Earth and Space > Beaufort Wind Scale

Page location: Info Library> Earth and Space > Beaufort Wind Scale
The Beaufort wind scale has been used for many years to describe wind speeds and conditions. Created in 1805 by Sir Francis Beaufort, the original scale consisted of 12 increments of increased wind intensity, based upon the wind?s affects on a ship of the Royal Navy. The description of scale one read ?just sufficient to give steerage? and wind scale 12- ?that which no canvas can withstand'.

The scale was adapted several times to accommodate the industrial revolution when steam powered ships replaced sailing vessels and to increase the range of numbers for extreme conditions in some countries.

In the UK, the Beaufort scale we tend to use has 12 bands representing increasingly extreme conditions. In Taiwan and China, the Beaufort scale has a further five categories from 13-17 to better represent hurricane and typhoon conditions.

Beaufort Number Speed km/h Speed mph Description Sea Conditions Land Conditions
0 0 0 Calm Flat Smoke rises vertically, calm
1 1-6 1-3 Light air Small ripples Wind direction visible in smoke
2 7-11 4-7 Light breeze Small wavelets, not breaking Wind felt on exposed skin, leaves rustle
3 12-19 8-12 Gentle breeze Large wavelets, crests begin to break Leaves and small twigs in constant motion
4 20-29 13-18 Moderate breeze Small waves Dust and loose paper raised, small branches begin to move
5 30-39 19-24 Fresh breeze Moderate (1.2m) longer waves, some foam and spray Smaller trees sway
6 40-50 25-31 Strong breeze Large waves with foam crests and some spray Large branches in motion, whistling heard in overhead wires
7 51-62 32-37 Near gale Sea heaps up and foam begins to streak Whole trees in motion, effort needed to walk against the wind
8 63-75 39-46 Gale Moderately high waves with breaking crests forming spindrift. Streaks of foam Twigs broken on trees, cars veer on road
9 76-87 47-54 Strong gale High waves (2.5m) with dense foam. Wave crests start to roll over. Considerable spray Light structural damage
10 88-102 55-63 Storm Very high waves. Sea surface white and considerable tumbling. Trees uprooted. Considerable structural damage
11 103-119 64-73 Violent storm Exceptionally high waves Widespread structural damage
12 120 74-95 Hurricane Hugh waves, air filled with foam and spray, sea completely white with driving spray. Visibility greatly reduced Considerable and widespread damage to structures