General Frontal Structure

AVIATION WEATHER

CHAPTER THREE

General Frontal Structure

The characteristics of each air mass on either side of the front diminish with increasing altitude.

At some level above the surface, usually above 15,000 to 20,000 feet, the differences between

the two air masses forming the front become negligible and the cloud and precipitation patterns

in the upper frontal zone are not easily attributable to one frontal type or another (Figure 3-6).

Therefore, the most significant frontal weather occurs in the lower layers of the atmosphere.

However, the temperature contrast between the air masses can sometimes extend as high as the

tropopause.

Figure 3-6 Frontal Zone Structure

Most fronts, regardless of type, have some common characteristics. First, fronts are named

according to the temperature change they bring. For example, if the temperature will become

warmer after the front passes, it is named a warm front. Second, fronts move across the country

with their attached low-pressure system and isobars, as the corresponding air masses move. As

they move, we are only concerned with any movement perpendicular to the line representing the

front; thus, fronts are considered to move perpendicular to the way they are drawn. Also, cold

Mechanics of Frontal Systems 3-7