Wind generally flows from an area of high pressure to an area of low pressure. There are a number of factors that affect wind direction and speed; the Coriolis force, friction, Rossby waves, pressure gradient, intensity of sunshine, and earth’s temperature control wind movements and directions.
High wind speeds are known by several names, such as cyclone, hurricane, tornado, typhoons, etc. Wind speed can be affected by various factors, such as pressure gradient, the temperature of earth’s surface, sunshine, jet streams, humidity, and Rossby waves. It is estimated that the wider the pressure gradient is in a particular place the faster winds are destined to blow there. This phenomenon is also widely known as high to low pressure transition. These gradient pressures are created due to unbalanced earth’s temperature. Some surfaces naturally absorb more heat than others and therefore crediting to an uneven temperature flow of heat. Similarly Rossby waves or Westerlies, significantly affect the speed of wind. These are rigid winds that are said to travel from West to East, thus deriving their name of Westerlies. Rossby waves are essentially much stronger winds that amplify the less stronger winds by coming into contact with them. The Coriolis Effect also comes into existence mainly due to Rossby waves. The Coriolis Effect basically results in a deflection of wind’s path, consequently making a brand new wind-course.
Wind’s direction is frequently irregular and uneven. Winds start to move in straight lines only when the pressure gradient force and the Coriolis force come into balance and correlation with each other. Straight winds and this correlation of the pressure gradient force and the Coriolis force is known as Geostrophic Wind. It is also observed that Geostrophic Winds are most likely to exist above earth’s surface because of no vital interference of earth’s heat.
Near the earth’s surface an additional element come into weight, that is friction. Winds passing near the earth’s surface are most likely to experience earth heat which lead to irregular wind tracks. The Coriolis force also becomes less prominent and winds start to move from areas of high pressure to low pressure. Oceans and seas witness a more even wind flow because water cools down faster than ground, as a consequence they give rise to semi-geostrophic winds.
Wind speed is also greatly affected by local weather conditions; for instance monsoons and cyclones can increase the wind velocity by a considerable amount. There is a scale which actually determines the speed of wind and its given name. From the weakest to the strongest are Calm, Light Air, Light Breeze, Gentle Breeze, Moderate Breeze, Fresh Breeze, Strong Breeze, High Wind, Fresh Gale, Strong Gale, Whole Gale, Violent Storm, and Hurricane, respectively.
Sources:
http://ezinearticles.com/?Wind-Speeds-and-the-Factors-Affecting-It&id=3754337
http://www.enotes.com/earth-science/wind
http://ww2010.atmos.uiuc.edu/%28Gh%29/guides/mtr/fw/geos.rxml
http://webcache.googleusercontent.com/search?q=cache:3x4ed8uAQVgJ:www.eng.warwick.ac.uk/staff/gpk/Teaching-undergrad/es427/Exam%25200405%2520Revision/TheWinds-b.ppt+Factors+that+affect+wind+direction+and+speed&cd=3&hl=en&ct=clnk
