Beaufort Wind Scale
Beauforts description and observation of wind and wind velocity
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The Beaufort wind scale, which is used to describe the force of the wind, was invented by Admiral Beaufort in 1805. With some experience in the use of the scale the wind force can be estimated with reasonable accuracy.
The Beaufort wind scale is divided into series of values, from zero for calm winds, up to twelve and above for hurricanes. Each value represents a specific range and a classification of wind velocity with an accompanying descriptions of the effects on surface features.
| Beaufort No. | Description of wind | Observation | Wind speed | |||
| m/s | mph | knots | ft/min | |||
| 0 | Calm | Smoke rises vertically | 0 - 0.15 | 0 - 0.3 | 0 - 0.5 | 0 - 25 |
| 1 | Light Air | Direction of wind shown by smoke drift but not by vanes | 0.15 - 2.7 | 0.3 - 6 | 0.5 - 3 | 25 - 525 |
| 2 | Light Breeze | Wind felt on face, leaves rustle, ordinary vanes moved by wind | 2.7 - 3.6 | 6 - 8 | 3 - 7 | 525 - 700 |
| 3 | Gentle Breeze | Leaves and small twigs in constant motion, wind extends light flag | 3.6 - 7.2 | 8 - 16 | 7 - 10 | 700 - 1400 |
| 4 | Moderate Breeze | Raises dust and loose paper, small branches moved | 7.2 - 8.9 | 16 - 20 | 10 - 15 | 1,400 - 1,800 |
| 5 | Fresh Breeze | Small trees in leaf begin to sway | 8.9 - 12.5 | 20 - 28 | 15 - 21 | 1,800 - 2,500 |
| 6 | Strong Breeze | Large branches in motion, whistling heard in telegraph wires | 12.5 - 14.5 | 28 - 32 | 21 - 27 | 2,500 - 2,800 |
| 7 | Moderate gale | Whole trees in motion, inconvenience felt when walking into wind | 14.5 - 20 | 32 - 44 | 27 - 33 | 2,800 - 3,900 |
| 8 | Gale | Twigs broken of trees, generally impeded progress | 20 - 22 | 44 - 50 | 33 - 40 | 3,900 - 4,400 |
| 9 | Strong gale | Straight structural damage, e.g. slates and chimney pots removed from the roofs | 22 - 28 | 50 - 62 | 40 - 48 | 4,400 - 5,450 |
| 10 | Storm | Trees uprooted, considerable structural damage | 28 - 31 | 62 - 70 | 48 - 55 | 5,450 - 6,150 |
| 11 | Violent Storm | Widespread damage | 31 - 37 | 70 - 82 | 55 - 63 | 6,150 - 7,200 |
| 12 | Hurricane | > 37 | > 82 | > 63 | > 7,200 | |
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