If the wind speed is less than one knot it does not register. It is 0. it is calm, Then comes
1 Light air 1 - 3 knots
2 Light breeze 4 - 6 knots
3 Gentle breeze 7 - 10 knots
4 Moderate breeze 11 - 16 knots
5 Fresh breeze 17 - 21 knots
6 Strong breeze 22 - 27 knots
7 High wind 28 - 33 knots
8 Gale 34 - 40 knots
9 Strong gale 41 - 47 knots
10 Storm 48 - 55 knots
11 Violent storm 56 - 63 knots
12 Hurricane force > 64 knots
