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Freak wavesA vessel is lost at sea every week. Two hundred of those lost in the past 20 years have been over200 meters long. Unlike heavily investigated airplane crashes, there is often little information onthe losses. Although human error and poor maintenance are frequently blamed, freak waves mayhave sunk many.

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What are they?Freak, or ‘rogue’, waves are exceptionallytall and abnormally shaped waves. Theyare steep mountains of water up to 30meters high – the height of a 12-storeybuilding. Although many freak wavesoccur in bad weather or near the coast,they can also appear in mid-ocean withoutwarning in good weather. Freak waves arenot tsunamis, which are caused by violentunderwater disturbances and causemainly coastal damage, as we have sotragically seen recently.

ExamplesIn February 1995, the Queen Elizabeth II,encountered a 29-meter high freak waveduring bad weather in the North Atlantic.The Master said it “came out of thedarkness” and looked like the “WhiteCliffs of Dover”.

In February and March 2001, the Bremenand Caledonian Star were each rocked by30-meter freak waves in the SouthAtlantic. The Bremen was left withoutnavigation or propulsion for two hours.The First Officer of the Caledonian Star,which was ‘blinded’ when all of itsinstrumentation was lost, noted that the

wave was “just like a mountain, a wall ofwater coming against us”.

On New Year’s Day 1995, the Draupner oilrig was in the middle of a storm in theNorth Sea. Its radar sensors were regularlyrecording waves with heights of 12meters, when it was suddenly hit by a freak wave 26 meters high.

Do they really exist?Since ships first sailed the oceans, marinershave spoken of “holes in the sea” andmonstrous waves. Such tales have largelybeen dismissed as folklore. The Draupnerwave attracted serious attention, however,as it had been measured by the oil rig’ssensors. A wave of 26 meters in abackground sea state of 12 meters wassimply not supposed to happen.

Until recently, scientists thought that allwaves conformed to the Linear Model,which sets out a bell-shaped graph ofthe probabilities of certain wave heights.According to this theory, a 30-meterwave should occur in a 12-meter seastate once in every 10,000 years. TheDraupner wave therefore called intoquestion the validity of the Linear Model.

The European Union started a freak waveproject called MaxWave in 2000. It issignificant because it analyses satellitedata covering the world’s oceans,including ‘raw imagettes’ with aresolution of ten meters. MaxWaveanalysed satellite data for a three-weekperiod in 2001 and identified more thanten individual freak waves around the

LOSS PREVENTION By Chris Hall, Lawyer, Skuld Hong Kong

Proof is in the data – evidence of an extreme wave in

August 1996

A vessel is lost at sea every week. Two hundred of those lost in the past 20 years have been over200 meters long. Unlike heavily investigated airplane crashes, there is often little information onthe losses. Although human error and poor maintenance are frequently blamed, freak waves mayhave sunk many.

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world that were greater than 25 metersin height. This was a shocking revelation.It showed that freak waves are real andmuch more common than expected.

What causes freak waves? Nobody knows yet. There may be multiplecauses. It is generally accepted thatsome exceptional currents create freakwaves. When waves head directly againsta strong current, the current can drivethe waves up unusually high and steep.The most famous of these is the AgulhasCurrent off the East Coast of South Africa,which produces waves 20 meters high.Since 1990, these waves have destroyedtwenty ships. Fortunately, freak waves ofthe Agulhas Current are often predictableand local authorities even provide wavewarnings. As a result, mariners can takeappropriate action.

There are other areas in the world thathave a particular tendency to be exposedto freak waves, including the seas offNorway, the Gulf Stream, the Kuroshiocurrent, the Nantucket Shoals and Cape Horn.

Unfortunately, satellite research showsthat freak waves also occur in high seasin areas that are not affected by knowncurrents or geographical formations.Such ‘random’ freak waves are moreproblematic because they are unpredictable.

Wave mathematicians are looking to thenon-linear realm of quantum mechanicsfor a new theory to understand such

unpredictable freak waves. It may be thatsome waves ‘steal’ energy from neigh-boring waves to grow into large, unstablewaves, characterized by ‘holes in the sea’and steep ‘breaking’ waves. Instead ofbreaking on sand, however, rogue wavesat sea can break on a vessel that has justfallen into the wave’s ‘hole’, or trough.

How strong are they?The force of a breaking freak wave istremendous. A 12-meter wave in theLinear Model has the force of about 6 MT/m2. A rogue wave, however, has aforce of about 100 MT/m2. Modern dayvessels are designed to withstand only 15 MT/m2. It is therefore understandablewhy some ships do not survive freakwaves.

Further research MaxWave has embarked on an ambitiousprogram to learn more about freakwaves, including assessing the risk of avessel encountering a freak wave, how torecognize freak waves and how todetermine their regional probability ofoccurrence. Although many freak waves

appear to occur randomly, there may bea deeper mechanism at work that couldgive a method of predicting their occurrenceor indicate which regions are most atrisk. MaxWave also hopes to apply newknowledge to improve ship design.

What can mariners do now?Current research may be of little comfortto crewmembers in danger of encounteringfreak waves now. Fortunately, there aresome things that mariners can doimmediately.

First, they should be aware of those areasthat are already known to have a higherrisk of freak waves.

Second, mariners should be aware thatthe following sea conditions may createfreak waves (by themselves or together):(1) low pressure systems, (2) windblowing in one direction for more than 12 hours, (3) waves traveling at the samespeed as a moving weather system, (4) waves going against a strong current,(5) fast waves catching a set of slowermoving waves and merging into a singlerogue wave.

Freak waves caused by the above are atleast somewhat ‘predictable’. The mostdangerous freak waves are those thatcannot be predicted and do not emergeout of a known set of factors likely tocreate large waves. Here, an alert watchby the crew could save the vessel. Inmany of the cases in which a vessel hassurvived a rogue wave encounter, the

IT IS GENERALLY ACCEPTED THATSOME EXCEPTIONAL CURRENTSCREATE FREAK WAVES. WHEN WAVESHEAD DIRECTLY AGAINST A STRONGCURRENT, THE CURRENT CAN DRIVETHE WAVES UP UNUSUALLY HIGH ANDSTEEP

Danger offshore – as opposed to a normal 12-meter wave with a force of 6MT/m2, a breaking freak wave reaches a force of around 100MT/m2

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wave was spotted just in time for thevessel to take at least some action tolimit the wave’s destructive effect.

Further, vessels should be well-equippedwith safety equipment, such as life rafts,life vests and cold weather gear, ifappropriate. Crews should be well

trained to handle a vessel in distress. Finally, owners and crewmembersshould monitor the on-going research on rogue waves. MaxWave hopes toeventually publish a ‘wave atlas’ of roguewave events and analyses, which couldbe invaluable to mariners.

See the MaxWave website athttp://www3g.gkss.de/projects/maxwave.

Acknowledgements: Marva Jo Wyatt ofWyatt Law Office in Long Beach, California,the MaxWave and BBC News websites.

The most dangerous freak waves do not follow any known model

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