Gustav cf Katrina

Posted by Greg Laden on August 31, 2008
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This is a rough sketch of the actual path of the eye of hurricane Katrina compared to the current projected path of the eye of hurricane Gustav.
i-de383649e0a41afd0b10645f4c7ca5f9-katrina_vs_gustav.jpg
Now, this is NOT Gustav’s actual path. We don’t know what the path is going to be. But this graphic allows for a few key points to be made.

First, realize that in the counter-clockwise spinning hurricane, the right hand side, and in particular, the ‘front right” quadrant, of the storm is where the winds are strongest … because we need to add together both the forward motion of the storm, maybe between 10 and 15 mph at landfall in this case, with the spinning rate of the storm. Also, this part of the storm is virgin … it is coming off the ocean, and it is probably carrying more rain. Most importantly, perhaps, is that the front right quadrant carries the highest storm surge, which in the case of Gustav, could be 15 feet plus waves.

Now, you’ll notice that Lake Ponchetrain and New Orleans itself was not in the right front quadrant of Katrina but it could be for Gustav. Gustav could also hit in a very different locaiton, putting N.O. in the left quadrant, or simply being far enough away that it does not matter too much.

But what is possibly more important, and actually predictable at this stage (probably) is the angle with which Gustav will strike the coast. Since it will be an oblique angle (if present predictions hold) this means more contact time with low coastal areas, and probably a prolonged period of weakening (meaning the storm stays strong longer then if it just plowed over land).

On addition, look at the shape of the bodies of water and delta formations here. A storm surge moving in a northwesterly direction could drive more water father inland, into steadily restricting channels, where the surge can be significantly magnified. If the eye is exactly where it is shown on this map, then the open water leading towards New Orleans could be 50 miles or so away from the eye, and an appreciable but diminished storm surge may be expected. But if the eye is half as far or less from New Orleans, and Gustav remains at, say, Category Three strength, Breton Sound and/or Mississippi Sound could become traps. This water would have to go somewhere, and this often means a fundamental reshaping of the landscape.

Right now, New Orleans is on Lake Pontchartrain. When this is over, Lake Pontchartrain could be on New Orleans.

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Comments

  1. #1 cthulhu's minion
    August 31, 2008

    The levees are not finished and there are still gaps left even now. And a storm surge of 10 feet will overtop the levees in the 9th ward and there is the flooding all over again. Combine that with the fact the nola will see much more wind damage this time and the ground is saturated from faye and this could be uglier than last time. One model i saw showed significant storm surge all the way up to Baton Rouge.

  2. #2 I am so wise
    August 31, 2008

    Perhaps it is time to give up on New Orleans and relocate it elsewhere.

  3. #3 yogi-one
    September 1, 2008

    There have been a lot of evacuations already. Gustav did not grow back into a cat 4 and may only be a cat 2 when it hits. The likelihood of it hitting exactly where Katrina hit is small.

    But it is still very risky, because the Gulf is warming and every year brings a new hurricane season. NO may dodge the bullet again this year, but that does not mean the coast is clear.

    At least people take it seriously now.

    Hanna is building and is expected to head up the East Coast to the Carolinas. That’s one to watch too.

  4. #4 Who Cares
    September 1, 2008

    Weather Underground has Gustav as a category 2 at the moment. It has shifted to the west from the trail it was most likely to follow.
    Also the expected storm surge levels have (in most places) been reduced from 20 feet plus to a ‘mere’ 12 feet.

  5. #5 Greg Laden
    September 1, 2008

    It has shifted but by a VERY small amount compared to what was predicted quite some time ago. That track was right on the money.

  6. #6 Alan Kellogg
    September 1, 2008

    One thing I’ve noticed in the stories out of New Orleans is that people are in a better mood than during Katrina. People were advised to evacuate well ahead of time, resources were made available. The feeling you get is more, “we’re here to help” than, “sucks to be you.” Might be some time before people get home, but at least now they’ll have reason to expect getting home.

    Now for some court reform. Abolishing out of court settlements for any action for which court proceedings of any sort have occurred would be a great first step.

    Proposed Wording: Once any civil action has begun court proceedings, that civil action must be decided by a judge or jury. The plaintiff or plaintiffs may not withdraw the action, but must continue it until completion. Nor may records of the case be sealed or otherwise made unavailable to the general public.

    In addition, should the plaintiff or plaintiffs come to the conclusion that their case is unwinable and ask that it be dismissed, the court shall find against them and the plaintiff or plaintiffs and the plaintiff or plaintiff’s attorneys shall pay the full cost of adjudicating the case; Plus all costs borne by the dependent or defendents and the dependent’s or defendents” attoneys.

  7. #7 Ben Zvan
    September 1, 2008

    I don’t think you’re going to convince anyone to abandon N.O. but maybe we can get them to build more appropriate housing?

  8. #8 Brendon Brewer
    September 2, 2008

    This map would have been interesting but it turned out to be useless. You did not even tell us which path was which! Also a scale would have been helpful.