Abstract:The main characteristics of the general atmospheric circulation in September 2017 are as follows. There was one polar vortex center in the Northern Hemisphere, slightly stronger than usual. The circulation in Eurasian middle high latitudes showed a multi wave pattern. The subtropical high in northwest Pacific Ocean lay westward and southward, and its intensity was slightly stronger than its average state during the corresponding period of normal years. The monthly mean precipitation amount is 62.0 mm which is less than normal in 5%, while the monthly mean temperature is 17.8℃, 1.2℃ higher than normal, which ranks the highest since 1961. Ten regional torrential rainfall events happened in September. Four tropical cyclones were generated over northwest Pacific Ocean and the South China Sea, and typhoon Mawar (1716) made landfall along the coastal areas over Guangdong Province in September. Sichuan and Yunnan received autumn rain notably; strong wind and hail disasters hit 13 provinces; drought situation in middle and eastern parts of Mongolia got relieved.