Scale force 0 - Calm
Wind speed
Description
< 1 km/h
< 1 mph
< 0.3 m/s
Calm, smoke rises vertically
Scale force 1 - Light air
Wind speed
Description
1.1 - 5.5 km/h
1 - 3 mph
0.3 - 1.5 m/s
Smoke drift indicates wind direction. Leaves and wind vanes are stationary.
Scale force 2 - Light breeze
Wind speed
Description
5.6 - 11 km/h
4 - 7 mph
1.6 - 3.4 m/s
Wind felt on exposed skin. Leaves rustle. Wind vanes begin to move.
Scale force 3 - Gentle breeze
Wind speed
Description
12 - 19 km/h
8 - 12 mph
3.5 - 5.4 m/s
Leaves and small twigs constantly moving. Light flags extended.
Scale force 4 - Moderate breeze
Wind speed
Description
20 -28 km/h
13 - 17 mph
5.5 - 7.9 m/s
Small branches begin to move. Dust and loose paper raised into the air.
Scale force 5 - Fresh breeze
Wind speed
Description
29 - 38 km/h
18 - 24 mph
8.0 - 10.7 m/s
Branches of a moderate size move. Small trees in leaf begin to sway.
Did you know?
Wind speed is measured most accurately using a gadget called an anemometer.
Here we can see a modern weather station that measures the wind speed and direction as well as temperature and air presure.
Did you know?
You can work out the wind speed from looking at the isobars on a weather map. the closer the lines are together, the stronger the wind will be.
Isobars show areas of similar air pressure and the further apart they are, the lower the wind speed will be. Next time you see a weather forecast, look at the isobars and predict the wind speed.
Scale force 6 - Strong breeze
Wind speed
Description
39 - 49 km/h
25 - 30 mph
10.8 - 13.8 m/s
Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult.
Scale force 7 - High wind / near gale
Wind speed
Description
50 - 61 km/h
31 - 38 mph
13.9 - 17.1 m/s
Whole trees in motion. effort needed to walk against wind.
Scale force 8 - Gale
Wind speed
Description
62 - 74 km/h
39 - 46 mph
17.2 - 20.7 m/s
Some twigs broken from trees. Cars veer on road. progress on foot is seriously impeded.
Scale force 9 - Strong Gale
Wind speed
Description
75 - 88 km/h
47 - 54 mph
20.8 - 24.4 m/s
Some branches break off trees and some small trees are blown over. Construction / temporary signs are blown over.
Did you know?
Some of the strongest winds on earth are recorded in hurricanes but at the very centre of a hurricane is a small curicular area, the eye, that is completely calm.
There is often confusion about the difference between cyclones and hurricanes and typhoons. They are all exactly the same thing, except for their location. Generally speaking, it is:
Hurricanes = Atlantic.
Typhoons = Pacific.
Cyclones = Indian Ocean.
High above most clouds can be found a fast stream of moving air called the jet stream. These high winds circle the globe and have a large impact on our weather and so they are monitored by meteorologists closely.
The jet stream can be found 7000-12000 metres above ground and the winds average 160 kilometres an hour.
Scale force 10 - Storm
Wind speed
Description
89 - 102 km/h
55 - 63 mph
24.5 - 28.4 m/s
Trees are broken off or uprooted. Structural damage to properties is likely.
Scale force 11 - Violent Storm
Wind speed
Description
103 - 117 km/h
64 - 73 mph
28.5 - 32.6 m/s
Wide spread damage to crops and to properties likely.
Scale force 12 - Hurricane
Wind speed
Description
>118 km/h
>74 mph
>32.7 m/s
Sever widespread damge to crops and property. Debris and unsecured objects are hurled around.
Strong winds
at sea
Devised by the Royal Navy in 1805, the Beaufort scale, is a measure of wind speed and is used to give guidance to ships in the weather forecast as to what weather they can expect. In 1805, all ships used sail for power and knowing what amount of wind was to be expected and therefore how much sail could safley be deployed was very important. Here we have a look at the Beaufort wind scale in more detail.
BEAUFORT SCALE
