Enormous rogue waves explained

Concerto

Concerto

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Rogue waves have been regarded as a maritime myth but a new study of 27500 wave records over 18 years in the North Sea, has measured the wave’s height, frequency, and direction in each 30 minute wave record. A rogue wave is caused by a combination of two simple effects. Firstly linear focusing occurs when waves traveling at different speeds and directions happen to align at the same time and place. The second is bound nonlinearities occurs when the natural effects of a wave stretch the shape of a wave making the crest steeper and taller, while flattening the trough. When these two combine then a much larger rogue wave is the result. So now you know.

Enormous rogue waves don't come out of nowhere
 
LittleSister said:
I thought this phenomenon had been proven and explained in pretty much the way you describe a few decades ago, and was now accepted fact. :unsure:

I'm still hoping not to meet an 80 foot wave when I'm out on the North Sea!
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Indeed. They have been known for sure ever since the Draupner wave was recorded in the North Sea. Of course there were anecdotal accounts before then, but that was the first that was measured unassailably.

The cause is, as @Concerto says, interference effects between wave trains.
 
AntarcticPilot said:
... interference effects between wave trains.
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We had a small tank and various shapes used at school to demonstrate interference, refraction, reflection of waves in water.

While many talk about rogue waves, there is also the same effect that causes holes in the ocean. There is an incident with a large vessel that lost its bow in such a hole but survived and diverted to South Africa. I can't remember the vessel's name or the time, but it was a few decades ago, last century. I remember reading the story and description of a hole opening up in front of the vessel and when it filled in, the bow was gone.
 
RunAgroundHard said:
We had a small tank and various shapes used at school to demonstrate interference, refraction, reflection of waves in water.

While many talk about rogue waves, there is also the same effect that causes holes in the ocean. There is an incident with a large vessel that lost its bow in such a hole but survived and diverted to South Africa. I can't remember the vessel's name or the time, but it was a few decades ago, last century. I remember reading the story and description of a hole opening up in front of the vessel and when it filled in, the bow was gone.
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That might have been the Bencruachon. She didn't lose her bow but rather had it smashed down by a big wave off Durban. She looked a bit like Concord and put into Durban for emergency repairs then limped back to Europe for a more permanent job. Pics and full story on the web or the Ben Line Facebook group.
 
Concerto said:
Rogue waves have been regarded as a maritime myth but a new study of 27500 wave records over 18 years in the North Sea, has measured the wave’s height, frequency, and direction in each 30 minute wave record. A rogue wave is caused by a combination of two simple effects. Firstly linear focusing occurs when waves traveling at different speeds and directions happen to align at the same time and place. The second is bound nonlinearities occurs when the natural effects of a wave stretch the shape of a wave making the crest steeper and taller, while flattening the trough. When these two combine then a much larger rogue wave is the result. So now you know.

Enormous rogue waves don't come out of nowhere
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You might be interested in reading up about Fourier Analysis as the evenings draw in.
 
100 foot waves occur in The North sea and experienced by many oil rigs operating there I believe that some may be connected with the shallower water at the Dogger Bank.

I went out on a supply ship tasked with changing two rig anchor chains in a December some years ago We experienced heavy weather and I was told there were many times that we became invisible from the rig as we dipped down in the swells .

Not all waves are weather related and as mentioned on other platforms I experienced such many moons ago.

A ship I was on encountered a single trough travelling in the opposite direction to us . The depth was far in excess of 100ft. Our ship was 450 ft long and the ship pitched down into the trough with the bow digging into the back. A course alteration had been made so we were on a slightly oblique angle to the trough.

The ship rode through it shipping an imense amount of water , By the time the skipper appeared on the bridge we were carrying on as if nothing had happened, however the sound of water running back into the ocean went on a while.

We were lucky it happened at lunchtime as the deck crew had all been out scaling the decks that morning.

I have never met anyone else who has experienced such an event but have had some interesting conversations with people involved in ocean research,The general consensus was that this was triggered by a subterranean event of some sort.

Possibly the Derbyshire encountered something simila

The Ben line ship experience happened in an area off south east Africa. Here under certain conditions and due to conflicting ocean currents and weather there is an area of sea at the edge of the continental shelf off Durban/ East London where serious conditions occur . The Ben Line ship was heading for the UK from the far East in the dark.

More recently a liner Oceanus departed East London and never made it to deep water. There are photographs on the Web with the stern totally visible and both propes seem to be entangled with mooring .

