What, really, is a rogue wave?

[rmhutch59]

There was a show on discovery channel Rogue Waves or Killer Waves, despite the salacious title, it was a very informative scientific explanation of the various causes of rogue waves.

Scientist using a sinusoidal model predictive model long predicted a very low frequency based on normal distribution. Turns out it ain't so. The newer math model predicts they are far more common.

[howlingengines]

Experienced a rogue wave in the centre of the Gulf of Morlaix(Northern France) maybe 10 years ago. As others have mentioned , this one , and only one , around 5 ft , hit us broadside at right angles to the prevailing swell. We went over around 60 degrees with lots of crashing pots , pans , etc.
We were OK but one of my crew ,(ex-Nav officer , Shell Oil) said he had heard other stories of 'mixed up water' in this area.

[dpreacher]

Rogue waves have been recorded at THREE times the height of the wave trains. Just FYI

[tthouses]

Having been hit by one during the NARC Rally in November of 2005 South of Bermuda. None were breaking thank God. We were in 20' seas for days..Then a "rogue" wave came about 45 degrees off prevailing sea state and hit the boat...How big? Bigger than the prevailing sea state..It was dark. But it hit the boat so hard it sounded like a bomb going off inside the boat, where I was. My friend was driving at the time along with the skipper who was stand by on deck. He was in a state of shock, as we all were, and said, " a wall of water came over the port side"...Other than rolling the boat about 15 degrees and some water through the companion way and scaring the shat out of us, the boat was fine. WE, OTOH, had to change out pants because we all shat ourselves. Not fun. Oh, we were sailing a ketch 45' Tayana.

[sailorladd]

A rogue wave usually is one (my understanding) that comes from an unexpected direction, not too serious in normal sailing conditions but can be very dangerous in heavy weather...

On the first night out of the start of my round the world cruise, myself and two youngster crew members had left the Royal Cape Yacht club South Africa, in a thirty knot Sou' easter which can blow for weeks at a time.

During the night, the two crew were below decks suffering badly from mal de mare, and I was above, keep tabs on our performance and progress. The Hydravane was doing a reasonable job considering we were almost running in a south south westerly course and I was dressed in sailing pants and a big warm jacket, sipping port from a little bottle I kept in one of the pockets (yes, bad boy) and chewing on a stick of beef jerky.

Something made me put on my safety harness, even though I felt very safe in the cockpit of my home built thirty footer. My safety harness, as a matter of interest,was merely a length of mainsheet rope with a carbine hook on the one side and a slip knot on the other!

Well all was going as planned, but the weather was getting pretty frisky and the running waves were becoming a little irksome when all of a sudden, I heard what sounded like a freight train rushing at us on the port side, almost ninety degrees from the prevailing direction of the waves! This mountainous wave knocked 'Deja vu' on her starboard side, ice cold Atlantic water poured into the cockpit and I was bodily washed out over the side through the gap between my aft taffrail stanchions! I was being dragged through the water, tethered to my rather short safety line!

Well, I was young and fit and was able to drag myself back on board, badly shaken, and thanking my lucky stars for wearing my harness!! The crew, who were roused out of their seasick lethargy, stood white eyed at the companionway entrance, all of us a lot wiser and aware of the frightening power of what I can only describe as a rogue wave.....

[betwys1]

Originally Posted by river251

Is this a fair assumption? A rogue wave is not defined by a certain height, but by how different it is from other waves the boat is sailing through. I imagine a boat all adjusted for sailing through certain conditions, and suddenly a wave bigger enough to upset that boat comes along.

But in other conditions if all the waves were that big, it would not be a rogue, and the skipper would have the boat set for those conditions and the same wave would not upset the boat.

If your definition of a soliton wave height is equal to your hull length, then I don't expect you will see many eye witness accounts here.

BrianW

[Tillikum]

Compliments of Miles Smeeton.

[john manning]

I have sailed in sea conditions which were approximately 6m swell/wave with the tops rolling off as white foam/water. In amongst those there were regular double height seas. I did not think of those as rogue waves because they were in the same direction as the rest. So while they were an alarming experience to sail over they were not unsafe.

My idea of a rogue wave is one that is as large or larger than the background seas and is moving, ( ie a wave not swell, ) and is moving in a different direction to the rest.

