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Marine forecasts glossary

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

Gale warnings

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
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.

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


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

Movement of pressure systems

Moving at less than 15 knots
Moving at 15 to 25 knots
Rather quickly
Moving at 25 to 35 knots
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 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
The changing of the wind direction clockwise, e.g. SW to W
The changing of the wind in the opposite direction to veering (anticlockwise), e.g. SE to NE

Sea state

Wave height less than 0.5 m
Wave height of 0.5 to 1.25 m
Wave height of 1.25 to 2.5 m
Wave height of 2.5 to 4.0 m
Very rough
Wave height of 4.0 to 6.0 m
Wave height of 6.0 to 9.0 m
Very high
Wave height of 9.0 to 14.0 m
Wave height more than 14.0 m

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