The Spectral Ocean Wave Model (SOWM) in use at the Fleet Numerical Oceanography Center since 1974 has been used to produce spectra for a 20-year ocean wave climatology for the Northern Hemisphere oceans. The data sources and concepts used to develop the computer model are described; and the equations and computer program structure for the model are given in this report. The accuracy of the model is evaluated by analysis of studies that used spacecraft radar altimeter measurements of significant wave height and by comparison of predicted and estimated frequency spectra and significant wave heights. This report also describes sampling variability effects and incorporates them into the interpretation of the accuracy of the model specifications. In addition, rapid spatial and temporal variations of actual waves that are not reproduced by the model are documented; and possible errors in the specification of swell are suggested. With care in interpretation, a SOWM wave climatology, which is in preparation, should prove to be more accurate than those based on conventional ship reports. (Author)