Weather Nerd

Gustav may stall out in Gulf

Dr. Jeff Masters reports on a “major long-term forecast change” as regards the eventual track of Tropical Storm Gustav:

A ridge of high pressure is expected to force Gustav west through Friday. By Saturday, a trough of low pressure moving across the Midwest U.S. should weaken the ridge, and allow Gustav to turn north across western Cuba into the Gulf of Mexico. The final landfall location of Gustav depends on the strength and speed of the trough. In this morning’s runs, we now have some indication that this trough of low pressure may not be strong enough to pull Gustav to the coast by Monday. In fact, the NOGAPS model predicts Gustav will stall offshore the Alabama coast on Monday, before finally edging ashore three days later. The UKMET model is also much slower with its latest run, and slows Gustav down as it approaches the Louisiana/Texas coast on Monday. The latest HWRF model is also slower than the last run, and doesn’t bring Gustav to the coast by the end of its forecast period (Monday). The HWRF foresees a Category 3 or 4 hurricane a few hundred miles south of the Louisiana coast on Monday. The latest ECMWF run is not much slower than the previous run, but does stall Gustav out over central Louisiana once it makes landfall near New Orleans Monday night. The latest GFDL model, though, is not much slower, and predicts landfall in Mississippi early Monday morning as a Category 3 hurricane. In summary, Gustav may slow down considerably just before landfall in the U.S., making its long-term track and landfall location very uncertain at this time. …

Gustav will likely be a major Category 3 or 4 hurricane in the Gulf of Mexico. However, Gustav not be able to maintain that strength all the way to landfall, if it slows down close to landfall, as some of the models are predicting.

Meanwhile, weatherblogger and chronic alarmist-puncturer Alan Sullivan, who has been uncharacteristically bullish about Gustav’s prospects until now, has reverted to form with his latest, skeptical post:

Tropical storm Gustav is still lingering over the SW tip of Haiti. The steering current is very weak and the storm is somewhat sheared by upper winds from the NE. I don’t think the shearing wind will end soon. The flow is coming over the front edge of an upper high centered near Florida, and round the backside of the upper low near Puerto Rico. Gustav is caught in a rather unfriendly environment. It would have to travel several hundred miles west before conditions would be better. At the current pace of 5 mph, that will take awhile.

I had thought we might have a clearer notion where Gustav might go by this time, but it is still too early to tell. The alarums regarding New Orleans are totally unjustified. The storm is undoubtedly causing death and destruction on Haiti at this time, but it may prove to be another Fay, weakened by contrary winds and land interaction, not another Katrina, rolling into the Gulf with strong steering flow, and spinning energy off the Loop Current to assail the coast. Upper winds are unfavorable in the northwestern half of the Gulf, and they have been for weeks. Even if Gustav does get onto open water south of Cuba, run the Yucatan Channel, and arrive in the SE Gulf as a category four hurricane, any US landfall at that strength would be very unlikely, given the present weather pattern.

I’m afraid I can’t agree with Sullivan’s “totally unjustified” language. It’s true that Gustav could be another Fay. It also could be another Katrina, or something even worse. As Sullivan says, we just don’t know yet. But, for better or worse, the current official forecast calls for a Category 3 landfall in New Orleans on Monday. That forecast is, of course, by no means certain to come true — but it is also by no means implausible.

It takes 72 hours to evacuate New Orleans; therefore, if the current forecast remains in place, evacuation orders would need to come Friday. Today is Wednesday. It is not at all unreasonable — particularly with a holiday weekend looming — to tell people they need to start making advance preparations for the possibility of an impending evacuation.

No doubt some elements of the media are going overboard — they always do, about everything — but from what I’ve seen, officials have been very responsible in noting that a Gustav landfall in New Orleans is only a possibility, not a certainty. What else are they supposed to say? Should they just sit on their hands and wait for more data, saying nothing to the public while precious time is lost? Should the Army Corps of Engineers not be preparing for all contingencies? Should folks not be dusting off their evacuation plans? Should the city not be activating its pre-evacuation 3-1-1 registration system? It’s easy to denounce such “alarums” from afar, particularly when the odds are they won’t ultimately prove necessary (the odds are always against any given scenario, 120 hours out) but if the public isn’t roused out of its complacency, and then the worst does happen, that’s a far bigger problem than “hype.”

In a perfect world, it would be possible to tell people “time to get ready, just in case,” and start taking the necessary, concrete preparatory actions, without triggering a certain degree of alarmism in the media and fear among the public — but we don’t live in a perfect world, and we never will. Bloggers can err on the side of snark and skepticism, but disaster planners must err on the side of caution. I just don’t understand what course of action the “anti-alarmists” like Sullivan would counsel in this situation. Seems to me Louisiana officials are — this time around — playing it just about right. When it comes to New Orleans and hurricanes, you need a lot of lead time, even if that increases the chances of false alarms. Better safe than sorry!