Figure 1-7 -- Warm front characteristics.
As with a cold front, the weather associated with a warm front varies depending on the
degree of stability and moisture of the warm air mass.
Certain characteristics and weather conditions are associated with the passage of warm
fronts. In the northern hemisphere, the winds veer from southeast to southwest or west,
but the shift is not as pronounced as with the cold front. Temperatures are colder ahead
of the warm front and warmer after the front passes. Clearing usually occurs after the
passage of a warm front, but under some conditions drizzle and fog may occur within
the warm sector. Normally, the speed of a warm front is less than that of cold fronts; the
average speed of a warm front is about 10 knots.
Sometimes the opposing forces of different air masses are such that the frontal surface
shows little or no movement. Since neither air mass is replacing the other, the front is
known as a stationary front.
Stationary Front Characteristics
The weather conditions occurring with a stationary front are similar to those found with a
warm front but are usually less intense. An annoying feature of the stationary front and
its weather pattern is that it may persist and hamper flights for several days in the same
An occluded front occurs when a cold front overtakes a warm front and forces the warm
front aloft as the first cold front approaches another cold front.