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The model guidance forecasters use to help shape their forecasts continues to bounce around a bit.  However, it's nothing like it was a couple of days ago.  There is beginning to be less run-to-run variation, increased focus on the mid-Texas coast for the eventual landfall of Hurricane Ike, and increased confidence.  Please keep in mind that with landfall still three days away the average track error remains well over 100 miles in the 3-day forecast.  Of course, some of these errors - like with Gustav - are "along track".  That is, the landfall point is accurate, but the timing of landfall is wrong, making for a near-perfect point-of-impact prediction, yet still having a large track error.  So, the actual landfall point errors at 3-days are less than that link shows.  Still, they are not insignificant.  So, while confidence is increasing, there remains room for error.  So, on to Ike...

The forecast tracks remain clustered around or just north of Corpus Christi, TX.  The mean of the model tracks is just north of Corpus, but there is enough spread so that there are also some model solutions just to the south.  Below is the image I've included with each of these posts, all of the tracks, off of Allan Huffman's weather page:


The mean of these may look like it's aimed right at Corpus, not "just north", as I stated above.  But, as always, remember, not all of the models are on that plot.  Frustratingly, one of the best models of the year, the Euro model, does not get into these plots, because NHC does not make that model available in their model database file (likely for prorietary reasons).  It has landfall just on the north side of Matagorda Bay on Saturday morning.  The Canadian model is also not on that map.  As I've stated numerous times, the Canadian model has been a poor performer this season.  Nonetheless, it has been no less poor than some other models on that plot.  So, a true model "mean"... a consensus, as it's referred to at NHC... should include the Canadian.  And it has the furthest north solution with a track up near Houston very early Saturday morning.  The legend on that track map is missing again, but that outlier southern solution is a variant of the Navy/NOGAPS model, which I'd largely dismiss.  The actual Navy model was the last one to make the northward shift, but it now has... it is the brown line on that map, tracking right into Corpus Christi.

And, as always, I cannot emphasize enough that the National Hurricane Center is the official word on these storms.  So, you'll want to check their forecast.  Their track forecast looks like this:


I truly can't dispute that NHC forecast.  If forced to lean one way or the other, I might go a shade north, to the north of Corpus, in deference to the excellent performing Euro model.  But, really, for a day three forecast, that would be within the noise.  Also, Ike had been a very small storm.  He has grown considerably in the last several days.  He is not a huge storm now, but he is fairly large.  So, the precise landfall point is a bit less important with Ike.  Obviously, as I argued with Gustav, the landfall point is more critical than NHC lets on, because the eyewall is a relatively narrow corridor and winds, though perhaps still intense beyond the eyewall, do drop off considerably outside of it.  Also, wind direction becomes critical for surge.  If Ike comes head on into Corpus Christi or just south, they'll get a tremendous surge (*if* Ike is as strong as expected) which will do considerable damage to the area.  On the other hand, if he comes in just to the north of Corpus, they'll catch offshore winds, somewhat lighter winds (though still severe if they're in the eyewall), and much lesser surge.  So, landfall point remains critical, but it is somewhat less critical with Ike.  To demonstrate what I mean, here's the GFDL's wind field near landfall, check out the right hand side, the zoomed in image:


...the greens are hurricane force winds.  Notice the expansive nature of these winds... from Matagorda Bay down almost to coastal Brownsville.  Tropical storm force winds (blue) stretch from Brownsville up to Galveston Bay... and this is believable given how long the Florida Keys saw sustained tropical storm force winds with Ike being a considerable distance from them.  The yellow is Category 2 force winds, which also covers a wide swath (you can assume the region covered by the lower winds in the middle would see the Category 2 winds as Ike approaches).  Point is, yes, Ike's precise landfall point is still very important for gauging who gets the most destructive winds and storm surge.  But in terms of generally very significant impact, the precise spot of landfall is somewhat unimportant (assuming, of course, it's not hundreds of miles off the prediction).

Bottom line on the track:  Excellent model and forecaster agreement on landfall near Corpus Christi or just a bit to the north early Saturday.  Forecast errors this far out dictate that all interests from Galveston to Beaumont remain on alert.  But, certainly, the forecast appears to be (and should be) narrowing in.

As for intensity, well, here's how the intensity models look (also from Allan Huffman's page - see link above):


I do my best not to be alarmist, but this image is disturbing.  The black line is NHC, with landfall at 105kts.  Every line below that is a global (or regional, in the case of the NGM) model, not designed for hurricane forecast.  Every line above NHC is a hurricane model.  All dynamic hurricane models are clustered between 110 and 125kts (125 and 145mph) at landfall.  This is between a strong Cat 3 and a mid-range Cat 4 at landfall.  NHC's conservatism is in deference to the weaker statistical models, showing Ike peaking as a Category 2.

But the current aircraft reconnaissance data and recent satellite imagery support the notion that intensification is already well underway.  The recon data has shown a 10mb pressure drop from last night (969mb last night to 959mb this morning).  That may not be "rapid" deepening, but its quite significant.  And the latest satellite image:


...shows a solid core of convection around Ike's eye, with deep convection blossoming around the eye.  This should yield further/continued deepening.  Ike could easily get to Category 2 (or beyond?) within the next 24 hours.

Bottom line on intensity:  The NHC official forecast is for a mid-range Cat 3 at landfall.  This is certainly very reasonable, and as I always emphasize, it is the official word.  But based on the information at hand, it seems like Ike is more likely to be stronger than that, rather than weaker, by landfall.  A strong Category 3, or even a low-end Category 4 is not out of the question.

