Getting & Interpreting Forecasts

Before leaving the dock, every skipper needs a forecast — and knowing where to get one matters as much as knowing how to read it. The classic source is VHF radio: coastguard and weather services broadcast at scheduled times on set channels. In the US, NOAA Weather Radio runs continuously on channels like WX1–WX7; in the UK, the Coastguard broadcasts the Shipping Forecast areas after an announcement on Channel 16. These give you wind (direction and force), sea state, visibility, and weather in a fixed, spoken order — so you can jot it down in a table.

For a richer picture, skippers download GRIB files (GRIdded Binary). A GRIB is raw computer-model data — wind, pressure, waves — mapped onto a grid of points and shown as arrows or colours on a chart plotter or app. The key thing to remember: a GRIB is model output, not a human forecast. No meteorologist has looked at it, so it can miss local effects like sea breezes or thunderstorms, and it's only as good as the model behind it.

Wind on forecasts is described by where it comes FROM, using the Beaufort scale (force 0–12) or knots. A "southwesterly force 5" means wind blowing from the southwest at roughly 17–21 knots. Watch for the words veering (wind direction shifting clockwise, e.g. S→W) and backing (shifting anticlockwise, e.g. S→SE) — recall from earlier cards how wind drives the waves and surface currents you'll actually feel.

The golden rule is to cross-check sources. If the VHF forecast, a GRIB download, and the barometer trend all agree, you can trust the picture; if they disagree, treat conditions as uncertain and reduce your exposure.