Rogue Wave study


#1

Interesting stuff. Particularly the “2 per day” part.

One of my biggest fears at sea. Completely out of your control and devastating to encounter.


#2

Avoiding heavy weather by using wave height limits for weather routing should at least greatly decrease the risk of encountering a dangerous rogue wave.

A rogue wave is defined as a wave that is more than twice the height of the significant wave height (SWH). If the ship is successfully using, say a 7 meter wave height limit, the highest wave expected is 14 meters.

The Draupner wave, which was actually measured at 25.6 occurred in SWH 12 meter seas. So a 24 meter wave would have been expected in those conditions… The Draupner was roughly 6% bigger than expected.

Given that, if the routing is using a 7 meter limit but the ship unavoidable encounters 9 meter seas the largest expected sea is 18 meters. Add 10%, that gives about 22 meters.

The QE2 was said to have encountered a 33 meter rogue wave, but she was in 18 meters seas at the time, technically, not a rouge.

Bottom line, avoid heavy weather.


#3

There are two types of Rogue waves. One happens in a storm that’s Bas enough for all “major work” to be stopped already. These are giant waves come mostly by surprise and leave you checking your pants while yelling WTF!

The second type happen only in certain areas of the world (that were, until recently, uncharted) or because of huge events like an earthquake. These types are #%*#! massive compared to the first and you can see them rising up on the horizon. When our lookout spotted it I had time to make a PA announcement, do aevery beeif watch turnover with the CM, put the ship in manual steering and alter her course. These second types leave you completely speechless and literally pinching yourself in disbelief that you are still alive.

Having experienced both I wish researchers would call them by different names. This article makes it sound kike a type 2 rogue wave when, what they are studying is clearly a type one.

I believe type one should be called freak waves because that’s what they are… Frankenstein like amalgamations with very little that can be done to protect yourself but more of a danger to smaller vessels and ships that are already experiencing other problems. We could also call these Death Nails because they are the final blow that sink a ship that’s already floundering.

I believe the term “Rogue Wave” should be reserved for the second type because the word “Rogue” connotates something that’s unpredictable, imposing and singularly dangerous and is not dependant on other factors like the weather.

P.S. I’d be willing to guess that any mariner here who has sailed for years in high latitude open ocean has witnessed a type one freak wave. But I’ve only met a very small handfull of mariners who have an authentic type two rogue wave story. As the article reports Feak Waves happen everyday twice PER STORM (meaning they happen much more than twice a day globally) but I’d be surprised if true Rogue waves occurred more than a handfull of times per week across all the world’s oceans.

P.S.2. There is one place in the world where it may be more difficult to differentiate between the two types… The southern ocean. The reason for this is that storms can circle the globe several times before dissipating generating true Rogue wtees from nothing more than the collision of weather patterns.


#4

The most researched phenomenon is the ‘hole in the sea’ in the Agulhas Current between Durban and Port Elizabeth Ships are tempted to keep on the 100 fathom line as that is where the current is strongest but is the most dangerous place to be.

http://www.swimhistory.org/files/Big%20Waves%20Transkei%20coast.pdf


#5

Question: It’s been a long time since I did any serious physical oceanography. Is there any truth to the concept of freak waves appearing in triplets or “3 sisters”. I’ve heard and read lots of anecdotal reports but on the few occasions of actually encountering what I considered a freak wave, it was always in storm conditions and always just a single WTF moment during an otherwise normal but rough ride. Thanks for everyone’s insight.


#6

Back in '76, the AHTS OCEAN MARLIN had an encounter with rogue waves in the Gulf of Alaska. The mate told me they had been running light boat 14 knts for several days in good weather. Then out of the blue he said it felt like they were being launched. They went through the next wave and it ripped the house loose forward on the O1 deck.


#7

The one I witnessed we had to look up at from the bridge of our drillship. The next wave was about 3/4 the size of the first and the third was about half the size of the first… after that it was just typically bad seas.


#8

Rogue Waves can occur in strong currents like the Gulf Stream: “Because waves slow when they encounter an opposing current, they also refract. Just as bends in the coastline concentrate or diffuse wave energy, bends and meanders in ocean currents similarly concentrate and diffuse wave energy. Wave refraction is one possible origin for rogue waves. Wave-current interactions increase exponentially as the current speed increases. This effect becomes significant when currents reach speeds of 1-1.5 knots.” http://oceanweatherservices.com/blog/2018/02/27/high-wind-and-wave-events-crossing-the-gulf-stream/