I have have never experienced one (thankfully) but I have seen photos from a ship (Hakula) which had one of these break over its deck.

[sailorboy1]

Rogue waves ate the ones that make go f*ck at 0000 when alone in the cockpit

[Cadence]

To many movies made with a rough wave coming from the bow as were the normal seas. Pure fiction that people buy into.
Everyone knows the third of fifth wave is going to be a little larger not a rough.
To much editorial latitude in movies.

[Timoz]

Originally Posted by newhaul

Put it simple here a 20 ft swell on a 15 second period is gentle but put the same swell on a wind driven 5 second period . The sides are steep enough to roll a vessel or pitch pole them as well .

There is an example in an old Sydney Hobart race where almost half the field was severely damaged due to steep non breaking was . ( Don't recall exactly what year)

It was 1998, but the waves were definitely breaking.
There were reports of 20 metre waves (65ft), there is no way a 65ft wave is not going to break. The amount of white water rushing down towards these yachts was immense. Not to mention the brave men who were lowered into the sea amongst these monster from helicopters to save sailors.

I agree with the sentiment that non-breaking swell will not roll a boat in the vast majority of cases, if navigated correctly. However I also agree that in combination with strong winds and an incorrect angle of approach uou will get into strife.

Steep wind driven waves are more inclined to break merely because they are, well more steep...

[alitaptap]

Rogue waves may be MUCH larger than the surrounding waves and they can happen in water where there are no obvious opposing currents/wave sets nor shallows.


Chinese New Year, 1996, at the helm of a 47-foot ferro monohull, voyaging Hong Kong to Subic Bay, Philippines, 220NM out of Hong Kong, wind force 6 and increasing; three out of five crew seasick. We turned back for Hong Kong.


3am, full moon, waves on the beam 8-12 foot, 180NM to run to Hong Kong. Monster wave, 50-foot at least (almost as tall as the mast), appears starboard beam, not breaking so I started to steer to 60 degrees up the face. The face broke before summit achieved; wall of foam; yacht at 90+degrees, with port spreader touching the water moving sideways; bookshelf scattered across the cabin; maybe after 200 meters sideways movement the wave subsided; yacht effectively stationary – no steering; I thought “f**k the rudder is gone”. Wind fills sails, boat picks up speed, steering returns.


I have seen these rogues occasionally while flying Hong Kong to Taipei but never thought I would be caught by one.


Funniest thing: my lookout man started to climb over the guardrail while we were at 90+degrees, he somehow thought he could stay dry if the yacht rolled, but he was still tied-on so did not get too far


Thought: if fibreglass and not ferro, would the yacht have been rolled? would I be here to write about it?

[Don C L]

It might have been a case of shallows, no? 180 miles off Hong Kong it is relatively shallow, perhaps around 200 feet? 300? And as I recall there is a current that comes down the coast from the Taiwan Strait. I have only been there once and it was long ago but I recall being impressed by how shallow it was far out to sea.
And I do know that waves don't become "transitional" until the depth is half the wave length, which means 200' should be plenty deep. A wave would have to have a 400' length to be affected there. It's just that it doesn't always seem to work out like that in one's experience.

[Singularity]

Originally Posted by Rennsail

Speaking of Alaska and tall waves, this story has stuck with me for years. Read the eyewitness accounts of the cruisers that lived through riding out this massive wave - actually a tsumani rather than a rogue. They appear at the end.

https://geology.com/records/biggest-tsunami.shtml

An impressive story. 7.8 Richter ~~2.4 exajoules. If the Nagasaki h-bomb was 100 terajoules, that earthquake was equal to roughly ~24,000 Nagasaki-type bombs...enough to make a pretty good ripple in the water. Reminds me of:

"You're meddling with powers you can't possibly comprehend" - Indiana Jones

[Don C L]

Originally Posted by Singularity

An impressive story. 7.8 Richter ~~2.4 exajoules. If the Nagasaki h-bomb was 100 terajoules, that earthquake was equal to roughly ~24,000 Nagasaki-type bombs...enough to make a pretty good ripple in the water. Reminds me of:

"You're meddling with powers you can't possibly comprehend" - Indiana Jones

Yeah but here we are talking about a wave caused by the fall of a mountainside and the rapid surface displacement of the water in the bay, not the quake. The strength of the quake itself seems only important insofar as it was enough to release the mountainside.