Wave period is the number of seconds between successive wave crests passing a fixed point. NDBC buoys report it as "dominant period" in seconds. Period is a strong indicator of wave quality and origin: long-period waves come from distant storms (groundswell), short-period waves are locally generated (windswell).

Groundswell is a wave train with a period of 10 seconds or more. These waves originate from storms hundreds or thousands of miles away — the long ocean journey filters out short-period chop, leaving clean, organized energy. Groundswells produce the cleanest, most powerful surf and the longest rides.

Windswell is locally-generated waves with periods below 7 seconds. They form from current or very recent wind blowing across the surface. Windswell is choppy, short-lived, and disorganized. Lakes and inland seas (Great Lakes, Sea of Cortez) only ever produce windswell because they lack the open-ocean fetch required for groundswell.

Does longer period mean bigger waves?

Not exactly — but long-period waves carry far more energy per foot of height than short-period waves. A 3-foot 14-second wave will break with more force than a 4-foot 6-second wave. Long-period waves are also more selective about where they break (they need the right bathymetry to "feel" the bottom), so they often deliver bigger surf at deep-water reef breaks than at shallow beach breaks.

Wave Period Explained — Groundswell vs Windswell

Wave Period Explained — Groundswell vs WindswellWhat "period" means on a buoy reading. Short-period (sub-6s) waves are local windswell — choppy. Long-period (10s+) waves are groundswell from distant storms — clean and powerful. The threshold matters more than wave height for surf quality.

Frequently asked questions

What is wave period?: Wave period is the number of seconds between successive wave crests passing a fixed point. NDBC buoys report it as "dominant period" in seconds. Period is a strong indicator of wave quality and origin: long-period waves come from distant storms (groundswell), short-period waves are locally generated (windswell).
What is groundswell?: Groundswell is a wave train with a period of 10 seconds or more. These waves originate from storms hundreds or thousands of miles away — the long ocean journey filters out short-period chop, leaving clean, organized energy. Groundswells produce the cleanest, most powerful surf and the longest rides.
What is windswell?: Windswell is locally-generated waves with periods below 7 seconds. They form from current or very recent wind blowing across the surface. Windswell is choppy, short-lived, and disorganized. Lakes and inland seas (Great Lakes, Sea of Cortez) only ever produce windswell because they lack the open-ocean fetch required for groundswell.
Does longer period mean bigger waves?: Not exactly — but long-period waves carry far more energy per foot of height than short-period waves. A 3-foot 14-second wave will break with more force than a 4-foot 6-second wave. Long-period waves are also more selective about where they break (they need the right bathymetry to "feel" the bottom), so they often deliver bigger surf at deep-water reef breaks than at shallow beach breaks.

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