Swept overboard – The science of rogue waves

Alex Cattrell – Southampton Marine Maritime Institute Ph.D. researcher.

“At 0624 there was a huge impact on the starboard side of the vessel. I felt my world spin upside-down. The shriek of the gale was silent, it was completely black and the floor was now the roof”; Rod Briggs recalls what happened to him on the 40ft Vyndi in the 1990s to YachtingWorld (2017).

“We had been running ahead of a southerly gale and the course change at 0600 would have brought the marching seas even further astern; yet something, powerful enough to cross 60ft breaking seas, had picked us up and thrown us over like a toy.

“It seemed much longer than the few seconds it must have actually been until the righting momentum started. When it happened it was sudden and severe. I pulled open the hatch to witness devastation.

“The wheel had been ripped off, as had many of the deck fittings. One of the masts was hanging over the side and Errol had disappeared overboard.

“Looking astern into a wall of water turned silver in the early morning sun, I saw Pete in the water with the ferry buoy. He called to me as he was pulled up and over the crest of the wave away from the boat. I shouted back that we would turn the yacht around as soon as we could rig some emergency steering.

“A moment later I saw him again on the crest of another 60-footer moving fast and then he was gone. Although it appeared that we were making good progress to windward, we were going backwards. Pete and Errol, at the mercy not of the wind but of the Agulhas Current running at up to five knots, were getting further away from us all the time.

“Over the next few hours we let off 48 flares. Not one person responded. No trace of Pete or Errol was ever found.”

Evocative recounts of encounters with extremely large and unexpected waves that appear from nowhere and disappear without trace, have been told by seagoers for centuries; however, little or no physical evidence led to scientists dismissing them as simply tales or excuses for malpractice.

On New Year’s Day 1995, a wave of 25.6 metres struck the Draupner platform in the North Sea, where the significant wave height, the average wave height of the wave field, was 12 metres. This formed the first rogue wave ever to be detected by scientific instruments, and was confirmed with the minor damage to the platform caused by the event.

Now that scientists knew they existed, how were they formed? Can they be predicted?

The phenomenon was defined in 2000 as a large oceanic surface wave that exceeds the significant wave height by more than a factor of 2, and research was undertaken to better understand the process; however, despite the two decades of research, the origin of this rare but destructive oceanic phenomenon is still disputed.

The next blog post will discuss the scientist theories on the processes of formations, and how my Ph.D. research at the University of Southampton is contributing to the field.

 

References:

YachtingWorld (2017, April, 12). Rogue waves – real-life stories of the destructive power of the sea. http://www.yachtingworld.com/special-reports/rogue-waves-real-life-stories-destructive-power-sea-106135/2#DQlaQ3jZYpo3dFh9.99

 

 

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