Jackson Parton

Sea States and Swell

SEA is the name given to the waves formed by the wind within a particular generating area. The height of the waves will depend on the length of time the wind has been blowing from a particular direction, the fetch (distance over which the waves have travelled), currents and strength of wind. Sea states are measured in accordance with a scale as follows:

Code
0
1
2
3
4
5
6
7
8
9

Calm — glassy smooth
Calm — rippled surface
Smooth wavelets
Slight
Moderate
Rough
Very rough
High
Very high
Phenomenal

Height in metres
0
0-0.1
0.1-0.5
0.5-1.25
1.25-2.5
2.5-4.0
4.0-6.0
6.0-9.0
9.0-14.0
Over 14.0

SWELL is the wave motion caused by a meteorological event (such as a storm). As the swell moves away from the generating area it will die down but retain its wavelength and speed. Swell can be measured as follows:

Length
Short
Average
Long

Metres
0-100
100-200
Over 200

Height
Low
Moderate
Heavy

Metres
0-2
2-4
Over 4