<P> Cold fronts and occluded fronts generally move from west to east, while warm fronts move poleward . Because of the greater density of air in their wake, cold fronts and cold occlusions move faster than warm fronts and warm occlusions . Mountains and warm bodies of water can slow the movement of fronts . When a front becomes stationary, and the density contrast across the frontal boundary vanishes, the front can degenerate into a line which separates regions of differing wind velocity, known as a shearline . This is most common over the open ocean . </P> <P> The Bergeron classification is the most widely accepted form of air mass classification . Air mass classifications are indicated by three letters . The first letter describes its moisture properties, with c used for continental air masses (dry) and m for maritime air masses (moist). The second letter describes the thermal characteristic of its source region: T for tropical, P for polar, A for arctic or Antarctic, M for monsoon, E for equatorial, and S for superior air (dry air formed by significant upward motion in the atmosphere). The third letter designates the stability of the atmosphere . If the air mass is colder than the ground below it, it is labeled k . If the air mass is warmer than the ground below it, it is labeled w . Fronts separate air masses of different types or origins, and are located along troughs of lower pressure . </P> <P> A surface weather analysis is a special type of weather map which provides a view of weather elements over a geographical area at a specified time based on information from ground - based weather stations . Weather maps are created by plotting or tracing the values of relevant quantities such as sea - level pressure, temperature, and cloud cover onto a geographical map to help find synoptic scale features such as weather fronts . Surface weather analyses have special symbols which show frontal systems, cloud cover, precipitation, or other important information . For example, an H may represent high pressure, implying fair weather . An L on the other hand may represent low pressure, which frequently accompanies precipitation . Low pressure also creates surface winds deriving from high pressure zones . Various symbols are used not just for frontal zones and other surface boundaries on weather maps, but also to depict the present weather at various locations on the weather map . In addition, areas of precipitation help determine the frontal type and location . </P> <P> There are two different meanings used within meteorology to describe weather around a frontal zone . The term "anafront" describes boundaries which show instability, meaning air rises rapidly along and over the boundary to cause significant weather changes . A "katafront" is weaker, bringing smaller changes in temperature and moisture, as well as limited rainfall . </P>

Which type of weather front is typically associated with low pressure