Sea States

Living in Jersey we are fortunate that the Jersey Met Office issues regular and accurate weather forecasts, including shipping forecasts.  As I sit here writing this there is howling gale blowing outside with trees down, roads closed and coastal floodingWhat is unusual is the Sea State, I can’t remember the last time that I saw “very high” given as the sea state in Channel Island waters.
As with most weather phenomena there are clear definitions. Most of us are probably familiar with definitions of some of the lesser sea states but the last couple are rarely seen in our waters:
Smooth:        Wave height less than 0.5 m
Slight:            Wave height of 0.5 to 1.25 m
Moderate:     Wave height of 1.25 to 2.5 m
Rough:          Wave height of 2.5 to 4.0 m
Very rough:   Wave height of 4.0 to 6.0 m
High:              Wave height of 6.0 to 9.0 m
Very high:      Wave height of 9.0 to 14.0 m
Phenomenal: Wave height more than 14.0 m

Forecast from 7pm Tuesday until 7pm Wednesday

Wind: Southeast to south gale 8 to severe gale 9 with gusts to 65kt, temporarily decreasing 7 to gale 8 around midnight, then veering south to southwest gale 8 to severe gale 9, perhaps locally storm 10 mid Channel for a time in the morning, veering southwest to west later.
Sea state: Rather rough to rough becoming very rough to high, locally very high for a time from late morning.
Weather: Rain clearing around midnight to squally showers Risk of hail and thunder.
Visibility: Moderate to poor in rain and in showers later, otherwise good.
Swell: Confused. Total waves becoming 20 ft in the south and 35ft in the north for a time.
 Corbiere Lighthouse.  Wind calm, 5 hours after high water
 Corbiere Lighthouse.  SSE Force 4 High Water +2
Corbiere Lighthouse.  SSE Force 8 gusting 48 knots.  High water + 2

It is difficult to imagine what it is like out there tonight with stronger winds, a bigger swell and a larger tide.