For now if ships avoid heavy weather as much as possible it reduces the chances for problems with non-rouge and rouge waves alike.
Regular waves have been studied since at least the 1960âs. They have length, height and period. A rogue wave is completely different. It has no length or period. Only height. Reason is that a rogue wave is the result of many old, regular waves (swells) that move in different directions that together build up height in one rogue wave in one location, maybe assisted by reduced depth and currents. It lasts a few seconds.
What about the triplet variety?
Sea waves are water molecules moving up and down locally due to wind forces. The top water displaces in the direction of the wind. The wind pushes the top molecules horizontally but most water down below remains in place just moving vertically. When the wind stops blowing the waves die down, which takes time. Looking at an ocean the surface is the result of old and new waves displacing in different directions and velocities. Sea currents and water depth also affect the surface waves. And here and there rogue waves develop, e.g. triplets. Another ship of mine was hit from the side by such a rogue wave out of nowhere! The weather was bad and suddenly a surface wave motion rolled the ship to one side - it was the fore side of the rogue wave - and when the ship rolled back, it was hit by solid water of the real rogue wave front ripping off the complete bulwark on the main deck. The whole thing took 10-20 seconds. And after that the sea was as before.
Iâve several yrs. sea time and a lot of it up north. I think talk of a ârogueâ wave is used a bit too much. Mind you, Iâve seen railings and bulkheads smushed up, cabins tore up pretty well and the usual stuff and seas out there thatâd make you stop work wondering whether you should run somewhere ⊠and though they exist someone posted here we now have buoyâs all over the place measuring these 24/7. I just think a lot of this is sensationalism for most of us have not encountered one of these ââepicââ waves that are usually theorized about after some tragedy.
Another time I was on a ship outside South Africa heading for Japan in a storm, when a big, fast wave from behind lifted up the stern, so the ship went/was pushed straight into the back of the wave in front and my ship disappeared into it like a submarine. It is one reason why the sills of weather tight doors above the free board deck is 2â.
Air gap of the Draugen Platform in the Norwegian Sea is 30 m.
In March 1995 it was hit by a frack (rough) wave that caused the platform to sway violently. High wave event was forecast by Aberdeen Weather Centre, but not necessarily the magnitude of this single wave.
Here is a link to a lengthy report about the event (PDF):
### Draugen Oil Field, North Sea - Offshore Technology | Oil and âŠ
www.offshore-technology.com âș projects âș draugenoilfâŠ
A few years ago I was CM on a break bulk freighter in the Indian Ocean southbound off the East Coast of South Africa.
I was on watch, It was a clear dark night, swell from ahead, ship was pitching into it easy.
Suddenly the ship just dropped into a big trough, when we reached the bottom the bow slammed into the face of the next wave with a big KA-BOOM.
Within a couple seconds the phone rang. It was the Captain, who was the unpleasant type. Evidently the slam had woken him up. He demanded to know how long weâd been in heavy weather without notifying him.
I told him the weather was good and weâd just hit a big one. Captain hung up on me without a word, ship continued along as before with no drama.
That area is know for producing big waves:
From here: https://magicseaweed.com/news/how-the-colossal-freak-waves-off-the-coast-of-south-africa-work/10997/
1 Like
I understand that youâre in doubt about the existence of rogue waves. I beg to differ. The evidence available these days is too overwhelming to ignore, the wave of 25.6 meters as measured on the Draupner oil rig is pretty clear proof of that.
Also in 2001, two cruise ships â the Bremen and the Caledonian Star â had their bridge windows smashed by waves estimated to be 30 metres (98 feet) tall in the South Atlantic. And in 2000, the British oceanographic research vessel, the RRS Discovery, sailing in the Rockall Trough west of Scotland encountered the waves up to 95 feet. Also the Smit-Lloyd 102, already mentioned above, met with one and sank.
U.S. Naval Research Laboratory ocean-floor pressure sensors detected a freak wave caused by Hurricane Ivan in the Gulf of Mexico, 2004. The wave was around 27.7 meters (91 feet) high from peak to trough and around 200 meters (660 feet) long.
On April 16, 2005, after sailing into rough weather off the coast of Georgia, Norwegian Dawn encountered a series of three 70-foot (21 meter) - a so called triplet - rogue waves. The third wave damaged several windows on the 9th and 10th decks and several decks were flooded. Damage, however, was not extensive and the ship was quickly repaired. Four passengers were slightly injured in this incident.
Youâre right that nobody on this forum, with together a impressive number of sea years, seem to have seen or met with such an extreme wave but that doesnât prove that they donot exist.
Dutchie, weâve discussed lotsa things here and will continue to do so but we gotta get squared away about this wave thing, I have NO DOUBT they are out there, yes, itâs only obvious they can and do happen ⊠iâm just saying their existance is a little over stated ⊠over used, like everyone calling into a talk radio show is a ex navy seal !!
My mistake. Seemed to have missed this oneâŠ
Maybe I should change the title:
Rogues , called 'extreme storm waves â by scientists , are those waves which are greater than twice the size of surrounding waves , are very unpredictable, and often come unexpectedly from directions other than prevailing wind and waves
Using the term âextreme storm wavesâ for large waves that form in storms but can not be explained by traditional means is more precise.
The term "rouge waveâ is also used to mean any wave that is larger than expected and/or comes from an unexpected direction.
Changed the title.
1 Like
Rogue waves luckily are not something most of us experience but they for sure are real. I was on the bridge one day discussing with the captain an upcoming port call the next day. We were in some rough weather, nothing out of the ordinary but rough none the less. The mate said, âWhat the f**k is that??â We all looked out and it was an oh shit moment. A wall stood in front of us. I raced to the ER and got knocked down before I got there. Eventually crawled into the control room and everyone was just hanging on to whatever was handy. We suffered some damage but survived of course but it was madness for about 30 minutes until we determined we had survived. I will never forget looking out that window and seeing something like out of a movie coming at us.
on the other hand iâve seen a few go under us that other than raising your ââawareness levelââ also made you wonder if they were âŠer. ⊠normal at all !!
1 Like
Good reference here:
Rogue Waves
Rogue waves have been part of marine folklore for centuries. They are generally considered to be unexpectedly high waves which in some instances come from a direction different from the predominant waves in the local area. A single rogue wave has certainly been known to spell disaster for the mariner. They have, over the past twenty or thirty years, come to be recognized as a unique phenomena albeit with several possible causes.
-
Constructive interference . Several different wave trains of differing speeds and directions meet at the same time. The heights of the crests are additive so that an extreme wave may result when very high waves are included in the wave trains. The effect is normally short lived since the wave trains continue to separate and move on.
-
Focusing of wave energy . When storm forced waves are developed in a water current counter to the wave direction an interaction can take place which results in a shortening of the wave frequency. The result is the superimposing of the wave trains and the generation of extreme waves. Examples of currents where these are sometimes seen are the Gulf Stream and Agulhas current. Extreme wave developed in this regime tend to be longer lived.
-
Normal part of the wave spectrum . The generation of waves on water results not in a single wave height but in a spectrum of waves distributed from the smallest capillary waves to large waves indeed. Within this spectrum there is a finite possibility of each of the wave heights to occur with the largest waves being the least likely. The wave height most commonly observed and forecast is the significant wave height. This is defined as the average of the one third highest waves. The random nature of waves implies that individual waves can be substantially higher than the significant wave height. In fact, observations and theory show that the highest individual waves in a typical storm with typical duration to be approximately two times the significant wave height. Some reported rogue waves are well within this factor of two envelope. Waves higher than roughly twice the significant wave height fall into the category of extreme or rogue waves.
