Enhanced freak wave occurrence with narrow directional spectrum in the North Sea

[1] Wind and wave records obtained from the Kvitebjorn platform (2.3°E, 61.0°N, 190 m deep) in the northern North Sea from 2003 to 2005 were analyzed. Among the 2723 20-min records taken during storm conditions, 57 cases included freak waves exceeding twice the significant wave height. Comparisons between various wave parameters and the freak wave occurrence index did not show any significant correlation. Thus, the in situ wave record was used to select the days when relatively more or less freak waves were observed. The days were classified into freakish and non-freakish days, respectively. On freakish days, the Icelandic low was enhanced. Hindcasts performed by a third-generation wave model suggest that this synoptic atmospheric pressure difference produces approximately 7.6 degrees narrower directional spreading of the wave spectra during freakish days at the Kvitebjorn platform. This result is consistent with the physical mechanism of freak wave generation through nonlinear self-focusing in random wave fields.

[1]  Efim Pelinovsky,et al.  Influence of wind on extreme wave events: experimental and numerical approaches , 2007, Journal of Fluid Mechanics.

[2]  Nobuhito Mori,et al.  On Kurtosis and Occurrence Probability of Freak Waves , 2006 .

[3]  Shang-Ping Xie,et al.  Mapping High Sea Winds from Space: A Global Climatology , 2007 .

[4]  Karsten Trulsen,et al.  Influence of crest and group length on the occurrence of freak waves , 2007, Journal of Fluid Mechanics.

[5]  G. Forristall On the statistical distribution of wave heights in a storm , 1978 .

[6]  Peter A. E. M. Janssen,et al.  Nonlinear Four-Wave Interactions and Freak Waves , 2003 .

[7]  C. Soares,et al.  Modeling freak waves from the North Sea , 2005 .

[8]  T. Waseda,et al.  Freakish sea state and swell‐windsea coupling: Numerical study of the Suwa‐Maru incident , 2009 .

[9]  Paul Stansell,et al.  Distributions of extreme wave, crest and trough heights measured in the North Sea , 2005 .

[10]  Luigi Cavaleri,et al.  Statistical properties of mechanically generated surface gravity waves: a laboratory experiment in a three-dimensional wave basin , 2009, Journal of Fluid Mechanics.

[11]  Takuji Waseda,et al.  Evolution of a Random Directional Wave and Freak Wave Occurrence , 2009 .

[12]  Takuji Waseda,et al.  Analysis of a Marine Accident And Freak Wave Prediction With an Operational Wave Model , 2009 .

[13]  Harald E. Krogstad,et al.  Oceanic Rogue Waves , 2008 .

[14]  Takuji Waseda,et al.  Interplay of Resonant and Quasi-Resonant Interaction of the Directional Ocean Waves , 2009 .