Indian Ocean Dipole may start to dissipate

Indian Ocean Dipole may start to dissipate | The Outlook

Weather
Widespread drought has provided more challenges to those whose livelihood depends on the land.

Widespread drought has provided more challenges to those whose livelihood depends on the land.

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This year commences with a little optimism following one of the most challenging years, in the past century.

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THIS year commences with a little optimism following one of the most challenging years, in the past century.

However, it is important we put any optimistic thoughts in perspective.

Widespread drought, along with record heat in the past decade has provided more challenges to those whose livelihood depends on the land.

First, the Indian Ocean Dipole (IOD) continues to drift back to neutral.

Most international climate models indicate the positive IOD will dissipate by mid-summer as the Indian monsoon moves into the southern hemisphere and the wet season starts in northern Australia.

The influence of the IOD is then minimal until late April or May, when it starts influencing the so called north-west cloud bands.

Secondly, the Southern Annular Mode (SAM) is back to near normal levels for this time of year so the negative effects of SAM on NSW and Queensland rainfall are no longer present.

Finally, in the tropical Pacific, the El Nio-Southern Oscillation (ENSO) remains neutral.

However, some unusually warm sea surface temperatures (SSTs) in the western tropical Pacific and further south off the east coast of Australia, may contribute to some changes in weather patterns over eastern Australia.

Many International climate models forecast ENSO-neutral for early 2020 and recently a couple have indicated that La Nina thresholds could be reached by around April 2020.

Apart from being an interesting development, this has potential to bring those optimistic thoughts to the forefront. Even a weak autumn La Nina would significantly increase rainfall potential in eastern Australia.

However, it is very early days and this prognosis is only linked to one or two model outputs, so at this stage it remains speculative at the best.

So what looks more likely is that slightly below average rainfall will persist for much of eastern Australia until towards the end of summer.

However, there also remains a slightly increased potential for localised "one off" events to bring pockets of useful rain, especially in eastern and north-eastern NSW and Queensland.

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