The Wave Period and time between swells is provided by and NOAA.
Check the peak wave period for the next seven days. Select your surf forecast region:



The technical notice made by NOAA:

The peak period identifies either the period (the time between waves) associated with the locally generated wind sea (in cases with strong local winds) or the dominant wave system (swell) that is generated elsewhere.

Note that this peak period field shows discontinuities.

These discontinuities can loosely be interpreted as swell fronts, although in reality many swell systems overlap at most locations and times.

NOAA - National Oceanic and Atmospheric Administration