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Hurricane Ivan’s waves bigger than expected

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WEST PALM BEACH, Fla. — Hurricane Ivan outdid even the "Perfect Storm," stirring up waves as tall as 131 feet last September as it crashed through the northern Gulf of Mexico toward its landfall west of Pensacola, Navy researchers said Thursday.

Their study, scheduled to appear today in the journal Science, indicates that scientists long have underestimated the ocean-churning impact of hurricanes. And it may point to a need to re-examine the safety standards for the gulf's thousands of oil rigs and platforms — seven of which were destroyed in Ivan's fury.

Such tall waves don't pose a direct threat to land, because they break up well before hitting shore, according to the oceanographers from the U.S. Naval Research Laboratory in Mississippi.

But you don't want to get in one's way.

"If you were standing at the top of a 10-story building looking down at a flat sea and one of those storms went by, your feet would get wet," said oceanographer Douglas Mitchell, one of the study's authors. "And it didn't take a perfect storm. It just took an intense hurricane."

Ivan, the third of four hurricanes that slammed Florida last year, was already renowned for killing at least 92 people and tearing a destructive swath through the western Panhandle and the northern Gulf Coast. Its storm surge — a separate effect from the tall waves — scoured the gulf beaches, wiping out a five-story condominium tower and other buildings in a way that some researchers called unprecedented.

Now, the study of Ivan's waves could bolster opponents of offshore oil drilling, who have resisted efforts by the petroleum industry, congressional leaders and President Bush's administration to move the wells closer to Florida.

"That concern would, of course, be underscored by this kind of report," said Dan McLaughlin, spokesman for U.S. Sen. Bill Nelson, D-Florida. "The most hurricane-prone state is Florida. Simple logic class in middle school tells you don't put oil rigs out there."

But industry representatives said existing rigs and platforms have withstood numerous storms during more than 50 years, although they're still studying how the structures stood up to Ivan.

"We feel very comfortable with the design standards," said Tim Sampson, coordinator of drilling and production operations for the American Petroleum Institute. "The track record is pretty impressive."

The federal Minerals Management Service estimates that 150 platforms and 10,000 miles of pipeline were in Ivan's path. The hurricane destroyed seven platforms, heavily damaged 24 others and damaged "numerous" pipelines, partly because of underwater mudslides, the agency reported earlier this year.

No serious pollution occurred, the agency said.

Steve Leverette, technology manager for Houston-based Atlantia Offshore Ltd. said he sees no need to revamp the standards based on the waves Ivan generated. Such huge wave heights were so extreme they would be expected to occur only once every 2,500 years, he said.

But Mitchell and one of his co-authors, William Teague, said such huge waves might not be so rare.

"Our results should suggest that the big waves, like the 90-footers, are not rogue waves but they're actually fairly common during hurricanes," said Teague, also an oceanographer.

Teague took no position on the drilling issue, but said authorities probably should re-examine the standards for designing platforms.

Accurate measurements of hurricanes' waves have been hard to come by, partly because buoys and other gauges are sparsely located and don't usually survive a storm's peak. For instance, one federal weather buoy near Ivan's path stopped transmitting useful data after waves hit 52 feet — which meteorologists had considered a record.

But through a lucky fluke, the naval researchers had placed gauges 200 to 300 feet deep on the gulf floor southeast of Louisiana for a six-month study of waves and tides. The instruments happened to lie directly in Ivan's path as the storm swept northward Sept. 15, a day before the eye sloshed ashore near Gulf Shores, Ala.

Gauges measured waves as high as 91 feet — one of the tallest waves ever recorded anywhere, and certainly the biggest measured during a hurricane, the scientists said. In Ivan's strongest zone, where they lacked direct measurements, they estimated that some waves exceeded 131 feet.

In contrast, the catastrophic "Perfect Storm" of 1991 — the subject of the bestselling book and Hollywood movie of the same name — produced waves estimated around 100 feet. In 1933, the crew of a U.S. Navy ship in the Pacific encountered a wave they estimated at 112 feet.

The catastrophic Southeast Asian tsunami that killed more than 174,000 people in December was lower, producing waves as high as 50 feet as it hit shore. But tsunamis are so powerful that they push the water much further inland.