A weather map shows meteorologists what type of weather is likely to occur in the near future. Meteorologists use the fronts and pressure systems to help predict the weather. While many of the fronts are either classified as warm or cold, some are considered stationary and yet others are occluded. An occluded front operates differently from the other types of fronts.
Cold Occluded Front
A cold occlusion takes place when the air on the back side of the front is is colder than that ahead of it. With this type of occluded front, it acts as if it is a cold front. Cold fronts are responsible for the strong, severe storms that can produce damaging winds, hail and tornadoes. The weather also tends to exhibit a dip in temperature prior to the storms and a drastic change in wind direction and speed.
Warm Occluded Front
A warm occlusion occurs when the air at the back of the front is warmer than that which is ahead of it. This causes a warm occluded front to act more like a warm front instead. A warm front is known for producing lighter rains that do not have the severe symptoms of the storms produced by cold fronts. The rain is often steady and covers a wide area of land. Winds do not change direction and the air temperature remains consistent.
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Occluded Front Formation
An occluded front is not a very common occurrence. To create an occluded front, an existing warm or cold front must catch up with another front ahead of it on the weather map. When the two fronts combine, the colder air is pushed beneath the warmer air, resulting in an occluded front that is either characterized as warm or cold, depending on the direction of the occlusion. These fronts are symbolized on a weather map by a purple line with both semicircles and triangles on it.
Because occluded fronts occur when one front overtakes another, these fronts are often characterized by storms that are dissipating. Even though severe storms can re-energize in this type of front, many of the storms are already waning by the time the two fronts blend. In the past, meteorologists thought that a faster moving cold front had to catch up with a slower moving warm front to create an occluded front. However, according to "USA Today," scientists have discovered that storm redevelopment can also cause an occluded front to form.