASUREMENTS…[115 MPH] IS A GENEROUS ESTIMATE FOR THE CURRENT INTENSITY. WSR-88D RADAR IMAGES SHOW THAT THE EYE WALL IS OPEN OVER THE SOUTHERN SEMICIRCLE…PERHAPS DUE TO THE MID- TO UPPER-LEVEL DRY AIR INTRUSION FROM THE SOUTH THAT WAS DISCUSSED EARLIER. IN FACT…THE AIR FORCE HURRICANE HUNTERS DID NOT REPORT AN EYEWALL. WATER VAPOR IMAGERY ALSO SUGGESTS A DRY INTRUSION AND A RESTRICTION OF THE UPPER-LEVEL OUTFLOW OVER THE SOUTHERN PORTION OF THE HURRICANE. ALSO THE CLOUD PATTERN HAS BECOME A BIT MORE RAGGED ON GEOSTATIONARY SATELLITE PICTURES. BASED ON CURRENT TRENDS AND THE PROXIMITY TO THE COAST…NO SIGNIFICANT INCREASE IN STRENGTH APPEARS LIKELY PRIOR TO LANDFALL.

Gustav is, in fact, weakening. The Hurricane Center’s 115 mph estimate is, as they say, “generous,” and frankly, although I’m generally reluctant to criticize the NHC, I’m not sure what purpose is served at this point by continuing to pretend Gustav is a major hurricane. This is a Category 2 hurricane, as it has been for most, if not all, of the last 24 hours. Maintaining its Cat. 3 status all day yesterday made some sense, as the possibility of restrengthening remained, and one didn’t want to sound a premature “all clear.” But now, calling Gustav a Cat. 3, when it’s really a Cat. 2 and isn’t going to get any stronger, simply risks creating more public cynicism, it seems to me. It’s not as if people will fail to notice when Gustav doesn’t cause major-hurricane-level damage or wind gusts.

That said, Gustav will still bring significant storm-surge flooding to the Houma area and environs along the east-central Louisiana coast. It may yet cause some flooding in New Orleans, particularly on the West Bank, depending on how the levees hold up. And it’s not like Category 2 winds are a pleasant day in the park. This will be a hellish morning and afternoon for folks in southeastern Louisiana. My thoughts and prayers are with the people there.

I will unfortunately be unable to liveblog the hours of Gustav’s landfall, like I did three years ago with Katrina. In fact, this will probably be my last update until midday, when Gustav will already be ashore. However, as I mentioned last night, there’s a wealth of good information at the sites listed in my sidebar at right, so just follow those links for the very latest. In particular:

* For the latest official information on the storm, the National Hurricane Center.

* For news from Louisiana, the Times-Picayune Hurricane Center, the WWL-TV live stream, and Best of New Orleans Blog.

* For Gustav liveblog coverage, Gustav Bloggers, Razor’s Kiss, New Orleans Metblogs, and Ridin’ Gustav. If you know of other good liveblog sites, please suggest ’em in comments. (I will try to keep approving comments even while away from my computer.)

* For aggregation of various Web 2.0 media on the storm, the Hurricane Gustav Aggregator.

* For all sorts of information, the Hurricane Gustav Wiki.

* For live satellite imagery of Gustav, the visible satellite loop and the infrared satellite loop.

* For radar imagery of Gustav, the New Orleans short-rang loop, and the Lake Charles, LA long-range and short-range loops.

* For weatherbloggers’ perspectives, Dr. Jeff Masters, Eric Berger and Alan Sullivan.

P.S. A reminder: timestamps at the top of each post are in PDT, which is three hours behind EDT.