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Rogue Waves

Freak waves spotted in microwave cavity
http://physicsworld.com/cws/article/news/40463
Sep 23, 2009



When lenses go bad
Freak waves towering as much as 30 m above the surrounding seas have long been reported by mariners, and recent satellite studies have shown that they are more common that previously expected. Now, a team of physicists in Germany and the US has gained important insights into the possible origins of such waves by scattering microwaves in the laboratory.

The work suggests that rogue waves can emerge from linear interactions between waves – contradicting some theories, which assume that non-linear interactions are required. The team believes that its insights could be used to calculate a "freak index", which would give the probability of encountering freak waves at specific locations in the oceans.

The experiment was inspired by a measurement made eight years ago by a group that included one of the present team – Eric Heller of Harvard University. Electrons flowing on a semiconductor sheet were seen to focus into several narrow beams, rather than scatter in random directions as had been expected. The reason, according to Lev Kaplan of Tulane University, is that random impurities in the semiconductor acted like a "bad lens", directing the electrons (which act like waves) towards several focal points.

Random currents
Kaplan and Heller realized that random currents in the ocean could also act as bad lenses, focusing smaller waves into larger – and even freak – waves.

According to Kaplan, it would be very difficult to test the theory using water in a wave tank because such facilities are set up to study waves propagating in only one direction. Instead, they joined forces with Ruven Höhmann, Ulrich Kuhl and Hans-Jürgen Stöckmann at the University of Marburg to study the effect in microwaves.

The team in Germany injected microwaves into a cavity comprising two parallel metal plates. The distance between the plates was much less than the wavelength of the microwaves, making the waves "quasi 2D" – just like ocean waves. Scattering from random currents was simulated by placing a number of metal cones in random positions in the cavity.



Orders of magnitude more
The team monitored the microwave intensity throughout the cavity and noticed the emergence of "hot spots", where the intensity was five or more times greater than background levels. The team counted the number of such freak waves that occurred over a finite time and discovered that they were many orders of magnitude more common than if they resulted from the random superposition of plane waves in the cavity. Random superposition had earlier been thought to govern the formation of freak waves in the ocean, which could explain why mariners and oceanographers seemed to differ on the frequency of such events.

Kaplan told physicsworld.com that the randomly-placed cones were behaving like a bad lens, which could occasionally focus the microwaves into a hot spot. The experiment is also the first to establish that freak waves can be generated via simple linear interactions between waves – the microwaves in the cavity only interact linearly. Previously, many oceanographers had believed that non-linear interactions – which become more prevalent in shallow water – were required to create freak waves.

Leonid Mezhov-Deglin of the Institute of Solid-State Physics of the Russian Academy of Sciences said that the microwave experiments should be of interest to physicists studying ocean and other surface waves. However, he cautioned that much more work was needed in the characterization of rogue ocean waves before they could be simulated accurately using microwaves.

Freak index
The experiment has also allowed Kaplan and colleagues to hone their "freak index", which defines the likelihood of encountering a rogue wave based on the average wave and current speeds and the angular spread of wave motion. This could help mariners to identify regions of the ocean where rogue waves could be a problem, but Kaplan points out that physicists will never be able to predict the formation of individual waves.

A preprint describing the work is available on arXiv.

About the author
Hamish Johnston is editor of physicsworld.com
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Physicists Are Discovering Ways To Build Rogue Waves Out Of Light
http://www.sciencedaily.com/releases/20 ... 122958.htm

Under the right conditions, colliding waves can add to create a rogue wave that's larger than the sum of its parts. (Credit: N. Akhmediev, J. M. Soto-Crespo and A. Ankiewicz)

ScienceDaily (Oct. 27, 2009) — Rogue waves—giant waves that spring up suddenly and tower over the seas around them—have inspired physicists to look for an analogue in light. These high-intensity pulses can cross large distances without losing information. Now a team of physicists have identified one set of conditions that produces optical rogue waves. Their findings are reported in Physical Review A and highlighted with in the October 19 issue of Physics.

