Wind


Meteosat image of Europe
 
The wind direction is shown by the direction of the weather symbol
 
 
Wind direction
  
Wind direction is measured in terms of which direction the wind is blowing from and is indicated by azimuth in degrees. A wind vane can be used to measure its direction.

Most wind vanes have a point, or arrowhead, which faces the wind. Therefore one may simply read the compass direction toward which the arrow is pointing. The reading is in the range of 0 to 360 degrees.

Remember to place the wind vane in such a way that nothing blocks or distorts the airflow.
 
 
 Wind speed
  
Wind speed can be measured with an instrument called an anemometer. Many different kinds can be bought. A simple and cheaper way is to observe how features around you react to the wind (see the table below).
 
 
 Wind speed table
  
Beafort
Knots
 Wind Observations on land Observations on sea
0
Less than 1
 Calm Calm, smoke rises vertically Sea surface smooth and mirror-like
1
1-3
 Light air Smoke drift indicates wind direction, still wind vanes Scaly ripples, no foam crests
2
4-6
 Light breeze Wind felt on face, leaves rustle, vanes begin to move Small wavelets, crests glassy, no breaking
3
7-10
 Gentle breeze Leaves and small twigs constantly moving, light flags extended Large wavelets, crests begin to break, scattered whitecaps
4
11-16
 Moderate breeze Dust, leaves, and loose paper lifted, small tree branches move Small waves 0.3048 m - 1.2192 m becoming longer, numerous whitecaps
5
17-21
 Fresh breeze Small trees in leaf begin to sway Moderate waves 1.2192 m - 2.4384 m taking longer form, many whitecaps, some spray
6
22-27
 Strong breeze Larger tree branches moving, whistling in wires Larger waves 2.4384 m - 3.9624 m, whitecaps common, more spray
7
28-33
 Near gale Whole trees moving, resistance felt walking against wind Sea swells up, waves 3.9624 m - 6.096 m, white foam streaks off breakers
8
34-40
 Fresh gale Whole trees in motion, resistance felt walking against wind Moderately high (3.9624 m - 6.096 m) waves of greater length, edges of crests begin to break into spindrift, foam blown in streaks
9
41-47
 Strong gale Slight structural damage occurs, slate blows off roofs High waves (6.096 m), sea begins to roll, dense streaks of foam, spray may reduce visibility
10
48-55
 Storm Seldom experienced on land, trees broken or uprooted, "considerable structural damage" Very high waves (6.096 m - 9.144 m) with overhanging crests, sea white with densely blown foam, heavy rolling, lowered visibility
11
56-63
 Violent Storm Widespread damage Exceptionally high (9.144 m - 13.716 m) waves, foam patches cover sea, visibility more reduced
12
64+
 Hurricane Excessive damage Air filled with foam, waves over 13.716 m, sea completely white with driving spray, visibility greatly reduced

 
 
 Weather symbol on maps
  
The wind direction is shown by the direction of the weather symbol.
The wind speed is represented by the numbers of stripes on the symbol.
One stripe indicates a wind speed of 10 knots.
One triangle indicates a wind speed of 50 knots.

 
 
  
Last update: 17 April 2013


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