Weather Nerd

Target: New Orleans? Too early to say, but...


The official forecast track for Tropical Storm Gustav has shifted a bit to the right as of 11:00 AM EDT, and now shows the storm aiming directly for New Orleans on Monday — the first day of the Republican National Convention (when Bush and Cheney are due to speak), and three days after the third anniversary of Hurricane Katrina.

But, there’s no cause for panic yet. As the NHC discussion says, “ONE SHOULD NOT READ MUCH INTO SUCH SHIFTS OF THE FORECAST TRACK SINCE THE TYPICAL ERROR OF A 5-DAY PREDICTION IS OVER 300 MILES.” And the Houston Chronicle‘s Eric Berger writes:

[U]ntil Gustav interacts with Cuba during the next two to three days it will be difficult to pinpoint a final landfall location, and anywhere from Texas to Florida remains very much in the mix.

He’s right. Also, the NHC discussion contains this hopeful note: “GLOBAL MODELS SHOW SOME INCREASE IN SOUTHWESTERLY SHEAR AT DAYS 4 AND 5.” Between that expected shear and the cooler waters offshore, it seems fairly likely that Gustav — even if he becomes a Cat. 4/5 monster — would probably peak over the central Gulf, then weaken a bit before landfall (as Katrina did).

That said, if I were in New Orleans, I would definitely be getting my ducks in a row to ensure that I have the ability to evacuate on Friday, if necessary. You do not want to be stranded there, over the “holiday” weekend, if a major hurricane is threatening to make a direct hit. (This applies even to people and places that successfully weathered Katrina. Katrina was not a fully direct, worst-case-scenario hit on New Orleans. Far worse scenarios are possible. “I survived Katrina, so I can survive anything” is not a valid statement!)

Anyway, Dr. Jeff Masters has a full update on Gustav, in which he echoes Berger’s sentiments (“While it currently appears that Louisiana is the most likely target, keep in mind that if you’re in the cone of uncertainty, you’re not safe. Final landfall of Gustav could occur anywhere from Texas to the Florida Panhandle”) and also writes, with regard to the intensity forecast:

One key question controlling Gustav’s short-term intensity is how close it will stay to land. Gustav will not be able to intensify much until it clears the southwest Peninsula of Haiti, which should occur late this afternoon. If Gustav passes close to the rugged southeastern tip of Cuba, this will also impede its intensification. However, all the models are forecasting that Gustav will be able to thread the narrow gap between Cuba and Jamaica, allowing Gustav to intensify back to hurricane status on Thursday. Gustav is currently under moderate wind shear (10-15 knots). This shear is expected to remain in the low to moderate range (0-15 knots) for the remainder of the week. By Friday, as Gustav approaches the Cayman Islands, the storm will be underneath an upper level anticyclone, and over the highest heat content waters of the Atlantic. The HWRF and GFDL models respond by intensifying Gustav to a Category 3 hurricane as it passes through the Caymans. I think it is plausible that Gustav could intensify further, to Category 4 strength, before hitting the Caymans. If you have plans to be on the northern Cayman Islands–Cayman Brac or Little Cayman Island–on Friday, be prepared to be stuck there for several days, as Gustav may heavily damage these islands. Grand Cayman Island is also at risk–the GFDL model predicts Gustav will pass very close to Grand Cayman on Friday afternoon.

Gustav will lose intensity when it crosses the western tip of Cuba–perhaps by 25 mph or so–but should easily regain that lost strength within 12-24 hours. Gustav will likely be a major Category 3 or 4 hurricane in the Gulf of Mexico, and make landfall in the U.S. as a major hurricane.

Dr. Masters also looks at Gustav’s intensification potential in the Gulf, particularly as regards the Loop Current. Read the whole thing.

UPDATE: Some preparations are already underway in New Orleans:

The Army Corps of Engineers and West Bank levee officials are huddling this morning to launch plans for closing up more than 20 miles of ongoing construction projects along the unfinished hurricane barrier.

“What we’re looking at is expectation of a hit,” said David Bindewald, outgoing president of the West Bank levee board. “We’re gearing up with that in mind.” …

The West Bank is in the thick of an unprecedented amount of levee and floodwall improvements, but it will continue to have some of the most vulnerable areas in metro New Orleans until the full system is complete. …

[H]ulking concrete floodwalls tower above Peters Road east of the Harvey Canal. They will eventually protect against 100-year hurricanes, but sit for the time being unconnected.

The levees in the West Bank area were largely spared by Katrina because the storm went east of the city. They might not be so lucky the next time around — whether that’s Gustav or some future storm. Anyway, it’s good to hear that officials are already planning how to deal with this potential threat.

Meanwhile, New Orleans Mayor Ray Nagin, a Democratic superdelegate, is leaving the Democratic convention to come home and deal with Gustav:

New Orleans Mayor Ray Nagin says he’ll leave the Democratic National Convention this afternoon to oversee preparation for Hurricane Gustav.

“I’ve been monitoring the storm,” Nagin said this morning. “We’re in the cone of probability. Once it gets into the Gulf of Mexico, we only have about 72 hours max (to decide on evacuation). I think it’s best that I go back and leave the convention.”

Nagin said that he is urging city residents to “dust off” their disaster plans to make sure they are ready.

“Make sure you know what you are going to do, where you’re going to go if we have to evacuate,” Nagin said. “Make you know where your relatives and neighbors are going, particularly senior citizens.”

And because the hurricane “will probably be a big rain event,” he urged residents to clean their storm drains around their homes.

Nagin said he had been looking forward to being a witness to history Thursday night when Barack Obama accepts the Democratic presidential nomination the first African-American nominee of any major political party. But he said that there’s no doubt in his mind that he needs to return to New Orleans quickly.

I’ve been harshly critical of Nagin for his failures in 2005, but so far he’s sounding all the right notes. Hopefully any potential evacuation order will be timely, and complete with an effort to actually help the people who need assistance leaving town. (Well, hopefully an evacuation order won’t be necessary at all. But if it is…)