Abstract:The accurate predictions of the first-time landing position and the second-time landing strength are very difficult because of the rarely-seen close distance for the binary typhoons Nesat (No.1709) and Haitang (No.1710). Although CMA issued an accurate official forecast, the performance of most models including ECMWF and NCEP was far from satisfactory. In this paper, forecast experience and focus in the forecasting operation are analyzed and summarized. The rationality of model prediction for the large-scale circulation such as subtropical high is analyzed based on synoptic models, deviation revision experience and the performance of ensemble forecasting system. The main circulation is determined by analyzing the relative strength of the closest time of the binary typhoons, so as to judge the difference between the landing time of the two typhoons, their extreme strengths and onshore maintenance mechanisms. Paying close attention to two influencing factors of the typhoon track angle with Taiwan’s central mountain range and cross-island time is helpful to revise the typhoon strength of the second-time landing.