Giant freak waves: Expect the unexpected

Department of Theoretical Physics, Institute of Physics - 03028 Kyiv, Ukraine

Received: 29 September 2008
Accepted: 12 December 2008

Abstract

Freak or rogue waves are unexpectedly large ocean waves possessing devastating effects on offshore structures and ships. Freak wave events are rare enough. However, freak waves occur more often than the standard statistical models predict. Here I propose a mechanism of rising a giant freak wave in mid-ocean. The swell (steady wave) is the initial condition for the wave evolution at the beginning of which the wave is driven by the gust of wind, and then the wave runs free up to its overturning. To that moment the wave may become huge. The time of the evolution is less than half of the swell period (a few seconds). In the course of the free evolution the wave height may also oscillate creating the “Three Sisters” effect. For the description of such wave patterns new evolutionary equations for water gravity waves are derived, and their exact numerical solutions are found. The theory describes oceanic and wave-flume data with freak and overturning events and gives quantitative forecasts of dangerous sea conditions.