Rogue waves were thought to be a sailor's tall tale until an 85-foot wave broke over an oil platform in the North Sea in 1995. Since then, scientists have tried to understand how such outsized waves arise from the erratic interactions of smaller waves on a choppy sea, with an eye toward creating them on purpose in the form of light traveling in an optical fiber.

While versions of quantum mechanical equations describe how optical rogue waves evolve, it's still difficult to pinpoint the conditions necessary to get them started. Now Nail Akhmediev of the Australian National University and his team have identified one possibility using theory—breathers, or small peaks that appear suddenly in one spot and disappear almost immediately, could seed rogue waves. Akhmediev's team found that two or three breathers, if they collide in exactly the right place at the right time, form an optical rogue wave. The researchers say the effect could be seen in water waves in a long, narrow tank. Their findings increase scientists' understanding of how to cook up optical rogue waves for communications applications.
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Two killed as giant waves hit Mediterranean cruise ship

Two people have been killed and six injured as giant waves slammed into a cruise ship in the Mediterranean, the ship's owners have said.

The 26ft (8m) high rogue waves hit the Cypriot-owned Louis Majesty off the north-east coast of Spain.

A spokesman for owner Louis Cruises said three "abnormally high" waves broke windows in the front of the ship.

The Louis Majesty was heading to Genoa on a 12-day Mediterranean cruise but has now returned to Barcelona.

"A wave broke the glass in the area of the saloon and water was taken on board," said a spokesman for Spain's coast guard.

The victims have been identified as a German and an Italian man.

"Louis Cruises extends its sincere condolences to the families of the two victims and its full support to the injured passengers while expressing its deep sorrow for the incident," a statement from the company said.

The ship was carrying 1,350 passengers and 580 crew.

A French naval official said there had been "no signs of the least problem with the Louis Majesty".

But Cmdr Bernard Celier said there had been winds of more than 100km/h (60 mph) in the area.

The ship is expected to resume its voyage to its final destination, Genoa, once the victims have been taken off the ship and the injured have received treatment.

http://news.bbc.co.uk/1/hi/world/europe/8548547.stm

AFAIK, this is the first case of a Rogue Wave in a relatively enclosed sea like the Mediterranean. Wave heights usually depend on the 'fetch' (the distance the wind blows over open sea), and in the Med this can't normally be more than a few hundred miles.
 
This report suggests the possibility of a tsunami:

...
The Marseilles coastguard spokesman said the waves were approaching 30ft high and may have been part of an isolated tsunami.

The Louis Majesty, which is operated by Louis Cruise Lines, was on its way from Barcelona to Genoa in Italy, but has returned to Spain following the accident.

A tsunami is a series of waves usually caused by the displacement of sea water. All kinds of factors can cause them, including earthquakes, volcanic eruptions, landslides and underwater explosions.

A new report issued last summer revealed that millions of people living and holidaying in the Mediterranean area are at risk of being hit by a tsunami.

The World Disasters Report, by the International Federation of Red Cross and Red Crescent Societies, said there is no tsunami early-warning alert system for the region, even though it is considered to be more vulnerable than the Indian Ocean.

Disaster expert Peter Rees-Gildea in July last year: ‘If you look at population density along the Mediterranean coast and the topography and what could happen with a major tsunami, the figures are self-evident. It would be absolutely catastrophic.

'Why we do not have an early warning system I do not understand. This is a real serious problem where millions of lives could be lost.’
...

Read more: http://www.dailymail.co.uk/news/worldne ... z0hDK7lVJb

But Tsunamis generally only peak up as they approach land, not out in the open sea. And surely there'd have been seismographic evidence, or big waves on shore somewhere as well?

Definitely freak waves for the locality, whatever the cause.
 
BBC have this to say today:

Over the last two decades more than 200 super-carriers - cargo ships over 200m long - have been lost at sea. Eyewitness reports suggest many were sunk by high and violent walls of water that rose up out of calm seas.

But for years these tales of towering beasts were written off as fantasy; and many marine scientists clung to statistical models stating monstrous deviations from the normal sea state occur once every 1,000 years.

[...]

