Beaufort Number or "Force"

Wind Strength

(Km/Hr)

    Description

0

<2

Calm: Still. Smoke will rise vertically. The sea is very smooth.

1

2-6

Light Air: Rising smoke drifts, weather vane is inactive. Scale-like ripples on sea, no foam on wave crests.

2

7-11

Light Breeze: Leaves rustle, can feel wind on your face, weather vane is active. Short wavelets, glassy wave crests.

3

13-19

Gentle Breeze: Leaves and twigs move around. Light weight flags extend. Long wavelets, glassy wave crests.

4

20-30

Moderate Breeze: Moves thin branches, raises dust and paper. Fairly frequent whitecaps occur.

5

31-39

Fresh Breeze: Small trees sway. Moderate waves, many white foam crests.

6*

41-50

Strong Breeze: Large tree branches move, open wires begin to “whistle”, umbrellas are difficult to control. Some spray on the sea surface.

7

52-61

Moderate Gale: Large trees begin to sway, noticeably difficult to walk. Foam from waves blows in streaks.

8

63-74

Fresh Gale: Small branches broken from trees, walking in wind is very difficult. Long streaks of foam appear on sea.

9

76-87

Strong Gale: Slight damage occurs to buildings, shingles are blown off roofs. High waves, crests start to roll over.

10

89-102

Whole Gale: Large trees are uprooted, building damage is considerable. The sea takes on a white appearance.

11

104-117

Storm: Extensive widespread damage. Exceptionally high waves, visibility affected.

12

>119

Hurricane: Extreme destruction. Storm waves at sea. Air is filled with spray and foam.

* Small craft advisories are usually issued when force 6 is reached.