Weather Nerd

September 13th, 2008 3:45 am

Ike’s storm surge apparently less severe than feared

[Caveat: I just woke up, and have watched very little storm coverage in the media as of yet. This post is based entirely on tidal data, not damage reports.]

6:45 AM EDT: Hurricane Ike made landfall in Galveston at 3:10 AM EDT. Actually the center of the eye — which looked as impressive on radar at the moment of landfall as it ever has — passed over the narrow passageway between Galveston Island and the Bolivar Peninsula, not over the island’s West End as previously anticipated, thanks to some last-minute northward wobbles.

The Houston Chronicle’s Eric Berger writes that, based on the landfall location, “the National Weather Service estimates that storm surge along the island will range from 14 feet on the island’s west end to 17 feet on the east end.” But as my tidal gauge data page shows, the surge appears to have peaked at between 9 and 10 feet at Galveston Pleasure Pier and Galveston Pier 21, both on the island’s east end, and the water level has been falling since shortly before the time of actual landfall.

Further up the coast, where computer models projected a surge of 20+ feet, the tidal gauge information is harder to definitively interpret. When Rollover Pass stopped reporting new data at around 2:00 AM EDT, the surge was at 11 feet and had not begun falling, although it looked like it was possibly beginning to plateau. The Sabine Pass North station is still reporting, and the surge there appears to have plateaued at around 10 feet, though the data looks somewhat sketchy. There are no NOAA tidal stations on the stretch of coastline in between Rollover Pass and Sabine Pass — where the heaviest surge would have been expected.

Nevertheless, it appears clear that Ike’s storm surge did not reach the catastrophic levels that experts had predicted. Before going to bed last night, I wrote, “I guess we can hope the surge projections are somehow flawed, due to the computer models failing to capture something about Ike’s bizarre structure, or whatever. In other words, we can hope against hope that things won’t be as bad as we presently fear. I don’t know that there’s any valid reason to hope that, but I’ll hope it anyway.” Initial indications are that these hopes were vindicated.

Alan Sullivan, who was a lone voice in the wilderness yesterday arguing against the computer models’ predictions of a supermassive surge, wrote yesterday morning, “Extreme surge scenarios are being propounded for this storm. I suspect we will learn that they are excessive. Ike is too broad and weak to follow models based on the tight core structure of a normal hurricane.” It seems he was right. Sullivan wrote at 3:30 AM this morning:

After viewing a lot of gauges, I can say the overall character of the surge fits my expectation so far. It is broader, but not as steeply pitched as models indicated. I do not think some of the extreme hypothetical values will be reached. But the surge is plenty bad nevertheless, and waves will exacerbate its damage, even on inland waters.

Sullivan is right: the light of day will undoubtedly reveal plenty of damage. I am certainly not intending to sound the “all clear.” Indeed, even as to Galveston itself, the Houston Chronicle reports at 5:31 AM EDT that “the east and west ends of Galveston Island are under water, and water [presumably from wave crests] is pouring over the seawall. Power and utilities are out. There are multiple fires; rain is helping extinguishing some.” Ike has delivered a heavy blow to the island, and its surge and waves will cut a wide and severe path of destruction in the bay and up the coast. How severe remains to be seen.

But, assuming the tidal gauges are reporting accurate data, it is clear that Ike’s storm surge was far less than feared, and for that, we should all be grateful.

P.S. Explanations of the discrepancy between the models and the reality will come later. It is premature to cry “hype,” and irresponsible to pretend that the threat was never real. That the storm surge apparently wasn’t as bad as the best scientific data, interpreted by the leading experts on the planet, had projected it would be, is cause for gratitude, not recrimination. Hindsight is 20/20, as always. The fear of a 20+ foot surge was genuine and, based on the available data, justified. Sullivan’s hunch that the surge would be lower than projected has evidently been vindicated, but that does not mean the dire warnings were uncalled for. Scientists must trust their data, and the data called for a Category 4 strength surge. Undoubtedly, Ike will lead to refinements in the models, and next time the data will be better. But as for this storm, the models’ inaccuracy is only certain in hindsight.

