The comments from the two anonymous reviewers helped to improve the manuscript substantially and are much appreciated. The authors thank Ms. Delia Y.-C. Chen for her help in manuscript preparation. This research is supported by the National Science Council of the Republic of China (Taiwan) under Grants NSC96-2745-M-002-005- and NSC97-2745-M-002-007-MY2.
Barnett, T. P., 1983: Interaction of the monsoon and Pacific trade wind system at interannual time scales. Part I: The equatorial zone. Mon. Wea. Rev., 111 , 756–773.
Barnett, T. P., 1984: Interaction of the monsoon and Pacific trade wind system at interannual time scales. Part II: The tropical band. Mon. Wea. Rev., 112 , 2380–2387.
Cheung, K. K. W., 2004: Large-scale environmental parameters associated with tropical cyclone formations in the western North Pacific. J. Climate, 17 , 466–484.
Dickinson, M., , and J. Molinari, 2002: Mixed Rossby–gravity waves and western Pacific tropical cyclogenesis. Part I: Synoptic evolution. J. Atmos. Sci., 59 , 2183–2196.
Kistler, R., and Coauthors, 2001: The NCEP–NCAR 50-Year Reanalysis: Monthly means CD-ROM and documentation. Bull. Amer. Meteor. Soc., 82 , 247–267.
Lee, C-S., 1986: An observational study of tropical cloud cluster evolution and cyclogenesis in the western North Pacific. Department of Atmospheric Sciences, Paper 403, Colorado State University, Ft. Collins, CO, 250 pp.
Lee, C-S., , and C. H. Lee, 2002: A numerical simulation of the environmental momentum influences on typhoon formation. Proc. Fourth Conf. on East Asia and western Pacific Meteorology and Climate, Singapore, World Scientific, 261–271.
Lee, C-S., , K. K. W. Cheung, , J. S. N. Hui, , and R. L. Elsberry, 2008: Mesoscale features associated with tropical cyclone formations in the western North Pacific. Mon. Wea. Rev., 136 , 2006–2022.
Montgomery, M. T., , M. E. Nicholls, , T. A. Cram, , and A. B. Saunders, 2006: A vortical hot tower route to tropical cyclogenesis. J. Atmos. Sci., 63 , 355–386.
Ritchie, E. A., , and G. J. Holland, 1999: Large-scale patterns associated with tropical cyclogenesis in the western Pacific. Mon. Wea. Rev., 127 , 2027–2043.
Wheeler, M. C., , and H. H. Hendon, 2004: An all-season real-time multivariate MJO index: Development of an index for monitoring and prediction. Mon. Wea. Rev., 132 , 1917–1932.