The wind's speed and direction in an area has a close relationship with surface isobars, which are lines joining areas of equal air pressure. In flat surface areas of equal air mass, wind speeds are accelerated between points with similar air masses. Areas spaced a long distance apart with a great difference between the pressure of the air mass see a low amount of wind speed developing between locations. The development of winds between two locations or air masses is known as pressure gradient force.
The wind's direction can also be affected by the development of temperature and moisture in an air mass. When it develops in a large flat region, such as over a subtropical region toward the Earth's center, the air mass produces warm winds that move in a northerly direction and develop into warm winds that heat areas such as the southern U.S. When an air mass develops in a northerly region, such as Canada or polar regions, the winds move in a southerly direction toward the warm center of the Earth and have a cooling effect on regions they cover. Winds that are produced by an air mass in the Atlantic Ocean usually move eastward toward the west coast of the U.K. and Northern Europe.
In an air mass, the vertical pressure is stronger than the horizontal, however the force of gravity stops winds produced by an air mass traveling directly upward. Some vertical movement of winds does occur, generally at around one mph. Stronger vertical winds can occur rarely at speeds of up to 60 mph. The greater an air mass's distance from the equator, the faster the wind travels. They are generally directed toward low pressure areas and away from high pressure masses.
The development of winds in an area of stable air mass produces winds with a high speed and in a direction affected by the air mass's position on the globe. The effect these winds have on a land region can be affected by the topography of a local region. Large mountains or hills can disperse a wind and reduce its effect on the local region. Where an upland area has deep valleys, wind direction can be altered by the funneling of winds through a valley that can produce stronger winds than those developed in an air mass.
