Weather News

Wet phase of Indian Ocean Dipole could be on the cards this year

Ben Domensino, Tuesday May 12, 2020 - 19:41 EST

There are signs that one of Australia's main climate drives could move into a 'wet phase' in the middle of the year, raising the odds of above average rain in parts of the country this winter and spring.

The Indian Ocean Dipole (IOD) refers to patterns of sea surface temperatures in the tropical Indian Ocean, which influence rainfall distribution in Australia and some other parts of the world. When the IOD is in a positive phase, large areas of Australia typically see below-average rain during winter and spring, and sometimes early summer. Last year was an example of this. On the other hand, a negative IOD usually causes above average winter-spring rainfall over parts of Australia.

While 2019 brought one of the strongest positive IOD events in modern history, 2020 could swing the other way.

There is growing consensus between international seasonal forecast models that a negative phase of the IOD could emerge this winter and persist into spring.

While IOD forecasts made at this time of year typically have less accuracy than those initiated in winter, there is an overwhelming signal in the models that a negative IOD could be on the cards in 2020.

When looking at six separate seasonal forecast models run by Australia, Canada, the European Union, France, the United States and the United Kingdom, five predict that the IOD will exceed its negative threshold by July and all six pick a negative IOD by August.

While this outlook doesn't guarantee lots of rain in Australia, it does raise the odds that large parts of the country could see above average rain this winter and spring. 

More accurate IOD forecasts will become available as we head into winter.

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