Beaufort Wind Strength Scale

Used to gauge wind speed using observations of the winds effects on trees
and other objects.  Often used in monitoring projects because it doesn't
require fancy equipment.

Format: Beaufort Number *** Wind Speed in Miles/hour(Km/hour) *** Description

0 *** <1 (<1.6)***Calm: Still: Smoke will rise vertically.

1***1-3(1.6-4.8)*** Light Air: Rising smoke drifts, weather vane is inactive.

2***4-7(6.4-11.3)***Light Breeze: Leaves rustle, can feel wind on your face, weather vane is inactive.

3***8-12(12.9-19.3)***Gentle Breeze: Leaves and twigs move around. Light weight flags extend.

4***13-18 (20.9-29.0)***Moderate Breeze: Moves thin branches, raises dust and paper.

5***19-24 (30.6-38.6)***Fresh Breeze: Moves trees sway.

6***25-31(40.2-50.0) ***Strong Breeze: Large tree branches move, open wires (such as telegraph wires) begin to "whistle", umbrellas are difficult to keep under control.

7***32-38 (51.5-61.2)***Moderate Gale: Large trees begin to sway, noticeably difficult to walk.

8***39-46(62.8-74.0)***Fresh Gale: Twigs and small branches are broken from trees, walking into the wind is very difficult.

9***47-54(75.6-86.9)***Strong Gale: Slight damage occurs to buildings, shingles are blown off of roofs.

10***55-63 (88.5-101.4)***Whole Gale: Large trees are uprooted, building damage is considerable.

11***64-72 (103.0-115.9)***Storm: Extensive widespread damage. These typically occur only at sea, and rarely inland.

12***>73 (>115.9)***Hurricane: Extreme destruction.

NOTE: The Beaufort number is also referred to as a "Force" number, for example,

"Force 10 Gale".

* To calculate knots, divide miles/hour by 1.15.

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

CREDITS:  This information was copied from:
http://www.im.nbs.gov/beaufort.html