This study examined the cause of seasonal variability in interdecadal changes of tropical cyclone genesis frequency (TCGF) during period 1982-2020, which have decreased significantly only during from October to December (OND) over the western North Pacific (WNP). Because the large-scale relative vorticity decreased significantly in the majority of the main development region (MDR) over WNP only in OND, the TCGF could decreased throughout the MDR significantly at 95% confidence levels only in OND. In consequences of linear baroclinic model (LBM) experiments, the changes in the large-scale circulation could be caused by diabatic heating induced by increased precipitation in climate convective region. When the precipitation in that region increased, which means that the convection also intensified, the low-level convergence was enhanced. Consequently, the anomalous easterly and the anomalous anticyclone can be formed on the east of the climate convective regions. Since the climate convective region was located more westward (5°S-10°N, 80°E-110°E) during OND, the large-scale anomalous anticyclone could extended westward than other seasons (Jan to Sep). According to the “rich-get-richer mechanism”, under increased sea surface temperature (SST) by zonally uniform global warming, precipitation could increase in climatological convective regions. To figure out that the rich-get-richer mechanism could occur in zonally different SST variation in tropics (i.e. La Niña-like SST pattern), which was identified in observed SST, we conducted the Model for Prediction Across Scales – Atmosphere (MPAS-A) consisted of three experimental designs. One of them was prescribed by climatological SST during period 1982-2020, another was forced by La Niña-like warming, and the other was forced by tropical uniform warming that supposed by global warming. As a results of MPAS-A run, for two forced by SST forcing, precipitation have increased in the climate convective regions, and the anomalous anticyclone also was located on the east of that regions. Thus, because of the increased precipitation in climate convective region over the tropical Indo-Pacific Ocean under La Niña-like warming SST, the large-scale atmospheric circulation was induced over the WNP, which is unfavorable for tropical disturbance to develop to tropical cyclone only in OND.