How to treat the pressure map of frontal cyclone?

Weather systems affecting weather include frontal system, low pressure system and high pressure system. In addition, there is a frontal cyclone, which combines frontal cyclone and ground cyclone. Frontal cyclones, also known as extratropical cyclones, are mainly active in middle and high latitudes, and are more common in temperate regions. When reading the frontal cyclone map, we should pay attention to the following problems.

Take frontal cyclone in the northern hemisphere as an example, briefly introduce the reading of frontal cyclone map, as shown in the following figure:

There is an air pressure field near the ground, and the isobar value decreases from outside to inside in turn, so it is judged that this air pressure system is a low pressure system.

1. Determine the forward position.

In the low-pressure system, the isobar extends outward to form a narrow low-pressure groove. In the trough of low pressure, the connecting line of the maximum curvature point on each isobar is called trough line of low pressure. In the above figure, the air pressure at any point on the slot lines AB and CD (indicated by dotted lines) is lower than that at each point on both sides. So the airflow flows from high pressure to low pressure, and the airflow on both sides will flow to the slot line. When air currents with different cold and warm properties meet, a front is formed.

Conclusion: The front appears near the sulcus line.

2. Determine the wind direction on both sides of the front and the type of front.

Take a point E and a point F on both sides of the AB slot line to determine the wind direction at two points. According to the drawing of the wind direction map in the northern hemisphere, the wind direction at point F is northerly and the wind direction at point E is southwest, and the northerly wind plays a positive role in promoting the front. Similarly, take a point G and H near the CD slot line, where the wind is southerly, and the southerly wind has a positive role in promoting the front. According to the law of temperature change in the northern hemisphere, the airflow from the north is a cold air mass, and the airflow from the south is a warm air mass.

Tropical cyclone is a low-pressure vortex rotating by cyclone, so the wind vector plume of the ocean surface wind field in the circulation of tropical cyclone shows the wind field rotating by cyclone, and the center of gas cyclone field is the center of tropical cyclone.

General classification of tropical cyclone wind field;

Good: It is circular or quasi-circular, and the wind force in each quadrant is generally large, and it is symmetrically distributed in windy areas. The wind speed in the inner area is obviously greater than that in the outer area.

Medium: it is round or quasi-round, and the wind force in each quadrant is generally small, which is asymmetric relative to the windy area.

Poor: long and narrow, trough-shaped, shear-shaped, and the wind force in each quadrant is generally small, which is asymmetric relative to the windy area.