Surf Glossary

Every term you see on a Swell Intel forecast, explained in plain English. Use this glossary to decode your forecast, learn how waves work, and make better decisions before you paddle out.

B

Breaking Wave Height

The actual size of waves as they break at the shore, calculated from offshore swell and spot-specific bathymetry.

The underwater topography of the seafloor, which controls how waves shoal, refract, and break.

A surf break that forms over a sand bottom. Shifts constantly with tides, swells, and currents.

C

Cross-shore Wind

Wind blowing parallel to the coastline. Clean at some spots, bumpy at others.

D

A surf session at or just after sunrise — often the cleanest conditions of the day.

G

Well-organized, long-period swell generated by distant storms. Produces the cleanest, most powerful surf.

M

Mean Absolute Error (MAE)

A forecast accuracy metric: the average difference between predicted and observed values.

N

NOAA's global numerical weather prediction model — the primary input to Swell Intel wave forecasts.

A moored ocean buoy operated by NOAA that measures real-time wave height, period, direction, and wind.

O

Wind blowing from the land out to sea — typically the cleanest condition for surf.

Wind blowing from the sea toward land — typically makes surf choppy and sloppy.

P

A surf break where waves peel along a headland, producing long, consistent rides.

R

A surf break that forms over a reef bottom. Produces consistent, powerful waves in a predictable location.

A narrow channel of water flowing seaward from the beach. Useful for paddling out but dangerous to swimmers.

S

The time between successive wave crests, measured in seconds. Longer periods mean more powerful, better-organized swell.

Swell Direction

The compass direction that swell is traveling from, used to determine which spots will receive wave energy.

An underwater ridge of sand that shapes how waves break at beach breaks.

T

Transect Bearing

The compass direction a surf spot faces the open ocean, used to match swells to each break.

The periodic rise and fall of sea level caused by lunar and solar gravity. Affects how and where waves break.

W

Short-period swell generated by local winds. Usually choppy and short-lived.