WIND
hello
We cannot see the wind, but we quite often see what it is
doing or what it has done.
Wind in tropical cyclones and tornadoes can cause enormous
damage, but most of the time the wind is gentle rather than
destructive.
Knowing about the wind is important for many reasons:
* for the safety of passengers in aircraft, of building
workers in high places, of fishermen at sea, and of residents in
cyclone-prone areas.
* it helps to fly kites, fills the sails of yachts, and
influences sports events.
* for forecasting the weather - to predict when a sea breeze
will provide relief on a hot day, or how quickly pollution will
be carried away from cities.
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| On the Beaufort scale, wind speeds are divided into 12 categories, each of which describes the physical
effect of the wind. |
| 0: calm |
(< 1 km/h, < 1 knot) |
| Smoke rises vertically. |
| 1: light air |
(1-5 km/h, 1-3 knots) |
| Wind direction shown by smoke-drift, but not by wind vanes. |
| 2: light breeze |
(6-11 km/h, 4-6 knots) |
| Wind felt on face; leaves rustle; ordinary vanes moved by wind. |
| 3: gentle breeze |
(12-19 km/h, 7-10 knots) |
| Leaves, twigs in constant motion; wind extends light flag. |
| 4: moderate breeze |
(20-28 km/h, 11-16 knots) |
| Raises dust and loose paper; small branches are moved. |
| 5: fresh breeze |
(29-38 km/h, 17-21 knots) |
| Small trees in leaf begin to sway; crested wavelets form on inland waters. |
| 6: strong breeze |
(39-49 km/h, 22-27 knots) |
| Large branches in motion; whistling heard in telephone wires; umbrellas hard to use. |
| 7: near gale |
(50-61 km/h, 28-33 knots) |
| Whole trees in motion; inconvenience felt when walking against the wind. |
| 8: gale |
(62-74 km/h, 34-40 knots) |
| Breaks twigs off trees; generally impedes progress. |
| 9: strong gale |
(75-88 km/h, 41-47 knots) |
| Slight structural damage occurs (chimney pots and roof tiles removed). |
| 10: storm |
(89-102 km/h, 48-55 knots) |
| Seldom experienced inland; trees uprooted; considerable structural damage occurs. |
| 11: violent storm |
(103-117 km/h, 56-63 knots) |
| Very rarely experienced on land; accompanied by widespread damage. |
| 12: cyclone/hurricane |
(118+km/h, 64+ knots) |
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