Beaufort Wind Scale
Sir Francis Beaufort
The Beaufort Scale was originally developed as a system for estimating wind strengths without the use of instruments. It was introduced in 1806 by Admiral Sir Francis Beaufort (1774-1857) of the British navy to describe wind effects on a fully rigged man-of-war sailing vessel, and it was later extended to include descriptions of effects on land features as well. It is currently still in use for this same purpose as well as to tie together various components of weather (wind strength, sea state, observable effects) into a unified picture.
The Beaufort scale is divided into a series of values, from 0 for calm winds to 12 and above for hurricanes. Each value represents a specific range and classification of wind speeds with accompanying descriptions of the effects on surface features.
| Force | Description | Conditions | Wind speed (mph) |
| 0 | Calm | Smoke rises vertically. | 0 |
| 1 | Light air | Direction of wind shown by smoke drift, but not by wind vanes. | 1-3 |
| 2 | Light breeze | Wind felt on face; leaves rustle; ordinary vanes moved by wind. | 4-7 |
| 3 | Gentle breeze | Leaves and small twigs in constant motion; wind extends light flag. | 8-12 |
| 4 | Moderate breeze | Raises dust and loose paper; small branches are moved. | 13-18 |
| 5 | Fresh breeze | Small trees in leaf begin to sway; crested wavelets form on inland waters. | 19-24 |
| 6 | Strong breeze | Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty. | 25-31 |
| 7 | Near gale | Whole trees in motion; inconvenience felt when walking against the wind. | 32-38 |
| 8 | Gale | Breaks twigs off trees; generally impedes progress. | 39-46 |
| 9 | Strong gale | Slight structural damage occurs (chimney-pots and slates removed). | 47-54 |
| 10 | Storm | Seldom experienced inland; trees uprooted; considerable structural damage occurs. | 55-63 |
| 11 | Violent storm | Very rarely experienced; accompanied by wide-spread damage. | 64-72 |
| 12 | Hurricane | Widespread damage occurs | 73+ |
