On January 1st 1995 a wave measuring a height of 18.5 meters was measured passing under the Draupner oil platform in the North Sea. Dubbed by the international scientific community as the "new year wave" it is an extreme wave. An observer on the platform would have seen a wall of water, twice as high as all other waves, approaching over a period of about one minute. Wave height being the distance measured from the trough to the crest of the wave, with a crest height 18.5 m above the mean water level, the wave height was 26m.
(See http://www.youtube.com/watch?v=K_JOBOvJEOg for reconstruction of the event - not good quality).
Measuring waves: Formed by wind blowing along the water’s surface, wave height depends on wind speed, fetch length (distance the wind blows over water with similar speed and direction), and duration of time the wind blows consistently over the fetch. High wind speeds blowing for long periods of time over long stretches of water result in the highest waves. Waves are still formed by the local wind, but once formed they continue to travel for thousands of miles.
Making waves: generating regular waves in a wave tank in Bergen, but our request for something more dramatic proved rather too challenging. We left them staring into their computer with Kristian Dythe's mathematical formulae for an extreme wave.... maybe next time..