In practical applications, it is usually assumed that the wave spectrum is of a single mode form, and well modeled by a JONSWAP or Pierson-Moskowitz spectrum. This assumption is of a reasonable accuracy for severe sea states. However, moderated and low sea states are often of a combined nature, consisting of both wind-sea and swell and should be characterized by a double peak spectrum. The present paper discusses two-peak spectra observed in Norwegian waters, which are particularly affected by swell. The analysis is based on 5-year of directional data from Haltenbanken. A directional distribution for swell is suggested. Further, a procedure for including directional spreading in two-peak spectra is proposed. The method is illustrated for the two-peak Torsethaugen frequency spectrum (Torsethaugen, 1996), which is currently used by the Norwegian industry.

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