Thirteen wind forces, from a sea like a mirror to hurricane force, rendered as real moving water. Pick a force or drag the wind.
Small waves becoming longer, with fairly frequent white horses.
Dust and loose paper are raised, and small branches move.
No land in any direction, so the wind has hundreds of kilometres of open water to work on. The wind direction dial changes nothing here — that is what makes this the control case.
Wind speeds are measured 10 metres above the surface. Wave heights are the probable height in the open sea, given enough time and fetch for the sea to build.
| Force | Description | Wind | Waves | Sea state |
|---|---|---|---|---|
| 0 | Calm | < 1 kn | 0.0 m waves | Sea like a mirror. |
| 1 | Light air | 1–3 kn | 0.1 m waves | Ripples with the appearance of scales, but without foam crests. |
| 2 | Light breeze | 4–6 kn | 0.2 m waves | Small wavelets, still short but more pronounced. Crests look glassy and do not break. |
| 3 | Gentle breeze | 7–10 kn | 0.6 m waves | Large wavelets. Crests begin to break, with scattered white horses. |
| 4 | Moderate breeze | 11–16 kn | 1.0 m waves | Small waves becoming longer, with fairly frequent white horses. |
| 5 | Fresh breeze | 17–21 kn | 2.0 m waves | Moderate waves taking a longer form. Many white horses, and some spray. |
| 6 | Strong breeze | 22–27 kn | 3.0 m waves | Large waves begin to form. White foam crests are extensive everywhere, with some spray. |
| 7 | Near gale | 28–33 kn | 4.0 m waves | The sea heaps up, and white foam from breaking waves blows in streaks along the wind. |
| 8 | Gale | 34–40 kn | 5.5 m waves | Moderately high waves of greater length. Crest edges break into spindrift, and foam blows in well-marked streaks. |
| 9 | Strong gale | 41–47 kn | 7.0 m waves | High waves with dense streaks of foam. Crests topple, tumble and roll over, and spray can reduce visibility. |
| 10 | Storm | 48–55 kn | 9.0 m waves | Very high waves with long overhanging crests. The sea surface looks white, and visibility is affected. |
| 11 | Violent storm | 56–63 kn | 11.5 m waves | Exceptionally high waves. The sea is completely covered in long white patches of foam, and visibility is reduced. |
| 12 | Hurricane force | 64+ kn | 14.0 m waves | The air is filled with foam and spray. The sea is completely white with driving spray, and visibility is very seriously affected. |
Francis Beaufort drew up the scale in 1805 for the Royal Navy, describing wind not by numbers but by what it did to a ship under sail. It has been tied to measured wind speeds ever since, and it is still what sailors reach for when they describe a day at sea.
The water here is the same ocean model that runs in MarineVerse Sailing Club. Wave height drives the wave spectrum, so each force builds a genuinely different sea rather than a faster version of the same one. Fetch, depth and swell all change what a given wind does to the water, so treat these as the open-sea case.