Abstract:The Weather Research Forecasting (WRF) model is used to simulate the tropical cyclone (TC) "Malakas" in sensibility experiments such as:ST (TC enhanced), NO (TC weakened), NW(TC approached to the trough) and ES (TC left away from the trough), and to investigate the development of downstream flow, especially the jet in mid-latitude. The results show that the interaction between TC and mid-latitude system would make the jet and its baroclinic instability enhance. The downstream flow is sensitive to the TC strength and TC position relative to the trough. If the TC strength enhances, the instability and intensity of TC outflow to the mid-latitude jet strengthen, resulting in the strengthening of both downstream jet and ridge-trough. Vice versa. Similarly, if TC is closer to the upstream trough, its effect on the mid-latitude jet would further strengthen, making the jet more instable and stronger, and the downstream jet and ridge-trough enhance too. If TC is far away from upstrearm trough, the result is opposite.