| Force | Wind Knots |
WMO Description |
Estimating Wind Speed | ||
|---|---|---|---|---|---|
| Effects At Sea | Effects Near Land | Effects On Land | |||
| 0 | 0-1 | Flat Calm | Sea like a mirror | Calm | Calm; smoke rises vertically |
| 1 | 1-3 | Light Air | Ripples with appearance of scales; no foam crests | Small sailboat just has steerage way | Smoke drift indicates wind direction; vanes do not move |
| 2 | 4-6 | Light Breeze | Small wavelets; crests of glassy appearance; not breaking | Wind fills the sails of small boats which then travel at about 1-2 knots | Wind felt on face; leaves rustle; vanes begin to move |
| 3 | 7-10 | Gentle Breeze | Large wavelets; crests begin to break, scattered whitecaps | Sailboats begin to heel and travel at about 3-4 knots | Leaves and small twigs in constant motion; light flags extended |
| 4 | 11-16 | Moderate Breeze | Small waves 1-4 ft., becoming longer; numerous whitecaps | Good working breeze, sailboats carry all sail with good heel | Dust, leaves, and loose paper raised up; small branches move. |
| 5 | 17-21 | Fresh Breeze | Moderate waves 4-8 ft taking longer form; many whitecaps; some spray | Sailboats shorten sail | Small trees in leaf begin to sway |
| 6 | 22-27 | Strong Breeze | Larger waves 8-13 ft forming white caps everywhere; more spray | Sailboats have double reefed mainsails | Larger branches of trees in motion; whistling heard in wires |
| 7 | 28-33 | Near Gale | Sea heaps up, waves 13-20 ft; white foam from breaking waves begins to be blown in streaks | Boats head for harbor; those at sea heave-to | Whole trees in motion; resistance felt in walking against wind |
| 8 | 34-40 | Gale | Moderately high (13-20 ft) waves of greater length; edges of crests begin to break into spindrift; foam is blown in wellmarked streaks | Whole trees in violent motion; difficulty walking against wind | |
| 9 | 41-47 | Strong Gale | High waves (20 ft); sea begins to roll; dense streaks of foam; spray may reduce visibility | Slight structural damage occurs; slate blows from roofs | |
| 10 | 48-55 | Storm | Very high waves (20-30 ft) with overhanging crests;sea takes a white apperance as foam is blown in very dense streaks; rolling is heavy and visibility is reduced | Seldom experienced on land; trees broken or uprooted; considerable structural damage occurs | |
| 11 | 56-63 | Violent Storm | Exceptionally high (30-45 ft) waves; sea covered with white foam patches; visibility still more reduced | ||
| 12 | 64 -up | Hurricane | Air filled with foam; waves over 45 ft; sea completely white with driving spray; visibility greatly reduced | ||
Note: The Beaufort Wind Scale goes to Force 12. It is only academic at this level. All sailors by this time are in port, wish they were, being beaten up, or sinking.
