I just talked to Tom Grace, the blog reader who e-mailed me last night saying he and his family would be leaving New Orleans this morning. They are indeed on the road, halfway to Jackson, MS. (Their destination is Memphis.) He said there’s moderate traffic, moving at 65 mph. He’s going to call back later, when he’s off the road, so I can give him the necessary information so he can file audioblog reports.

Here’s what he e-mailed me a few hours ago, before leaving:

We have the house almost buttoned up and the car half packed. We will be leaving New Orleans within a couple of hours. Have to pick up my 87 y.o. mom, then head North, across Lake Pontchartrain, where we will meet up with my wife’s family before taking I-12 to Memphis. At the moment, we are planning to take both cars, though we may leave one of them on the North Shore, in Covington, LA, which might be a safe place for it. … I just want to leave early, before “the lemmings” as I call them. Most people will decide to leave about the same time, then it could take 10 hours to get 30 miles, as it did for my son and his family last year when they waited just a few hours to evacuate for Hurricane Ivan.

Anyone else in Katrina’s path — or in the process of evacuating from it — please feel free to e-mail me if you’d like to file some first-hand reports, either by audio, or if you have a camera phone, or whatever.

Tulane University, in New Orleans, is closing at 5:00 PM today. The dorms are closing until Wednesday. Classes are cancelled until Thursday. Orientation is cancelled. Everything is shutting down. Everyone is being told to leave:

New first-year students who are arriving on campus today should make plans to leave campus as soon as possible.

* If you can leave with your parents today, do so.
* If you have friends or relatives with whom you can seek shelter, do so now.
* Students who are unable to leave New Orleans should contact their Resident Assistant immediately for university assistance.

No students will be allowed to occupy residence halls after 6 p.m. today.

We’re at a critical moment in Hurricane Katrina’s development right now. The next few hours are probably the last, best chance for a serious disruption that could ultimately prevent Katrina from making landfall as a monster hurricane. Weatherblogger Steve Gregory explains:

Katrina is currently in a presumably temporary weakening cycle due to an eye wall replacement that began 5 hours ago … In all likelihood, Katrina’s max winds at the surface are now of only CAT 2 intensity. … Katrina will complete the eye wall replacement cycle, and the eye will again begin to shrink down by this evening …

NOTE: Katrina’s eye wall cycling, that has resulted in a 50NM wide eye, leaves Katrina in a ‘vulnerable’ state — and dry air intrusion could take place during the next 6 hours which will trash the intensity forecast. Until this evening, we really won’t know for sure. …

[T]here will be a period of time on Sunday when the shears will approach zero, and, the outflow to the NNW of the storm will be enhanced by the high level, southwesterly winds ahead of the developing TROF. This 12-18 hour period of ‘perfect’ environmental conditions and winds, including even warmer waters associated with the loop current, and the semi-permanent ‘pool’ of warm water in the Gulf south of Louisiana — will provide ideal conditions and the opportunity for Katrina to rapidly intensify, and the ability to attain strong CAT 4 if not CAT 5 intensity (assuming she manages to re-intensify this evening!)

So, what happens in the next six hours or so is absolutely critical. Hopefully some dry air will get in there and mess things up.

Katrina officially became a major hurricane overnight, with 115 mph winds, and her expected intensity at landfall was upped to 145 mph. Moreover, according to the 10:00 AM discussion, “IT IS NOT OUT OF THE QUESTION THAT KATRINA COULD REACH CATEGORY 5 STATUS AT SOME POINT BEFORE LANDFALL.”

Also at 10:00 AM, the NHC issued a Hurricane Watch for southeastern Louisiana, including New Orleans and Lake Ponchartrain.

“This is not a test,” said New Orleans mayor Ray Nagin. Evacuation orders for the city will be issued very soon. Already, nearby Placquemines and St. Bernard parishes have urged people to leave. (”According to the state’s plan, New Orleans and Orleans Parish call for evacuations after the low-lying areas to allow people who live south and east of the city to get on the road first and head for safety.”) Mayor Nagin urged New Orleanians to “get their supplies, get their medications in order, clean up storm drains and get ready. Because it looks as if we’re going to get hit.”

The Hurricane Center will likely expand the Hurricane Watches eastward, to cover the Mississippi and perhaps Alabama coastlines as well, later today. It sounds like they did follow my advice and fudge the normal timetable a bit for New Orleans, where hurricane preparedness is a uniquely difficult prospect.

