In 1805, Francis Beaufort conceived a scale of classification of the strength of the wind, numbered from 0 to 12 degrees.
This scale, initially intended to improve the precision of the newspapers of edge, is of a universal use in marine meteorology today.
|FORCE||APPELLATION||VITESSE DU VENT||ÉTAT DE LA MER||EFFETS À TERRE|
|0||Calm||1||1||Sea like a mirror||Calm. Smoke rises vertically.|
|1||Light air||1 to 3||1 to 5||Ripples with the appearance of scales are formed, but without foam crests||Smoke drift indicates wind direction. Leaves and wind vanes are stationary.|
|2||Light breeze||4 to 6||6 to 11||Small wavelets, still short bute more pronounced ; crests have a glassy appearance and do not break||Wind felt on exposed skin. Leaves rustle.Wind vanes begin to move.|
|3||Gentle breeze||7 to 10||12 to 19||Large wavelets. Crests begin to break ; scattered whitecaps||Leaves and small twigs constantly moving, light flags extended.|
|4||Moderate breeze||11 to 16||20 to 28||Small waves with breaking crests. Fairly frequent whitecaps.||Dust and loose paper raised. Small branches begin to move.|
|5||Fresh breeze||17 to 21||29 to 38||Moderate waves of some length. Many whitecaps. Small amount of spray.||Branches of moderate size move. Small trees in leaf begin to sway.|
|6||Strong breeze||22 to 27||39 to 49||Long waves begin to form. White foam crests are very frequent. Some airborne spray is present.||Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult. Empty plastic bins tip over.|
|7||High Wind, moderate gale, near gale||28 to 33||50 to 61||Sea heaps up. Some foam from breaking waves is blown into streaks along wind direction. Moderate amounts of airborne spray.||Whole trees in motion. Effort needed to walk against the wind.|
|8||Gale, fresh gale||34 to 40||62 to 74||Moderately high waves with breaking crests forming spindrift. Well-marked streaks of foam are blown along wind direction. Considerable airborne spray.||Some twigs broken from trees. Cars veer on road. Progress on foot is seriously impeded.|
|9||Strong/severe gale||41 to 47||75 to 88||High waves whose crests sometimes roll over. Dense foam is blown along wind direction. Large amounts of airborne spray may begin to reduce visibility.||Some branches break off trees, and some small trees blow over. Construction/temporary signs and barricades blow over.|
|48 to 55||89 to 102||Very high waves with overhanging crests. Large patches of foam from wave crests give the sea a white appearance. Considerable tumbling of waves with heavy impact. Large amounts of airborne spray reduce visibility.||Trees are broken off or uprooted, structural damage likely.|
|11||Violent storm||56 to 63||103 to 117||Exceptionally high waves. Very large patches of foam, driven before the wind, cover much of the sea surface. Very large amounts of airborne spray severely reduce visibility.||Widespread vegetation and structural damage likely.|
|12||Hurricane force||64 and +||118 and +||Huge waves. Sea is completely white with foam and spray. Air is filled with driving spray, greatly reducing visibility.||Severe widespread damage to vegetation and structures. Debris and unsecured objects are hurled about.|