Hurricane Ike is about to make its second landfall in Cuba, very close to where Gustav hit the island. You can follow its progress on Cuban radar, Key West radar, visible satellite and infrared satellite loops.Beyond Cuba, Ike’s predicted track keeps shifting further and further south. The 5:00 AM EDT forecast has Ike going ashore about halfway between Brownsville and Corpus Christi — and the discussion says this track is “STILL IS ON THE NORTHERN SIDE OF THE GUIDANCE ENVELOPE.” In other words, if the models don’t lurch back northward, the track will soon shift further south. [UPDATE: Or not. See full update below.]
Could Ike end up coming ashore somewhere in Tamaulipas, Mexico? At this rate, I wouldn’t rule it out. Over the last several days, Ike’s forecast track has been lurching to the left faster than Dennis Kucinich.
You can see the forecast evolution for yourself by watching the NHC’s five-day track animation. The trend is unmistakable. First we thought Miami was at risk, then Tampa, then Pensacola, then New Orleans, then Houston, then Corpus Christi, now perhaps Brownsville. Next stop: Tampico?
The reason for this shift is actually fairly simple. The key factor in determining Ike’s course through the Gulf will be an upper-level high pressure system to the storm’s north. So long as this ridge of high pressure is in place, the upper-level winds will rotate clockwise around it, resulting in east-to-west steering currents over Ike, pushing the storm westward. Originally, the computer models thought a significant “weakness” — i.e., a trough of low pressure, with its counterclockwise rotation — would swoop in and disrupt this high-pressure system, pulling Ike northward. (At first, this was supposed to happen just east of Florida; then just west of Florida; then in the central Gulf; then near Texas; etc.) Over the last several days, however, the models’ analysis has gradually changed, predicting a stronger ridge and a weaker trough. This means a more vigorous east-to-west flow, and less impetus to pull the storm northward. That, in turn, reduces the northerly component in Ike’s expected long-term track, keeping the storm moving closer to due west.
[UPDATE: As of 11:00 AM, the track forecast has shifted to the right, and now favors a landfall right near Corpus Christi. Of course, we should not read too much into the exact location of the “track line” 4 days out, as it will inevitably shift around, but the reversal of the leftward trend is noteworthy. The discussion explains:
THERE IS CONSIDERABLE UNCERTAINTY NEAR THE END OF THE FORECAST PERIOD…WITH THE ECMWF AND UKMET MODELS SHOWING A SHORT-WAVE TROUGH COMING OUT OF THE ROCKIES THAT INDUCES A RIGHT TURN ON DAY 4. THE GFS AND NOGAPS HAVE A DIFFERENT PATTERN…WITH MORE RIDGING EXTENDING WESTWARD TO THE NORTH OF IKE THAT KEEPS THE HURRICANE MOVING BASICALLY WESTWARD. THE ECMWF HAS DONE VERY WELL WITH IKE THUS FAR…AND HAS RELATIVELY HIGH SKILL IN FORECASTING THE LARGE SCALE PATTERNS AT THE LONGER RANGES. OUT OF RESPECT FOR THIS MODEL THE OFFICIAL FORECAST IS SHIFTED SLIGHTLY SLOWER AND TO THE RIGHT OF THE PREVIOUS FORECAST…AND IS PRETTY CLOSE TO THE DYNAMICAL MODEL CONSENSUS.
You can see some of the key models here, though not the important ECMWF, which can be seen here. The NHC discussion also notes that NOAA’s high-altitude Gulfstream jets will sample Ike’s environment tomorrow morning, which should improve the accuracy of the computer models beginning late tomorrow and early Thursday. In the mean time, Houston/Galveston can’t breathe easy just yet. This reversal of the leftward trend serves as a reminder that the entire Texas coast remains within the at-risk zone.]
How strong will Ike be when it reaches southern Texas or northern Mexico? Eric Berger writes that we really don’t know: “The computers call for everything from a strong tropical storm to a category 4 hurricane. Not much help there.” The official forecast errs on the side of caution, predicting a 115-mph Cat. 3 landfall.
Then again, the NHC is probably slightly inflating Ike’s current intensity, allegedly at 80 mph, as the discussion tacticly acknowledges:
ALTHOUGH THE MINIMUM PRESSURE HAS BEEN AROUND 963-965 MB [WHICH IS USUALLY INDICATIVE OF A BORDERLINE CAT 2/3 HURRICANE]…THE MAXIMUM FLIGHT LEVEL WINDS MEASURED SO FAR WERE ONLY [79 MPH, WHICH WOULD NORMALLY TRANSLATE TO AN ESTIMATED MAXIMUM SURFACE WIND SPEED OF 70 MPH]. THE INITIAL INTENSITY IS KEPT AT [80 MPH] ASSUMING THAT THE PLANE HAS NOT SAMPLED THE ENTIRE CIRCULATION…BUT THIS VALUE APPEARS QUITE GENEROUS AT THIS TIME.
In all likelihood, Ike may be a glorified tropical storm right now, albeit one with an unusually low barometric pressure. (This can be partly explained by the fact that, as Ike has weakened due to land interaction, its wind field has expanded, such that a broader swath of land and ocean is now feeling tropical-storm force winds.)
But for purposes of predicting what type of storm the U.S. (or Mexico) will eventually see, the current top wind speed doesn’t matter all that much. What matters more is whether Ike will emerge later tonight from its passage of Cuba with its core structurally intact, so that it can re-organize quickly and begin re-strengthening over the Gulf. Only time will tell the answer to that question.
Alan Sullivan writes that “Ike may have a better chance to go ashore with some force while staying so far south” — presumably because the waters will stay warmer and the wind shear is more likely to remain weak — but he nevertheless predicts that “the eventual Texas landfall will be over-reported and predictably hyped.” Perhaps. Personally, my gut tells me Ike will hit northern Mexico as a Cat. 2. But that’s not a forecast, it’s a wild guess.
UPDATE: Dr. Jeff Masters has a full update on Ike.
Also, Eric Berger will host a live chat about Ike at 3:00 PM EDT.
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