Isobars are lines on a weather map that connect locations with equal atmospheric pressure as each other. These lines are used to observe atmospheric pressure changes over an area and to make predictions concerning wind flow. Regions of low pressure at sea level tend to be areas of bad weather, especially in winter. At higher elevations, the wind blows approximately parallel to the isobars, with low pressure to the left in the Northern Hemisphere and to the right in the Southern Hemisphere with respect to the direction of air movement. The closer together the isobars are, the stronger the wind speed. Only sea-level pressure patterns are routinely used in meteorology.