Surf forecast glossary — every term explained

Every hobby builds a wall of jargon, and surfing built two — one for the water, one for the forecast. Here’s the second wall, dismantled term by term. (The first wall you learn the fun way.)

The swell itself

Swell — wind energy that has travelled away from the storm that made it, organised into smooth, powerful lines. Swell is what surfers wait for; local wind makes something else entirely.

Groundswell — long-period swell (roughly 12 seconds and up) from a distant storm. Travels thousands of kilometres with little energy loss, wraps around points, and lights up spots that miss ordinary waves. The good stuff.

Windswell — short-period swell (under ~9 seconds) generated by local wind. Stacky, disorganised, quick to fade. Better than flat; barely.

Set — a group of larger waves arriving together. Lull — the quiet minutes between sets. Sets usually count 2–5 waves; on long-period days they can be 5 minutes apart. Patience through lulls is a core surfing skill.

Period (seconds) — time between waves. Bigger period = more energy = deeper water bends the wave sooner = bigger, faster surf. The single best quality indicator on any forecast.

Significant wave height — the official measure of swell size: the average height of the tallest third of waves. Individual sets will be up to twice that height, which is why a “2 m” forecast can serve up head-and-a-half monsters.

Direction & the spot

Swell direction — the compass bearing the swell travels from (northwest swell moves toward the southeast). Each spot has a swell window — the directions its coastline exposes it to.

Refraction — as swell enters shallow water, it bends toward the bank or point, focusing energy. Why point breaks peel so perfectly and why the same swell is flat one beach over.

Shoaling — the amplification of a wave as it feels the bottom. Nazaré is shoaling weaponised by a canyon.

Offshore / cross-shore / onshore — wind blowing from land to sea (holds faces open), along the coast (choppy but workable), or from sea to land (closeouts). All wind directions are quoted from — “offshore E 15 km/h” means wind blowing from the east at 15 km/h.

Sea breeze — the afternoon onshore that most coasts develop as land heats up. The reason dawn patrol exists.

Santa Ana / Mistral / Tramontana / Chergui — famous local offshore winds that turn good days perfect. Each region has one; locals will happily tell you theirs.

The wave and the ride

Peak — the spot where a wave first starts breaking; the deepest position. Right of way belongs to the surfer nearest the peak.

Shoulder — the unbroken part of the wave outside the whitewater. Take off on the shoulder and you’re behind the peak — polite, but late.

Closeout — a wave that breaks all at once along its length instead of peeling. “Beach break closing out” is forecast-speak for “manage expectations”.

Section — part of a wave’s face. A wave “opens up” on good sections and “ shuts down” on bad ones.

Barrel / tube — the hollow part of a barreling wave. The reason surfers forgive everything else.

Channel — the deeper path beside a breaking area, used to paddle out without fighting every wave.

Duck-dive — pushing your board under an incoming wave to get out. Turtle-rolling is the longboard version: flip, hold, flip back.

Rip current — the river of water returning seaward through the impact zone. It looks scary and calm; it is your free ride out if you stay on your board and don’t fight it. Learn to spot them before you need to.

Reading our pages

• Rating (0–100) — our per-hour quality score combining size, period and offshore wind for that exact spot.
• Stars — the same score, squinted at.
• Period line — the amber curve on the wave chart (right axis, seconds).
• Green/blue/red wind bars — offshore / cross-shore / onshore for that spot specifically.
• Tide curve — predicted water level from NOAA stations; the steep parts are when the tide is running fastest.

Twenty minutes with this glossary and a week of comparing forecast to reality will teach you more than a year of guessing. Pair it with how to read a surf forecast, then pick a spot and test yourself. That’s the whole idea.