As part of the project, Esa tasked two of its Earth-scanning satellites, ERS-1 and ERS-2, to monitor the oceans with their radar.

The radars sent back "imagettes" - pictures of the sea surface in a rectangle measuring 10 by 5km (6 by 2.5 miles), which were taken every 200km (120 miles).

Around 30,000 separate imagettes were produced by the two satellites during a three-week period in 2001 - and the data was mathematically analysed.

Esa says the survey revealed 10 massive waves - some nearly 30m (100 ft) high.

"The waves exist in higher numbers than anyone expected," said Dr Rosenthal.
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See the rest here: http://news.bbc.co.uk/2/hi/science/nature/3917539.stm
 
ramonmercado said:
[...]

The experiment has also allowed Kaplan and colleagues to hone their "freak index", which defines the likelihood of encountering a rogue wave based on the average wave and current speeds and the angular spread of wave motion. This could help mariners to identify regions of the ocean where rogue waves could be a problem [...]
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I cannot be the only one who finds his or herself thinking "Bermuda Triangle!" when I read the above?
 
RabidReader said:
BBC have this to say today:
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Er, it wasn't today, though - that article is from Thursday, 22 July, 2004!
 
rynner2 said:
RabidReader said:
BBC have this to say today:
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Er, it wasn't today, though - that article is from Thursday, 22 July, 2004!
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Eek! :oops:

For some reason they linked to that article from their front page today. Very sorry for raising anybody's hopes.
 
RabidReader said:
rynner2 said:
RabidReader said:
BBC have this to say today:
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Er, it wasn't today, though - that article is from Thursday, 22 July, 2004!
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Eek! :oops:

For some reason they linked to that article from their front page today. Very sorry for raising anybody's hopes.
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In fact, that's the very article that started this thread!

Sometimes an old story gets searched for a lot (probably because of something new and related) so it again finds itself on the Most Popular now list.
 
rynner2 said:
In fact, that's the very article that started this thread!

Sometimes an old story gets searched for a lot (probably because of something new and related) so it again finds itself on the Most Popular now list.
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I guess I should take heart that I at least realised the article's relevance to this thread. :roll: Will try to do better in future.
 
What Makes Freak Waves Stable? Modelling Non-Linear Giant Waves
By News Staff | June 19th 2010

Giant freak waves - seriously, that is what oceanographers and physicists call them - are called that because they can appear on the open sea out of nowhere.

Researchers from the Ruhr- Universität Bochum and the University of Umeå, Sweden say they have developed a new statistical model for non-linear, interacting waves in computer simulations which will allow them to be theoretically calculated and modeled.

They say their model explains how the water-wave system evolves, behaves and, above all, how it stabilizes itself. They say their model is also suitable for the calculation of other 'extreme occurrences - yes, more numerical models by physicists on the stock market, because we have seen how well that works - or more complex phenomena in plasma physics. Bochum’s physicist Prof. Padma Kant Shukla and his Swedish colleague Prof. Bengt Eliasson report on their findings in Physical Review Letters.

Shukla and Eliasson simulated how the giant freak wave occurs four years ago. If two or more waves meet at a certain relatively small angle, they can progressively “amplify” each other. Two non-linear interacting waves therefore act very differently to a single wave which shows normal instabilities and breaks up into several small waves, which then run diagonally to each other. Two non-linear waves, however, cause the water to behave in a new way, for example, the emergence of downright “wave packets” with amplitudes three times higher than that of a single wave. Buoyed by strong currents and powerful – opposing – winds, the giant wave can continuously build up from there.

With their new statistical model, they say they have succeeded in taking another crucial step towards explaining this freak wave: it results from combined non-linear effects in the wave-to-wave interaction and the dispersion of the “wave packets” in a certain direction.

This causes the energy of the water to be concentrated “in a narrow band across a confined wavelength spectrum”, and with sudden, large amplitude. The actual instability of individual waves is “saturated” through the broadening of the wave spectrum, thus the water-wave system temporarily stabilizes itself.

This behavior is typical for the localized giant wave, the researchers explain. Their calculations tally with observations from experiments in large water tanks. “These show that long-crested water waves, i.e. groups of waves propagating in approximately the same direction, have an increased tendency to evoke extreme events,” said Shukla and Eliasson.

