In the present study, the SWAN model was employed to estimate the wave field on an open sandy beach at the west coast of Portugal, north of Sines Harbour. The SWAN model is a discrete spectral model based on the action balance equation and was designed to include shallow waters physics. It is the purpose of the work hereby reported to evaluate the sensitivity of the nearshore wave propagation modelling to the type of information used in the offshore boundary. For that, the SWAN model was forced

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... with bulk parameters and with directional spectra derived from a large scale implementation of the WAM model. Wave measurements from an ADCP sensor moored in 17 m depth (datum), and operating during a rather stormy period, were used to model comparisons. Verification statistics, like the bias, the root-mean-square error and the scatter index show that the significant wave height and the mean direction in the SWAN results depend on the method of specifying the incoming wave field. An improvement on the accuracy of these results is observed when directional spectra are employed to drive the coastal model.