Beaufort Scale for Wind Speed

Admiral Sir Richard Beaufort devised his scale for wind speed in 1805 to permit standardized reporting of wind conditions.

Measurement:

• Wind speed measurement is performed at a point 10 meters above the surface of ground or water.

where:

• 1 knot = 1.1516 miles per hour

Beaufort Number	Appearance On Land	Appearance At Sea
0	smoke rises straight up	glassy appearance
1	smoke drifts in direction of wind	ripples but no wave crests
2	leaves rustle bout, wind felt in face	small crests that do not break
3	leaves move, light flags wave	crests start to break, large wavelets
4	small branches move; dust and paper blown about	small waves, some with whitecaps
5	small trees bend	moderate waves, many with whitecaps
6	difficulty in holding umbrellas, large tree limbs move	large waves, with spray
7	walking difficult, large trees bend	large waves breaking with white foam
8	walking very difficult, trigs break	moderately high waves breaking into foam and spindrift forms
9	loss of roof shingles	high waves, sea rolls, dense foam
10	moderate damage to buildings; trees uprooted	very high waves, blowing foam, heavy rolling seas
11	widespread damage	sea covered with foam, extremely high waves
12 - 17	violent and destructive	poor visibility, air filled with spray and foam

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