Beaufort Scale

Estimating the strength of thewind

Force 0 - Calm

• Sea like a mirror

• 0 knots

Force 1 – Light Air

• Ripples with theappearance ofscales are formed,but withoutfoam crests.

• 1-3 knots

Force 2 – Light Breeze

• Small wavelets, stillshort,but more pronounced.Crestshave a glassyappearance anddo not break.

• 4 – 6 knots

Force 3 – Gentle Breeze

• Large wavelets.Crests beginto break. Foam ofglassyappearance. Perhapsscatteredwhite horses.

• 7 – 10 knots

Force 4 – Moderate Breeze

• Small waves,becoming larger;fairly frequent whitehorses.

• 11 – 16 knots

Force 5 – Fresh Breeze

• Moderate waves,taking a morepronounced longform; manywhite horses areformed.Chance of somespray.

• 17 – 21 knots

Force 6 – Strong Breeze

• Large waves begin toform; thewhite foam crests aremoreextensiveeverywhere.Probably some spray.

• 22 – 27 knots

Force 7 – Near Gale

• Sea heaps up andwhite foamfrom breaking wavesbegins tobe blown in streaksalong thedirection of the wind.

• 28 – 33 knots

Force 8 – Gale

• Moderately highwaves of greaterlength; edges ofcrests begin tobreakinto spindrift.The foam isblown in well-markedstreaksalong the direction ofthe wind.

• 34 – 40 knots

Force 9 – Strong Gale

• High waves. Densestreaks offoam along thedirection of thewind. Crests of wavesbegin totopple, tumble and rollover. Spray mayaffect visibility.

• 41 – 47 knots

Force 10 – Storm• Very high waves with long

over-hanging crests. Theresultingfoam, in great patches, isblownin dense white streaks alongthedirection of the wind. On thewhole the surface of the seatakes on a whiteappearance.The 'tumbling' of the seabecomesheavy and shock-like.Visibility affected.

• 48 – 55 knots

Force 11 – Violent Storm• Exceptionally high waves

(smalland medium-size ships mightbe fora time lost to view behind thewaves). The sea iscompletelycovered with long whitepatchesof foam lying along thedirectionof the wind. Everywhere theedgesof the wave crests are blownintofroth. Visibility affected.

• 56 – 63 knots

Force 12 – Hurricane

• The air is filled withfoam andspray. Sea completelywhite withdriving spray; visibilityveryseriously affected.

• 64 knots and over