BEAUFORT WIND SCALE

FOR AN EFFECTIVE HEIGHT OF 10 M ABOVE SEA LEVEL

BEAUFORT NUMBER	DESCRIPTIVE TERM	MEAN WIND SPEED EQUIVALENT		DEEP SEA CRITERION	PROBABLE MEAN WAVE HEIGHT IN METRES
		KNOTS	M/SEC
0	CALM	< 1	0 – 0.2	SEA LIKE A MIRROR	-
1	LIGHT AIR	1 – 3	0.3 – 1.5	RIPPLES WITH THE APPEARANCE OF SCALE ARE FORMED, BUT WITHOUT FOAM CRESTS	0.1 (0.1 )
2	LIGHT BREEZE	4 – 6	1.6 – 3.3	SMALL WAVELETS,STILL SHORT BUT MORE PRONOUNCED,CREST HAVE A GLASSY APPEARANCE AND DO NOT BREAK	0.2 ( 0.3 )
3	GENTLE BREEZE	7 – 10	3.4 – 5.4	LARGE WAVELETS,CRESTS BEGIN TO BREAK ,FOAM OF GLASSY APPEARANCE ,PERHAPS SCATTERED WHITE HORSES	0.6 ( 1 )
4	MODERATE BREEZE	11 – 16	5.5 – 7.9	SMALL WAVES, BECOMING LONGER , FAIRLY FREQUENT WHITE HORSES	1 ( 1.5 )
5	FRESH BREEZE	17 – 21	8.0 – 10.7	MODERATE WAVES,TAKING A MORE PRONOUNCED LONG FORM, MANY WHITE HORSES ARE FORMED (CHANCE OF SOME SPRAY)	2 ( 2.5 )
6	STRONG BREEZE	22 – 27	10.8 – 13.8	LARGE WAVES BEGIN TO FORM,THE WHITE FOAM CRESTS ARE EXTENSIVE EVERYWHERE (PROBABLY SOME SPRAY)	3 ( 4 )
7	NEAR GALE	28 – 33	13.9 – 17.1	SEA HAPS UP AND WHITE FOAM FROM BREAKING WAVES BEGINS TO BE BLOWN IN STREAKS ALONG THE DIRECTION OF THE WIND	4 ( 5.5 )
8	GALE	34 – 40	17.2 – 20.7	MODERATELY HIGH WAVES OF GREATER LENGTH, EDGES OF CRESTS BEGIN TO BREAK INTO SPINDRIFT, FOAM IS BLOWN IN WELL-MARKED STREAKS ALONG THE DIRECTION OF THE WIND	5.5 ( 7.5 )
9	STRONG GALE	41 – 47	20.8 – 24.4	HIGH WAVES, DENSE STREAKS OF FOAM ALONG THE DIRECTION OF THE WIND , CRESTS OF WAVE BEGIN TO TOPPLE,TUMBLE AND ROLL OVER, SPRAY MAY AFFECT VISIBILITY	7 ( 10 )
10	STROM	48 – 55	24.5 – 28.4	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 T47HE WHOLE, THE SURFACE OF THE SEA TAKES A WHITE APPEARANCE, THE TUMBLING OF THE SEA BECOMES HEAVY AND SHOCK-LIKE, VISIBILITY AFFECTED	9 ( 12.5 )
11	VIOLENT STROM	56 – 63	28.5 – 32.6	EXCEPTIONALLY HIGH WAVES(SMALL AND MEDIUM SIZED SHIPS MIGHT BE FOR A TIME LOST TO WIEW 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 WAVES CRESTS ARE BLOWN INTO FROTH, VISIBILITY AFFECTED	11.5 ( 16 )
12	HURRICANE	64  and over	32.7 and over	THE AIR IS FILLED WITH FOAM AND SPRAY, SEA COMPLETELY WHITE DRIVING SPRAY, VISIBILITY SERIOUSLY AFFECTED.	14 ( - )