Emergence of phase_1/phase_2 of the Madden Julian oscillation implies increased vertical motion and lowering upper level wind shear in the tropical North Atlantic (where tropical cyclones develop) and tropical Africa (where tropical waves which become Atlantic tropical cyclones develop). The MJO has anchored over Maritime Continent/West Pacific tropics recently certainly contributing to an increase in tropical cyclone activity. However, today’s ECMWF MJO forecast indicates MJO weakens over Maritime Continent and is likely to regenerate over the tropical North Atlantic/Africa in 2 weeks.

A summary of seasonal forecasts of North Atlantic basin tropical cyclone activity issued initially in April and updated in June and August by the Tropical Meteorology Project at Colorado State University, Tropical Storm Risk of U.K. and Climate Impact Company indicate each revision is slightly more active due to less inhibiting upper shear due to a weakening El Nino (compared to early forecasts) coupled with a warmer than normal North Atlantic basin especially just north of the tropics.