ya, your about right. This is my call: 6 @ 7 seconds, would be around chest high, maybe some bigger shoulder high peaks. I would call 6 @ 12 to be solid head high, with some 1-3' OH sets. Also, remember, it depends on the break. For example a reef break in Puerto Rico will go bigger on the long period swells than most breaks on the east coast for the same swell. The longer the period, the more variability you will see between different breaks due to the refraction process as the swell feels the bottom further off the coast. The short period swells are going to more peaky and overall weaker.
swell period is the time it takes for the wave to traverse one wavelength. The wavelength is the distance between adjacent crests or adjacent troughs. It would be best to describe with illustrations, but I"m not that motivated at the moment. swell period and swell height will both increase with 3 factors: - wind speed - wind duration - wind fetch (the distance over which the wind blows). Most people think that it depends on how far away the storm is, but this is not true, it just so happens that the fetch and duration are generally higher with storms out in the middle of the ocean. Take a look at a buoy when it is blowing 40+ directly offshore. You will see how high the periods get in such a short distance, because of how strong the winds are.
