Negative Indian Ocean Dipole Ahead

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Highlight: -IOD To Develop. Coupled with La Nina, a wet climate is ahead for Australia.

Discussion: A shift of the Indian Ocean Dipole (IOD) toward the negative phase is likely to develop over the next 1-2 months. During -IOD western and southern Australia are wetter-than-normal. The ECMWF global SSTA forecast for November 2020 indicates the mature phase of -IOD as anomalous warmth in the tropical Indian ocean shifts toward Australia (Fig. 1). The Australia Bureau of Meteorology also indicates a -IOD pattern evolving (Fig. 2). Meanwhile a La Nina episode is also indicated. During La Nina wet weather patterns dominate eastern Australia. -IOD years with La Nina at the same time during OCT/NOV/DEC occurred in 1998 and 2010. The precipitation pattern produced was wet to very wet for northern and eastern Australia (Fig. 3).

Fig. 1: The ECMWF global SSTA forecast indicates a mature negative phase Indian Ocean Dipole AND La Nina episode. The combination of each climate regime should bring a wet climate to most of Australia for late 2020.

Fig. 2: The Australian Bureau of Meteorology indicates increasing risk of -IOD developing over the next several months.

Fig. 3: 1998 and 2010 were -IOD years with La Nina developing by late each year. During Q4 of each year wet weather dominated north and east portions of Australia.