A step towards prediction

Since the cruise liner Queen Elizabeth 2 encountered a freak wave in 1995, giant freak waves have been a source of study, finally being outside mariner 'tall tales'. The damage to passenger and cargo ships and also oil platforms at sea can be considerable. Shukla and Eliasson’s statistical model may lead to predicting freak waves in certain regions, such as the North Atlantic or the Mediterranean, and provide early warning in future. The deeper physical understanding of the giant wave and statistical calculation would have to be combined with new, improved methods of observation, the researchers say.

Citation:
Bengt Eliasson and P. K. Shukla: Instability and Nonlinear Evolution of Narrow-Band Directional Ocean Waves. Physical Review Letters 104, Editor: Jens Wylkop. DOI: 101103
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SOURCE: http://www.scientificblogging.com/news_ ... iant_waves
 
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Not a monster wave, but freaky enough for this thread...

Huge wave capsizes Cornwall fishing boat

A helicopter has airlifted a fisherman from the sea after his boat was tipped over by huge wave in Cornwall.
The small fishing boat Donna Mary capsized outside Porthleven harbour at about 1330 BST.

Coastguards said one of the crew made his way to shore while the other was rescued by a helicopter crew from RNAS Culdrose.
He was flown to the Royal Cornwall Hospital at Treliske suffering from cold and exhaustion.

Holidaymaker Nina Schofield, who captured the moment the fishing boat capsized on camera, said: "I was taking a picture thinking it was a really lovely scene and out of the blue a huge wave came and literally flipped the boat over.

She said that for the next 15 minutes people on the shore were trying to get to the sticken sailor.
"Your heart was in your mouth thinking 'please make it' because he couldn't get into the shore," she said.
"It was quite scary."

The Donna May, which was virtually broken in two by the wave, was washed into shore by the tide before being washed out again and sinking.
Attempts will be made to salvage it once weather conditions improve, Falmouth Coastguard said.

http://www.bbc.co.uk/news/uk-england-cornwall-11479541

I know the area well. Porthleven often features in bad weather stories, when waves break dramatically over the stone pier and the seafront. But even in less severe weather the harbour can be inaccesible as the entrance faces the prevailing SW winds. However, yesterday's weather was reasonable, and a local boatman would know about the usual dangers, so a freak wave it was!
 
Did a Rogue Wave Kill 4 Fishermen?

The U.S. Coast Guard announced on Sunday (April 21) that it was suspending the search for four fishermen whose boat is believed to have been destroyed by a rogue wave.

The 50-foot Nite Owl vessel was tied to an oil rig in the Gulf of Mexico about 115 miles (185 kilometers) southeast of Galveston, Texas, in rough weather on Friday morning (April 19), according to the Associated Press.

But in the early morning darkness, "a rogue wave, a freak wave or something hit the side of the boat," John Reynolds, the sole survivor of the accident, told the AP.

The wave "tore the wheel house and canopy off the boat," Larry Moore, owner of the commercial fishing vessel, told the Beaumont Enterprise from his home in Golden Meadow, La. "Everyone was asleep when it happened." The shattered craft sank within two minutes."

Rogue waves, sometimes called "freak waves," are extremely large waves that occur far out at sea in apparent isolation and without any obvious cause. The waves can easily reach 100 feet (30 meters) or more in height.

Though researchers have yet to understand how rogue waves develop, some scientists claim atmospheric pressure may play a role. Other research suggests rogue waves could result from the clash of two interacting wave systems traveling perpendicular to each other.

After a possible rogue wave destroyed the Nite Owl, all five men aboard were thrown into the choppy water without life jackets.

Though Reynolds tried to help the other men into the life raft he found, his efforts were thwarted by the rough sea's 12-foot (3.7 m) waves and his crewmates' poor swimming ability, he said.

