BEAUFORT WIND SCALE Force 0 1 2 3 4 5 6 7 8 9 10 11 12 Limits of wind speed in knots (A knot is one nautical mile per hour) Less than 1 1-3 4-6 7-10 11-16 17-21 22-27 28-33 34-40 41 7 48-55 56-63 64+ Description Calm Light air Light breeze Gentle breeze Moderate breeze Fresh breeze Strong breeze Near gale Gale Strong gale Storm Violent storm Hurricane Sea Sea like, a mirror.

Ripples with appearance of scales formed but without foam crests.

Small wavelets, still short but more pronounced. Crests have glassy appearance and do not break.

Large wavelets. Crests begin to break. Foam of glassy appearance.

Perhaps scattered white horses.

Small waves, becoming longer: fairly frequent white horses.

Moderate waves, taking a more pronounced long form: many white horses (chance of some spray).

Large waves begin to form : white foam crests more extensive everywhere. Probably some spray.

Sea heaps up and white foam from breaking waves begins to be blown in streaks along direction of wind.

Moderately high waves of greater length; edges of crests begin to break into spindrift. Foam is blown in wellmarked streaks along direction of wind.

High waves. Dense streaks of foam along direction of wind.

Crests of waves begin to topple, tumble and roll over.

Spray may affect visibility.

Very high waves with long overhanging crests; resulting foam in great patches is blown in dense white streaks along direction of wind; surface of sea takes a white appearance.

Tumbling of sea becomes heavy and shocklike. Visibility affected.

Exceptionally high waves. (Small and medium-sized ships might be for a time lost to view behind the waves.) Sea completely covered with long white patches of foam lying along direction of wind. Everywhere edges of wave crests are blown into froth. Visibility affected.

Air filled with foam and spray. Sea completely white with driving spray. Visibility very seriously affected.

Wave height in metres, open sea Probable — , 0.15 0.60 1.0 1.80 3.0 4.0 5.50 7.0 9.0 11.30 13.70 Probable maximum — 0.30 1.0 1.50 2.50 4.0 6.0 7.50 9.75 12.50 16.0.