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All the units used to measure wind
Voici une petite explication des correspondances des unités utilisées sur le site Infos-Plages.
Knots (nds ou kts)
The knot is the main unit of measurement of the wind in the maritime sector.
It stands for a move of a nautic mile in an hour, i.e 1.852 km/h or 0.514 m/s.
All our weather stations record wind news in knots.
› Go on Wikipédia to learn more about it
Kilometre per hour (km/h)
The kilometre per hour is the more frequent unit of measurement for speed in our daily life (navigation excluded).
It comes from an unit basis which is the meter per second (m/s).
As for the Anglo-saxon system, it uses the mile per hour (pmh).
› Go on Wikipédia to learn more about it
Mile by hour (mph)
The mile per hour, mph symbol, is a unit of measurement used for speed in nautical meteorology.
It is also used as unit of measurement used for speed on roads in some countries of United Kingdom.

The land mille measures approximately 1609 meters, whereas the nautic mille is equivalent to 1852 meters.
› Go on Wikipédia to learn more about it
Meter per second (m/s)
The meter per second is the unit of speed used in the international system.
It defines in meters the traveled distance per second.
› Go on Wikipédia to learn more about it
Beaufort Scale (fbt)
The Beaufort scale is an empirical measure that relates wind strength to observed conditions at sea or on land on a scale going from 0 to 12.
The scale was devised in 1805 by Francis Beaufort. Initially destinated to improve the concision and precision of logbooks, it is now universally used in nautical meteorology.

The creation of the Beaufort scale has been developed and adapted over years. The last adaptation dates from 1946.
› Go on Wikipédia to learn more about it

Strength
Terme
Speed
(nd ou kt)
Speed
(km/h)
State of the Sea
0
Calm
< 1
< 1
Sea like a mirror
1
Light air
1 - 3
1 - 5
Ripples with appearance of scales, no crests form
2
Light breeze
4 - 6
6 - 11
Wavelets, small but pronounced. Crests with glassy appearance, but do not break
3
Gentle breeze
7 - 10
12 - 19
Large wavelets, crests begin to break. Glassy looking foam, occasional white horses
4
Moderate breeze
11 - 16
20 - 28
Small waves becoming longer, frequent white horses
5
Fresh breeze
17 - 21
29 - 38
Moderate waves of pronounced long form. Many white horses, some sea spray
6
Strong breeze
22 - 27
39 - 49
Some large waves, extensive white foam crests, some spray
7
Near gale
28 - 33
50 - 61
Sea heaped up, white foam from breaking waves blowing in streaks with the wind
8
Gale
34 - 40
50 - 61
Crests break into spin drift, blowing foam in well marked streaks
9
Severe gale-force winds
41 - 47
75 - 88
High waves, dense foam streaks in wind, wave crests topple, tumble and roll over. Spray reduces visibility.
10
Storm
48 - 55
89 - 102
11
Violent storm
56 - 63
103 - 117
12
Hurricane
> 64
> 118