Weather characteristics of frontal cyclone

Frontal cyclone is a combination of frontal cyclone and surface cyclone. Frontal cyclone, also known as extratropical cyclone, is mainly active in the middle and high latitudes, mostly in the temperate zone.

The front is the interface formed by the intersection of cold and warm air, and it is a narrow and inclined transition zone. Cyclones are low pressure. In the northern hemisphere, it is a weather system in which air flows counterclockwise from all sides to the center.

As shown in the figure, this is a low pressure area. According to the wind map of the northern hemisphere, it can be determined that the south wind blows in the east and the north wind blows in the west. The narrow area where low pressure extends outward is called low pressure trough, just like the valley on the terrain. AB and CD are two slot lines in the figure. Fronts are usually formed in the trough of low pressure of surface cyclones. The southerly wind to the east of the cyclone in the picture comes from low latitude and the temperature is high. When moving northward, it meets cold air at higher latitudes (near CD in the figure) to form a warm front. Similarly, the airflow in the west of the cyclone comes from the northerly wind at the higher latitude in the north, and it will meet with warm air at the lower latitude in the south to form a cold front (near AB in the figure), thus forming a frontal cyclone in the surface weather system. The cyclone in the northern hemisphere is a vortex that flows counterclockwise, and it also moves counterclockwise with the generated front.

After the formation of frontal cyclone system, what impact will it have on the weather controlled by the original single weather system?

As we know, because the airflow flows into the cyclone center from all directions, the central airflow is forced to rise, causing rainfall, so when the cyclone passes by, the cloud amount increases, and rainy weather often occurs, that is, cyclone rain. In the frontal weather system, whether it is a cold front or a warm front, the warm air mass above the frontal surface rises along the frontal surface, which will form cloudy and precipitation weather, that is, frontal rain. When the two systems combine to form a frontal cyclone, there will be more convergence.

In the picture, the precipitation area in cold and warm fronts will be slightly different. Because the density of the cold air mass is higher than that of the warm air mass, the cold air mass is always under the warm air mass, the front is always biased to the side of the cold air mass, and the precipitation area is always on the side of the cold air mass on the front. In the picture, a wide warm front cloud system and continuous precipitation weather will be formed in front of CD, and a narrow cold front cloud system and precipitation weather will be formed behind AB. The middle of the cyclone (between the cold front rain area and the warm front rain area) is controlled by a single warm air mass.

Frontal cyclones also have their processes of occurrence, development and extinction. There are two understandings of frontal cyclone: one is that a front (quasi-static front or cold front) is disturbed, gradually forming a low-pressure center and evolving into a frontal cyclone, which can be simply understood as an existing front and then forming a cyclone; The other is that the ground depression is formed first, and then a frontal cyclone develops. Although the initial development conditions of the two frontal cyclones are different, the development process after their formation is very similar.