Mapping of wave trains during four flights over the ocean off southern California showed the consistent presence of a high 10-second swell from the westnorthwest, of one or two low 3- to 5-second swells from other westerly directions, and of local wind waves; occasionally a low 13-second swell from the west and southwest was also present. Islands reduce the height of swells but produce little discernable crossswell in their lee....
Emery, K. O.. 1958. "Wave patterns off southern California." Journal of Marine Research 17, (1). https://elischolar.library.yale.edu/journal_of_marine_research/909