Four methods for determining the extratropical transition (ET) onset and completion times of Typhoons Mindulle (2004) and Yagi (2006) were compared using four numerically analyzed datasets.The open-wave and scalar frontogenesis parameter methods failed to smoothly and consistently determine the ET completion from the four data sources,because some dependent factors associated with these two methods significantly impacted the results.Although the cyclone phase space technique succeeded in determining the ET onset and completion times,the ET onset and completion times of Yagi identified by this method exhibited a large distinction across the datasets,agreeing with prior studies.The isentropic potential vorticity method was also able to identify the ET onset times of both Mindulle and Yagi using all the datasets,whereas the ET onset time of Yagi determined by such a method differed markedly from that by the cyclone phase space technique,which may create forecast uncertainty.