Wind facts

Strong breeze. Top speed of Usain during setting up the 2009 100m world record was 12.3 m/s. This corresponds to the 6 on the Beaufort scale. During such wind conditions, large branches are in motion and whistling is heard in overhead wires.

Roaring forties. The Roaring Forties are strong westerly winds found in the Southern Hemisphere, generally between the latitudes of 40 and 50 degrees. The strong west-to-east air currents are caused by the combination of air being displaced from the Equator towards the South Pole, the Earth's rotation, and the scarcity of landmasses to serve as windbreaks.

Anemometer. An anemometer is a device used for measuring the speed of wind, and is also a common weather station instrument. The term is derived from the Greek word anemos, which means wind, and is used to describe any wind speed measurement instrument used in meteorology.

Kármán vortex street. When a cloud layer is present at the relevant altitude, the streets become visible. Such cloud layer vortex streets have been photographed from satellites. Kármán vortex street caused by wind flowing around the Juan Fernández Islands off the Chilean coast. It is named after the engineer and fluid dynamicist Theodore von Kármán.

12. Beaufort scale force 12 is the strength of the hurricane: huge waves, air filled with foam and splashes, sea completely white.

Simoom is a strong, dry, desert wind. The name means "poison wind" and is given because the sudden onset of simoom may also cause heat stroke. Its temperature may exceed 54 °C (129 °F) and the humidity may fall below 10%.

Psychrometer . Humidity is the measure of the amount of moisture in the air. A psychrometer is an example of a hygrometer. A psychrometer uses two thermometers to measure relative humidity; one measures the dry-bulb temperature and the other measures the wet-bulb temperature.