taken that intersect both fronts show two inversions.
The warm type of occlusion (like the cold type) appears
on upper air charts at approximately the same pressure
level. However, one distinct difference does appear in
the location of the warm isotherm ridge associated with
occlusions. The warm isotherm ridge lies just to the rear
of the occlusion at the peak of its development.
REVIEW QUESTIONS
Q4-16. What is the difference between warm and cold
occlusions?
Q4-17. Where does the most violent weather occur
with the occlusion?
THE QUASI-STATIONARY FRONT
LEARNING OBJECTIVE: Describe the
characteristics
of
stable
and
unstable
quasi-stationary fronts.
A quasi-stationary front, or stationary front as it is
often called, is a front along which one air mass is not
appreciably replacing another air mass. A stationary
front may develop from the slowing down or stopping
of a warm or a cold front. When this front forms, the
slope of the warm or cold front is initially very shallow.
The dense cold air stays on the ground, and the warm
air is displaced slowly upward. The front slows or stops
moving because the winds behind and ahead of the
front become parallel to the stationary front. It is quite
4-43
WARM AIR
COOL AIR
FLOW
COLD AIR
CUMULONIMBUS
CIRRUS
STRATOCUMULUS OR STRATUS
NIMBOSTRATUS
STRATOCUMULUS
RAIN AND FOG
250
200
150
100
A
DISTANCE MILES
B
A
AG5f0441
50
0
A'
Figure 4-41.—Illustration of warm type of occlusion. (A) Vertical structure through points A and A'; (B) Horizontal structure.
