The Beaufort scale is divided into a series of values, from 0 for calm winds to 12 and above for hurricanes. Each value represents a specific range and classification of wind speeds with accompanying descriptions of the effects on surface features, as follows:
- 0 (calm): 01 knot, smoke rises vertically, and the sea is mirror smooth.
- 1 (light air): 13 knots, smoke shows the direction of the wind.
- 2 (light breeze): 46 knots, wind is felt on the face and leaves rustle in the trees.
- 3 (gentle breeze): 710 knots, wind extends a light flag.
- 4 (moderate breeze): 1116 knots, loose paper blows around, and fairly frequent whitecaps occur.
- 5 (fresh breeze): 1721 knots, small trees sway.
- 6 (strong breeze): 2227 knots, wind causes whistling in telephone wires and some spray on the sea surface.
- 7 (moderate gale): 2833 knots, large trees sway.
- 8 (fresh gale): 3440 knots, twigs break from trees, and long streaks of foam appear on the ocean.
- 9 (strong gale): 4147 knots, branches break from trees.
- 10 (whole gale): 4855 knots, trees are uprooted, and the sea takes on a white appearance.
- 11 (storm): 5663 knots, widespread damage.
- 12 (hurricane): 64 knots and higher, structural damage on land and storm waves at sea.
by Roger A. Pielke