Rogue Waves

ROGUE WAVES
Paris - 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 analyze 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
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." - AFP, full story:
http://story.news.yahoo.com/news?tmpl=story&u=/afp/science_sea

 

Ship-devouring waves, once legendary, common sight on satellite By Robert Roy Britt, SPACE.com

Monster waves of mysterious origin prowl the oceans, surprising ship captains as they appear on the horizon like great walls before crashing across the bow, or worse.

Windows of luxury liners get broken. Supertankers are disabled and left vulnerable to the whim of the next wave. Many ships disappear.

"Two large ships sink every week on average, but the cause is never studied to the same detail as an air crash," says Wolfgang Rosenthal of the GKSS Forschungszentrum GmbH research center in Germany. "It simply gets put down to bad weather.

"A significant handful of these sunken ships — about 200 over the past two decades — are supertankers or large container ships, according to a statement explaining Rosenthal's new research.

The cause for most of the mishaps is a mystery, but so-called rogue waves as tall as 10-story buildings are believed to be the major culprit in many cases.

Yet until recent years, scientists doubted such strangely huge waves occurred so frequently.A new study based on satellite data and lab experiments reveals the rogues are fairly common and helps explain how they form.

The Queen Elizabeth II was struck by a 95-foot (29-meter) rogue wave in February 1995. Captain Ronald Warwick said "a great wall of water" appeared. "It looked as if we were going into the White Cliffs of Dover.

On Jan. 1 1995 an oil rig in the North Sea was hit by an 85-foot (26-meter) wave. The waves around it were less than half as tall.

In one week during early 2001, two tourist vessels, the Bremen and the Caledonian Star, were smacked by separate 98-foot (30-meter) waves in the South Atlantic while the ships were 620 miles (1,000 kilometers) apart. Windows on the bridge of each ship were broken and the Bremen was disabled and left adrift for about two hours.

Rosenthal, an expert on rogue waves, and his colleagues obtained satellite data taken during the time of the mishaps with the two cruise ships. The data were collected by the European Space Agency's twin spacecraft ERS-1 and 2, which employ a technique called synthetic aperture radar to measure wave height.

In the three weeks of satellite data, researchers found 10 waves in various parts of the world that were more than 82 feet (25 meters) high. That added a global perspective to information collected from various oil platforms. (A radar device on the North Sea's Goma oilfield counted 466 rogue waves over 12 years.)

The giants often form where normal waves meet strong ocean currents or eddies, the new analysis shows. A current can concentrate wave energy, causing a wave to grow. Also, a series of fast waves can catch a set of slower-moving waves and merge into a single beast.

Rogues also develop from weather fronts and low-pressure systems. Winds blowing in one direction for long periods of time — more than 12 hours — can create unusually large waves. Scientists already know that, and anyone living along the southeast coast of the United States has seen large waves arrive days in advance of an approaching hurricane.

The new research found that some waves travel in sync with the wind, setting up superb growth conditions. Quicker waves move ahead of the storm and slower waves fall behind, in both cases causing them to dissipate somewhat.

More needs to be learned, including whether the deadly waves can be predicted.

"We know some of the reasons for the rogue waves, but we do not know them all," Rosenthal said.

 

Catamarans at Sea

Brian wrote recently in a motorsailer discussion/justification:
"Storm survivability should be considered at the design stage for any vessel making offshore passages. Loss of power (clogged filters, etc, etc) often occurs at the most inopportune time (during a storm), and this can put the solely powered vessel at peril in short order. A vessel with a modest sailing rig could save your life, and the vessel’s. Add a proper sea anchor installation, and I would challenge a hurricane. The catamaran planform rated ‘best in survivability’ in huge breaking wave tests* carried out by Lock Crowther at the prestigious Univ of Southampton"
______________


*During the 90's, Lock Crowther, Australia's guru of multi-hull designs, both sail and power, researched the survivability of his designs in a wave tank at Univ of Southampton (Source: "Lock Crowther Designs Catalogue 1980")

"This work has indicated that the well designed catamaran is remarkably safe in breaking waves up to considerable height, even when beam on, we were unable to capsize a power catamaran yacht in the largest wave which could be generated (ED: in this tank). This corresponded to a 52' wave for a catamaran of 40' beam. Scaling this down to a typical 24' beam cruising cat means she should be O.K. in a 31' breaking beam sea. An equivalent size mono-hull power boat was easily capsized by a 25' breaking sea, and in tests with conventional yachts after the Fastnet disaster, it was found that a 40' mono-hull yacht could be capsized in a 12' breaking sea."

