Relationships between tropical cyclone motion and surrounding flow with reference to longest radius and maximum sustained wind

This study statistically examined the relationships between the motion of a tropical cyclone (TC) and its ambient flow, stratifining the TC with reference to the longest radius (LR) and maximum sustained wind (MSW). TC motion, MSW, and LR were derived from the best track datasets compiled by the Regional Specialized Meteorological Center (RSMC) Tokyo - Typhoon Center. The environmental flow was estimated by averaging reanalyzed wind data (JRA25/JCDAS) between 1000 to 300 hPa over areas within a radius of 300, 400, and 500 km from the TC center. It was found that TCs with larger LRs or more intense MSWs are more likely to move to the northeast relative to the ambient wind. This preference for northeastward migration was confirmed when only TCs in the subtropical zone (20°N-30°N) were sampled. The bias of northeastward migration was found to be robust when components with wavelengths less than about 12° latitude-longitude were filtered from the total environmental wind field.