This ship encountered heavy weather and the passengers were saved by the ships entertainers helped by helicopters . The officers I believe didn't wait . Interesting reading!
 
Biggles Wader said:
That might have been the Bencruachon. She didn't lose her bow but rather had it smashed down by a big wave off Durban. She looked a bit like Concord and put into Durban for emergency repairs then limped back to Europe for a more permanent job. Pics and full story on the web or the Ben Line Facebook group.
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It ben known off the east coast of Africa for years as it is the interference between the wing blown north wind and the southern flowing current

I sail that aera and we always have to take the current and wing into account when sailing along the coast

Fourier Analysis takes me back to my Uni days as I hated Fourier Analysis
 
rogerthebodger said:
It ben known off the east coast of Africa for years as it is the interference between the wing blown north wind and the southern flowing current

I sail that aera and we always have to take the current and wing into account when sailing along the coast

Fourier Analysis takes me back to my Uni days as I hated Fourier Analysis
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And I'm the other way - in the field of image analysis, I can't understand why people do things badly in the space domain when they're easy and accurate in the frequency domain! And switching between the two has been dead easy since the Cooley-Tukey algorithm was devised.
 
Biggles Wader said:
That might have been the Bencruachon. She didn't lose her bow but rather had it smashed down by a big wave off Durban. She looked a bit like Concord and put into Durban for emergency repairs then limped back to Europe for a more permanent job. Pics and full story on the web or the Ben Line Facebook group.
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Quite common in the late 60's/early 70s off Port Shepstone/ Poet St Johns. May have been what did for the Waratah in 1909(?) and an RN cruiser experienced an 'event' there in WW2. Also the mail steamer 'Edinburgh Castle' shipped water back to the accomodation front in the early 60s.
My event was in 1971, loaded 100,000 dwt OBO so maybe 120,000 tons of oil and steel. On watch on the afternoon 12 to 4 , slow steaming down the coast at about 7 knots. Not a remarkably big sea running. All of a sudden I beheld a missing wave, just a quite remarkable hole in the sea. Down down down went the bow and then the frd half of the ship disappeared, speed dropped on the instant to somewhere between 0 and 2 knots.
Then up she came again and we continued as if nothing had happened.
Having been built for Norwegian owners she had an enclosed crows' nest on the foremast with a window and clear view screen , when loaded that was about 70 feet above the waterline. Discovered that this frd facing window was smashed and the foremast was set back maybe 5 degrees with the deck plating just in front of it cracked over about a metre.
 
Bilgediver said:
More recently a liner Oceanus departed East London and never made it to deep water. There are photographs on the Web with the stern totally visible and both propes seem to be entangled with mooring .

This ship encountered heavy weather and the passengers were saved by the ships entertainers helped by helicopters . The officers I believe didn't wait . Interesting reading!
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Never heard of it. But interesting indeed: MTS Oceanos - Wikipedia
 
I recall from a book about 'The Shetland Bus' of WW2 a tale recounted of an RN battlecruiser making full speed up past Wick and westabout round the corner into a full Atlantic gale and a weather-going tide. At some point in the vicinity of The Merrie Men of May she shoved her bows very deep into a hole in the sea and, when she rose again, her fore main gun turret was missing.
 
I always think it's rather unhelpful to label them 'rogue' waves.

Very large or enormous waves are a routine, though infrequent, natural phenomenon. We don't call a family with triplet children a 'rogue family', or a big win on the National Lottery a 'rogue result'.

The problem with the 'rogue' label is that it confuses two different ideas - that the wave isn't a pleasant thing to meet (true) and that the wave is contrary to nature because it doesn't follow the normal rules of physics (false). The enormous wave isn't the Loch Ness monster or a yeti.
 
These waves are obviously scary things....my question is....can a small boat survive?.....is there anything that the crew and skipper can do to increase the odds of survival?
 
Bouba said:
These waves are obviously scary things....my question is....can a small boat survive?.....is there anything that the crew and skipper can do to increase the odds of survival?
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The hull and basic structure of a yacht would PROBABLY be OK - the mast and rigging not. A yacht is far stronger in relation to the stresses imposed on it than a ship is. So if there was sufficient warning, I'd be getting into as small a space within the cabin as possible (to avoid being thrown around) and close all hatches as well as possible. I think that would give the best chances of survival, but it wouldn't be a sure thing!
 
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