۱۴۰۰ بهمن ۲۸, پنجشنبه

 

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Beaufort wind scale table

Beaufort Wind Scale Table
Force Wind Speed Descriptive Term Effects Observed at Sea Effects Observed on Land
Km/h Knots
0 Less than 1 Less than 1 Calm Sea surface like a mirror, but not necessarily flat. Smoke rises vertically.
1 1 - 5 1 - 3 Light air Ripples with the appearance of scales are formed, but without foam crests. Direction of wind shown by smoke drift, but not wind vanes.
2 6 - 11 4 - 6 Light breeze Small wavelets, still short but more pronounced. Crests do not break. When visibility good, horizon line always very clear. Wind felt on face. Leaves rustle. Ordinary vane moved by wind.
3 12 - 19 7 - 10 Gentle breeze Large wavelets. Crests begin to break. Foam of glassy appearance. Perhaps scattered whitecaps. Leaves and small twigs in constant motion. Wind extends light flag.
4 20 - 28 11 - 16 Moderate breeze Small waves, becoming longer. Fairly frequent whitecaps. Raises dust and loose paper. Small branches are moved.
5 29 - 38 17 - 21 Fresh breeze Moderate waves, taking a more pronounced long form. Many whitecaps are formed. Chance of some spray. Small trees with leaves begin to sway. Crested wavelets form on inland waters.
6 39 - 49 22 - 27 Strong breeze Large waves begin to form. The white foam crests are more extensive everywhere. Probably some spray. Large branches in motion. Whistling heard in telephone wires. Umbrellas used with difficulty.
7 50 - 61 28 - 33 Near gale Sea heaps up and white foam from breaking waves begins to be blown in streaks along the direction of the wind. Whole trees in motion. Inconvenience felt in walking against wind.
8 62 - 74 34 - 40 Gale Moderately high waves of greater length. Edges of crests begin to break into the spindrift. The foam is blown in well-marked streaks along the direction of the wind. Breaks twigs off trees. Generally impedes progress. Walking into wind almost impossible.
9 75 - 88 41 - 47 Strong gale High waves. Dense streaks of foam along the direction of the wind. Crests of waves begin to topple, tumble and roll over. Spray may affect visibility. Slight structural damage occurs, e.g. roofing shingles may become loose or blow off.
10 89 - 102 48 - 55 Storm Very high waves with long overhanging crests. Dense white streaks of foam. Surface of the sea takes a white appearance. The tumbling of the sea becomes heavy and shock-like. Visibility affected. Trees uprooted. Considerable structural damage occurs.
11 103 - 117 56 - 63 Violent storm Exceptionally high waves. Sea completely covered with long white patches of foam. Visibility affected. Widespread damage.
12118 - 13364 - 71HurricaneAir filled with foam and spray. Sea entirely white with foam. Visibility seriously impaired.Rare. Severe widespread damage to vegetation and significant structural damage possible.