Western North Pacific Tropical Cyclone Characteristics Stratified by Genesis Environment

We studied the characteristics of tropical cyclones (TCs) in the summer and autumn seasons over the western North Pacific that are associated with different environmental factors that influence TC genesis (TCG), using the TCG detection method. We objectively categorized factors into the five TCG factors classified by Ritchie and Holland (1999): monsoon shear line (SL), monsoon confluence region (CR), monsoon gyre (GY), easterly wave (EW), and the Rossby wave energy dispersion from a preexisting TC (PTC). GY-TCs tended to develop slowly, and the highest rates of occurrence of rapid intensification were found for CR-TCs, whereas GY-TCs rarely experienced RI. The average size of GY-TCs at the time of formation was the largest of the averages of the other TC types, while EW- and PTC-TCs were smaller, although these differences disappeared when the TCs matured. Due to their favorable environmental characteristics, such as high tropical cyclone heat potential, convective available potential energy and weak vertical shear, PTC-TCs tended to develop as intense TCs. These results provide important information for use in disaster prevention.