Forecast of tropical cyclone (TC) formation has long been a great challenge owing to lack of reliable observations over vast open oceans. Recent satellite products provide a unique opportunity to reveal detailed atmospheric wave structures prior to TC formation. Using the QuikSCAT surface wind and the Tropical Rainfall Measurement Mission Microwave Image data, we document temporal and spatial structures of Rossby wave trains induced by energy dispersion from a pre-existing TC and easterly wave propagation characteristics prior to cyclogenesis in the western North Pacific. Using a baroclinic model, we further simulate cyclogenesis processes associated with the TC energy dispersion and easterly waves.