 

additional comments from Scuttlebutt:

* From Andrew Troup:
Robin Knox-Johnson asks why oceanographic scientists have denied freak waves for so long. To paraphrase their attitude, freak waves "may be all very well in practice, but they simply don't work in theory". I suspect the theory has neglected -or given insufficient importance to - many contributing factors, including vertical currents, upwellings, and shear gradients in horizontal currents. Who's to say there aren't even more subtle but still significant influences - perhaps underlying bodies of water at higher density, similar to those within which "internal tides" have recently been demonstrated.

Many recent "discoveries" by oceanographers, to do with influences on wave
behaviour, have been common knowledge among deepwater sailors for decades. Even the simple theory of shoaling bottom influence has given unrealistically shallow values for the depths at which waves of a given rms height will feel the bottom.

Tom Cain asks:
Why buoys and seashores did not blow the cover on "rouge" (sic) waves. I think this represents a common misconception. Rogue waves (and troughs) typically do not persist, and may not reoccur: they're a transitory, fleeting phenomenon, arising when a statistically unlikely event causes unusually high peaks from a number of underlying wavetrains of different wavelengths to coincide at a given place and time. The longer wavetrains, travelling faster, will soon "outrun" their slower cousins and those atypical peaks will no longer coincide. This explains why you have to be a satellite or a sailor to catch them in the act.


* From Mike Leneman, Oceanographer:
Rogue waves do not show up on offshore bouys or come to shore because they are the "momentary" constructive interference of a number of waves. They "appear" out of nowhere and then "disappear" because, in fact, that's what they do. They are temporary; they exist for only a short period of time. They are not a solitary wave which moves across the ocean for any notable distance. Once the waves that made them pass each other, they are gone.

 

* From Jim Gardiner: In 1980 I met an 85 year old ship captain with 25
circumnavigations in his career. From his wallet he pulled a tattered
photograph taken from the bridge of his 685' ship crossing the North
Atlantic in November. The photograph showed a wave towering over the fwd
mast shortly before they took it over the bridge. By knowing the height of
the deck above the sea and counting the ladder rungs on the mast and
comparing the height of the wave above the mast using the ladder rungs as
a scale, the wave was 85'.

 

more comments from Scuttlebutt:

* From Sir Robin Knox-Johnston: What is terrifying about the report on rogue waves is not that they exist, sailors have known that for centuries, but that scientists refused to even accept that the sailors stories might be accurate. How many sailors lives have been lost because officialdom failed to accept the fact of frequent rogue waves and insist on designs and scantlings capable of withstanding them?


* From Stephen A. Van Dyck: As a life long ocean sailor I was interested in your reprinting of the Yahoo "rouge waves" article. As the Chairman of a NYSE tanker company and Intertanko, the world's tanker owner/ operators entity, I would like to correct a factual misstatement in the article that I know will interest those who sail the oceans. It is simply not true that "super tankers" have sunk/ disappeared from rouge waves. We know of no such accident. It is true that very large bulk carriers (coal, ore, etc) have sunk or disappeared, but in conditions often known to be far less severe than produce rouge waves. There are design/ construction/ scantling/maintenance issues with some bulkers, leading to the loss of about 500 seaman in ten years. What is impressive to me is how well most vessels tolerate the enormous loads imposed by extreme storm/rouge wave conditions.
The scientific satellite work on rouge waves is very important and valuable even if the journalistic "supertanker" facts were wrong.


