How is the heavy rainfall in North China and other places formed?

It is reported that on the 20th, the No.1 13 typhoon "Tian Ge" was generated in the northwest Pacific. During the day on the 23rd, it will land in the coastal area from Shenzhen to Maoming, Guangdong, with a peak landing. When the typhoon ravaged the south, there was a strong rainfall process in the eastern part of northwest China and north China from 2/kloc-0 to 23/north China.

Talking about the causes of rainfall, Ma Xuekuan, chief forecaster of the Central Meteorological Observatory, analyzed that it was mainly the result of the westward extension of the western Pacific subtropical high, the interaction between warm and humid air flow around the subtropical high and cold air at mid-latitude. There are two warm and humid air currents at the bottom of troposphere, one is the southwest ring humid air current formed at the periphery of subtropical high, and the other is the southeast air current at the lower level, which transports water vapor to the northwest and north China. At the same time, there are high-altitude short-wave troughs in the Qinghai-Tibet Plateau and the mid-latitude westerly belt, which lead to the development of low-altitude systems such as vortex, shear line and southwest jet, leading to the strengthening of convergence and uplift.

"With abundant water vapor and strong convergence and uplift, there will be relatively strong precipitation, in which convective weather is dominated by short-term heavy precipitation, accompanied by thunderstorms and strong winds in the local area. The main rainfall areas appear in northern Shaanxi, northern Hebei, Beijing and Tianjin, and Heilongjiang, Jilin. The rainfall is generally between 30 and 80 mm, and the local processes in northern Shaanxi and central Shanxi will reach about 100- 130 mm, "Ma Xuekuan said.