Contributions of the Large-Scale Environment to the Typhoon Genesis of Faxai (2019)

This study investigated the atmospheric and oceanic contributions to genesis of Typhoon Faxai in 2019. Our statistical analysis using tropical cyclone score (TGS) attributed disturbance that developed into (Pre-Faxai) easterly waves (EWs). The EW evaluated by a grid version TGS (Grid-EW) averaged around occurrence Pre-Faxai was approximately twice as large climatological mean, it second largest value past 38 years. area with high Grid-EW scores could be traced back eastern North Pacific (ENP) August 25, lower-troposphere environment characterized favorable for vortex formation because provided containment moisture entrained developing circulation or lofted deep convection therein. moved westward due background flow over ENP then entered western (WNP). Intensity Forecast Scheme (TIFS) showed important environments its were ocean conditions vertical wind shear. contributed development traveled WNP. enhancement shear subsequent suppression caused winds associated scores. They also upper-troposphere westerly an upper cold low northwest Pre-Faxai. When decreased weakening low, reached storm intensity on September 4. Therefore, TIFS detected 10 days before typhoon arose, which indicates monitoring environmental factors such are disaster prevention.