Surf Forecasting Glossary

Last updated 2026-04-20

Answer: The six surf forecasting terms surfers ask about most — groundswell vs. windswell, surf period, offshore vs. onshore wind, swell direction, clean-up sets, and the two ways surf height is measured (Hawaiian vs. face). Each page below is a plain-English answer, with the specific NDBC buoy fields that carry that signal.

Surf forecasts are full of shorthand. These pages unpack the terms surfers actually see on buoy reports and forecast apps.

Groundswell vs. windswell

Groundswells come from distant storms, carry longer periods, and produce more organized waves. Windswells are generated by local wind and arrive short-period and disorganized.

Surf period (seconds between waves)

Period is the time in seconds between passing wave crests. Longer periods mean more wave energy — and usually, better surf. Why 14s matters more than 6ft at 8s.

Offshore vs. onshore wind

Offshore wind blows from land out to sea and cleans up wave faces. Onshore wind blows sea-to-shore and flattens them. Why surfers watch wind more than swell.

Swell direction

The compass bearing a swell is coming from. West-facing coastlines want west swells; east-facing breaks want east. How swell-direction angle affects a spot.

Clean-up set

A group of waves noticeably larger than the surrounding sets — big enough to break outside the lineup and "clean up" surfers sitting on the inside. Why they happen and how to spot one.

Surf height: Hawaiian vs. face

Hawaiian measures the back of the wave (typically half the face height). Face height measures the front the surfer is actually riding. The same day is "4ft Hawaiian" or "8ft face".