Module 13 - Meteorology
Shipping Forecast Terminology
What you will learn
Decode a Shipping Forecast phrase into wind, timing, weather, visibility and sea-state implications using the stated issue time.
Shipping Forecast words have defined meanings. Timing terms run from the forecast issue time, while wind direction names where the wind comes from.
The Shipping Forecast covers 31 sea areas around and approaching the British Isles. Each issue contains gale-warning information, a general synopsis and area forecasts. Start with the printed issue and validity times; a recording or cached page can otherwise sound current when it is not.
Veering is a clockwise wind-direction change; backing is anticlockwise. ‘Imminent’ means within six hours of issue, ‘soon’ means six to 12 hours from issue, and ‘later’ means more than 12 hours from issue within the forecast period.
The official visibility categories are very poor below 1,000 metres, poor from 1,000 metres to 2 nautical miles, moderate from 2 to 5 nautical miles and good above 5 nautical miles. Fog may be the weather, but ‘very poor’ is the visibility category. Smooth sea is below 0.5 m, moderate is 1.25–2.5 m and rough is 2.5–4 m.
Worked example
A 0500 UTC issue says Force 6 ‘soon’, and the exposed leg is planned for 1400.
- 10500 + 6 hours = 1100; 0500 + 12 hours = 1700.
- 2The planned 1400 leg lies inside the ‘soon’ window.
- 3Plan for the increase, then verify the latest issue, warnings and observations before departure.
Sense check: The arithmetic locates the forecast window; it does not remove forecast uncertainty or local effects.
| Term | Defined meaning | Practical use |
|---|---|---|
| Veering / backing | Clockwise / anticlockwise direction change | Reassess exposure and point of sail |
| Imminent | Within 6 hours of issue | May affect the early passage |
| Soon | 6–12 hours after issue | Compare with the route timetable |
| Later | More than 12 hours after issue | Check where the vessel will then be |
| Very poor | Visibility below 1,000 m | Prepare for restricted-visibility workload |
| Poor / moderate / good | 1,000 m–2 M / 2–5 M / above 5 M | Relate range to lookout and pilotage |
Decode the sequence before applying it
At 0500 UTC an issue says: ‘Southwest 4 or 5, increasing 6 soon, veering west later. Moderate. Rain then showers. Moderate or good, occasionally poor.’
1. Anchor the clock
‘Soon’ is approximately 1100–1700 UTC. ‘Later’ begins more than 12 hours after the 0500 issue.
2. Decode wind
The wind comes from the southwest, increases to Force 6, then changes clockwise towards west.
3. Decode conditions
The sea is 1.25–2.5 m; rain gives way to showers; visibility may occasionally enter the poor band.
4. Apply
Compare that timing with exposed legs, opposing tide, lee shores, harbour approaches and alternatives.
Sense check: If the 0500 issue is heard from a recording at 0900, ‘soon’ still runs from 0500, not from 0900.
Common mistake or limitation
- Reading a westerly as wind travelling west; forecast direction is where it comes from.
- Starting ‘soon’ or ‘later’ from the time the bulletin was heard rather than its issue time.
- Calling below 1,000 metres the ‘fog’ visibility category; the official category is ‘very poor’.
Recap
- Decode timing from the issue time and wind from the direction it comes.
- Below 1,000 metres is ‘very poor’ visibility in the marine glossary.
- Apply the sequence to the route rather than treating each word in isolation.
Optional quick check
Section 3 of 15
A 0600 issue says an increase is expected ‘soon’. Which window applies?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
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