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.


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