Weather pattern term which means that all of the storm activity in one particular region is moving in a consistent west-to-east pattern along the same latitude. While this can happen anywhere in the world it is usually associated with the Southern Ocean (around Antarctica) and is caused by large ridges of high-pressure in the mid-latitudes 'pancaking' the active storm track into the upper lattitudes. Since most of the swell energy in these storms will only travel the direction the fetch is pointed it means that all of the swell is also going west-to-east. For most of the eastern half of the Pacific (California, Baja, Mainland Mex, and Central America) zonal activity in the SPAC is bad for swell production -- good for an area in its path like Chile -- but bad for the rest of us.