glossaire des prévisions marines (anglais)

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