"I got in the raft. I heard them call out. There was a little ring inside there with a 60-foot line on it," Reynolds told the AP. "I threw it in the direction I heard [a crewmate] hollering from, hoping he could grab ahold of it and pull himself to the life raft. Apparently, he couldn't get ahold of it."
Reynolds, 56, was rescued by the Coast Guard later that morning after firing flares into the air. Though he has worked as a commercial fisherman for 35 years, Reynolds told the Beaumont Enterprise that this was the first time he had ever ended up in the water.
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SOURCE: http://news.yahoo.com/did-rogue-wave-ki ... 24356.html
 
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The 50-foot Nite Owl vessel was tied to an oil rig in the Gulf of Mexico about 115 miles (185 kilometers) southeast of Galveston, Texas, in rough weather on Friday morning (April 19)
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I just typed a long reply to this, but my internet connection dropped out before I could post! :evil:

But in short, it's not sensible to tie up to another ship or object in rough weather in the open sea. There are better ways to ride it out.

It may have been a big wave, but I suspect being tied up had more to do with the problem encountered - it's better when the vessel can ride with the waves.
 
Yeah - I was wondering about that. The story doesn't specify how closely the boat was 'tied up to' the platform. It also never mentions the boat being swamped or any other clue that it was overwhelmed with water when the big impact occurred. Plus - everyone was asleep.

I don't see any clues that specifically indicate a big wave (as opposed to slipping its lines and getting rammed into the oil rig directly).
 
EnolaGaia said:
Yeah - I was wondering about that. The story doesn't specify how closely the boat was 'tied up to' the platform. It also never mentions the boat being swamped or any other clue that it was overwhelmed with water when the big impact occurred. Plus - everyone was asleep.

I don't see any clues that specifically indicate a big wave (as opposed to slipping its lines and getting rammed into the oil rig directly).
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Plus, a real 'freak wave' should have damaged the rig as well, but there's no mention of that.
 
7 rogue wave disasters, from Columbus to cruise ships
21:00 29 July 2014 by Stephen Ornes

In 2007, Paul Liu at the US National Oceanic and Atmospheric Administration compiled a catalogue of more than 50 historical incidents probably associated with rogue waves. Here are some of the most significant

1498 Columbus recounts how, on his third expedition to the Americas, a giant wave lifts up his boats during the night as they pass through a strait near Trinidad. Supposedly using Columbus's words, to this day this area of sea is called the Bocas del Dragón – the Mouths of the Dragon.

1853 The Annie Jane, a ship carrying 500 emigrants from England to Canada, is hit. Only about 100 make it to shore alive, to Vatersay, an island in Scotland's Outer Hebrides.

1884 A rogue wave off West Africa sinks the Mignonette, a yacht sailing from England to Australia. The crew of four escape in a dinghy. After 19 days adrift, the captain kills the teenage cabin boy to provide food for the other three survivors.


1909 The steamship SS Waratah disappears without trace with over 200 people on board off the coast of South Africa – a swathe of sea now known for its high incidence of rogue waves.

1943 Two monster waves in quick succession pummel the Queen Elizabeth cruise liner as it crosses the North Atlantic, breaking windows 28 metres above the waterline.

1978 The German merchant navy supertanker MS München disappears in the stormy North Atlantic en route from Bremerhaven to Savannah, Georgia, leaving only a scattering of life rafts and emergency buoys.

2001 Just days apart, two cruise ships – the Bremen and the Caledonian Star – have their bridge windows smashed by waves estimated to be 30 metres tall in the South Atlantic.

http://www.newscientist.com/article/dn2 ... urce=NSNS&

I've posted about the Mignonette story a few times before. Not only were the survivors first put on trial here in Falmouth, but it involves a remarkable coincidence:
Don't go sailing if your name is Richard Parker

In 1838, Edgar Allan Poe published The Narrative of Arthur Gordon Pym of Nantucket, a seafaring tale in which three shipwreck survivors decide their only chance of survival is to eat their fourth comrade, Richard Parker. The story is little known these days but for the grisly coincidence behind its storyline – particularly grisly for the men who boarded the yacht Mignonette in Southampton in 1884. The vessel was wrecked in the Atlantic, leaving only four survivors, three of whom were rescued. The fourth member of their party had not survived – because they had eaten him. His name? Richard Parker.

http://www.independent.co.uk/news/scien ... 69110.html
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Rogue wave ahoy! New technique can predict surprise sea threat

Giant rogue waves that rise from the deep can do massive damage to shipsand oil platforms. That's because they can be up to twice as tall as surrounding waves; and also seem to strike without warning. Now a new study says thesesea monsters may give some hints before they appear.

