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Beaufort Wind Scale 

Beaufort Number Descriptive Term Speed in Knots Effects on Open Waters
 0  Calm  0 Sea like a mirror
 1  Light Air  1 to 3 Ripples with the appearance of scales are formed, without foam crests
 2  Light Breeze  4 to 6 Small wavelets, still short, but more pronounced; crests have a glassy appearance but do not break
 3  Gentle  7 to 10 Large wavelets; crests begin to break; foam of glassy appearance, perhaps scattered white horses (white caps)
 4  Moderate  11 to 16 Small waves, becoming longer; fairly frequent white horses
 5  Fresh  17 to 21 Moderate waves, taking a more pronounced long form; many white horses are formed (chance of some spray)
 6  Strong  22 to 27 Large waves begin to form; the white foam crests are more extensive everywhere (probably some spray)
 7  Near Gale  28 to 33 Sea heaps up and white foam from breaking waves begins to be blown in streaks along the direction of the wind
 8  Gale  34 to 40 Moderately high waves of greater length; edges of crests begin to break into the spindrift; the foam is blown in well-marked streaks along the direction of the wind
 9  Strong Gale  41 to 47 High waves; dense streaks of foam along the direction of the wind; crests of waves begin to topple, tumble, and roll over; spray may affect visibility
 10  Storm  48 to 55 Very high waves with long overhanging crests; the resulting foam, in great patches, is blown in dense white streaks along the direction of the wind; on the whole, the
sea surface takes a white appearance; the tumbling of the sea becomes heavy and shock-like; visibility affected
 11   Violent  56 to 63 Exceptionally high waves (small and medium size ships might be lost to view for a time behind the waves); the sea is completely covered with long white patches of foam lying along the direction of the wind; everywhere the edges of the wave crests are blown into froth; visibility affected
 12  Hurricane  64 and over The air is filled with foam and spray; sea completely white with driving spray; visibility very seriously affected

Statute Mile = 5,280 feet

Nautical Mile = 6,076.11549... feet in length (The length of the nautical mile is very close to the mean value of the length of 1 minute of latitude)


To convert wind speeds in knots to statute miles per hour - Speed in Knots X 1.15

To convert wind speeds in statute miles per hour to knots - Speed in MPH X 0.868


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