NavList:

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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