How did the rainstorm in Alamo come into being?

A lot of water vapor. Bai Yang Township is located in the southeast of Songpan County, 289 kilometers away from Songpan County and 0/40 kilometers away from Mianyang City, covering an area of 542.56 square kilometers. According to public comments, the main physical conditions of this rainstorm are sufficient and continuous water vapor, strong and persistent updraft and unstable atmospheric structure. The atmosphere refers to the atmosphere around the earth, which is mainly composed of nitrogen and oxygen. The thickness of the atmosphere around the earth exceeds 1000 km. There is no obvious boundary from the upper boundary of the atmosphere to the space, which is a process of decreasing atmospheric density and atmospheric molecules.