Madden Julian oscillation to Activate and Shift Eastward Across Pacific

Fig. 1: The Madden Julian oscillation activates this week and shifts eastward into the tropical West Pacific over the next 14 days.

Discussion: As expected, the next transient tropical Pacific Madden Julian oscillation (MJO) episode is evolving. A large area of anomalous convection across Indonesia extending to Northern Australia is expected over the next week (or more) producing excessive rainfall in these regions. The convective rains in this region are characteristic of MJO phase_4/phase_5 (Fig. 1) which is expected to strengthen over the next 7-10 days. Forecast models indicate continued eastward drift of the MJO across the tropical Pacific (phase_6) in the 10-14-day period. The farther eastward shift produces a strong warming influence on the U.S. pattern. The eastward shift of the MJO will weaken equatorial Pacific trade winds and allow warm subsurface water to continue shifting eastward (Fig. 2) into early January, likely to further erode the La Nina pattern. The emerging Maritime Continent MJO episode usually has a drying influence on South America. However, effects from a strong positive southern annular mode (+SAM) may prevent drying in Southern America (certainly Brazil although Argentina is a question mark).

Fig. 2: An eastward shifting MJO across the tropical Pacific would force subsurface warming eastward to erode La Nina.