Moreover, to the extent Galveston & environs “dodged a bullet” with Ike (which remains to be seen; as I said, the damage will doubtless be plenty bad), this storm should be seen as a wake-up call, not a license to be cavalier with future storms. As even the hype-averse, Ike-deflating Sullivan writes: “One day there will be a category four storm arriving in this area at speed on a perpendicular course, and Houston will be devastated.” The threat to this metro area is real, regardless of whether Ike did less damage than feared. (Which, again, remains to be seen.) And the people in low-lying areas who refused to follow mandatory evacuation orders are still fools, even if they survived. (That, too, remains to be seen.) Next time they might not.

UPDATE: In comments, Jacflash writes, “Brendan, as you surely remember, at this moment with Katrina we thought NO had dodged a bullet, too. Let’s give it a few hours before we go too far down this line of thinking. Surges and tides are notoriously funny things.” He’s right, of course — that’s why I tried to emphasize that it remains to be seen what the damage will look like. It may look pretty terrible. We don’t know yet. But this post is about the tidal gauges. Those gauges say what they say, and I cannot imagine that a 20-foot surge will now suddenly materialize, with the storm moving inland and away from the coast.

UPDATE 2: Here’s Sullivan’s take. His title is “Overhyped After All,” which I object to as a matter of principle: it was either overhyped or it wasn’t, based on information available at the time; a storm cannot become “overhyped” in retrospect (“after all”). That’s 20/20 hindsight talking. Moreover, although Sullivan has license to crow a bit because of his correct prediction yesterday morning that the surge would be less than projected, he himself admitted this was only a “suspicion,” and last night he sounded about as alarmed as everybody else (recall “the most expensive hurricane in history”).

But I don’t mean to bash Sullivan. ;) He did a fine job blogging this storm, and was fundamentally right in his two core against-the-grain predictions: that Ike’s unusual structure meant it wouldn’t strengthen significantly, and that the storm surge would be lower than expected. Anyway, his latest post is worth reading. Money quote: “[Maximum storm surge] heights were only three to five feet above the levels everyone found so scary when the cameras were rolling yesterday. The early rise of the sea was not a harbinger of an excessive climax, but merely a measure of the storm’s breadth.”

UPDATE 3: Sullivan responds:

When it appeared for a few hours that landfall would be 20-30 miles SW of where it actually was — and I was fully persuaded of that — I was alarmed about Houston. This was the one place where I thought it was possible that model heights might be better justified. If the course of the eye had held NW for longer, onshore wind would have kept piling surge into the mouth of the bay, while flooding rains fell inland.

But as soon as it became apparent the eye was coming right over Galveston, that concern was alleviated.

As for the larger picture, my hive versus pimple analogy was plain common sense. I have learned in my sixty years that when somebody’s model defies common sense, it is usually best to ignore the model.

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16 Comments

1. Steve Clouthier:

I am north of Houston about 32 miles and we are still getting continuous heavy rain and large wind gusts that i would say are in the eighty to ninety mile range.

Sep 13, 2008 - 3:59 am 2. Jacflash:

Brendan, as you surely remember, at this moment with Katrina we thought NO had dodged a bullet, too. Let’s give it a few hours before we go too far down this line of thinking. Surges and tides are notoriously funny things.

Sep 13, 2008 - 4:09 am 3. Brendan Loy:

I do remember that, Jacflash, and it is partly for that very reason that I tried to make clear, repeatedly, that the extent of the damage remains to be seen. However, the tidal gauges say what they say. As I said, my analysis is based purely on those gauges, not any damage reports. That’s different from Katrina, when the “dodged a bullet” concept was based on a flawed initial on-the-scene reports of “no flooding” (flawed because reporters weren’t in right places to see the initial flooding, and it took the waters longer to reach the places they were at).

The reason I posted this now — particularly the “P.S.” at the end — is, I’ve been doing this weatherblogging thing long enough to know that the people who love to scream “HYPE!!!” whenever a prediction of disaster isn’t borne out, will not wait. This post is a pre-emptive strike against their unthinking, reactive lashing out.

Sep 13, 2008 - 4:15 am 4. Brendan Loy:

P.S. You’re right that “surges and tides are notoriously funny things,” but I cannot imagine that a 20-foot surge will now suddenly materialize, with the storm moving inland and away from the coast.

