It is associated with periods when a weakened pressure gradient causes the trade winds to diminish. A major El Ni o event triggers extreme weather in many parts of the world. Local winds are small-scale winds produced by a locally generated pressure gradient. The two basic wind measurements are direction and speed . Winds are always labeled by the direction from which they blow .
Wind speed is measured using a cup anemometer .
The instrument most commonly used to measure wind direction is the wind vane . When the wind consistently blows more often from one direction than from any other, it is termed a prevailing wind . In general, regions influenced by high pressure, with its associated subsidence and divergent winds, experience relatively dry conditions. Conversely, regions under the influence of low pressure and its converging winds and ascending air receive ample precipitation.