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    Re: Rogue Waves
    From: Robert Eno
    Date: 2006 Sep 17, 11:42 -0500

    Thanks for that fascinating essay Peter. I have long been interested in this
    phenomenon.

    Couple of stories (not personal) to relate:

    Some years ago -- and perhaps someone out there can help me with this -- a
    US submarine officer related a story about his encounter with a rogue wave
    which materialized out of nowhere on a calm placid day on the Pacific Ocean.
    The details are hazy so don't take my figures as gospel. The gist of the
    story goes like this: The submarine was cruising on the surface on a calm
    sunny day in the Pacific. The commander decided to conduct a dive so the
    hatches were closed and down they went. The commander instructed the
    planesman to take her down 30 feet (I think). Suddenly, the depth recorder
    went from 30 feet to 180 feet (again, the numbers may be off here). Alarmed,
    the commander said something to the planesman like "I said 30 feet, not
    180!". The planesman assured the commander that he had, in fact, made the
    correct adjustments for the desired depth. Shortly thereafter, the depth
    returned to 30 feet and the commander popped up the periscope to have a look
    around. Receding in the distance was a huge green wall of water. The letter
    writer wrote that had they still been on the surface, the sub would likely
    have been lost.

    Again, I wish I could lay my hands on the copy of the issue of Ocean
    Navigator where that letter was published but alas, I gave away all of my
    copies to a worthy cause. I am confident someone on this list will be able
    to dig it up. I wouldn't mind seeing again myself.

    A more dramatic example can be found from the story of Shackelton's amazing
    voyage from Elephant Island to South Georgia Island in the 25 foot open
    whaleboat "James Caird" (which I consider to be the greatest ever feat of
    seamanship and navigation). The crew saw what they believed to be a rift in
    the clouds and a clearing in the sky but it was the crest of a monster wave
    accompanied by hissing and roaring (Endurance by Alfred Lansing pp. 237 -
    239). Needless to say, they survived to tell the tale.

    Whenever I read about this stuff, my normally strong desire to be at sea
    wanes considerably. Thankfully, this bout of cold feet does not last much
    past the front door of my house. Hell, I'd rather get snuffed out by a rogue
    wave than languish in a hospital bed with tubes running in and out of my
    emaciated body.

    Thanks again Peter. Superb and interesting reading....

    Robert


    ----- Original Message -----
    From: "Peter Fogg" <peter.fogg@gmail.com>
    To: "NavList" <NavList@fer3.com>
    Sent: Saturday, September 16, 2006 6:52 PM
    Subject: [NavList 1295] Rogue Waves


    [Below an article by Frank Robson entitled 'Sea Monsters' from the
    local rag (SMH, 'Good Weekend', 16 Sep 06). Those of you who have
    'Nanny Guard' or some such protective filter may not get this as,
    while it comes from a 'family magazine', it contains 'coarse
    language'. This warning is mainly directed towards our American
    readers who seem particularly prudish about such matters, while overly
    libertine about others (to my taste) such as the graphic depiction of
    violence. While I would not have included the vernacular I'll be
    buggered if I'm going to go through it playing the censor either. Have
    included a pic from the article that shows the height of a 30 metre
    wave against a building (the Sydney Town Hall) and cars. PF]



    IMAGINE YOURSELF ON WATCH IN THE COCKPIT of a yacht in mid-ocean. It's
    a calm night, with a moderate swell and winds under 10 knots. The
    auto-pilot is on, and the large, sea-proven vessel is slipping along
    nicely under sail, leaving you little to do but monitor the course,
    sip coffee and listen to the snores of crewmates in their bunks below.
    At first, when you hear a distant hissing, you think it might be
    static from the yacht's radio. So you go below to make sure it hasn't
    been left on. When you return, the noise - a sustained sssshhhh - is
    louder.

    Then moonlight illuminates the sea through a break in the cloud and
    you see it: a mountain of dark water a kilometre in front of the boat,
    its white-etched top completely eclipsing the horizon. It's coming at
    you against the prevailing swell direction, and moving so quickly its
    height seems to double by the moment.

    For a few seconds, you're immobilised by terror. You know it's a freak
    or rogue wave, but your brain can't cope with the immensity of it.
    Desperately close now, it's an almost vertical wall at least 30 metres
    high, and the hissing from its snowy crest has become a grumbling
    roar.

    Screaming a warning to your companions, you start the motor, flick off
    the auto-pilot and grab the wheel. For an instant, you try to imagine
    a trajectory that might get the boat up and over the beast, but that's
    before the sea at its base opens into an enormous black trough. The
    yacht pitches down into it, and then everything is in free-fall to
    oblivion. At this point, the horrendous wave rears even higher and
    expends itself upon the submerged yacht with pressures of up to 100
    tonnes per square metre - more than six times the pressure ships built
    to international design standards are built to withstand.