Gotta run, as work calls (and, once again, no time to proofread, so sorry if there are typos - if anyone picks up one the alters the context of what I'm writing, let me know in the comments and I'll do a quick fix), but the gist of it is quite simple:  Ike is a major threat to Texas, with the threat focus still on the central Texas coastline.  But we're still just far enough out, and Ike is rather large, so the entire Texas coastline needs to remain on alert.  There is a late northward turn expected from Ike, which brings the storm to near Corpus.  The precise timing and degree of the turn will determine where Ike comes in... and that's why some uncertainty remains.  But, clearly, the focus and confidence on the mid-Texas coast is increasing.  As is the confidence that Ike comes in as a major hurricane.  Let's hope that part is wrong.

UPDATED 11:25AM EDT  ...very short and sweet update right now.  Time is short for me, and there's limited new info in.  But, with the new National Hurricane Center forecast available, I wanted to get an update out.  The NHC has increased their landfall intensity a bit... to 110kts (125mph)... a strong Category 3.  They have left their track alone for the most part... perhaps just tweaking it slightly north (tough to tell interpolating between points), with landfall still very near Corpus Christi, TX on Saturday morning.

No new models... they are just beginning to come in now, and I'll do an update between 2 and 4PM on that new info (bookmark or subscribe if you'd like, in case we roll off the rec list).  And limited new reconnaissance data... though it does show continued strengthening - down to 957mb (and the official intensity now up to 80kts)... but this may be slowed now by an eyewall replacement cycle.  Thereafter, intensification should resume.

UPDATE 3:30PM EDT  Afternoon model runs force me to remind myself (and you) that three days out remains just a bit too early to nail things down.  To be clear, we should not expect major shifts in the models any more.  And, indeed, we haven't seen that.  But the small adjustments can still be significant... especially if they creep in the same direction each run.  In this case, northward nudging with every run, as we saw with Rita - as noted by a commenter below - would be quite bad, particularly if the adjustments were a bit less than with Rita (as bad as Rita was, she came in into an area which spared both the Houston/Galveston and Beaumont/Port Arthur areas from her worst).  And, unfortunately, we saw in the latest model runs that dreaded northward shift and we're likely too close in time for there to be enough Rita-like forecast shifts to push Ike up and beyond Houston/Galveston.

Again, let me be clear, the afternoon model shifts were small (except for the GFDL).  Virtually all models remain pointed at Matagorda Bay... with some models a shade to the south, some a shade north.  There is excellent agreement on that.  But, the GFDL did shift more, up to near Galveston.  And the short-term motion of Ike does favor a slightly more north track.

So... while it still looks unlikely that Ike comes up as far north as Galveston or Houston, we do need to remain open to the possibility of northward track adjustments up that far.  And adjustments up to a point near, say, Freeport, TX would be easy to attain.  At this point, my thinking has shift north a bit, but not much.  I'm following the European model.  It is very slightly on the north side of the models and has been the best model.  So, my new expectation is from north of Corpus Christi to just north of Matagorda Bay.

And let me re-emphasize something I mentioned above...  The precise landfall is less critical with Ike than most storms.  He has a wide wind field.  Moreover, the concave shape of the coastline means that, unfortunately, high storm surges would be expected all the way up to and including Galveston Bay.  Consider Hurricane Carla in 1961, for example.  While I do not expect Ike to be quite a severe as Carla, it could be close.  And, like Carla, Ike is large.  Carla struck around 100 miles south of Galveston... that is well within range for Ike (in fact, Ike may well come in a little closer than that).  Carla brought tides of 9+ feet to Galveston with sustained hurricane force winds.  So, make no mistake, whether Ike hits Corpus Christ, Matagorda or Freeport, Galveston, and to a slightly lesser degree, Houston (because they are somewhat protected) will see some serious effects.  Obviously, landfall in Freeport, TX would be far worse than landfall in Corpus Christi, but the point is simple...  Ike is big, and will likely be powerful.  Effects will be felt pretty far out from the storm center.  So, the specific landfall point is of a bit less importance than most storms.

That said, landfall location is very important for those right near it.  So, we still need to nail that down.  Again, I'm thinking just north of Matagorda Bay.

As for intensity, no change in expectation there.  As of 2PM EDT NHC has officially upped Ike to a Category 2 hurricane of 85kts (100mph).  That is a good estimate, given the discrepancies between flight level and surface estimated winds.  But I should warn that the most accurate estimator, a dropsonde, came in higher... 92kt surface sustained wind.  It could be written off as an isolated high wind in a burst of convection, or whatever.  But, it is not at all unlikely that Ike already has 90+kt (105mph+) sustained winds.  And, so, it could quickly get to Category 3 strength as early as late tonight or early tomorrow morning.  I'm not saying it will... Ike is fighting off a bit of dry air, and some dueling eyewall issues.  But slow intensification has gone on in spite of this, and with some evidence (that dropsonde) that Ike is already over 90kts, it would take less than 10kts of additional intensification to push Ike to a Category 3 (which starts at 100kts, or 115mph).

As always, my apologies for the graphics-free, boring update.  But I'm trying to relay this info in a timely manner under the time-crunch of work responsibilities.

Bottom line:  Track shifted north a little.  Not much, but we do need to be open to the possibility of further minor northward shifts.  So, Galveston/Houston remain beyond the highest risk area, but are definitely still within the envelope of possibilities... and they will almost certain be subject to some significant effects.

Originally posted to millwx on Wed Sep 10, 2008 at 06:28 AM PDT.

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