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August 2012

Isaac Taking the “Impossible” Path Towards the Central Gulf Coast

   Posted by Levi at 4:03pm on August 26, 2012

Isaac remains a tropical storm this morning, and though he has restrengthened some since yesterday, his proximity to Cuba has filled his large circulation with lots of dry air, and the inner core remains rather ragged on satellite and radar imagery. Due to Isaac’s large size it will take a while to mix out all of this dry air, but once he does, significant strengthening may be possible over the open waters of the Gulf of Mexico. Radar is showing spiral bands with tropical storm force winds already moving into the Florida keys and the southern Florida peninsula. The forecast intensifies Isaac into a hurricane tonight, and a category 2 hurricane over the central Gulf of Mexico. Currently an upper-end Cat 2 is forecasted at landfall on the gulf coast, but if Isaac mixes out the dry air and establishes an inner core more quickly, he could easily strengthen more than forecast, and it is not out of the question that Isaac becomes a major hurricane before landfall.

The track forecast has been a wreck over the last few days, and everyone is having to shift westward with the models, which now take Isaac into Louisiana or Mississippi. This is the path I called highly improbable, but it looks like it may happen. Isaac has hit the “sweet spot” between the trough over the eastern seaboard and the ridge over the Rockies, a situation similar to what we had with Debby earlier this year, where my forecast also had to flip. When a storm is in this kind of a position, it is very hard to predict whether the storm will get recurved by the trough or brought westward by the ridge. This is the time when we are very glad to have computer models that can catch on to which path the storm will ultimately take at least 2-3 days in advance of landfall. The track forecast now calls for a landfall on the Mississippi coastline, very close to the 11am NHC track, though it should be noted that the cone of uncertainty fans out considerably near the gulf coast, and it is still possible that Isaac could deviate significantly to the right or the left, and everyone on the north gulf coast should be prepared for a hurricane hit. The NHC has expressed the abnormally high uncertainty with this track forecast as well.

We shall see what happens!




  • Mike says:

    I really still appreciate your clear analysis of what you see driving a storm like Issac. Keep up this good work and I’m sure you will reach your personal goals.

  • Jeff H. says:

    Levi, how do you view the TCHP, tropical cyclone heat potential. I know that the water temperatures are very warm in the GOM but it appears that the TCHP is favorably low which shouldn’t allow this system to build into a major category force storm? Does that play into your forecast of cetagory 2 upon landfall.

    • Levi says:

      TCHP is lower because of a weaker loop current than in recent years, but there is enough there with this favorable pattern aloft to allow a major hurricane, and any swift organization of Isaac’s inner core could up the intensity forecast abruptly.

      My forecast incorporates the fact that the storm has to get rid of a pretty large amount of dry air, and could have to undergo a quick eyewall replacement cycle right away after the initial ramp-up, but such things are nearly impossible to predict more than 12 hours in advance. If this gets a solid core more quickly than expected, it could be a major hurricane easily.

  • Jeff H. says:

    Thanks, understood. Do you see anything in the circumstances that would prevent the system from going further west more into the Texas coast. Or does that have some level of possibility?

    • Levi says:

      It would likely have to run into Louisiana first. Right now the GFS is the only model showing this. The model trend westward has stalled today and stabilized, so I think a direct landfall west of Louisiana is pretty unlikely at this point.

  • Ronald Sutherland says:

    Thanks as always for the great analysis!

  • Gary Z says:

    When it comes to weather, the stock market, world events, whatever.
    No one can really know what will happen. Most of the time, they are wrong.
    It takes courage to put yourself out there..if you have the guts to do it.
    Good luck…

  • Anonymous says:

    What effects do you think south east Texas will get if Isaac goes the way the GFS model says?

    • Jason says:

      Hey I’m wondering the same thing. Hopefully Levi will rspond back.

    • Levi says:

      Right now on the path the GFS suggests, Isaac would be interacting with Louisiana first, so heavy rain would be the main impact for Texas. If the track shifts even farther westward, then wind could become even bigger of an issue, though right now the models seem to have somewhat stabilized, so hopefully the track will not shift too much more.

  • Jeff H. says:

    I am going to stick up for Levi and the weather folks with regard to the earlier comments. The forecasting abilities have increased tremendously over the years, to where it is far from throwing darts at a board. The vast array of data input that they have to work from is really something. A credit to our meteorology and scientific disciplines. Most of the time in recent history that I have been watching closely the models have been quite good at coming in line in time to warn the concerned areas for evacuation or emergency measures. They are close enough and sometimes spot on. The folks in the Antillies and the Florida Keys can vouch for the advance notice they were given. This storm has been quite difficult with its considerable passage over land and with the weather systems over the CONUS that play into the determination. I am old enough to remember when we navigated by sextant and when it came to a tropical storm the best we had was Buy’s Ballot.'s_law

    • Gary Z says:

      “experts” are hardly ever right. They just like to hear themselves talk.
      I don’t believe anything I hear. I’m glad you have more confidence than I do.

  • Bobbo says:

    Man plans, God laughs.
    Yiddish proverb

    What a W shift in 3 days… And how about that early on-target European model!

    An unprecedented track is so cool to experience and it’s what makes meteorology a subtle science.

  • David says:


    Question: Do the BAMM, GFDL and HWRF models feed the GFS operational model? A friend says he sees a shift west in the 0Z GFS run but I can’t find any 0Z GFS output yet. When I pressed him, he said that it was the 0Z run of the referenced models which feed the GFS. Doesn’t make sense so I thought I’d ask.

    Thanks for any help. Love your new site.

    • Levi says:

      The BAM suite is initialized off of the previous GFS run, so the 0z BAM is based on the 18z GFS. The GFDL and HWRF models are given boundary conditions and initialization by the GFS.

      • David says:

        Thanks Levi. That makes far more sense.

        • Thayanne says:

          We haven’t really seen a huge deireffnce in him, but we have some friends who swear by it so we figured it was worth a shot. As for easing helping the drool we also haven’t seen any change. Erin read something the creator of the necklace said, apparently one of her kids had to have two necklaces in order for it to kick in.As for pulling on it, Isaac’s never even acknowledged that he wears it. He’s never shown any desire to play or pull on it (while he’s wearing it).

  • Cunninglinguine says:

    All the models call for it to skirt the coast of LA and come ashore somewhere in central/west LA. The models were indicating that forecast prior to the 8PM NHC update, which still shows it heading more or less directly at New Orleans.

    Do you think Isaac will go west and come ashore to the west, or continue on track for eastern LA? Why do you think the NHC stuck with their previous prediction rather than shifting the path farther west?

    Last, why should we trust anything you have to say? Didn’t you screw up Debby’s forecast as well?

  • ge2655 says:

    Not sure if the structure of Isaac will persist but in my case, being under the north-east section as it past through the Straits, he was one nasty, wet boy who pelted us with howling winds and torrential rain from pre-dawn Sunday morning throughout the entire day. The conditions were especially evil last night.

    The winds were different from Wilma in that Wilma sounded like a freight train right outside my house and Isaac’s winds sounded like a freight train off in the distance. I believe Isaac was a ‘wetter’ storm than Wilma but Wilma’s winds were devastating to my area. We lost every power pole for blocks and were without power for almost three weeks. Since that event, I take no storm lightly.

    Whoever is unfortunate to experience the finality of this storm, be prepared for the oncoming multitude of rainfall.

    Hollywood Florida

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