    SORRY ABOUT THAT ... YOU'VE JUST BEEN reduced to minute flotsam by the
    worst type of freak wave nature can conjure. Generated only in deep
    oceans by a process sometimes called the nonlinear Schrodinger
    equation (NLS), such a wave starts out average sized, then draws
    energy from the waves around it, reducing them to ripples and building
    itself into the physical manifestation of every mariner's worst
    nightmare. Characterised by the abyss-like trough preceding it, the
    monster's scariest trait is that it really can "come from nowhere" -
    rearing from otherwise calm waters and existing for only a matter of
    minutes before either breaking, or reverting to normal size.

    In the worst-case situation described, even a large ship would have
    little chance of surviving the phenomenal pressures exerted by the
    breaking wave. Yet until recently, scientists tended to dismiss talk
    of such leviathans as mariners' myths, insisting their mathematical
    models showed waves higher than 15 metres to be rare, "once in 10,000
    years" events.

    They were wrong. Advanced satellite imaging over a three-week period
    early in 2001 showed no less than 10 so-called freak waves (all more
    than 25 metres high) churning around the globe. The results of the
    European "MaxWave" project blew away long-held assumptions about the
    nature of ocean waves, and raised the possibility that many cargo
    vessels - which sink at the astonishing average of two a week - are
    victims of individual freak or rogue waves rather than the officially
    stated "bad weather".

    Conducted through the European Space Agency, MaxWave involved a
    conglomerate of research groups but was essentially the brainchild of
    Dr Wolfgang Rosenthal, senior scientist with the GKSS research centre
    in Geesthacht,  Germany. The veteran oceanographer staked his
    reputation (and vast sums of research money) on the untested belief
    that modern imaging radar techniques would confirm the existence of
    massive individual waves throughout the world's oceans.

    "Our group was the first who believed you could use imaging radar this
    way" Rosenthal tells me from - of all places - the deck of a yacht
    sailing from Norway to Denmark.

    "And I can tell you we were really relieved when we found the monster
    waves, because a zero result would have been bad for us."

    At 67, Rosenthal is semi-retired and enjoying a cruising holiday with
    friends, whose laughter rings in the background. Now that he's helped
    to confirm their existence, how does he feel about the possibility of
    encountering such a wave? "Terrified!" he says. "But we're in the
    Oslofjord right now, and monster waves are relatively rare in
    semi-enclosed waterways."

    The nearby North  Sea is a different matter. The world's first
    scientifically confirmed freak wave was measured at 26 metres by a
    laser device when it struck and damaged the Draupner oil rig in the
    North Sea off Norway in 1995. Even then, before the MaxWave project
    began, shipping operators were growing uneasy. International
    design-strength calculations for ships are predicated on a maximum
    wave height of 15 metres from trough to crest, and pressures of about
    15 tonnes per square metre.

    "The [Draupner wave] was really the start of what led to the MaxWave
    project," says Rosenthal. "Now the International Maritime Organisation
    is looking for improvements [in ship design and strength]. Already,
    the hatch covers on freighters have been increased in thickness, and
    something obviously needs to be done about the strength of window
    mountings on ships' bridges."

    In 2001, even as the MaxWave project's twin ERS satellites orbiting
    800 kilometres above the planet were using synthetic aperture radar
    (SAR) to acquire 10 kilometre x 5 kilometre intervals, nature provided
    further evidence that old notions of maximum wave heights were flawed.
    Within a fortnight in February and March, two sturdily built cruise
    ships - the Bremen and the Caledonian Star - barely survived eerily
    similar encounters with 30- to 35-metre freak waves in South Atlantic
    storms.

    Both had their lofty bridge windows smashed by "vertical walls of
    solid green water" that took out the electronics and temporarily
    disabled their motors. Listing perilously, the crippled Bremen - with
    137 passengers on board — lay side-on to the pounding seas for 30
    minutes before an auxiliary diesel could be started to bring her bow
    into the wind. Her captain, Heinz Aye, retired after the near-tragedy
    and has been prohibited from discussing it by the ship's owners.

    The Caledonian Star, renamed Endeavour after her encounter with what
    sailors once called "the fist of God", was returning from an Antarctic
    cruise when first officer Goran Persson saw a wave the size of a
    10-storey building roaring towards them. Just before it struck, the
    ship pitched almost vertically into the deep trough preceding it,
    hurling people against walls and bulkheads. "We were more or less in
    free-fall," Persson later told the BBC. "The whole bridge was like an
    explosion. I was blown away, as if by a water jet. The helmsman and I
    were lying on top of each other underwater. I had to swim and crawl to
    get back to the controls and put the ship back on course."

