Research on the generating mechanism of strong tropical storm etau numbered as 0909

In the context of NCEP/NCAR reanalysis data, the potential vorticity (PV) inversion data and numerical simulation are made to examine the genesis of the 0909 strong tropical storm Etau in Chinese convention system. Analysis of PV inversions indicates that the high- and low-level large-value PV disturbances have great impact on Etau´s genesis, showing that when the PV disturbances in both the levels approach each other, the middle-lower-layer convergence between them is strengthened, making pressure decrease so as to trigger the fast development of Etau´s embryo. Sensitivity experiments show that the appropriate time when high-level large-value PV meet the disturbance of the monsoon trough acts as an important cause of Etau´s production, whereupon a conceptual model is constructed for the cyclogenesis of this kind. Besides, the sensitivity runs indicate that Etau has great impact on the strength and track of typhoon Morakot, which is also one of the aspects of practical significance to the study of Etau´s genesis.