Wave Period

Wave period is the time, in seconds, between two successive wave crests passing a fixed point or the vessel. In marine forecasts it describes the spacing and energy of waves, alongside height and direction. A 12-second sea is generally longer, more organised swell; a 5-second sea is short, steep chop.

For boaters, period often explains comfort and risk better than height alone. Short-period waves can cause pounding, spray, reduced speed and higher fuel burn, while long-period swell may be powerful at harbour entrances or over shoal water. Assess it with Wave Height, Sea State and Wind against Current.

PredictWind wave forecasts and GRIB downloads show wave period for planning coastal hops and offshore passages. In Weather Routing or Departure Planning, combining period with swell direction, wind and current helps avoid slamming angles, optimise arrival times and choose safer sea room.