* From Tom Cain: Rogue and Tidal wave stories strike a raw nerve in most
sailors....a real ongoing attention getter. If there are that many rouge waves running around out there, then why don't the deep sea tidal buoys pick up these variations? And if they do, is nothing said about it? How come these waves do not make it to shore? Or ....do they?

 

BE: Hope I'm not boring anyone. Just thought these discussions should exist on the forum under a singular heading on the subject, as I had not found one when I conducted a search.

* From G. Bruce Knecht: How can it be that we can send men to the moon and create things like the Internet and GPS but that scientists, even sailors, still can't fully explain waves?


* From Paul Miller, US Naval Academy: Although some oceanographic texts don't address rogue waves, naval architects have employed the statistically-based "extreme value theory" for wave height and maximum ship load prediction for many years. As the "rogue" waves are so rare, and so large, it becomes unfeasible (economically and competitively) to design vessels to withstand all possible waves. Ships are designed to withstand the statistically very unlikely (but not impossible) wave.


* From Guy Doran: On a smaller scale, rogue waves are commonly evident at some beaches, much to the delight of surfers. The intersection of two approaching swells just outside the surf line produces a momentary focal point of energy, or peak, that breaks ideally for surfing and makes salivating surfers rush to get their boards. A surf break called The Wedge next to the jetty in Newport Beach, California, is a remarkable example of the rogue wave phenomenon. When a large South swell is running, waves bounce off the jetty at an oblique angle, producing the perfect momentary crossing energy for the following wave in a set. This intersection results in the sudden rise and spectacular fall of a quintessential rogue wave. Watching from the beach at The Wedge affords one a unique opportunity to witness the development of rogue waves--as well as the damage they can cause. Broken bones, dislocations and serious spinal injuries are commonly suffered by surfers who take on the crushing force of a wave at The Wedge.
Check out the monster waves: www.romanoskyphoto.com/html/wild_wedge1.html

 

....continued...

* From John Rousmaniere: As Robin Knox-Johnston says, the possibility of colliding with a rogue wave is perpetual. Rogues don't have to be immense 80-footers, just unusually high and nasty in comparison with the surrounding sea state. And there are plenty of them: in his text book Oceanography and Seamanship, William G. Van Dorn estimated that one deep-water wave out of 20 is a rogue. One cause is a collision of nonparallel waves, some running at one angle due to the local wind, others running at another angle from a storm many miles beyond the horizon. Rogues may also be caused by rapidly shifting, gusting, or otherwise irregular winds. The British meteorologist Alan Watts ascribed the violence of the 1979 Fastnet storm in large part to 'corridors of extremely strong winds.'
That such events are more likely than our concept of 'steady breeze' admits was made clear by NOAA meteorologist Joseph M. Sienkiewicz when he said, at a safety-at-sea seminar, 'Wind is not a blanket. It is, rather, like a colander.'

Curmudgeon's Comment: The book that John refers to is in the Scuttlebutt
Sailing Club Library: www.sailingscuttlebutt.com/ssc/books


* From Paul Hansen (re rogue waves): For anyone worried that rogue waves are not being taken seriously take a look at the following article on a possible cause of shallow water extreme waves. http://www.copernicus.org/EGU/npg/10/2003/6/npg-10-503.pdf. Don't try to follow the math as it might hurt your head but rather look at the extensive list of references at the end and realize that the scientific community is trying to understand them. Only when you understand something can you work with it constructively with a view to forecasting high risk conditions. Note that superposition of waves is not completely accepted as the cause. Something keeps them together for much longer than superposition would allow. A soliton doesn't seem to fit either. What would be really scary is to see the superposition of two of these waves, one overtaking the other. Trough and crest cancel initially to reduce the first wave (that's good), and then immediately add on top of each other. (150' wave anyone?). I wish some of the people listed in the references would read this newsletter and chime in with some real insight. Al Osborne of Texas perhaps:
http://www.physicscentral.com/people/people-02-6.pdf

 

Not boring at all Brian,

Lake Superior also has stories of rogue waves. The most persistent one is the “three sisters”, a group of three waves forming abnormally large and thought to be responsible for many of the missing boats on the great lake.

