In weather analysis knowledge of wind direction and wind velocity is of great importance. Direction and velocity can be measured accurately by means of instruments or they may be estimated by direct observations.
Winds are always named by the direction from which they blow. For example, a west wind blows from the west towards the east; a south wind blows from the south towards the north. Wind vane is the most common type of instrument used to determine wind direction.
To determine wind direction and speed in the upper air, pilot balloons are utilized. The direction from which a wind blows is called windward; that towards which it blows is called leeward.
For measuring wind direction there are several types of instruments manufactured by different companies.
Wind speed is commonly measured by an instrument called anemometer. The most common type is the cup anemometer. There is another instrument called propeller-type anemometer which combines speed and direction transmitters in a single unit for all-purpose use.
An instrument called anemograph makes a continuous record of wind mileage. A more sophisticated self-recording instrument called meteorograph or triple register gives a graphic record of both wind direction and speed as well as of sunshine and precipitation.
With the help of the Beaufort scale also quite accurate estimation of wind speed can be made.