| Number and
Description |
Specifications
for use on land |
Air speed
– mph |
| 0: Calm |
Calm;
smoke rises vertical. |
0
– 1 |
| 1:
Light Air |
Direction
of wind shown by smoke drift, but not by wind vanes. |
1
– 3 |
| 2:
Light Breeze |
Wind
felt on face; leaves rustle; ordinary vanes moved by wind. |
4
– 7 |
| 3:
Gentle Breeze |
Leaves
and small twigs in constant motion; wind extents light
flag. |
8
– 12 |
| 4:
Moderate Breeze |
Raises
dust and loose paper; small branches are moved. |
13
– 18 |
| 5:
Fresh Breeze |
Small
trees begin to sway; crested wavelets form on inland
waters. |
19
– 24 |
| 6:
Strong Breeze |
Large
branches in motion. |
25
– 31 |
| 7: Near
Gale |
Whole
trees in motion; difficulty felt when walking against the
wind. |
32
– 38 |
| 8: Gale |
Breaks
twigs off trees. |
39
– 46 |
| 9:
Severe Gale |
Slight
structural damage occurs. |
47
– 54 |
| 10:
Storm |
Trees
uprooted; considerable structural damage occurs. |
55
– 63 |
| 11:
Violent Storm |
Widespread
damage. |
64
– 72 |
| 12:
Hurricane |
Violence
and destruction |
73
– 83 |
| Beaufort Scale – 10 m. above
the ground or approximately 33 ft. |