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Japanese artist Katsushika Hokusai's famous painting, known as "Under the Wave off Kanagawa" and "The Great Wave," is thought to be a so-called freak wave.
Credit: Katsushika Hokusai; Henry L. Phillips Collection, Bequest of Henry L. Phillips, 1939
▼ It takes a perfect storm to generate a freak wave, a wall of water so unpredictable and colossal that it can easily destroy and sink ships, a new study finds.
Take, for instance, the Draupner freak wave, which struck on Jan. 1, 1995, near the Draupner Oil Platform off the coast of Norway. That wave reached an incredible 84 feet (25.6 meters) tall, or about the height of four adult giraffes stacked on top of one another. Another famous rogue wave is depicted by Japanese artist Katsushika Hokusai in his19th-century woodblock print called "The Great Wave," which shows an enormous surge of water moments before an inevitable crash.
To figure out why these freak waves appear so suddenly and without warning, an international team of researchers from England, Scotland and Australia reproduced a scaled crest of the Draupner wave in a lab tank.
The team successfully decoded the rogue wave's recipe: It simply needs two smaller wave groups that intersect at an angle of about 120 degrees, they found.

A rogue wave breaking, as seen by Véronique Sarano in the Southern Ocean.
Credit: Copyright V. Sarano
The discovery shifts scientists’ understanding of freak waves "from mere folklore to a credible real-world phenomenon," study lead researcher Mark McAllister, a research assistant in the Department of Engineering Science at the University of Oxford in England, said in a statement. "By recreating the Draupner wave in the lab, we have moved one step closer to understanding the potential mechanisms of this phenomenon."
When ocean waves break under typical circumstances, the fluid velocity (the speed and direction of the water) at the top of the wave, known as the crest, exceeds the velocity of the crest itself, McAllister told Live Science in an email. This causes the water in the crest to overtake the wave, and then crash downward as the wave breaks.
However, when waves cross at large angle (in this case, 120 degrees), wave-breaking behavior changes. (▪ ▪ ▪)
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