Callum MacLeod
A language worth learning
The shipping forecast has a rhythm many of us know by heart: the sea areas, the measured numbers, the words that sound almost like poetry. But every one of those words is doing a job. The bulletin is a technical document, and its phrases are standardised and chosen to tell you something specific about wind, visibility and sea state. Learn the vocabulary and you can judge a day before you leave the house.
Two forms matter most to coastal users. The shipping forecast covers the large sea areas around our coasts. The inshore waters forecast covers a narrower band, generally within about twelve nautical miles of the shore, and adds detail that matters when you are close in.
Wind: the heart of the forecast
Wind comes first because it drives almost everything else. Speed is quoted in knots and tied to the Beaufort scale. A moderate breeze, Force 4, is 11 to 16 knots; a fresh breeze, Force 5, is 17 to 21; a strong breeze, Force 6, is 22 to 27. At Force 7 you have a near gale, 28 to 33 knots, and Force 8 is a gale at 34 to 40. Beyond that come severe gale, storm, violent storm and, at Force 12, hurricane force.
Direction arrives with a verb that tells you how it will change. Veering means the wind will shift clockwise, say from south-west to west or north-west. Backing means the opposite, anticlockwise. Both matter enormously on a coast that faces one way: a veer can turn a friendly offshore breeze into an onshore one within an hour or two, and the sea responds quickly.
Timing has its own code. Imminent means within six hours, soon means six to twelve hours, and later means after twelve. Words such as occasionally, at times, at first and squally add texture, warning that the average figure will not be the whole story.
Visibility, weather and the quiet hazards
Visibility is graded with the same discipline, and it is the term most often ignored by people who only go out in fine weather. Fog means less than a kilometre; mist sits just above that. Forecasts then run through poor, moderate, good, very good and excellent, each with a range attached. "Visibility moderate to poor" tells you how quickly you will lose sight of a headland, a buoy or a companion on the path.
The weather description is brief but telling. Showers are intermittent; frequent showers mean the gaps between them are short. Thundery signals squalls and sudden shifts in wind. Drizzle and rain are graded by persistence rather than intensity, and occasional genuinely means less than you might fear.
Sea state and swell
Sea state is given in words matched to wave height: smooth, slight, moderate, rough, very rough, high, very high and phenomenal. A slight sea is under about a metre of wave; moderate runs to roughly two and a half metres. In a small boat, or even waist-deep at a favourite swimming spot, those are very different days.
The important subtlety is that sea state and swell are not the same thing. A forecast may offer "slight or moderate" while a long swell rolls in from a distant weather system, arriving with almost no local wind to explain it. Allow for that on a flat calm day, particularly at a harbour entrance or over a shallow bar.
Reading the inshore waters forecast
The inshore waters forecast is the one most coastal users should reach for. It is issued several times a day and gives wind, sea state, weather and visibility, followed by an outlook for the next period, so you can see whether conditions are improving or deteriorating.
Read it in a fixed order and you will miss nothing:
- Wind first. Speed, direction, and whether it is veering or backing. A calm forecast with a strong veer is not a calm day.
- Then sea state. This is what your boat, kayak or swimming spot will actually feel, whatever the wind is doing overhead.
- Then visibility. Fog matters more than rain for anyone navigating a rocky shore or a narrow channel.
- Then weather and the outlook. Squalls and a change of air mass often tell you more than the average numbers.
Timing, tides and the sea breeze
A forecast is a snapshot of a moving system, so set it against the tide. Wind against tide makes a short, steep sea in an estuary or channel; wind with tide carries you along but can make a shallow bar unpredictable. Know your local tide times and notice how the strongest wind is timed against high and low water.
On calm, sunny days, watch for the sea breeze. As the land warms, air moves onshore and can build to a steady Force 4 or 5 by mid-afternoon, even when the general forecast suggests almost nothing. It arrives as a dark line on the water with a sudden drop in temperature. Coastal walkers feel it as a chill on a hot day; sailors treat it as a reason to reef early rather than late.
The forecaster's vocabulary is, in the end, a courtesy. It gives you the shape of the day in a few words, and it rewards anyone who takes the trouble to learn it.
