Origin of Swell Recorded at Monterey, California.

Selected swell wave records from Monterey, California and the associated weather maps were analyzed to determine at what stage in the storm history the peak energy in the swell trains was produced. The apparent origin of the swell, derived by frequency-time analysis of the wave records, was found to lie within the fetch determined from the weather maps, and to occur during the stage in the storm history when the fetch velocity was rapidly decreasing. The group velocity of the peak energy swell was found to equal the fetch velocity at the time of swell origin, a condition suitable for the generation of large wave energy because of a long effective wind duration. By assuming fully arisen seas at the apparent swell source, an average value of the ratio of surface to geostrophic wind speed of 0.77 was obtained. This value was derived from surface winds obtained from the wave data and geostrophic winds obtained from the weather maps. These results confirm the assumption that the peak energy swell was generated in fully arisen seas, and that no shift occurred in the peak swell period in shallow water off Monterey. Author