Swell Period

Swell period is the time it takes for two wave crests to pass a fixed point, measured in seconds. It is one of the most important numbers in a surf forecast because it reveals how much energy a swell carries. Short-period swell (under 8 seconds) is usually wind-generated chop that fades quickly as it nears shore. Medium-period swell (9–12 seconds) produces consistent, fun surf at most breaks. Long-period groundswell (13 seconds and above) has traveled thousands of miles, carries enormous energy, and wraps into coves, points, and reefs that smaller swells never reach. A 3ft swell at 16s can easily produce bigger, more powerful waves than a 5ft swell at 7s.