Sep 13, 2008 - 4:16 am 5. Jacflash:

Brendan, understand I didn’t mean that as a potshot — I’ve been a big fan of your weather-wonking since the runup to Katrina, and I greatly appreciate your efforts here and now — just a cranky early morning caveat from a sailor who has learned to distrust heavy weather, that’s all. I think preempting recriminations is wise. Best of luck.

Sep 13, 2008 - 4:25 am 6. Brendan Loy:

Heh. No worries, I didn’t take it as a potshot. In fact, I’m about to quote a portion of our exchange in an update on the post, because I think your point is worth making.

Sep 13, 2008 - 4:28 am 7. et_reader:

Does anyone know the ranges of these stations? The reason that the surge may not have shown up as badly may simply be to the fact that the water simply submerged the gauges…

Sep 13, 2008 - 4:39 am 8. Alan Sullivan:

Topography is different in NOLA. Galveston Bay can drain much more swiftly to the ocean, as it is doing right now. Strain will come off the local flood defenses immediately in Houston; it will persist longer at Port Arthur, where wind is still onshore.

Sep 13, 2008 - 5:12 am 9. Trent Telenko:

Reports over night are that the Ike storm surge was no where as big as predicted. There were 6-9 foot surges measured on the various storm gages on the coast.

This means that the sand erosion that a heavier surge would have caused did not happen. There will be bad scenes this morning, but nothing like a 1900 class wipe out of the city.

What is being reported on WFAA in Dallas — which is rebroadcasting channel 11 from Houston — is bad enough.

Most of Galveston Island is underwater, in some places 10-15 feet. There are over 200(+) unanswered 911 calls. Power is out.

There are trees down everywhere. More than 90% of Centerpoint Energy’s 2 million Houston area customers are without power. They are saying it will be weeks before all power is restored.

All Houston area refineries went to a full shut down (a three day process) and there are no reports as yet as to damage.

Also unknown is the extent of the silting of the Galveston Bay and Houston ship channel shipping lanes.

Sep 13, 2008 - 5:30 am 10. Trent Telenko:

Early Houston Channel 11 Reports from Houston show Buffalo Bayou is flooding from combined effects of the rain and the storm surge.

Sep 13, 2008 - 5:32 am 11. Trent Telenko:

Houston Mayor White reports 4746 unanswered 911 calls over night. Emergency 1st responders will go out a 9:00am after the weather bands exit Houston.

One of the main pumps for the Houston water system is down and he is asking people to conserve water to keep up the water pressure.

Sep 13, 2008 - 5:45 am 12. Trent Telenko:

Channel 11 Houston just showed the east side of the JP Morgan tower — a 75 story sky scraper — and every window on the east side of the building has been blown out by wind.

Harris County also just briefed that only under ground power lines in Down Town Houston and the Texas Medical center survived the storm. All above ground electrical power lines are heavily damaged and inoperative in the Houston Area.

Harris county said that the Houston 911 center got 1200~ calls over night, about 60% more than a normal night.

Sep 13, 2008 - 6:01 am 13. Trent Telenko:

Harris county officials just briefed that the storm surge peaked at 11-12 feet.

All the Houston south eastern area creeks and Bayous are under a flood watch.

A ship is loose in the Houston ship channel and threatens the I-610 bridge. Harris county officials say no one should try and cross the bridge until tugs have the ship stabilized. ETA for that operation is unknown.

Sep 13, 2008 - 6:05 am 14. Trent Telenko:

An eye witness report broadcast from Galveston by a reporter from Dallas Channel 8 said that 80% of Galveston Island went underwater.

This has not been confirmed by Galveston emergency management.

Sep 13, 2008 - 6:13 am 15. Alan Sullivan:

If Houston sustained this much damage in a cat 2 direct hit, imagine cat 4. It sounds as though local infrastructure needs review and upgrade. Maybe the city without zoning also lacks a building code, or fails to enforce the one it has.

Sep 13, 2008 - 7:16 am 16. SteveSadlov:

This was Houston’s Ivan, a barely dodged bullet. For the dumbed down masses, like their counterparts in NoLA in 2004, they now say to themselves:

“See, I told ya! Dey allllllllllllways turn!”

When Houston’s direct hit by front right quadrant of a cat 4 or cat 5 comes, 10s of thousands will ignore evac orders and will die.

Sep 16, 2008 - 10:08 am

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