JPATS Weather - NETC

JPATS AVIATION WEATHER BOOKLET
JX103 FRONTAL MECHANICS
OVERVIEW
The main purpose of this chapter is to introduce frontal systems, since most of the active weather
is concentrated along fronts. The goal of this chapter is to present a broad description of each of
the frontal types, along with the general flight conditions associated with each. With this
knowledge, an aviator is in a much better position to carry on a conversation about flight
conditions with the meteorologist during the weather brief, as opposed to having a one-way
conversation. Because only the flight crew understands the details and ramifications of the
mission, it would be impossible to expect a meteorologist to foresee all the possibilities and to
brief the weather accordingly.
REFERENCES
AFH 11-203, Weather for Aircrews, Volume 1, Chapter 8
AIR MASSES
The weather in the mid-latitude regions is a direct result of the continuous alternation of warm
and cold air masses. Warm air masses predominate in the summer and cold air masses
predominate in the winter. However, both cold and warm air may prevail almost anywhere in the
temperate zone–the region between 30 and 40 degrees North latitude, which covers the
continental United States–at any season.
An air mass is a large body of air that has essentially uniform temperature and moisture
conditions in a horizontal plane, meaning that there are no abrupt temperature or dew point
changes within the air mass at a given altitude. It may vary in size from several hundred to more
than several thousand square miles (Figure 3-1).
Figure 3-1 — Air Mass Profile
Version 3.2/Dec 08 3-1