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. Weather fronts are air masses that carry some energy (typically a cold air mass, warm air mass, or occluded front). While many of the fronts are either classified as warm or cold, some are considered stationary and yet others are occluded. Stationary fronts usually occur when a warm front moves directly against a cold front resulting in a stationary front. An occluded front operates differently from the other types of fronts.
TL;DR (Too Long; Didn't Read)
Warm fronts are represented by red lines with red triangles pointing in the direction of travel, cold fronts are designated by blue lines with blue semi-circles oriented in the direction of movement, and occluded fronts are represented by purple lines with a combination of semi-circles and triangles.
Weather fronts form when a pocket of warmer or cooler air begins to group together. These masses of air then move into air ahead of them; they have a leading edge that defines the boundary between the weather front and the area it encroaches on.
Cold Occluded Front
A cold occlusion takes place when the air on the back side of the front 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 often responsible for more extreme weather conditions 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, speed, and precipitation. Cold occluded fronts can also bring the formation of cumulonimbus and cumulus clouds that also bring thunderstorms.
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.
Occluded Front Formations
An occluded front is not a very common occurrence. To create an occluded front, an existing warm or cool air mass 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.
When a cold front catches up to a warmer front, it creates a pressure difference that drives a lot of these weather systems. As a front passes by, we will often notice the meteorological effects just as much if not more than the actual change in temperature.
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.
Other Weather Patterns
The kind of weather can be very dependent on the fronts converging or diverging around an area. However, the air pressure or atmospheric pressure also plays a significant role in defining these weather patterns. Low pressure systems often bring bad weather, with winds and heavy rain, while high pressure areas bring calmer, more stable, and drier weather.
The movement of fronts and the subsequent formation of an occluded front can oftentimes be directly influenced by these high and low pressure areas.
About the Author
Kimberly Turtenwald began writing professionally in 2000. She has written content for various websites, including Lights 2 You, Online Consultation, Corpus Personal Injury and more. Turtenwald studied editing and publishing at Wisconsin Lutheran College.