Numéro : 2550 - Year : 2009
Analysis of the sea states associated to the Prestige casualty
Jean-Michel LEFEVRE, Météo-France – Division Marine et Océanographie
Alessandro TOFFOLI, Swinburne University of Technology (Australie)
On 13 November 2002, the hull of the tanker « Prestige » has been severely damaged by a wave while sailing in the area of Cape Finisterre. After several days of towing, the ship broke off resulting in a massive oil spill. This study aims to describe the sea-state conditions as they have been observed and modelled in the accident area. The changing conditions of the sea-state during the day of the accident is examined in the light of work carried out since in the field of rogue waves. These conditions are first described in terms of power spectral densities obtained by solving an action density balance equation. The most advanced, so-called third generation wave models solve this equation explicitly. From these spectra, we can then calculate a number of synthetic parameters adapted to marine forecasting, mainly the significant height, period and mean direction of total sea, wind sea and dominant swell. Examination of an accidents database has demonstrated that knowledge of these parameters alone does not establish alert criteria for dangerous sea-states. Other parameters must be taken into account. Progress has been made in understanding some of the mechanisms responsible for the formation of abnormal waves and are presented here in connection with the accident of the «Prestige ».
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