How is a typhoon formed?

The basic condition of typhoon formation is that there is a tropical disturbance at low altitude, which causes a convergence field, which is the basis of tropical cyclone development. There is a vast high-temperature ocean surface here, which evaporates a lot of water vapor into the air and condenses, providing huge latent heat needed for typhoon formation. There is a certain geostrophic deflection force, which makes the disturbed airflow gradually transform into a horizontal vortex with cyclone rotation. The vertical shear of the basic airflow is smaller, so that the latent heat does not spread, forming and maintaining the warm core structure, and strengthening the convection movement.

Where can these conditions be met at the same time? Only in tropical waters. The temperature there is very high, and it is also the place with the richest water vapor on the earth. According to statistics, the ocean that produces typhoons mainly includes the ocean east of the Philippines, the South China Sea of China, the West Indies and the east coast of Australia. These places are relatively high in seawater temperature, and they are also areas where the trade winds in the northern and southern hemispheres meet, so typhoons are easy to occur.

How do typhoons generated in the ocean affect China's coastal areas? This will start with the path of the typhoon. Although the typhoon path is ever-changing, it still has its own characteristics under the influence of similar situations and conditions. According to its main characteristics, the basic paths of typhoons in the western Pacific can be summarized into the following three categories.

The first category is the westward movement path: the typhoon moves westward from the sea east of the Philippines, passes through the South China Sea of China, and lands in South China, Hainan Island and the Vietnamese coast. The typhoon along this route has a great influence on South China.

The second category is the northwest movement path: the typhoon moves northwest from the Philippine East China Sea, passes through the straits of Taiwan Province Province and Taiwan Province Province in China, and lands in Fujian and Guangdong; Or cross the Ryukyu Islands and land along the coast of Jiangsu and Zhejiang. Typhoons along this route often attack Chinese mainland, which has a great impact on East China and South China, so some people call it "landing typhoon path".

The third category is the turning path: the typhoon first moves to the northwest and then turns to the northeast in the waters east of the Philippines, which is the most common path. If the typhoon turns in the open sea, it will mainly attack Japan or disappear at sea; For example, when the typhoon turns offshore, most of it moves to the northeast, affecting North Korea, but a small part will turn to the northwest in the late northward period and land on the coast of Liaoning and Shandong in China. In winter, the turning point of this typhoon is very south, which may affect the Philippines and Taiwan Province Province of China.

The moving path of typhoon changes with the seasons. Generally speaking, typhoons in summer mostly belong to the second category, while typhoons in other seasons mostly belong to the first and third categories. Among them, the westward path from east to west moves slowly from low latitude to high latitude from winter to summer, and returns to low latitude from summer to winter. According to statistics, typhoons mostly move from the south to the west of 10 N from June to May, and from 10 N to 15 N from July to August, and the main path obviously moves northward, affecting China's 15 N to 25 N and 65438+/kloc-from September to June. From winter to summer, it regularly moves from low latitude to high latitude, reaches the northernmost point in summer, and the turning point moves from east to west. From summer to winter, the turning point moves from high latitude to low latitude and from west to east.

The above typhoon paths are typical paths averaged for many years, reflecting the general law of typhoon movement. But in fact, the paths of typhoons have never been exactly the same twice in history, and some typhoons even have abnormal paths such as rotation, swing, quasi-static or even retrogression. As for typhoons in the South China Sea, some will move southwest or southeast.

When forecasting typhoons, meteorologists always say how long it will take for Typhoon XXX to land in the southeast coastal areas of China. What's going on here? It turns out that people named typhoons. According to the resolution of the 3rd 1 session of the World Typhoon Committee, since1year, tropical cyclones generated in the northwest Atlantic Ocean and the South China Sea have been named in Asian style to help people to be more alert to tropical cyclones and enhance the early warning effect.