Anecdotal evidence, in comments and elsewhere, suggests that a distressing number of Texans in low-lying coastal areas, directly in Hurricane Ike’s path and vulnerable to storm surge, are choosing to “ride out the storm” rather than heed mandatory evacuation orders. This is a terrible, terrible idea.

I realize that evacuating is a enormous pain, and that there have been a lot of false alarms in recent years, but folks, this storm could kill you if you don’t get out of its way. I don’t care if you weathered previous storms with no problems. Ike is different. Its storm surge will be like a slow-motion tsunami. Whether or not the storm’s wind speed ever increases, its massive, sprawling size has already guaranteed an historic storm surge, far greater than you’d expect in a normal Category 1 or 2 hurricane. The only question is where that surge will go. And right now, Galveston Bay is in the bullseye.

Already, Ike’s surge is causing flooding in New Orleans and Pensacola, hundreds of miles away. Imagine what it will be like in the actual area where the storm hits! According to Dr. Jeff Masters:

Ike will probably inundate a 250-mile stretch of Texas coast from Port O’Connor to the Louisiana border with a 10-15 foot storm surge. This will occur even if Ike is a Category 1 storm at landfall. If Ike is a Category 3+ hurricane at landfall, surges of 20+ feet are possible. The latest experimental storm surge forecast from NOAA’s SLOSH model shows a 10% chance that Ike’s storm surge will exceed 18-21 feet at Galveston. The Galveston sea wall is 17 feet high, so it may get overtopped. At noon today, a mandatory evacuation of the entire island was ordered in case this worst-case scenario is realized. The official NHC forecast is calling for maximum storm surge heights of 20 feet.

Ike very probably isn’t going to be “The Big One” in terms of wind, but for folks near the center and northeast of it, the storm surge threat is very, very serious. Deadly serious. Say what you will about “overhype,” and about the National Weather Service’s “certain death” pronouncement this afternoon being “over the top,” but at least the statement drove home the point: refusing to evacuate from a surge-vulnerable coastal areas in advance of this storm is wolf-face crazy. Get out!

There is one hope for Galveston Bay and its estuaries to avoid a calamitous surge: pray for a landfall just northeast of the bay, which would keep the highly vulnerable metro area out of the storm’s “right front quadrant.” Unfortunately, that is not the forecast right now:

If the above forecast is what actually happens, it’ll be very bad for the Galveston area. But Eric Berger thinks a near-miss to the east is a realistic possibility, and I agree with him:

For the last 36 hours or so the models have trended eastward, which is reflected by the official track moving from Matagorda Bay to Galveston Island. Persistence, the notion that trends are more likely to continue than not, and climatology suggest this may continue. …

As I showed earlier this week, the landfall location of Ike is critical for determining where the maximum surge occurs. And a landfall around High Island would substantially reduce the surge on Galveston Island, possibly even to below six feet.

That would be wonderful (though not for Beaumont and Port Arthur), but coastal residents cannot count on it. It’s no better than a 50/50 shot right now. It is absolute folly to play games with this storm surge if you have a reasonable chance of being in Ike’s right front quadrant, which everyone from at least Freeport northeastward does. If the authorities are telling you leave — leave!

P.S. An earlier post by Dr. Jeff Masters, cited here, stated that Ike’s storm surge was 50% greater than Katrina’s surge, as measured by “Integrated Kinetic Energy,” which is determined “by squaring the velocity of the wind and summing over all regions of the hurricane with tropical storm force winds or higher.” It turns out this was not quite right: t

[The figures] saying Ike had an IKE of 180, 50% higher than Katrina’s, were found to be in error due to some bad data from one of the Hurricane Hunter observations (the IKE is an experimental product, after all). Thus, this morning’s IKE was actually a little lower than Katrina’s.

Now, however, Ike’s IKE really has surpassed Katrina’s IKE, albeit only just: “The amount of water Ike has put in motion is about 10% greater than what Katrina did, and thus we can expect Ike’s [total] storm surge damage [across all impacted areas combined] will be similar to or greater than Katrina’s.”