DYNAMIC FACTORS RELATED TO DECAY PROCESS OF OFFSHORE TROPICAL CYCLONES IN NORTHWEST PACIFIC

Intensity variation of tropical cyclones （TCs）, especially that of coastal or landfalling TCs, is of great concern in current research. Most of the research papers, however, focus on intensification processes of TCs; only a few discuss decay processes in the lifetime of a TC. In the daily weather operation related to TCs, it is challenging when a TC weakens and/or disappears suddenly, because it brings more difficulties than the forecast of intensifying TCs does. Overestimation of a decaying landfalling TC would lead to over-preparation of defensive measures and result in ＂crying wolf＂ mentality with adverse effects. This study summarized physical mechanisms that dominate the decaying process of TCs and listed several possible dynamical factors： reduced level ofairtemperature, too large or too small speed, contraction of TC size amplification of TC＇s core, and lightning number in a TC.