Elements of Weather
2. Because cold fronts are steeper and move more rapidly than warm fronts, the vertical displacement of air is often rapid enough that latent heat released by condensing water vapor adds appreciably to the air's buoyancy. The common result is cumulonimbus clouds with their characteristic heavy showers and occasionally severe weather.
3. The first line of the proverb pertains to warm fronts. It refers to the fact that these fronts are often preceded by a succession of clouds that foretell of the coming nimbostratus clouds that usually produce light to moderate precipitation of relatively long duration. The second line refers to a cold front. Since cold fronts usually do not have a series of clouds preceding them, there is little or no forewarning of the cumulonimbus clouds and showery precipitation that often accompany a cold front.
5. During occlusion, the warm sector is forced aloft. When this process is complete, the cyclone has lost its primary source of energy, the sinking of cold air and the rising of warm. Hence, the storm comes to an end.
6. As the warm front approaches, winds would blow from the east or southeast and pressure would drop steadily. Cirrus clouds would be sighted first, followed by cirrostratus, altostratus and finally nimbostratus. Cloud cover would get progressively greater, from a few tenths coverage with cirrus, to completely overcast with the coming of the nimbostratus clouds. Gentle precipitation would begin as the nimbostratus clouds moved overhead. As the warm front passed, temperatures would rise, precipitation would cease and winds would shift to the south or southwest. Further, the sky clears and the pressure tendency steadies. Later, with the approach of the cold front, cumulonimbus clouds fill much of the sky and bring the likelihood of heavy precipitation and the possibility of hail and tornado activity. The passage of the front is accompanied by a drop in temperature, clearing skies, a wind shift to the northwest, and rising pressure. Fair weather can probably be expected for the next day or two.
7. As the low approaches, cool temperatures are the rule, and winds are easterly because the warm sector of the cyclone is to the south. The pressure drops and the sky becomes increasingly overcast. Further, precipitation is to be expected, and if it is winter or early spring, possibly snow, sleet, or glaze. As the occluded front slowly passes, winds shift from the north or northeast to the north west. The sky begins to clear and the barometric tendency rises. Temperatures, however, remain cool or cold.
8. When winds shift in a clockwise manner, as from east to south, it is termed a veering wind shift. Such wind shifts occur when the center of a wave cyclone passes to the north of an observer. When winds shift in a counterclockwise direction, it is called a backing wind shift. Such a shift is to be expected when the center of a low passes to the south of an observer.
10. Because flow aloft is a primary cause of cyclone development (do you know what divergence aloft does?), and also determines the speed and direction of movement of these systems.