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Swell period & how it affects waves

Swell period is the amount of time in seconds between 2 waves & is often categorized as short (< 10s), medium (10-14s), or long period (> 14s).

While this definition isn’t all that helpful, knowing how it affects waves at your local break is.

Why? Because a 3 ft swell at 7s, 12s, & 18s will each produce a different sized wave with varying quality.

Shorter period swells (i.e. “wind swells”) produce shorter, peakier waves & have less energy, fewer waves to a set, shorter lulls between sets, & will produce smaller waves than a longer period swell of equal height.

Longer period swells (i.e. “groundswells”) produce longer waves & have more energy, more waves to a set, longer lulls between sets, & will produce bigger waves than a shorter period swell of equal height.

Longer period swells are often preferred & result in a higher quality wave, but longer isn’t necessarily better as it depends on what works best for your local break.

For example, point breaks are a great place for longer period swells as they allow the long lines to break evenly from left to right or right to left.

Contrary to a beach break where those long lines need to be “broken up” or “refracted” in some way with well-defined sandbars or another type of bathymetric (ocean floor) interruption, which is why some beach breaks can handle long periods & others leave you with nothing but closeouts.

A 3 ft swell at 7s, 12s, & 18s will each produce a different sized wave with varying quality.

The opposite is true for shorter period swells. At a point break, a shorter period swell won’t span the full length of the point & you’ll end up with multiple sections not allowing the point to do its thing.

At a beach break though, there’s a better chance of having nice, peaky waves with fewer closeouts & less need for solid sandbars.

These are just general guidelines though & every spot handles various swell periods differently, so what’s considered the ideal period is relative to your local break (not to mention other variables).

💬 Have you noticed what periods work best for you local break?

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