B
The terms and definitions found in the glossary relate to the science of meteorology.
For descriptions and definitions of words used in the Bureau's forecasts and warnings, please refer to Weather Words.
Beaufort Wind Scale
Please note: Beaufort scale numbers and descriptive terms such as 'near gale', 'strong gale' and 'violent storm' are not normally used in Bureau of Meteorology communications or forecasts.
| Beaufort scale number | Descriptive term | Units in km/h | Units in knots | Description on Land | Description at Sea |
|---|---|---|---|---|---|
| 0 | Calm | 0 | 0 | Smoke rises vertically | Sea like a mirror. |
| 1-3 | Light winds | 19 km/h or less | 10 knots or less | Wind felt on face; leaves rustle; ordinary vanes moved by wind. | Small wavelets, ripples formed but do not break: A glassy appearance maintained. |
| 4 | Moderate winds | 20 - 29 km/h | 11-16 knots | Raises dust and loose paper; small branches are moved. | Small waves - becoming longer; fairly frequent white horses. |
| 5 | Fresh winds | 30 - 39 km/h | 17-21 knots | Small trees in leaf begin to sway; crested wavelets form on inland waters | Moderate waves, taking a more pronounced long form; many white horses are formed - a chance of some spray |
| 6 | Strong winds | 40 - 50 km/h | 22-27 knots | Large branches in motion; whistling heard in telephone wires; umbrellas used with difficulty. | Large waves begin to form; the white foam crests are more extensive with probably some spray |
| 7 | Near gale | 51 - 62 km/h | 28-33 knots | Whole trees in motion; inconvenience felt when walking against wind. | Sea heaps up and white foam from breaking waves begins to be blown in streaks along direction of wind. |
| 8 | Gale | 63 - 75 km/h | 34-40 knots | Twigs break off trees; progress generally impeded. | Moderately high waves of greater length; edges of crests begin to break into spindrift; foam is blown in well-marked streaks along the direction of the wind. |
| 9 | Strong gale | 76 - 87 km/h | 41-47 knots | Slight structural damage occurs -roofing dislodged; larger branches break off. | High waves; dense streaks of foam; crests of waves begin to topple, tumble and roll over; spray may affect visibility. |
| 10 | Storm | 88 - 102 km/h | 48-55 knots | Seldom experienced inland; trees uprooted; considerable structural damage. | Very high waves with long overhanging crests; the resulting foam in great patches is blown in dense white streaks; the surface of the sea takes on a white appearance; the tumbling of the sea becomes heavy with visibility affected. |
| 11 | Violent storm | 103 -117 km/h | 56-63 knots | Very rarely experienced - widespread damage | Exceptionally high waves; small and medium sized ships occasionally lost from view behind waves; the sea is completely covered with long white patches of foam; the edges of wave crests are blown into froth. |
| 12+ | Hurricane | 118 km/h or more | 64 knots or more | Very rarely experienced - widespread damage | The air is filled with foam and spray. Sea completely white with driving spray; visibility very seriously affected |