Force
Description
Average Speed (knots)
Average Speed (km/h)
Sea Conditions
0
Calm
1 knot
1 km/h
Mirror-like sea
1
Light Air
1 to 3 knots
1 to 5 km/h
Small ripples
2
Light Breeze
4 to 6 knots
6 to 11 km/h
Small wavelets
3
Gentle Breeze
7 to 10 knots
12 to 19 km/h
Large wavelets and scattered whitecaps
4
Moderate Breeze
11 to 16 knots
20 to 28 km/h
Small waves with frequent whitecaps
5
Fresh Breeze
17 to 21 knots
29 to 38 km/h
Moderate waves, many whitecaps and spray
6
Strong Breeze
22 to 27 knots
39 to 49 km/h
Large waves, extensive white foam crests and spray
7
Near Gale
28 to 33 knots
50 to 61 km/h
Moderate waves with streaks of foam
8
Gale
34 to 40 knots
62 to 74 km/h
Moderately high waves with well-defined foam streaks
9
Strong Gale
41 to 47 knots
75 to 88 km/h
High to very high waves, exceptional sea conditions and severely reduced visibility.
10
Storm
48 to 55 knots
89 to 102 km/h
Very high waves
11
Violent Storm
56 to 63 knots
103 to 117 km/h
Very high waves. Navigation not recommended.
12
Hurricane Force
>=64 knots
>=118 km/h
Very high waves. Navigation impossible.
