Used to guage 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
