| Index of Secondary Text Terms | Figure 3.1: Network Map of Wind-related Concepts |
The Beaufort Scale -- originally developed by Sir Francis
Beaufort in 1805 for use at sea -- has since been adapted
to estimate wind speed over land as well.
| Beaufort Scale | |||||
|---|---|---|---|---|---|
| Observable Effects | International Description | Beaufort Number | Wind Speed (meters/sec.) (km/hour) (miles/hour) |
||
| Air calm; smoke rises vertically | Calm | 0 | <0.5 | <1 | <1 |
| Direction of wind shown by smoke drift but not by wind vanes | Light Air | 1 | 0.5-1.5 | 1-5 | 1-3 |
| Wind felt on face; leaves rustle; wind vanes moved by wind | Light Breeze | 2 | 2-3 | 6-11 | 4-7 |
| Leaves and small twigs in continual motion; wind extends light flags | Gentle Breeze | 3 | 4-5 | 12-19 | 8-12 |
| Raises dust, loose paper; moves small branches | Moderate Breeze | 4 | 6-8 | 20-29 | 13-18 |
| Small trees in leaf begin to sway; white crested wavelets form on inland waters | Fresh Breeze | 5 | 9-10 | 30-39 | 19-24 |
| Large branches in motion; umbrellas used with difficulty; telephone wires "whistle" | Strong Breeze | 6 | 11-13 | 40-50 | 25-31 |
| Whole trees in motion; inconvenience felt walking against wind | Moderate or Near Gale | 7 | 14-17 | 51-61 | 32-38 |
| Breaks twigs off trees; wind generally impedes progress | Gale or Fresh Gale | 8 | 18-20 | 62-74 | 39-46 |
| Slight structural damage occurs | Strong Gale | 9 | 21-24 | 75-87 | 47-54 |
| Trees uprooted; considerable structural damage occurs | Whole Gale or Storm | 10 | 25-28 | 88-101 | 55-63 |
| Widespread damage | Violent Storm | 11 | 29-33 | 102-118 | 64-73 |
| Devastation | Hurricane | 12 | >33 | >118 | >73 |
A description of the Beaufort Scale for use on the open sea can be found at: http://www.marinedata.co.uk/ref/beaufort.html
Estimating wind speed near shore is a more complex endeavor. For example, it is the case that the correlation of wave description and height to wind speed changes as you move further away from land. (Water depth is also a factor.) The following book provides a detailed analysis and description of this complex set of factors:
Title: Instant Wind Forecasting Copyright: 1975 Author: Alan Watts Publisher: Dodd, Mead & Company, NY, USA ISBN: 0-396-07187-2
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