What Is a Rogue Wave?

Rogue waves (also called freak waves or monster waves) were long considered maritime legend until the Draupner wave was measured on 1 January 1995 at an oil platform in the North Sea: a 25.6-metre wave emerged from seas with a significant wave height of only 12 metres. Rogue waves are defined as waves at least twice the significant wave height (the average of the highest one-third of waves). They can form through several mechanisms: constructive interference (when multiple wave trains coincide to temporarily produce a much larger wave), wave-current interactions (opposing currents steepening waves, common off South Africa Agulhas Current), and nonlinear focusing effects (where wave energy concentrates into a small area). Satellite measurements have shown that rogue waves are far more common than linear wave theory predicts — about 10 rogue waves may occur in any given ocean area per day. Historical shipwrecks attributed to rogue waves include the SS Edmund Fitzgerald (1975) and possibly the MS Munchen (1978).