Negative Indian Ocean Dipole Fading But La Nina to Strengthen Which Keeps Australia Avoiding Drought Risk

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The wet influence of negative phase Indian Ocean Dipole on Australian climate, particularly across southern areas is fading. However, a persistent La Nina climate may strengthen during quarter 4 of 2021 enabling more wet climate particularly for north and east portions of the continent.

Fig. 1: The meteorological winter 2021 percent of normal precipitation observations across Australia.

Discussion: Negative phase of the Indian Ocean Dipole (-IOD) is fading. Meanwhile La Nina is redeveloping. In fact, according to multivariate ENSO index, a La Nina climate lingered throughout 2021 despite the oceanic component fading earlier this year. The combination of -IOD and a lingering La Nina climate pattern brought copious rainfall to much of the eastern third of Australia during meteorological winter including marginally above normal amount to the South Coast (Fig. 1). The -IOD wet bias is across southern continent while the La Nina wet bias is across eastern continent (Fig. 2-3). With -IOD fading (Fig. 4) but La Nina expected to reorganize and strengthen during quarter 4 of 2021 (Fig. 5) the east and north portion of the continent should stay wet for mid-to-late spring and into the summer 2021-22 season. Australian crop areas should avoid a drought for the second year in a row.

Fig. 2: A schematic from the Australia Bureau of Meteorology identifying the dynamics of negative Indian Ocean Dipole on Australia.

Fig. 3: A schematic from the Australia Bureau of Meteorology identifying the dynamics of La Nina on Australia.


Fig. 4: Australia Bureau of Meteorology Indian Ocean Dipole forecast.

Fig. 5: The Climate Impact Company ENSO phase forecast.