Abstract:Typhoon Haikui (2311) moved west-northwestward and repeatedly wobbled, forming a serpentine path. It strengthened into a super typhoon category before landing on Taiwan Island. Then, it moved slowly after entering the Taiwan Strait. After it landed again, its residual vortex sustained for about 5 days, resulting in the long-time precipitation and large accumulated rainfall. Different models and different members of ensemble forecast also had large errors and uncertainties in forecasting the landing spots and landfall strength of Haikui, which brought great challenges to forecast correction. ECMWF, NCEP and CMA deterministic forecast and ensemble forecast data are used to analyze the main characteristics of Haikui and critical difficulties in the process of operational forecast. There exist large errors and differences in the forecast of typhoon track in the offshore waters of China, and the operational correction problems in the intensity forecast are affected by the uncertainty of the track forecast. Besides, it is difficult to quantitatively estimate the time of the typhoon’s slowly moving that was caused by weak steering flow and terrain influence after the typhoon crossed Taiwan Island and entered the Taiwan Strait. Moreover, it is also difficult to quantitatively estimate the time of typhoon’s residual circulation maintenance, track and precipitation influence after the typhoon made landfall weakening.