The rainfall started at 8: 00 pm on July 17 and lasted until 8: 00 pm on the 20th. The total rainfall for three days reached 6 1 1. 1 mm ... It began to rain at 6 am on July 20th, when the rainfall reached 50 mm and reached about 200 mm at 4 pm. At 8: 24 pm, the total rainfall reached 552.5 mm, and the average annual rainfall in Zhengzhou was only 640 mm. This is equivalent to the total rainfall of three days in the previous year.
Reason:
On July 18, the subtropical high formed a typhoon called Fireworks. In this picture, we can see that the water vapor condition of fireworks is very sufficient. Although it is still about 1000 km away from Zhengzhou, the rainstorm in Henan was remotely controlled.
Because Henan is in its marginal area, Zhengzhou happens to have convection with him. To put it bluntly, it can receive each other's water vapor. It can be seen that it rotates clockwise, and a large amount of water vapor is transported to Zhengzhou during the rotation.