The rainfall caused by typhoon in North China and even Northeast China is called "long-distance typhoon rainstorm". The "long-distance typhoon rainstorm" is caused by the invisible "air mass" and visible "terrain" after the typhoon landed.

The analysis of weather and climate shows that the gas affecting Du is called subtropical high zone, which moves to 25-30 north latitude from July to August every year, that is, Guizhou, Hunan, Jiangxi, Fujian and Zhejiang.

After landing, Du made a positive "head-on" with the subtropical high, squeezing it to the north, but at the same time it was resisted by the subtropical high. Under the guidance of the southerly airflow on the west side of the subtropical high, part of the residual circulation went northward.

Du remnants in the north can continuously transport water vapor from the sea to North China, providing sufficient "water source" for rainfall, and forming a "jet stream" at the intersection with subtropical high, which also caused the precipitation.

Unlike the "air mass" like the subtropical high, the "terrain" will not make any concessions, so the "jet stream" generated by "Du" can only be forced to rise when it meets the terrain such as Taihang Mountain and Yanshan Mountain, and it will condense into rain at high altitude to strengthen precipitation. This is the cause and effect of Du's heavy rainfall in Beijing, Tianjin and Hebei.

Du's strength

On July 25th, 2023, the Central Meteorological Observatory of China Meteorological Bureau issued an orange warning for typhoon. Typhoon Du landed in the coastal area from central Fujian to eastern Guangdong on the morning of 28th. When landing, the maximum wind force near the center is 13 to 15 (40-48m/s, typhoon level or strong typhoon level).

Affected by Typhoon Du, from 20: 00 on the 25th to 20: 00 on the 26th, there were heavy rainstorms in the southeast coast of Zhejiang, the northeast coast of Fujian and parts of Taiwan Province Island, among which some areas east of Taiwan Province Island had heavy rainstorms (100 to 200mm).

From 26 14 to 27 14, there were heavy rains in parts of eastern Zhejiang and Taiwan Province Island, among which there were heavy rains in parts of the southeast coast of Zhejiang (100 ~ 150mm) and heavy rains in parts of eastern and southern Taiwan Province Island (250 ~)

At 9: 55 on July 28, "Du" landed on the coast of Jinjiang, Fujian. When landing, the maximum wind force near the center 15 (50m/s, strong typhoon level).