Rogue waves, towering at least twice as high as the other waves present, seem to appear at random. Their rarity makes them difficult to study, and for years they were considered a sailors’ myth. They are especially common off the east coast of Africa, making this a fruitful area for rogue wave research.
A key factor is the how the fast-running Agulhas current runs south and collides with ocean swells running north from the Southern Ocean. The current modifies the shape and height of the waves, tending to make them steeper and amplifying them.
The effect varies depending on the angle between the current and the swell. This interaction may produce a “swell train” of waves moving together, which can contain a small number of extreme waves.
While it is difficult to observe rogue waves directly, it is now possible to measure average wave height from space with a radar altimeter. This allows scientists to observe what happens under various conditions and test their computer models against reality.
Even in this one small and well-studied region, rogue wave formation is not well understood. But ships in the area are still being damaged or sunk by monster waves, and being able to predict when and where they are most likely to form could save many lives.