Swell height is the vertical distance (meters) between any swell crest and the succeeding swell wave trough.
Swell Period is the time (usually measured in seconds) that it takes successive swell wave crests or troughs pass a fixed point. If more than one swell is present, this is the period of the swell containing the maximum energy.
This is the direction that the swells are coming from. Swells are waves not produced by the local wind and come in at a higher period (longer wave length) than waves produced by the local wind. Direction is given on a 16 point compass scale. The units are degrees from true North, increasing clockwise, with North as 0 (zero) degrees and East as 90 degrees.
Note: MM or -99 denote missing data. Less than half of our buoy stations report directional wave data because of the costs involved with additional instrumentation. NO indicates that no swells could be determined.
Significant Wave Height
This is the estimated average height of the highest one-third of the swells. It is estimated from determining how the wave energy is distributed among various periods (frequencies), determining if a separate swell energy peak exists, and then, picking a frequency to separate swell and wind-waves. The swell height is calculated from the wave energies below the separation frequency.
Wave steepness is the ratio of wave height to wave length and is an indicator of wave stability. When wave steepness exceeds a 1/7 ratio; the wave becomes unstable and begins to break.
Average Wave Period
Average Wave Period is the average period (seconds) of the highest one-third of the wave observed during a 20 minute sampling period.