rains without tornadoes. Extremely cold air masses in winter give rise to Artic air often preceded by snowstorms. The warm fronts are gentler in nature when they occur as the warm air simply slides over the cooler and denser air that has less power overall. You can feel the transition more gradually with cirrostratus clouds seen rather than cumulonimbus clouds. Snowflakes and gray skies are seen in the wintertime as the front approaches. A low pressure system is still generated with cold air initially beneath warm air. You will still feel coldness between the two air masses until the warm air overtakes the colder air. The worst weather is when the front goes through. Snow will become freezing rain and then rain will occur. It might be foggy until the front passes. Occluded fronts are those where a cold front finally catches up to a warmer front. You might see airmasses to be cold, warm, and finally colder again. These are seen as purple line with triangles and half circles along the line. Because of the Coriolis effect, the front lines will curve with a low in the middle. Figure 36 shows these fronts. Remember that there is a low pressure system behind these fronts and not a high pressure system. There is very bad weather behind this front. Look for these along the Pacific coastline.
MID-LATITUDE CYCLONE STORMS Mid-latitude cyclones are of course seen in the middle latitudes, between 30 and 55 degrees North in the northern latitudes. Like all storm systems, these circle around low pressure systems but, in no way are these same thing tropical storm or hurricane. The differences are twofold. First, they are found in the mid-latitudes and not in the tropical areas of the world. Second, they are much larger than hurricanes and tropical storms. How do these mid-latitude cyclones form? They seem to occur whenever there is much colder and drier air to the north and moisture warmer air and the South. Using the initials for air masses, you would label these a joining of CP and MT air masses. Due to the Coriolis effect, this boundary will begin to circulate in a counterclockwise direction. Warm air is drawn further up and cold air is pulled down from the north. This is called the process of cyclogenesis.
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