By looking at surface weather chart, we can find that high-pressure system spawned by the Yangzi jiang air mass and the high-pressure system spawned by the tropical monsoon air mass are struggling with each other on the South China Sea and the front has been formed between them.
地上天気図でみると、揚子江気団からできた高気圧と熱帯モンスーン気団からできた高気圧が南シナ海上でせめぎあい、その間に前線ができていることがわかる。