    Years earlier, in 1995, the huge QE2 was rocked by a similar impact
    with a 30-metre wave off Newfoundland: "... a great wall of water...
    it looked as if we were going into the White Cliffs of Dover,"
    reported Captain Ronald Warwick, now a retired commodore.

    Rosenthal believes these ships were lucky to survive. Controversially,
    the high-profile scientist has claimed that "200 large ships of
    600-feet long or more in the past two decades sank without trace", and
    that many of them were probably victims of rogue waves. (In British
    media reports, this became "200 large ships were lost to freak waves
    in the past two decades" - difficult to sustain when, as Lloyd's
    Register records, only 142 ships of that size were lost in the time
    frame, most with known causes.)

    Given the comparative fragility and isolation of cruising yachts and
    deep-sea trawlers, and their numbers across the world's oceans, it
    seems likely that many more small craft than ships have been "lost at
    sea" to giant waves. To visualise their final moments, ventures
    Rosenthal, we need only view the closing scene in the 2000 film The
    Perfect Storm, in which a trawler is destroyed by the mother of all
    waves during the convergence of three violent storms.

    As improbable as it looked, the giant in the movie was based on the
    same wave tank modelling used by scientists to simulate extreme waves.
    "Smaller boats like yachts and trawlers do not have the mass to
    resist," says Rosenthal. "A small vessel would go up, but as it tried
    to cross the [breaking] crest it would fall right off the wave, and go
    down, you know, head over..."

    Arse over tit? "Yes. Exactly."



    FOR THE RECORD, THE LARGEST WAVE EVER recorded was measured at 42.7
    metres by a rescue helicopter in Bass Strait during the disastrous
    1998 Sydney to Hobart yacht race. (Roughly the height of a 14-storey
    building, the apparition was a storm-driven, cresting swell rather
    than the "wall of water" brute depicted in The Perfect Storm.) But the
    risks of cruising under sail are nowhere near as great as those faced
    by gung-ho ocean racing types, who relish the challenge of pitting
    themselves against the worst nature can throw at them.

    After 160,000 kilometres of inter-ocean cruising over several decades,
    Brisbane yachtsman Paul Slivka has yet to lay eyes on anything like a
    rogue wave. "Mostly, at sea, you're just going up and down these
    little hills formed by [unbroken] swells," says the former US Navy
    navigator. And if he ever did confront these "hills" as a raging
    mountain? What then?

    A grim laugh. "Well, I think the boat might be safer if you had time
    to turn it around and ride with the wave," he says. "But I'm not dead
    sure about that. If you did manage to turn and go with it - and
    presuming it was cresting and not actually breaking - you'd accelerate
    to some frightening speeds. It'd be like dropping off a cliff. The
    question then would be whether you could stop the boat from broaching
    [slewing side-on to the wave]. If you did broach, it'd be one of those
    situations where you might as well just kiss your arse goodbye."



    VETERAN SEAMAN MlKE BARBER WAS JUST 18 when his ship was stopped dead
    by a 25-metre wall of water in the notoriously dangerous Bay of
    Biscay, off the coast of France, in 1966. Now, at 57, the
    near-disaster remains his most vivid memory of life at sea. Barber was
    a cook's assistant on the Patroclus, a 9500-tonne British
    cargo/passenger vessel returning to Liverpool from Asia when the wave
    struck.

    "We'd been thumping into big seas from a southerly gale all night," he
    tells me from his home in northern NSW. By noon the next day the seas
    were worse, and an order was given to batten down everything and stand
    by for "dramatic" conditions. "She was a very strongly built ship,"
    notes Barber, "but every time she buried her bows in a wave the thing
    running through our minds was, Ts she going to come out of this one?'
    I could see the steel plates near the bow actually moving like a
    concertina. Then, within five minutes, the waves went from 20 feet
    [six metres] to at least 35 feet [10.5 metres]. Then the huge one just
    rose up to [25 metres]... It was that frightening, people took one
    look and ran to grab their life jackets."

    The wave was a "white waller" like the one in The Perfect Storm, and
    it stopped the Patroclus in her tracks: "You couldn't see the bow; you
    couldn't even see the mastheads for spray. All we could see before us
    was this wall of water, with the top curling over like those big
    rollers in Hawaii. And we all just went, 'Fucking hell!' The ship went
    down and down into that trough, like she was never going to come up.
    They sounded the alarm from the bridge and shut all the external
    doors. Then the engine just stopped, and we were dead in the water."

    The ship wallowed helplessly for an hour before the motor was
    restarted, then made it to Liverpool with only a slightly buckled bow.
    "On a really solid ship," says Barber, "you get a sense of security
    that makes you forget how dramatic the forces of nature can be. I've
    been through cyclones, and most seamen can tell you stories about
    horrific seas. But a wave that stops a fully laden ship dead in the
    water is more than horrific, it's life threatening. And they're the
    ones you don't forget."