To find out how random rogue waves actually are, Günter Steinmeyer and his colleagues at the Max Born Institute in Berlin, Germany, examined wave heights measured over time at the Draupner oil platform off the coast of Norway, where a rogue wave struck in 1995. They sliced the data into segments of varying length, looking for those with nearly identical features. Then they randomly shuffled the data and again looked for such repeated events.

The team found more repeated events in the original data than in the shuffled versions, meaning that the rogue wave had identifiable precursors, rather than appearing completely randomly. "You can be sure that there is some determinism in the data," says Steinmeyer. ...

http://www.newscientist.com/article...technique-can-predict-surprise-sea-threat.htm
 
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A new system that warns of potentially ship-destroying ocean waves

STORMY seas can wreak havoc on ships and oil rigs, but the damage they do pales beside that which a rogue wave can dole out. These behemoths, which may be up to 30 metres (100 feet) high, can badly damage, and even sink, all but the largest merchant vessels. They form when smaller, harmless waves meld into one. Until now, predicting them has proved impossible. But Will Cousins and Themistoklis Sapsis, two mechanical engineers at the Massachusetts Institute of Technology, think they have cracked the problem.

Most ocean waves move independently of one another. Sometimes, though, they travel in groups. Waves within a group have the potential to share energy via a phenomenon called modulation instability, in which one wave grows at the expense of the others and all of the group’s power is thus concentrated into it.

Past teams of researchers who have attempted to predict such rogues have tried monitoring every wave in a region using radar, and then forecasting the behaviour of each of them. This needs a lot of processing power—far more than is carried on board an average merchant vessel. Moreover, it can take hours to run the calculation, which rather diminishes its value. Yet Dr Cousins and Dr Sapsis suspected they could bypass these problems by ignoring most of the waves in an area and homing in on only a tiny, relevant subset of them.

http://www.economist.com/news/scien...-waves-incoming?fsrc=scn/tw/te/pe/ed/incoming
 
This incident apparently didn't involve all that huge a rogue wave, but it was sufficient to swamp and sink a 61-foot fishing vessel.

Rogue waves hit Hawaii fishing vessel that sank, owner says
... The owner of a fishing vessel that sank off Hawaii over the weekend said Tuesday two massive rogue waves hit the boat, swamping it and forcing the crew to abandon ship.

One wave hit the back of the of the 61-foot (19-meter) fishing vessel, the Princess Hawaii, and another hit the side, said owner Loc Nguyen in a telephone interview ... The boat was hundreds of miles off the coast of Hawaii's Big Island at the time.

"It was so big, they've never seen that before," Nguyen said. There was "too much water on the top and it went down."

Nguyen said the fishing crew had already set about 15 miles (24 kilometers) of line when the waves crashed, knocking five workers into the water. He said the captain, a federal observer and another crew member had been inside and were able to deploy the vessel's life raft.

The eight people aboard were rescued by the vessel's sister ship about 12 hours later. No injuries were reported. ...

According to the U.S. Coast Guard, the Princess Hawaii was was in 10-foot (3-meter) seas with winds around 20 mph (32 kph) when it sank.
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FULL STORY (with photos): https://www.yahoo.com/news/rogue-waves-hit-hawaii-fishing-vessel-sank-owner-013207343.html
 
This news item about a storm-generated wave may or may not reflect the sort of 'rogue wave' phenomenon other reports above cite. However, researchers are definitely claiming this is the tallest recorded wave to hit shore in the Southern Hemisphere.

The story also includes some interesting factoids about evaluating tallest composite or collective wave height generated by a given storm.

