# Rogue and Extreme Storm Waves

Interesting video explaining rogue waves in some detail. Also the less known rogue holes are mentioned, the opposite of the rogue waves.

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Have experienced rogue waves. Tore my shit up and busted out a window or two. I donāt miss that part of it.

Normal waves are linear waves, rogue waves are nonlinear second-order waves, including triplets. Fundamental rogue waves can emerge from the second-order nonlinear SchrĆ¶dinger (NLS) equation

Not a very impressive formula but the emerging rogue waves from that equation are no joke at all.

Computer generated examples of a single rogue wave and two triplets.

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āā¦considered to be unsinkableā¦ā

Iāve heard that beforeā¦

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So what would the wave height distribution graph look like if the so-called rogue waves were included? Would it be a Rayleigh distribution but with a fat tail?

This version is from actual observations.

The NWS says thisā

Several recent marine incidents have highlighted the importance of knowing the height of the largest wave that can be expected for a given wave forecast. Since the Rayleigh distribution actually goes to infinity to the right of its peak, a wave is theoretically not bounded by a limiting height. This is where the Rayleigh assumption breaks down.

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In the Rayleigh distribution rogue waves are defined as individual waves whose height is larger then 2Hs or 2.5Hs. The probability that a wave exceeds 2.5Hs can be calculated as 0.00000374 what means that only one wave can be expected out of 267326 that exceeds 2.5Hs.

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My understanding the Rayleigh distribution isnāt useful for large waves more then about 2*swh because the curve is just statistical but the larger waves are in fact more rare because the larger ones would tend to break before reaching an extreme heightā

Even the rogues are short lived.

In other words in the Rayleigh distribution the tail is too fat.

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I never met or have seen rogue waves nor that we had heard of such in those days. What I have seen several times in the North Atlantic in stormy weather were triplet waves of about 15 meters height while the other waves were 10 - 12 meters so they were far from real rogue waves of 2.5Hs. They were unstable and as rogue waves they suddenly disappeared. We called them the three sisters. Still in the learning phase?

I donāt believe Iāve ever encounter one either. If the ship was in 6 meter seas and a 10 meter wave came along, (aka āa big oneā) itād be notable for sure.

We supposed that the triplets were the result of the summing of two swells with different azimuths, heights and periods. A linear adding exercise, we had no idea about second order systems at the time and that one wave would literally feed another.

Something like this but then more complicated.

Have heard the term three sisters.

Surfers refer to those as sets.

Surfers usually say that a āsetā is a series of ocean waves that travel in groups of seven, with the seventh wave being the biggest and most powerful.

Not sure whatās going on there. The three guys not going for the wave in the foreground should be heading further out as the next one will be bigger and better than the other and they are not in place to get it.

Yes, a big part of surfing is sitting an waiting and getting the feel of the set. It isnāt always the seventh one but thereismusually a pattern.

I have only experienced a rouge wave once in a storm. It hit the ship from behind at the stern and buckled the aft bulkhead of the deck house, smashed some windows there and flooded the galley. A complete surprise.

Maybe I am missing something obvious but I donāt understand why the first rouge wave discovered was so big. The Draupner wave was the first rouge wave to be measured accurately at 25.6 meters. But presumably there are wave measuring instruments, weather buoys all over the place.

If the definition of a rouge wave is one that is more than twice Hs isnāt it far more likely that the first rouge wave to be measured would be much smaller? Because smaller waves are much more common?

Or is there some reason rouge waves donāt form in lower seas?

Had a wave poop us. I didnāt actually see it but I sure felt it. The containers stayed in place but it punched the floors up in 4 boxes. The next morning the Pacific Island crew were very appreciative. One of the boxes had been full of tinned corn beef.

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This seems like a good article, fairly recent, Feb 2020.

For centuries sailors have told stories of enormous waves tens of metres tall. They were dismissed as tall tales. With little or no hard evidence, and the size of the waves often growing with each telling, there is little surprise that scientists long dismissed them as tall tales.

Until around half a century ago, this scepticism chimed with the scientific evidence. According to scientistsā best understanding of how waves are generated, a 30m wave might be expected once every 30,000 years! Rogue waves could safely be classified alongside mermaids and sea monsters.

In this respect I remember that when we informed the Royal Dutch Weather Society for the first time about the sighting of triplets they ridiculed us by stating that these kinds of waves were impossible to exist and that it must have been an optical illusion. They probably meant to say that it was a hallucination. They dismissed it as boozerās talkā¦

However, we now know, especially since the recorded Draupner rogue wave, that they are no maritime myths but hard facts. Since that occurrence some serious research has been going on. The help of
satellites to trace rogue waves in the immense stretches of ocean is of utter importance.

In wave mode the satellite acquires 10 by 5 km āimagettesā of the sea surface every 200 km. These small imagettes are then mathematically transformed into averaged-out breakdowns of wave energy and direction, called ocean-wave spectra. ESA makes these spectra publicly available; they are useful for weather centres to improve the accuracy of their sea forecast models.

With the resolution of ten metres it is believed that they contain a wealth of useful information. Ocean wave spectra provide mean sea state data but imagettes depict the individual wave heights including the extremes they are interested in.

ESA can provide three weeksā worth of data ā around 30,000 separate imagettes ā selected around the time that the Bremen and Caledonian Star were struck. The images were processed and automatically searched for extreme waves at the German Aerospace Centre (DLR)."

There are also attempts made to forecast rogue waves but to be successful they have to fully understand this phenomenon and driving forces.