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