ABSTRACT

Tropical cyclones (TCs) in monsoon gyres (MGs) were observed to take a sharp northward turn. To understand what controls the direction of TC motion in MGs, a typical northward turn TC Megi (2010) is investigated using the full-physics Weather Research and Forecasting (WRF) Model. It appears that the low-frequency monsoon gyre interacted with Megi and affected its track. Tracks of the relative positions between the Megi and the MG centers suggest that a Fujiwhara effect may exist between the MG and Megi. Vorticity diagnostic analysis shows that the sharp change of the maximum vorticity tendency direction before and after the track turning point is primarily attributed to the change of the horizontal vorticity advection. The interactions between TCs and MGs with different structure and intensity are also investigated using a non-divergence barotropical model. TC interacting with smaller MG preferentially undergoes a sharp north turn and larger TC makes the occurrence of recurvature earlier. This study reveals that the TC track is sensitive to the initial wind profiles of both MG and TC, suggesting that improvement in the observation of TC and MG structures is very important for predicting TC in MG.