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Surfline forecaster and buoy wonder Adam Wright responds:

It depends on the buoys and the amount of energy in each swell.

NOAA buoys generally give just the surface wind speed and the primary swell period, which is whatever energy band happens to be the biggest. The public data that most people can access does not show swell direction or break the incoming energy into its seperate periods. (That data is out there... Surfline has had access to it for a number of years and we are now offering it in our premium services but it is one of the only places to get it).

Scripps Buoys on the other hand do give both the swell direction and if you click through the link to the individual buoy you can see the full spectrum of incoming energy.

So to answer your question: If you are listening to the weather radio or looking at the NOAA buoys expect to see/hear the primary swell period... so if the wind swell has the most energy you will hear that one, if the ground swell is bigger you should hear it instead. Remember that the swell height they give is from all of the swells combined not just one or the other. (IE: 14' at 10-seconds could be made up of 10' of 10-second wind swell and 4' of 18-second ground swell).