AEROGRAPHER'S MATE 3 & 2 



PRIMARY 

 FRONT 



COID 

 AIR 



WARM 

 =J> AIR 



(C) 



(D) 



A. COLD AND WARM 



B. FORMATION 



C. TYPICAL WAVE 



AIR FLOW 



D. GROWTH 

 £. OCCLUSION 

 F. DISSIPATION 



Figure 14-18. — Life cycle of a wave cyclone. 



209.65 



bring bad weather can disrupt flight operations 

 for several days in succession. 



Knowledge of the speed of the frontal system 

 is necessary for accurate forecasting. If the 

 front has a somewhat constant speed, it makes 

 the forecaster's job comparatively easy. How- 

 ever, if the speed is erratic or unpredictable, 

 the forecaster may err as far as time and 

 severity are concerned. His forecast may 

 never materialize in cases in which the front 

 becomes stationary and dissipates without 

 passing over the forecaster's area. 



Modifications 



There are many factors that can modify the 

 movement of frontal systems. In this section 

 only a few of the more important factors are 

 considered. 



EFFECT OF MOUNTAINS. — Mountain ranges 

 affect the speed, the slope, and the weather 

 associated with a front. The height and hori- 

 zontal distance of the mountain range, along with 

 the angle of the front along the mountain range, 

 are the influencing factors. The effect of 

 mountain ranges differs in regard to cold 

 fronts and warm fronts. 



As a COLD FRONT approaches a mountain 

 range, the lower portion of the front is retarded 

 as the upper portion pushes up and over the 

 mountain. On the windward side of the mountain, 

 precipitation is increased due to the additional 

 lift as the warm air is pushed up along the 

 mountain slope. After the front reaches the 

 crest of the mountain, the air behind the front 

 commences to flow down the leeward side of 

 the range. If the air on the leeward side of the 

 mountain is warmer than the air in the rear 



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