The proportion of intense tropical cyclones (Category 4 and 5 on the Saffir-Simpson scale) has increased.  It is demonstrated that the increase of the proportion of intense typhoonsduring 1980-2015 is consistent with the corresponding changes in the ocean/atmosphere environment. The deepening of the ocean mixed layer resulting from the temporal variations and track shifts plays a dominant role in the observed increase of the proportion of intense typhoons. The annual mean latitude where tropical cyclones (TCs) reach their lifetime maximum intensity (LMI) over the western North Pacific basin (WNP) has shifted northward since the early 1980s and it is suggested that the shift is due to the northward migration of the mean TC formation location. It is suggested that the observed poleward trend in the mean latitude of LMI is physically consistent with changes in the large-scale ocean/atmosphere environment and TC track. This study also demonstrates that the temporal change in the environmental parameters has little influence on the observed shift of the mean LMI latitude. The poleward migration of the mean LMI latitude is mainly due to the TC track shift, which results primarily from the change in the large-scale steering flow.