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#246767 - 27/07/2004 14:12 Rogue waves
Craig Arthur Offline
Wind hazard researcher

Registered: 08/05/2001
Posts: 3549
Loc: 149.152009°E 35.187056°...
Came across the following story via Boating OZ. I haven't read much about the mechanics behind these events, but I have not doubted that they do occur. I am slightly surprised that with the numerous waverider-type buoys going around, thse events haven't been cpatured. Considering that giant waves (not on the 30m scale, but reasonably large at +12 m Hsig) were reported in the '98 Hobart race, there is evidence to suggest they can occur in non-remote areas. I'll try and find some more info about rogue waves, and maybe try to source the paper the report below is talking about (sure to be something being published)

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'Rogue waves' reported by mariners get scientific backing
Wed Jul 21, 1:07 PM ET

PARIS (AFP) - European satellites have given confirmation to terrified mariners who describe seeing freak waves as tall as 10-storey buildings, the European Space Agency (ESA) said.
"Rogue waves" have been the anecdotal cause behind scores of sinkings of vessels as large as container ships and supertankers over the past two decades.
But evidence to support this has been sketchy, and many marine scientists have clung to statistical models that say monstrous deviations from the normal sea state only occur once every thousand years.
Testing this promise, ESA tasked two of its Earth-scanning satellites, ERS-1 and ERS-2, to monitor the oceans with their radar.
The radars send back "imagettes" -- a picture of the sea surface in a rectangle measuring 10 by five kilometers (six by 2.5 miles) that is taken every 200 kms (120 miles).
Around 30,000 separate "imagettes" were taken by the two satellites in a three-week project, MaxWave, that was carried out in 2001.
Even though the research period was brief, the satellites identified more than 10 individual giant waves around the globe that measured more than 25 metres (81.25 feet) in height, ESA said in a press release.
The waves exist "in higher numbers than anyone expected," said Wolfgang Rosenthal, senior scientist with the GKSS Research Centre in Geesthacht, Germany, who pored over the data.
"The next step is to analyse if they can be forecasted," he said.
Ironically, the research coincided with two "rogue wave" incidents in which two tourist cruisers, the Bremen and the Caledonian Star, had their bridge windows smashed by 30-metre (100-feet) monsters in the South Atlantic.
The Bremen was left drifting without navigation or propulsion for two hours after the hit.
In 1995, the British cruise liner Queen Elizabeth II (news - web sites) encountered a 29-metre (94.25-feet) wall of water during a hurricane in the North Atlantic.
Its captain, Ronald Warwick, likened it to "the White Cliffs of Dover."
In the next phase of research, a project called Wave Atlas will use two years of "imagettes" to create a worldwide atlas of rogue wave events and carry out statistical analyses, ESA said.
The goal is to find out how these strange, cataclysmic phenomena may be generated by ocean eddies and currents or by the collision of weather fronts, and which regions of the seas may be most at risk.
Finding out could help ship architects and the designers of oil rigs and their operators to skirt the menace.

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#246768 - 27/07/2004 16:25 Re: Rogue waves
thermalben Offline
Weather Freak

Registered: 17/04/2001
Posts: 769
Loc: Tweed Coast
Interesting topic - the source article is here for reference. There's been a few similar studies done on this topic, and the Agulhas Current regularly comes up with interesting figures; here's one study utilising Hsig data from the Topex/Posiedon satellite.

The ESA's article also mentions the occurence of rogue waves away from significant currents:
Quote:
However the data show rogue waves also occur well away from currents, often occurring in the vicinity of weather fronts and lows. Sustained winds from long-lived storms exceeding 12 hours may enlarge waves moving at an optimum speed in sync with the wind too quickly and they'd move ahead of the storm and dissipate, too slowly and they would fall behind
I think that they're inferring resonant waves/dynamic fetch - when the swell generating areas moves with the waves it's producing. If the group velocity is equal to the fetch speed, then wave heights will be amplified significantly.

I'll add a little more to this when I get some time later tonight, but for now here's a couple of references worth checking out:

Dysthe, K.B., and Harbitz, A., 1987: Big Waves From Polar Lows?. Tellus, 39A, 500-508.

Shemdin, O.H., 1980: Prediction of Dominant Wave Properties Ahead of Hurricanes. Proceedings 17th International Coastal Engineering Conference, Sydney, Australia, ASCE, pp. 600-609.

MacAfee and P.J. Bowyer, 2000b: Trapped-Fetch Waves In A Transitioning Tropical Cyclone (Part II - Analytical And Predictive Model). Proceedings of the 24th Conf. On Hurricanes and Tropical Meteorology, Ft.Lauderdale, FL, Amer. Meteor. Soc., 165-166.

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#246769 - 19/01/2005 10:14 Re: Rogue waves
Mad Maury Offline
Junior Member

Registered: 17/01/2005
Posts: 7
Loc: Sydney, Australia 151.14E 33....
The link to the group coordinating the research (Institute for Coastal Research)in Germany is: http://w3g.gkss.de/projects/maxwave/

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