A 65-yr climatology of unusual tracks of tropical cyclones in the vicinity of China's coastal waters during 1949-2013

Abstract

Despite steady improvements in tropical cyclone (TC) track forecasts, it still remains challenging to predict unusual TC tracks (UNTKs), such as the tracks of sharp turning or looping TCs, especially after they move close to coastal waters. In this study 1059 UNTK events associated with 564 TCs are identified from a total of 1320 TCs, occurring in the vicinity of China's coastal waters, during the 65-yr period of 1949-2013, using the best-track data archived at the China Meteorological Administration's Shanghai Typhoon Institute. These UNTK events are then categorized into seven types of tracks-sharp westward turning (169), sharp eastward turning (86), sharp northward turning (223), sharp southward turning (46), looping (153), rotating (199), and zigzagging (183)-on the basis of an improved UNTK classification scheme. Results show significant annual variability of unusual tracking TCs, ranging between 2 and 18 per year, many of which experience more than one UNTKevent in the same or differentUNTK types during their life spans. The monthly distribution of the UNTK events resembles that of TCs, with more occurring in June-November. An analysis of their spatial distributions reveals that all of the UNTK events tend to take place in the areas to the south of 308N, most frequently in the South China Sea and to the east of the Philippines. The results suggest that more attention be paid to the improved understanding and prediction of UNTK events so that the current positive trend in TC track forecast accuracy can continue for many years to come.