Beaufort Scale
Wind is simply known as the movement of air in horizontal motion. Air moves due to different factor those are –
- Horizontal pressure – gradient
- Rotation of the Earth(the coriolis force),
- Frictional forces,
- Centrifugal action of wind ,
Beaufort scale is used to measure the wind speed and it was discovered by Francis Beaufort in 1805.
The following table represents the Beaufort scale number and wind speed and observable descriptions.
| Beaufort scale Number | Knots (unit of speed) | Explanatory terms | Observable description |
| 0 | Less than 1 | Calm | Calm smoke rises vertically |
| 1 | 1-3 | Light air | Direction of wind shown by smoke drift, but not by wind vanes |
| 2 | 4-6 | Light breeze | Winds felt on face, leaves rustle; ordinary vane moved by wind |
| 3 | 7-10 | Gentle breeze | Leaves and small twigs in constant motion wind extends light flag |
| 4 | 11-16 | Moderate breeze | Raises dust and loose paper; small branches are moved |
| 5 | 17-21 | Fresh breeze | Small trees in leaf begin to sway; wavelets form on inland water |
| 6 | 22-27 | Strong breeze | Large branches in motion , whistling heard in telegraph wires; umbrellas used with difficulty |
| 7 | 28-33 | Moderate gale | Whole trees in motion, inconvenience felt when walking against wind. |
| 8 | 30-40 | Fresh gale | Breaks twigs from trees , impedes progress generally |
| 9 | 41-47 | Strong gale | Slight structural damage occurs, chimneys and slates carried away |
| 10 | 48-55 | Whole gale | Seldom experienced inland ,trees, uprooted, considerable structural damage done |
| 11 | 56-63 | Storm | Very rarely experienced ; accompanied by widespread damage |
| 12 | 64-71 | Hurricane | Violence and destruction |