Prior work has suggested that Rossby wave accumulation in the lower troposphere may be an important mechanism for the development of synoptic-scale disturbances in the western north Pacific in northern summer. This work examines the intraseasonal and interannual variability of wave accumulation by computing the barotropic wave activity flux divergence at 850 hPa for different phases of the Madden-Julian oscillation (MJO) and El Ni¿o/southern oscillation (ENSO). Indirectly, and without ruling out other influences, the results suggest a physical mechanism behind previously identified relationships between tropical cyclogenesis statistics and these two modes of variability (MJO and ENSO). ¿ 2000 American Geophysical Union