Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Nat. Hazards Earth Syst. Sci., 14, 945-957, 2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
22 Apr 2014
Predicting freakish sea state with an operational third-generation wave model
T. Waseda1, K. In1,*, K. Kiyomatsu1, H. Tamura2, Y. Miyazawa2, and K. Iyama1,** 1Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Japan
2Japan Marine and Earth, Science and Technology, Yokohama, Kanagawa ,Japan
*now at: Automobile R&D Center, Honda Automobile, Tochigi, Japan
**now at: R&D Center, JR East Group, Saitama, Japan
Abstract. The understanding of freak wave generation mechanisms has advanced and the community has reached a consensus that spectral geometry plays an important role. Numerous marine accident cases were studied and revealed that the narrowing of the directional spectrum is a good indicator of dangerous sea. However, the estimation of the directional spectrum depends on the performance of the third-generation wave model. In this work, a well-studied marine accident case in Japan in 1980 (Onomichi-Maru incident) is revisited and the sea states are hindcasted using both the DIA (discrete interaction approximation) and SRIAM (Simplified Research Institute of Applied Mechanics) nonlinear source terms. The result indicates that the temporal evolution of the basic parameters (directional spreading and frequency bandwidth) agree reasonably well between the two schemes and therefore the most commonly used DIA method is qualitatively sufficient to predict freakish sea state. The analyses revealed that in the case of Onomichi-Maru, a moving gale system caused the spectrum to grow in energy with limited downshifting at the accident's site. This conclusion contradicts the marine inquiry report speculating that the two swell systems crossed at the accident's site. The unimodal wave system grew under strong influence of local wind with a peculiar energy transfer.

Citation: Waseda, T., In, K., Kiyomatsu, K., Tamura, H., Miyazawa, Y., and Iyama, K.: Predicting freakish sea state with an operational third-generation wave model, Nat. Hazards Earth Syst. Sci., 14, 945-957,, 2014.
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