Module 13 of 17
Meteorology
Shipping forecasts, Beaufort scale, weather systems, and broadcast meteorological information.
Weather and the Sailor
Weather is one of the most critical factors in safe seamanship. Wind strength and direction determine sailing conditions, sea state affects comfort and safety, and visibility impacts navigation. As a Day Skipper, you need to obtain, interpret, and act on weather forecasts before and during every passage.
Key Points
- Check the weather forecast BEFORE every passage
- Monitor conditions and forecasts throughout the passage
- Be prepared to change plans if weather deteriorates
The Beaufort Scale
The Beaufort Scale describes wind force from 0 (calm) to 12 (hurricane). It links wind speed in knots to the conditions you can observe at sea, such as wave size, whitecaps, spray, and whether a small yacht should reef or seek shelter.
For Day Skipper purposes, the most useful range is Force 3 to Force 7. Force 3-4 is often comfortable sailing, Force 5 is fresh and more demanding, Force 6 normally means reefing early, and Force 7 or above is near gale or gale conditions where most training and family cruising yachts should be in harbour.
Forecasts normally give wind direction and Beaufort force, not just knots. Learning the force numbers helps you turn a shipping forecast into practical decisions about passage timing, sail plan, crew comfort, and safe harbour options.
Key Points
- Force 0: Calm (< 1 knot), sea like a mirror
- Force 3: Gentle breeze (7–10 kn), large wavelets
- Force 4: Moderate breeze (11–16 kn), small waves, whitecaps
- Force 5: Fresh breeze (17–21 kn), moderate waves, many whitecaps
- Force 6: Strong breeze (22–27 kn), large waves, spray. Reef sails.
- Force 7: Near gale (28–33 kn), sea heaps up. Seek shelter.
- Force 8+: Gale and above. Dangerous for small craft.
| Force | Name | Knots | mph | km/h | Sea state / sailing note |
|---|---|---|---|---|---|
| 0 | Calm | <1 | <1 | <1 | Sea like a mirror |
| 1 | Light air | 1-3 | 1-3 | 1-5 | Ripples; little steerage under sail |
| 2 | Light breeze | 4-6 | 4-7 | 6-11 | Small wavelets; gentle sailing |
| 3 | Gentle breeze | 7-10 | 8-12 | 12-19 | Large wavelets; comfortable sailing |
| 4 | Moderate breeze | 11-16 | 13-18 | 20-28 | Small waves and whitecaps; good sailing |
| 5 | Fresh breeze | 17-21 | 19-24 | 29-38 | Moderate waves; many yachts reef soon |
| 6 | Strong breeze | 22-27 | 25-31 | 39-49 | Large waves and spray; reef early |
| 7 | Near gale | 28-33 | 32-38 | 50-61 | Sea heaps up; seek shelter |
| 8 | Gale | 34-40 | 39-46 | 62-74 | Moderately high waves; dangerous for small craft |
| 9 | Strong gale | 41-47 | 47-54 | 75-88 | High waves; severe conditions |
| 10 | Storm | 48-55 | 55-63 | 89-102 | Very high waves; avoid being at sea |
| 11 | Violent storm | 56-63 | 64-72 | 103-117 | Exceptional waves; dangerous survival conditions |
| 12 | Hurricane force | 64+ | 73+ | 118+ | Air filled with spray; extreme danger |
Common Questions
What wind speed is Beaufort Force 4?
Beaufort Force 4, a moderate breeze, is 11-16 knots, about 13-18 mph or 20-28 km/h.
What wind speed is gale force?
Gale force starts at Beaufort Force 8, which is 34-40 knots. Force 7 is a near gale.
What Beaufort force should a Day Skipper reef at?
Reefing depends on boat and crew, but Force 5 often prompts early preparation and Force 6 usually requires reefed sails on a cruising yacht.
4 more sections in this module — full lesson, quizzes, flashcards, and interactive tools with Day Skipper Revision (£4.99).
Unlock the complete module
Get every section, quizzes, spaced-repetition flashcards, and mock exams — one-time purchase.