78-Foot Wave Is the Largest Ever Recorded in Southern Hemisphere
... An eight-story monster wave that crashed down in the Southern Ocean off the coast of New Zealand has set a record. It's the largest known wave to ever hit the Southern Hemisphere, according to New Zealand scientists.

Nobody actually saw the 78-foot-tall (23.8 meters) wave crash down, but a buoy moored by New Zealand's Campbell Island managed to log the amazing wonder on May 8, according to MetOcean Solutions, a subsidiary of the Meteorological Service of New Zealand.

The colossal wave eclipsed its record-breaking predecessor by nearly 6 feet (1.77 m). That wave — a 72.2-foot (22.03 m) swell recorded by an Australian buoy, reared up just south of Tasmania in 2012, MetOcean Solutions said. ...

"This [new wave] is a very exciting event and to our knowledge it is [the] largest wave ever recorded in the Southern Hemisphere," Tom Durrant, a senior oceanographer with MetOcean Solutions, said in a statement. "This is a very important storm to capture, and it will add greatly to our understanding of the wave physics under extreme conditions in the Southern Ocean."

In this case, a deep, low-pressure system and high winds exceeding 74 mph (65 knots or 120 km/h) helped to create the perfect conditions for the enormous wave. "What is interesting about [Tuesday's] event is the storm speed appears to match the wave speed, allowing wave heights to grow dramatically as the system tracks eastward," Durrant said. ...

The storm that produced this giant wave could have generated even larger waves, with up to 82-foot-tall (25 m) peaks, Durrant noted. But because the solar-powered buoy needs to conserve its battery energy during its one-year deployment, it takes measurements for only 20 minutes every 3 hours. The buoy then sends these logs — which include the height, period and direction of every wave — to scientists via satellite. So, an even larger wave could have hit while the buoy was not recording ...

He noted that the World Meteorological Organization (WMO) uses a measurement known as "significant wave height" to characterize the state of the sea. To get this number, meteorologists take the average of the highest third of measured waves. For this storm, the significant wave height was 48.8 feet (14.9 m), which is a record for the Southern Ocean.

But it's not the world record. That honor goes to a significant wave height of 62.3 feet (19 m) logged in the North Atlantic in February 2013.
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FULL STORY: https://www.livescience.com/62543-largest-wave-hits-southern-hemisphere.html
 
This recent study indicates abrupt changes in the seafloor can increase the possibility of generating rogue waves by up to 50 times.
Variations in seafloor create freak ocean waves
Florida State University researchers have found that abrupt variations in the seafloor can cause dangerous ocean waves known as rogue or freak waves -- waves so catastrophic that they were once thought to be the figments of seafarers' imaginations.

"These are huge waves that can cause massive destruction to ships or infrastructure, but they are not precisely understood," said Nick Moore, assistant professor of mathematics at Florida State and author of a new study on rogue waves.

The study is published in the journal Physical Review Fluids, Rapid Communication.

Once regarded as a myth, these waves have stumped the scientific community for several decades.

Over the years, researchers across the globe have examined a number of different factors they thought might contribute to these waves, including the seafloor, wind excitation and a phenomenon called Benjamin-Feir where deviations from a periodic waveform are reinforced by nonlinearity. ...

Moore's laboratory experiments were the first to examine the effect of abrupt seafloor variations on wave statistics. ...
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FULL STORY: https://www.sciencedaily.com/releases/2019/02/190201114157.htm

ABSTRACT of Published Article: https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.4.011801
 
This recent study recreated a well-documented freak / rogue North Sea wave and demonstrated how such waves' generation is sensitive to the angle at which contributing waves intersect.
Famous freak wave recreated in laboratory mirrors Hokusai's 'Great Wave'
The Draupner wave was one of the first confirmed observations of a freak wave in the ocean; it was observed on the 1st of January 1995 in the North Sea by measurements made on the Draupner Oil Platform.

Freak waves are unexpectedly large in comparison to surrounding waves. They are difficult to predict, often appearing suddenly without warning, and are commonly attributed as probable causes for maritime catastrophes such as the sinking of large ships.

