Shipping Forecast Terminology

The Shipping Forecast has to be written in as concise a manner as possible consistent with clarity. partly to conform with the requirements of the BBC to keep the forecast text to a maximum of about 330 words and partly to minimise length of NAVTEX transmissions. Words are used in a precise manner as indicated below. Although never specifically stated, the same terms will be used in all UK marine forecasts. Internationally recommended abbreviations that might be found in NAVTEX texts are on another page of this site.

These terms are defined on the Met Office pages describing the Shipping forecast. They are also to be found in Almanacs such as that published by the Cruising Association and in RYA Booklet G5. The sea areas used in UK Shipping forecasts can be found elsewhere on this site and at http://www.metoffice.gov.uk/leisure/newshiparea.html

Gale terminology

Gale timing

Visibility

Synopsis

Pressure changes

Wind

Gale warning terminology

The description of gales is in accordance with internationally agreed definitions . However, the UK Met Office also issues gales using gust criteria even when the mean speed is below gale force.
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 an intense tropical cyclone of the kind that affects the Caribbean and Eastern Pacific. In the China Sea, it would be called a typhoon. Such tropical cyclones are not experienced in British waters. In that sense, Mike Fish was correct in 1987. But, winds did reach Hurricane force! This is not a case of semantics It was a very deep low that deepened rapidly. Nevertheless. to a meteorologist it was not a hurricane.

Gale warning timing

The UK uses the following terms to indicate the expected times of onset of a gale.

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

Perhaps* Later Used when a gale is considered possible in the "later" period, but the forecaster is not sufficiently sure to issue a warning.

* Note: If there is doubt about gales in the immediate or soon category, then the forecast may say "perhaps locally" or some such phrase, BUT a warning MUST be issued,

Visibility

These are internationally agreed definitions of visibility. NOTE - these relate to the usage. Over land, for driving a vehicle, a fog would be below 200 m.

Fog 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

These terms are used in the synopsis to describe speed of movement of weather patterns

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

Reports from coastal stations and Light vessels or buoys will give the pressure and a description of how the pressure has been changing.

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

Note that wind and current use different conventions. A wind blows FROM the stated direction. Currents are described as the direction that they are going TO. We talk about and East going tide

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 E

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The UK uses the following terms to indicate the expected times of onset of a gale.
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
*Perhaps Later**		Used when a gale is considered possible in the "later" period, but the forecaster is not sufficiently sure to issue a warning.

These are internationally agreed definitions of visibility. NOTE - these relate to the usage. Over land, for driving a vehicle, a fog would be below 200 m.
Fog		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

These terms are used in the synopsis to describe speed of movement of weather patterns
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

Reports from coastal stations and Light vessels or buoys will give the pressure and a description of how the pressure has been changing.
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 that wind and current use different conventions. A wind blows FROM the stated direction. Currents are described as the direction that they are going TO. We talk about and East going tide
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 E