Every surf break has an exposure window — the range of compass angles that actually reach it. Some breaks are extremely narrow (a cove that only opens to a 20° window); others are wide open (a long beachbreak that sees anything from W to NW). Local surfers memorize the window; newcomers can figure it out by watching which forecasts produce surf and which don’t.
NDBC buoys report two wave-direction fields:
Buoys like NDBC station 46042 (Monterey Bay) and NDBC station 44025 (Long Island, NY) both publish MWD alongside height and period.
Waves don’t just travel in straight lines once they approach the coast. Long-period swell in particular refracts around headlands and wraps into bays. A 280° swell at an open ocean buoy might hit a south-facing break at 230° after wrapping. This is why two breaks a mile apart can have totally different surf on the same swell.
Swell direction is one of seven parameters LazySurfer’s Similarity Score compares against your logged sessions. The on-device ML model learns which swell-direction windows produce your best sessions at each spot and weights future forecasts accordingly — you don’t need to memorize the exposure window, the model does.