beaufort scale
The Beaufort Scale of Wind Force was developed in 1805 by Admiral Sir Francis Beaufort as a means for sailors to gauge wind speeds through visual observations of the sea state.
The scale runs from Force 0 (calm) to Force 12 (Hurricane).
| Force | Wind (Knots) | Classification | Wind Effect |
|---|---|---|---|
| 0 | <1 | Calm | Sea surface smooth and mirror-like. |
| 1 | 1-3 | Calm | Scaly ripples, no foam crests. |
| 2 | 4-6 | Light Breeze | Small wavelets, crests glassy, no breaking. |
| 3 | 7-10 | Gentle Breeze | Large wavelets, crests begin to break, scattered whitecaps. |
| 4 | 11-16 | Moderate Breeze | Small waves 1-4 ft. becoming longer, numerous whitecaps. |
| 5 | 17-21 | Fresh Breeze | Moderate waves 4-8 ft taking longer form, many whitecaps, some spray. |
| 6 | 22-27 | Strong Breeze | Larger waves 8-13 ft, whitecaps common, more spray. |
| 7 | 28-33 | Near Gale | Sea heaps up, waves 13-20 ft, white foam streaks off breakers. |
| 8 | 34-40 | 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 | Strong Gale | High waves (20 ft), sea begins to roll, dense streaks of foam, spray may reduce visibility. |
| 10 | 48-55 | Storm | Very high waves (20-30 ft) with overhanging crests, sea white with densely blown foam, heavy rolling, lowered visibility. |
| 11 | 56-63 | Violent Storm | Exceptionally high (30-45 ft) waves, foam patches cover sea, visibility more reduced. |
| 12 | 64+ | Hurricane | Air filled with foam, waves over 45 ft, sea completely white with driving spray, visibility greatly reduced. |
This is the scale that we use in our book Busy Doing Nothing.