Heavy rain hit Henan and become the center of heavy rain?
Experts remind you to be wary of the superimposed effects of strong winds and heavy rains
According to the Central Meteorological Observatory's forecast, from August 21 to 24, my country will experience a heavy rainfall from west to east.
Among them, Henan, which has just experienced the "July 20" torrential rain, will encounter heavy rainfall again after a month.
What is the intensity of this heavy rainfall compared with the "7.20" heavy rainstorm?
Is there a big disaster risk?
A reporter from China Meteorological News invited Zhang Tao, chief forecaster of the Central Meteorological Observatory, to give an authoritative interpretation.
The strongest rainfall affects 9 provinces and cities in Sichuan and Henan
Zhang Tao said that the heavy rainfall has the characteristics of wide impact, strong local rainfall, and rapid system movement. At the same time, it was accompanied by strong winds in the Huanghuai area.
Due to the relatively fast moving speed this time, the accumulated rainfall will not be extremely extreme, but the short-term rain intensity is relatively large, which needs attention; this rainfall superimposed on the early disaster area in Henan, the impact is very large, and reservoirs, lakes, and rivers need to be prepared. .
Zhang Tao explained that from the perspective of the system configuration, the heavy rainfall process is a very typical monsoon rain. The subtropical high pressure extends westward, allowing the warm and humid airflow from the Indian Ocean, South China Sea, and Western Pacific to move smoothly northward along the western edge of the subtropical high. The cold air is in confrontation, causing widespread rainfall.
Heavy rainfall affects a wide range.
Sichuan, Chongqing, Shaanxi, Shanxi, Henan, Hubei, Anhui, Shandong, Jiangsu and other 9 provinces (cities) are all in the heavy rainfall area. The overall rainfall is mainly moderate to heavy, but in a few more concentrated places, there will be It's heavy rain.
Among them, the Sichuan Basin and Henan have the strongest rainfall, with local rainfall reaching 250-400 mm, which is already at the level of extremely heavy rain.
Henan needs to be vigilant against superimposed impacts and disasters
During this process, Henan was again the center of heavy rain.
One month later, I can't help but remind people of the "July 20" heavy rain in Henan last month. What are the similarities and differences in the intensity and causes of the two processes?
Zhang Tao stated that the process of this heavy rain in Henan is different from that of July 20.
The rainfall process this time is mobile and will not reproduce the “stuck in progress” of the previous rainfall, so the accumulated rainfall will not be particularly extreme.
Furthermore, this process is a torrential rain formed by a combination of guided airflow and water vapor on the west side of the subtropical high, which is a typical flood season torrential rain configuration; in contrast, the typhoon and the subtropical high were far away at sea during the "7.20" process. It is an indirect effect, coupled with the "chemical reaction" caused by water vapor and terrain, which is not only unique this summer but also rare in history, and eventually led to that rare record-breaking rainstorm.
However, Zhang Tao specially reminded that although the accumulated rainfall this time will not be particularly extreme, it may still have a very large and very unfavorable impact on Henan.
Because the impact of the extreme rainstorm a month ago on Henan has not completely passed, the rainfall area this time overlaps with the area affected by the previous rainstorm. Therefore, it is particularly recommended that the local area prepares for flood prevention and drainage and emergency response in advance.
Henan, Shandong and other places still need to guard against gale
Zhang Tao said that a very typical feature of this rainfall process is not only heavy rain, but also particularly strong wind.
As the summer and autumn seasons change, the cold air in the north becomes more active. During the collision with the warm and humid air from the south, three cyclones are "twisted" and landed on the line from the southwest to the northeast. They are located in the northeast and the east of the northwest to Henan and Shandong. , And the Sichuan Basin.
These three areas are also concentrated areas of rainfall in this round.
In particular, the cyclones from the east of the northwestern region to Henan and Shandong carry strong winds when they move eastward along Henan and Shandong. The strong winds increase the rain and are more destructive.
From the perspective of prevention, the area along the route that this cyclone passes through can treat this process as a "terrestrial cyclone on land," and prevent it with high standards.
According to forecasts, from 22 to 24, there will be rotating winds of magnitude 4 to 6 and gusts of magnitude 7 to 9 in central and eastern Henan, most of Shandong, and the Yellow Sea. Local gusts can reach magnitudes of 8 to 11.
Therefore, Henan, Shandong and other places need to reinforce outdoor billboards and temporary structures to reduce or avoid high-altitude operations; the Yellow Sea waters need to prevent the adverse effects of high winds on passing ships and offshore operations.
The process is still uncertain and needs to pay attention to strong convective weather
Zhang Tao pointed out that the three cyclones that were "twisted" during the confluence of cold and warm air in this process can currently predict the approximate location and intensity of the three rainfall centers.
But what we also need to pay attention to is the much smaller scale of strong convective weather processes that may be hidden under the three rainfall centers.
These strong convective processes like "small blisters after water boiling" are small and medium-scale systems that really determine the extremes of single-point rainfall.
In terms of natural laws, the smaller the scale, the greater the uncertainty and the lower the predictability. Therefore, all regions need to dynamically pay attention to the short-term nowcasting and early warning information updated by the local meteorological department.
Source: China Meteorological News Agency