The Beaufort scale is an empirical measure for describing wind intensity based on observed sea conditions and is the primary used international scale for wind strength measurement in the marine environment.
| Beaufort wind scale | Mean Wind Speed | Limits of wind speed | Wind descriptive terms | Probable wave height | Probable maximum wave height | Seastate | Sea descriptive terms | ||
|---|---|---|---|---|---|---|---|---|---|
| Knots | ms-1 | Knots | ms-1 | in metres | in metres | ||||
| 0 | 0 | 0 | <1 | <1 | Calm | – | – | 0 | Calm (glassy) |
| 1 | 2 | 1 | 1-3 | 1-2 | Light air | 0.1 | 0.1 | 1 | Calm (rippled) |
| 2 | 5 | 3 | 4-6 | 2-3 | Light breeze | 0.2 | 0.3 | 2 | Smooth (wavelets) |
| 3 | 9 | 5 | 7-10 | 4-5 | Gentle breeze | 0.6 | 1.0 | 3 | Slight |
| 4 | 13 | 7 | 11-16 | 6-8 | Moderate breeze | 1.0 | 1.5 | 3-4 | Slight – Moderate |
| 5 | 19 | 10 | 17-21 | 9-11 | Fresh breeze | 2.0 | 2.5 | 4 | Moderate |
| 6 | 24 | 12 | 22-27 | 11-14 | Strong breeze | 3.0 | 4.0 | 5 | Rough |
| 7 | 30 | 15 | 28-33 | 14-17 | Near gale | 4.0 | 5.5 | 5-6 | Rough-Very rough |
| 8 | 37 | 19 | 34-40 | 17-21 | Gale | 5.5 | 7.5 | 6-7 | Very rough – High |
| 9 | 44 | 23 | 41-47 | 21-24 | Severe gale | 7.0 | 10.0 | 7 | High |
| 10 | 52 | 27 | 48-55 | 25-28 | Storm | 9.0 | 12.5 | 8 | Very High |
| 11 | 60 | 31 | 56-63 | 29-32 | Violent storm | 11.5 | 16.0 | 8 | Very High |
| 12 | – | 64+ | 33+ | Hurricane | 14+ | – | 9 | Phenomenal | |
* Notes
- These values refer to well-developed wind waves of the open sea.
- The lag effect between the wind getting up and the sea increasing should be borne in mind.
Images