The team of researchers set out to reproduce the Draupner wave under laboratory conditions to understand how this freak wave was formed in the ocean. They successfully achieved this reconstruction by creating the wave using two smaller wave groups and varying the crossing angle -- the angle at which the two groups travel.

Dr Mark McAllister at the University of Oxford's Department of Engineering Science said: 'The measurement of the Draupner wave in 1995 was a seminal observation initiating many years of research into the physics of freak waves and shifting their standing from mere folklore to a credible real-world phenomenon. By recreating the Draupner wave in the lab we have moved one step closer to understanding the potential mechanisms of this phenomenon.'

It was the crossing angle between the two smaller groups that proved critical to the successful reconstruction. The researchers found it was only possible to reproduce the freak wave when the crossing angle between the two groups was approximately 120 degrees. ...

To the researchers' amazement, the wave they created bore an uncanny resemblance to 'The Great Wave off Kanagawa' -- also known as 'The Great Wave' -- a woodblock print published in the early 1800s by the Japanese artist Katsushika Hokusai. Hokusai's image depicts an enormous wave threatening three fishing boats and towers over Mount Fuji which appears in the background. Hokusai's wave is believed to depict a freak, or 'rogue', wave. ...
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FULL STORY: https://www.sciencedaily.com/releases/2019/01/190122125553.htm
 
They haven't gone away ye know.

Rogue waves - huge swells that can appear from calm seas - are occurring less often but becoming more extreme, data from the US coast suggests.

In the largest study of its kind, scientists analysed 20 years of observations from buoys situated along America's western seaboard. They found that between 1994 and 2016, the waves decreased slightly in frequency but increased in height. Scientists want to better understand how and when these waves may strike. They pose a growing threat for the global shipping industry.

Defined as a wave that's more than twice as high as the background ocean, some can reach more than 30m and at their most destructive can sink a ship or sweep people out to sea. It's estimated that one in 10,000 waves is a rogue wave - but while they've been the subject of marine folklore for centuries, they were first officially recorded in the 1990s. Since then scientists have been trying to study them.

https://www.bbc.com/news/science-environment-47642346
 
ramonmercado said:
They haven't gone away ye know.

Rogue waves - huge swells that can appear from calm seas -

https://www.bbc.com/news/science-environment-47642346
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Typical BBC, rubbish at anything vaguely scientific. A rogue wave doesn't appear from a calm sea. A single sudden wave appearing from an otherwise calm sea would be in defiance of the laws of physics. Or, to put it facetiously, if the sea was flat calm, then the wave that was twice as high as nothing at all would also be flat calm.
 
Mikefule said:
Typical BBC, rubbish at anything vaguely scientific. A rogue wave doesn't appear from a calm sea. A single sudden wave appearing from an otherwise calm sea would be in defiance of the laws of physics. Or, to put it facetiously, if the sea was flat calm, then the wave that was twice as high as nothing at all would also be flat calm.
Click to expand...

I think they mean relatively calm seas, or seas with average wave height.
 
Human_84 said:
I think they mean relatively calm seas, or seas with average wave height.
Click to expand...

What they should mean is that a rogue wave is a wave that is more than twice as high as the average height of other waves in the area at the time. What they said is something different from that.

For comparison: Earlier this week, a Times headline said that "10 minutes' exercise a week could reduce your risk of early death by a fifth."

The truth, embedded deep in the story, was that the risk was improved by 18% (nearer to a sixth than a fifth) for people who reported that they did "between 10 and 59 minutes' exercise a week."

As 10 minutes is clearly going to be at or very near the low end of the bell curve, those who only do 10 minutes' exercise are not going to be very representative of the group who do "between 10 and 59 minutes".

I would add that people who do only 0–9 minutes' exercise a week may well have an underlying condition that limits their ability to exercise, and therefore a raised rate.

It is this sort of reporting by supposedly credible media sources (BBC, the Times, et al) that contributes to us being such a scientifically illiterate society.

Is it then any surprise when people who are busy and skim read the news form a mish mash of vague ideas that "there must be something in..." chem trails, the MMR vaccine and autism, the Atkins diet, homeopathy, feng shui, the lunar landing "hoax", and a hundred other things?
 
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