| 0 | Calm | 0–1 kn | 0 m | Sea like a mirror. |
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| 1 | Light air | 1–3 kn | 0.1 m (max 0.1 m) | Ripples like scales, no foam crests. |
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| 2 | Light breeze | 4–6 kn | 0.2 m (max 0.3 m) | Small wavelets with glassy crests that do not break. |
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| 3 | Gentle breeze | 7–10 kn | 0.6 m (max 1 m) | Large wavelets. Crests begin to break; scattered white horses. |
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| 4 | Moderate breeze | 11–16 kn | 1 m (max 1.5 m) | Small waves becoming longer; fairly frequent white horses. |
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| 5 | Fresh breeze | 17–21 kn | 2 m (max 2.5 m) | Moderate waves, many white horses, chance of some spray. |
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| 6 | Strong breeze | 22–27 kn | 3 m (max 4 m) | Large waves form; white foam crests everywhere; probably some spray. |
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| 7 | Near gale | 28–33 kn | 4 m (max 5.5 m) | Sea heaps up; white foam from breaking waves blows in streaks. |
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| 8 | Gale | 34–40 kn | 5.5 m (max 7.5 m) | Moderately high waves; crests break into spindrift; foam in well-marked streaks. |
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| 9 | Severe gale | 41–47 kn | 7 m (max 10 m) | High waves; dense foam streaks; crests topple and roll over; spray may reduce visibility. |
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| 10 | Storm | 48–55 kn | 9 m (max 12.5 m) | Very high waves with long overhanging crests; the sea looks white; heavy tumbling. |
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| 11 | Violent storm | 56–63 kn | 11.5 m (max 16 m) | Exceptionally high waves; sea covered in long white patches of foam. |
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| 12 | Hurricane force | 64+ kn | 14 m+ | Air filled with foam and spray; sea completely white; visibility very seriously affected. |
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