The difference between typhoon and normal rainy day.

A typhoon is a mass of rotating air, with a low central air pressure, and the surrounding air rotates rapidly counterclockwise. The low-level air flows to the low-pressure center while rotating, and the faster the air flow, the greater the wind speed.

A circular area with an average diameter of about 40 kilometers in the center of a typhoon is usually called the eye of the typhoon. Because the air around the typhoon eye rotates too much, it is difficult for outside air to enter the typhoon center under the action of centrifugal force, so the typhoon eye area is like an isolated tube surrounded by a cloud wall. The air inside hardly rotates and the wind is weak.

The air outside the typhoon eye area rotates to the center of low pressure, carrying a lot of water vapor. Because it is not easy to enter the eye area, it rises on its periphery, forming a large gray-black bloated and towering cloud layer, and it is raining cats and dogs. However, there was a downdraft in the eye area of the typhoon, so the clouds disappeared and twinkling stars could be seen at night. As shown in the satellite image of Typhoon rammasun No.5 this year, the weather in typhoon eyes is usually sunny to partly cloudy, so in the satellite image.

In the eyes of typhoons, there are often many birds. These countless seabirds, which were blown to the typhoon eye area by the typhoon airflow, found a "safe haven" and sometimes flew far away with the movement of the typhoon.

Although the weather is fine in the center of the typhoon, the waves on the sea are very big. This is because the air pressure in the center of the typhoon is very low compared with its surroundings. Therefore, the landing site of typhoon center often causes high waves and causes great damage.

The typhoon is warm and low pressure, so the ground flow field within the typhoon range is a cyclone convergence field. According to the convergent airflow speed, the lower layer of a mature typhoon can be divided into three areas along the longitude: (1) outer ring: from the edge of the typhoon to the outer edge of the maximum wind speed zone, the wind speed increases sharply towards the center, with a wind force of more than 6 and a radius of about 200-300 kilometers; (2) The middle circle: from the outer edge of the maximum wind speed area to the eye wall of the typhoon, it is the area with the strongest convection and wind and rain in the typhoon, with a radius of100 km; (3) Inner ring: the eye area of the typhoon, where the wind speed drops rapidly and the radius is about 5-30 kilometers.

Generally speaking, the typhoon eye is the inner ring, and the typhoon center is the place between the central ring and the inner ring.