The international scale used to describe wind speed
Devised by Sir Francis Beaufort
, a British admiral of the time of Nelson
. It rates winds from calm
- "that which no canvas could withstand" as Beaufort
originally put it.
For official readings, measurement
s are taken at 32.8ft (10m) above the ground where speed
s will be considerably more than at ground level. When a meteorological
report says that a wind
is something like "Gale Force
9", it is the Beaufort scale to which it refers.
To suppliment CentrX's scale above, here is a verbose description of the numbers on the scale:
0: Calm, smoke rises vertically.
1: Wind direction shown by smoke, but not flags.
2: Wind felt on face, leaves whisper, flags move.
3: Leaves and thin twigs move, pennants extended fully.
4: Paper and dust lifted, twigs and thin branches move.
5: Small trees in leaf begin to sway, white horses on lakes.
6: Thicker branches move, whistling in telephone lines, umbrellas difficult to use.
7: Whole trees moving, resistance to movement against wind perceptible.
8: Twigs broken from trees, movement in open difficult.
9: Minor damage to houses (awnings and TV antennas)
10: Trees uprooted, major damage to houses.
11: Widespread damage.
12: Severe destruction.