Gary

 

Photos!

Couple of interesting sites for some photos:

http://tv-antenna.com/heavy-seas/
http://www.sailingscuttlebutt.com/photos/04/bigwaves/

It should be noted that its really tough to capture the size of the sea from onboard a vessel as your reference plane is a 'bit' distorted.

'Most' big seas out in the ocean are not breaking waves.....some are. If you are 'bouyant' enough you will rise up over the crest (even big ones) and float with the irregular surface.

I wrote recently in defense of a catamaran motorsailer, "What many people forget about a good ride in a heavy sea is that it is very much a function of weight in addition to hull shape. More weight, more robust, more form resistance it offers to moving thru the ocean, the more the sea acts to resist the vessel's progress, and thus the more uncomfortable ride, and we must slow down. A big headsea is a particular challenge. Heavy boats carry their momentum into each trough and crest in a battle with the sea, while lighter weight vessels with slender hulls slice through with less battering. Per a sign at the Naval academy, 'you can out-think the ocean, but you can’t out-slug the ocean.'”

I was in a 3 day 65knt blow on a trip to St Thomas from the Chesapeake Bay on a 47' wood ketch. It was part of an ususually intense low pressure system that came off the east coast of the US in Dec and its center went north of Bermuda. We surfed these ever-increasing size seas, and tried to take some pictures. Three vessels were reported sunk in that storm. Looking at the photos later just did no justice to our personal recollections. But each time we thought the wave was going break over our stern, we rose slightly and surfed out from under it. It was only when I took down the jib and we slowed down (to challenge the sea) that we did get those waves breaking over our stern. Finally the three of us were so tried of steering while surfing we turned back into the sea, backed the reefed jib and deployed a little mizzen. We were probably sailing backwards over the bottom, but our vessel rose to each of the big waves and rode down their backside. We were limiting our challenge to the sea, 'going with the flow you might say', even if backwards. We got some much needed rest for some number of hours until we could once again start surfing toward our destination.
In thinking back about the situation, I had made the descision to leave the Chesapeake Bay knowing of an approaching cold front, but not knowing of its intensity. Thank goodness I had figured that we would be out pass the Gulf Stream prior to its arrival of the storm. I've come to find out that it's those meandering circular eddies at the irregular edges of the Gulf Stream that can produce some very 'freak' waves in storm conditions. Phil Weld spent 5 days under his inverted racing tri Gulf Streamer off of Burmuda as a result of one of these freaks. He named his next tri 'Rouge Wave'.

 

Mega Waves

Here is a real interesting site that was brought to my attention on another forum:http://www.seafriends.org.nz/oceano/waves.htm#megatsunami

And this site has a reference to that potential giant tidal wave that could strike the east coast of the USA when a big volcanic event eventually occurs in La Palma (off Morocco).

 

Regrettably you didn't seem to read the Crowther comments properly. He was discussing POWER cats verse monos. And I'm not sure that his test had anything to do with the Fastnet investigations other than these test were conducted at the same facility.

 

Sorry Brian
I got excited, have deleted my post. Thanks for the info on the waves now we need to know which areas they occur most, I would guess thay were in the shallower seas .

 

Brian

Why the interest, so much, now? This can't be new to anybody who has been doing serious deepwater design for the past 20 years. Wiegel's Oceanographical Engineering was published in '64 and Bhattacharyya Dynamics of Marine Vehicles in '78 just to mention two common texts that cover this well.

I will admit that when I became involved in predicting the chance and effect of "Statistically Significant Events" on ships about 17 years ago the "Ivory Towers" were more interested in oceanic mega-processes than micro-processes, but this is nothing new. Now that they think they've got their arms around global warming (and beaten it to death ) they’re looking at other things that make good copy and get funding.

One thing to point out though, it is not wave height that causes concern for vessels, it is wave steepness. It is my opinion, based upon statistical formulation, that most small vessels are in greater danger in SS5 than in SS7 or 8.

 

Hey Guys,
Relax
The chances of striking a rogue crew member, incompetent navigator, or useless skipper is infinitely more likely.
JT