Force |
Wind |
Classification |
Appearance of the Water |
0 |
Less than 1 knot |
Calm |
Smooth and mirror-like surface |
1 |
1-3 knots |
Light Air |
Scaly ripples, no foam crests |
2 |
4-6 knots |
Light Breeze |
Small wavelets, glassy crests, no breaking |
3 |
7-10 knots |
Gentle Breeze |
Large wavelets, crests starting to break, a few whitecaps |
4 |
11-16 knots |
Moderate Breeze |
Small waves 1-4 ft. becoming longer, numerous whitecaps |
5 |
17-21 knots |
Fresh Breeze |
Moderate waves 4-8 ft taking longer form, many whitecaps, some spray |
6 |
22-27 knots |
Strong Breeze |
Larger waves 8-13 ft, whitecaps common, more spray |
7 |
28-33 knots |
Near Gale |
Sea heaps up, waves 13-20 ft, white foam streaks off breakers |
8 |
34-40 knots |
Gale |
Moderately high (13-20 ft) waves of greater length, edges of crests begin to break into spindrift, foam blown in streaks |
9 |
41-47 knots |
Strong Gale |
High waves (20 ft), sea begins to roll, dense streaks of foam, spray may reduce visibility |
10 |
48-55 knots |
Storm |
Very high waves (20-30 ft) with overhanging crests, sea white with densely blown foam, heavy rolling, lowered visibility |
11 |
56-63 knots |
Violent Storm |
Exceptionally high (30-45 ft) waves, foam patches cover sea, visibility more reduced |
12 |
64+ knots |
Hurricane |
Air filled with foam, waves over 45 ft, sea completely white with driving spray, visibility greatly reduced |