    WHILE MONSTER WAVES INDUCE AWE AND FEAR in mariners (and the rest of
    us), mathematicians tend to see them as just another numerical
    challenge. Even as a young bodysurfer, Sydney's Michael Banner - who
    went on to become a world authority on wave dynamics - felt no
    curiosity over how large waves might become at sea. "I never even
    thought about it," he tells me in his office at the University  of
    NSW. "The beach was just somewhere to escape the tyranny of the
    schoolyard. But if my mother had known how far out I was going at
    Bondi, she would have freaked."

    Now emeritus professor at the university's school of mathematics,
    Banner is at the forefront of research into what makes ocean waves
    break, and how their patterns of breaking might be forecast.
    Forecasting sea states is a competitive field among oceanographers,
    driven by the collapse of the old "rules" about wave dynamics and the
    need to protect shipping and oil rigs from increasingly intense storms
    (widely recognised as a by-product of global warming) and destructive
    waves.

    Banner, elected a fellow of the esteemed American Meteorology Society
    for his contributions in the field, says his team has already cracked
    the formula for predicting when ocean waves will break. "It's a
    horribly complicated phenomena," he adds, "but we've found the
    underlying physics to confirm the threshold for breaking, and we're on
    the verge [using computer modelling] of being able to forecast the
    strength of the breaking."

    Banner fires up a computer model of a typical wave group at sea, and
    points to a series of circles (depicting energy distribution) spread
    along the base of the graph. As the waves travel, energy from those at
    either end of the group is forced towards the middle, eventually
    pushing the centre wave up to more than twice the height of those
    around it. The rate at which this energy transfer occurs, what Banner
    calls the "squeeze factor", determines the severity of the wave it
    produces.

    "Squeeze it gently," he says, his hands at either end of an imaginary
    wave group, "and it'll rise gently in the middle. Squeeze it faster,
    and it'll converge faster. Then do it very fast, and - pow! - not only
    will it break, but the strength of the break will reflect the squeeze
    rate ... that's the underlying mechanism for rogue wave formation." In
    the next stage of his research, Banner wants to be flown over the sea
    in a helicopter during a severe storm so that he can "follow" a real
    wave group and compare its behaviour to his modellings.

    N

    OT ALL FREAK WAVES ARE GENERATED solely by the energy transfer
    process. Sustained blows over vast distances of sea, or wind "fetch",
    can also create the sort of giant swells that roll unimpeded across
    the Southern Ocean. But it's the squeeze factor that causes one in
    1000 of them to grow several times larger than the others and perhaps
    break - not just at the crest, but like a surf beach dumper.

    Freak waves that materialise in otherwise calm seas still have their
    origins in storms, but maintain the energy exchange process over long
    distances before recurring (often influenced by opposing currents, or
    swells converging from different directions) in the sort of tranquil
    conditions where they're least expected.

    Known danger areas for rogue waves include the Agulhas Current off the
    southern tip of Africa (a shipping graveyard), the North Sea, northern
    parts of the Pacific during winter storms, both ends of the English
    Channel, the east coast of North America (including the warm,
    storm-prone waters of the Bermuda Triangle), Cape Horn, Bass Strait
    and the Great Australian Bight, and anywhere oceans converge, such as
    the turbulent waters off the tip of New Zealand's North Island.

    Freak ocean waves are quite different from tsunami or mega-tsunami.
    Tsunami are displacement waves, typically generated by earthquakes,
    which travel much faster than ocean swells yet are almost
    indiscernible - until they near the shoreline. Then, as we know from
    the 2004 Boxing Day tsunami, the destruction and loss of life makes
    huge-breaking ocean waves seem merely boisterous by comparison.

    But what if waves suddenly stopped their bothersome breaking? What if
    the incalculable amounts of energy being pumped into the sea by storms
    weren't released by recurring wave groups, but remained trapped within
    the liquid covering two-thirds of the planet? Appropriately, given
    their preoccupation with things unseen, it's the mathematicians -
    Banner and his meteorologist colleague at the UNSW, Russell Morrison -
    who raise this question.

    The answer, of course, is that oceans without breaking waves would
    mean the end of beach culture as we know it - and a snappy rethink on
    the desirability of coastal real estate. "You'd have this huge,
    accumulating sea state [a destructive maelstrom] piling up against the
    shore," says Banner. It would be the ultimate "sea change", with most
    coastal cities having to hoist their skirts and scurry inland as waves
    dissipated huge amounts of energy on the coast.

    So long live the breaking ocean wave. But next time you're in charge
    of a cruising yacht on a calm night, and you hear that sinister
    hissing sound, swallow something stronger than coffee. Chances are it
    will be your last drink.




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