Exploring freak waves

We’ve all heard (at least in Ireland) the unfortunate announcements of people losing their lives at the coast due to “freak waves”. Freak waves and rogue waves are the same thing, and are generally not what take unsuspecting people at the coast, since those are more generally set waves, which I’ve written about before, and people just don’t seem to understand that all waves around the same time are not the same size.

By the way, I’ll take this opportunity to remind you of the surfer’s saying to help ensure safety at the coast: watch the sea for twice as long as the waves are high.

Freak or rogue waves are the monsters that happen out to sea, that were long reported but generally not believed until very recently even though reports seemed to occur around the world. In Ireland the old lighthouse high up on Skellig Michael had its windows broken back in the 1950’s by waves breaking up at about 30 metres. On the 11th March 1861 at midday the lighthouse on Eagle Island, off the West coast of Ireland was struck by the sea smashing 23 panes, washing some of the lamps down the stairs, and damaging the reflectors with broken glass beyond repair. In order to damage the uppermost portion of the lighthouse, water would have had to surmount a seaside cliff measuring 40 m (133 ft) and a further 26 m (87 ft) of lighthouse structure.

VLCCs (very large cargo carriers) are notoriously lost going around Cape Horn (in the Agulhas Current), the theory is, being so long and heavy the wave can cause both ends of the ship to be suspended, (or the ends to be raised) and they break under their own unsupported weight.

In one those weird coincidences, when I was writing this, the M4 Buoy off Ireland’s North West registered a waves height of over 20 metres, truly extraordinarily large. I have seen 11 metre waves off Clare on the west coast, and, no word of lie, I remember looking out to sea and thinking to myself, I don’t remember there being an island there, before I realised what I was actually looking at. And then I went surfing.

Now the scientific and the orbital evidence (even you ignore reading and visuals) supports the existence of rogue waves after the measurement of The Draupner Wave, in 1995, (below). Here’s a scientific paper explaining the causal factors. There are a few factors, primarily high winds and strong currents.

I’m not sure if yesterday’s wave would qualify as rogue, since there were significant size waves before and after it. The strict(-ish) definition is that the wave is more than twice the significant height of the waves in the wave train, which wasn’t the case yesterday. But directly contradicting myself above, what the buoy did show was the wind blowing from the prevailing south-south-west direction. Rogue waves may occur when one wave travels in the opposite direction of the others and occur more frequently in areas with strong currents, such as the Agulhas off South Africa, the Kuroshio off Japan, and the Gulf Stream off the eastern United States. In 2000 a ship encountered an open water wave height of over 29 metres.

A Freak Wave took out the whole forepeaktank of the Norwegian tanker "Wilstar", 1974

Location is also important. VLCCs, which were too large to go through the Suez Canal have long had to take the long route to Europe around the Cape of Good Hope and some were mysteriously lost in the Agulhas Current. As many as 200 supertankers have been lost in the past 25 years, and many are now estimated to have been caused by freak waves with the SS Munchen being the best known. It also seems that the famous Edmund Fitzgerald may have been sunk by a peculiar freak wave phenomenon in Lake Superior!

A (short) YouTube clip of a collection of very large waves breaking at sea.

One scientist estimated there may be up to 10 of these waves in existence worldwide at any time, and in an important part of science, it’s been possible to recreate them in wave tanks, validating the science.


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