Are monster waves predictable?

A comparative analysis of monster waves in different physical systems comes to the surprising conclusion that these rare events are by no means always completely unpredictable.

Meteorological events are very often unpredictable; a "century storm" is sometimes surpassed the following year. Emerging insurance damages often turn out to be beyond any statistical expectation. Such events are subject to a statistical extreme value distribution, in which extraordinary events occur much more frequently than even a long-term analysis of more normal events would expect.

A prominent example of completely unpredictable events are so-called monster waves (also known as cavemen) on the ocean. These waves may be very rare, but if they hit a ship, massive damage to the hull, which can lead to the sinking of the ship.

The exact causes of such monster waves are still controversial and it is unclear whether they can be predicted. Is there any way to derive a last minute or second warning from the recorded wave patterns? Are there any characteristic wave patterns that announce a monster wave? Unfortunately, there are very few records of ocean monster waves, but there are some analog systems in optics that exhibit qualitatively similar behavior.

This is where the work of Simon Birkholz and co-workers begins. Based on the data from three different extreme events, an accurate prediction and prediction analysis was conducted for each case. Here data from the famous New Year wave in 1995 flowed in on the Draupner oil platform, optical measurements of the group around Bahram Jallali at the University of California at Los Angeles and extreme events in nonlinear multifilaments measured at the Max Born Institute in Berlin. In the multifilament system, monster waves are directly observable as short flashes of light in the beam profile. The wave height in the ocean thus corresponds to the light intensity in the optical systems.

The amazing result of this comparative analysis is that monster waves are quite predictable in some systems, but completely random and unpredictable in others. An extreme value statistic therefore does not allow conclusions to be drawn about the predictability of the system. A special role is played by ocean waves. Unlike previously thought, monster waves are not completely random. It is therefore untrue that monster waves "appear from nowhere and disappear without a trace," as has often been said. Nonetheless, a practical prediction is still a long way off, and at best may allow a last minute warning of these "deep sea monsters".

Original publication

Predictability of rogue events

S. Birkholz, C. Brée, A. Demircan, G. Steinmeyer

Physical Review Letters 114 (2015) 213901/1-5