It bears repeating just what we’re dealing with here: the potential destruction of a city, and the deaths of many thousands who are unable or unwilling to evacuate. Dr. Jeff Masters puts the odds of this scenario at one in ten:

I’d hate to be an Emergency Management official in New Orleans right now. Katrina is pretty much following the NHC forecast, and appears likely to pass VERY close to New Orleans. I’m surprised they haven’t ordered an evacuation of the city yet. While the odds of a catastropic hit that would completely flood the city of New Orleans are probably 10%, that is way too high in my opinion to justify leaving the people in the city. If I lived in the city, I would evactuate NOW! There is a very good reason that the Coroner’s office in New Orleans keeps 10,000 body bags on hand. The risks are too great from this storm, and a weekend away from the city would be nice anyway, right? GO! New Orleans needs a full 72 hours to evacuate, and landfall is already less than 72 hours away. Get out now and beat the rush. You’re not going to have to go to work or school on Monday anyway. If an evacuation is ordered, not everyone who wants to get out may be able to do so–particularly the 60,000 poor people with no cars.

And it only gets worse. In addition to increasing in strength, Katrina has also substantially increased in size, as you can see for yourself here. Hurricane-force winds now extend outward up to 40 miles, and tropical-storm-force winds up to 150 miles, from the center; that’s up from 25 and 85 miles, respectively, just 12 hours ago. Katrina “will deliver a widespread damaging blow wherever she comes ashore,” says Dr. Masters.

Okay, now for the good news, such as it is. Katrina hasn’t strengthened since she reached 115 mph about eight hours ago. She’s been going through an eyewall replacement cycle, and it’s possible she might weaken a bit this afternoon (though I’m not sure if that’s good or bad news, as it might cause people to become dangerously complacent, only to have Katrina blow up into a monster tomorrow). Also, according to the discussion, “There is a possibility that southerly or southwesterly shear could affect Katrina starting at 48 hr…and as always happens in hurricane of this intensity additional concentric eyewall cycles could occur.” That would be good… although, 48 hours from now, she’ll already have come ashore, won’t she? Hmm… HURRY UP, SHEAR!!!

Those two things — wind shear and eyewall replacement cycles — are the only factors that might prevent Katrina from being another Charley, or worse, another Camille, at landfall. Water temperatures aren’t going to do the trick, as they did with Opal and Dennis. The sea-surface temperatures near the shoreline have warmed since July, there’s a patch of water due south of New Orleans that is extremely warm and deep; that could easily be the engine that boosts Katrina to Cat. 5 during the final hours before landfall. Which, of course, would be very, very, very bad.

Hurricane Katrina now has maximum sustained winds of 110 mph, putting her on the threshold of Category 3. I’m going to bed now; by the time I wake up, I expect her to be a major hurricane.

Here’s an excellent essay, written in 2002, about the mortal threat that New Orleans faces.

If you live in New Orleans, here is the official evacuation info from the Louisiana State Police that you’ll probably be needing tomorrow.

If there’s a storm surge into Lake Pontchartrain, this storm-surge gauge (located here) will see it, as will these water-level monitors: 1, 2, 3. (More data here and here.)

Finally, here are some traffic cams from the New Orleans area. Could get interesting tomorrow.

UPDATE: I just got an e-mail report from Tom Grace, a resident of Metairie, LA, just west of New Orleans. He writes:

I just got back from tieing up my boat, putting out extra lines and fenders, and generally preparing her as best I could for Katrina, in case she comes here.

We are in the process of putting things together to load into the car, so we can leave in the morning. We have reservations in Memphis, the closest place we could find a pet-friendly hotel.

Wish us luck. We will need it. Our press reports that because of the gradual destruction of the barrier islands, which used to provide protection for us, our city now faces extreme danger from even a Category 2 storm. In the past it was believed that we faced that danger only from a Category 3 or stronger storm.

See, for example: [here and here].

More later, if we get a chance.

Good luck, Tom and family. And thanks for the e-mail.

Anyone in Hurricane Katrina’s path, whether staying behind or preparing to evacuate, if you would be interested in guestblogging here, please e-mail me. I can make it possible for you to guestblog via cell phone if you are evacuating. Whatever the situation, I’d love to have some first-hand reports.