Abstract

A front is a boundary between different air masses in the atmosphere and, as such, constitutes a region of strong temperature gradient. Fronts may also be associated with changes in wind speed and direction, water vapor content, pressure, clouds, and precipitation. Fronts slope with height over the more stable air mass. Fronts form from large-scale wind patterns that increase the horizontal temperature gradient, resulting in rising warm air and sinking cold air. Most fronts are associated with low-pressure systems. There are three types of fronts that occur near the Earth’s surface: cold, warm, and occluded fronts. In addition, upper-level fronts can be connected to the tropopause, associated with the strong winds of the jet stream. Smaller-scale fronts associated with sea breezes, land breezes, and convective storms also occur. The dryline is a front-like phenomenon unique to the southern and central United States. Fronts can also be associated with heavy precipitation and improving air quality.