THE MEANDERING NATURE OF TROPICAL CYCLONE TRACKS

The observed tendency for tropical cyclones to meander about a longer- term track with periods of several days and amplitudes around 100 km i s investigated. An analysis of 26 cyclones in the western North Pacifi c Ocean does not support the theories by Syono and Futi that tropical cyclone track oscillations occur from excitation of inertial oscillati ons. The observations and related numerical modeling studies also do n ot support the vortex patch and rotating cylinder theories by Yeh and Kuo. It is suggested that many meanders occur from interactions with m esoscale vortices and convective systems within the cyclone circulatio n. This hypothesis is supported by a case study of the effects of meso scale convective complexes that developed in Typhoon Sarah (1989).