The rainy season in North China has officially started. Why is this round of rainfall so intense?

　　Xinhua News Agency, Beijing, July 12th.

　　Xinhua News Agency reporter Huang Yao

　　On the evening of the 11th, the Central Meteorological Observatory issued the first orange warning of heavy rain this year. The Beijing-Tianjin-Hebei region encountered heavy precipitation, and precipitation in many places exceeded the July extreme.

According to the monitoring and analysis of the Central Meteorological Observatory, the precipitation process that began on the 11th can be regarded as the beginning of the rainy season in North China this year.

On the morning of the 12th, the Central Meteorological Observatory continued to issue yellow warnings for heavy rain and severe convective weather.

　　The Central Meteorological Observatory showed that from 5 am on the 11th to 14:00 on the 12th, heavy rains or extreme rains occurred in parts of central and southern Beijing, central and southern Hebei, southeastern Shanxi, northern Henan, and central and northern Shandong.

Thunderstorms of magnitude 8 to 10 occurred in the above-mentioned areas, and hail weather occurred in Beijing and Hebei.

　　Zhang Fanghua, chief forecaster of the Central Meteorological Observatory, said: "From the perspective of extremes, local rainfall in Handan, Shanxi, Jincheng and Changzhi, Henan, Jiyuan, Anyang, and Hebi reached 220 to 342 mm; there are 7 countries in central and southern Hebei and northern Henan. The station’s daily rainfall exceeded the July extreme."

　　Experts said that this round of heavy rainfall has the characteristics of wide impact, high rainfall intensity, long duration, large accumulated rainfall, accompanied by strong convection and windy weather, and high disaster risk.

　　According to reports, this heavy rainfall process is affected by the deep low vortex system, and the east side of the low vortex is accompanied by a strong low-level jet, which brings abundant water vapor and unstable energy, which is very conducive to the production of heavy precipitation.

At the same time, due to the slow movement of the low vortex system, this round of precipitation takes a long time, and the accumulated precipitation increases.

In addition, the low-level jet stream converges and rises on the windward slope of Taihang Mountain, which is conducive to the local production of stronger precipitation.

　　As of 12:00 on the 12th, the heavy rainfall in North China has moved to the northeast, and the intensity has also weakened.

The rainfall on the 12th is expected to be mainly located in northern China and eastern Huanghuai; on the 13th, the precipitation area will further move east to north, mainly affecting Liaoning, Heilongjiang and eastern Inner Mongolia, and the intensity will be further weakened.

　　Immediately entering the critical period of "seven lower and eight upper" flood control, precipitation and weather in North China and Northeast China are showing an increasing trend. Experts have warned that the public should pay attention to the upcoming weather forecast and take relevant precautions.

　　“Heavy rainfall is likely to cause slippery roads, reduced visibility, and water accumulation in low-lying sections, which will have a greater impact on urban operations such as traffic and drainage. It is necessary to take countermeasures in advance.” Zhang Fanghua said. Prevention of tree lodging, reinforcement of outdoor structures and billboards, and safety protection for outdoor high-altitude operations; measures such as drainage and waterlogging prevention, wind prevention and reinforcement are required for agricultural production to reduce disaster losses.