• home

Marine forecasts glossary

Marine forecasts contain a number of terms which are used to convey specific meanings.

Gale warnings

Gale
Winds of at least Beaufort force 8 (34–40 knots) or gusts reaching 43–51 knots
Severe gale
Winds of force 9 (41–47 knots) or gusts reaching 52–60 knots
Storm
Winds of force 10 (48–55 knots) or gusts reaching 61–68 knots
Violent storm
Winds of force 11 (56–63 knots) or gusts of 69 knots or more
Hurricane force
Winds of force 12 (64 knots or more)

Note: The term used is ‘hurricane force’; the term ‘hurricane’ on its own means a true tropical cyclone, not experienced in British waters.

Imminent
Expected within six hours of time of issue
Soon
Expected within six to 12 hours of time of issue
Later
Expected more than 12 hours from time of issue

Visibility

Very poor
Visibility less than 1,000 metres
Poor
Visibility between 1,000 metres and 2 nautical miles
Moderate
Visibility between 2 and 5 nautical miles
Good
Visibility more than 5 nautical miles

Movement of pressure systems

Slowly
Moving at less than 15 knots
Steadily
Moving at 15 to 25 knots
Rather quickly
Moving at 25 to 35 knots
Rapidly
Moving at 35 to 45 knots
Very rapidly
Moving at more than 45 knots

Pressure tendency in station reports

Rising (or falling) more slowly
Pressure rising (or falling) at a progressively slower rate through the preceding three hours
Rising (or falling) slowly
Pressure change of 0.1 to 1.5 hPa in the preceding three hours
Rising (or falling)
Pressure change of 1.6 to 3.5 hPa in the preceding three hours
Rising (or falling) quickly
Pressure change of 3.6 to 6.0 hPa in the preceding three hours
Rising (or falling) v. rapidly
Pressure change of more than 6.0 hPa in the preceding three hours
Now rising (or falling)
Pressure has been falling (rising) or steady in the preceding three hours, but at the time of observation was definitely rising (falling)

Note: For those more familiar with the millibar, 1 hPa = 1 mb

Wind

Wind direction
Indicates the direction from which the wind is blowing
Becoming cyclonic
Indicates that there will be considerable change in wind direction across the path of a depression within the forecast area
Veering
The changing of the wind direction clockwise, e.g. SW to W
Backing
The changing of the wind in the opposite direction to veering (anticlockwise), e.g. SE to NE

Sea state

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


Get updates