Climate indicators sending mixed messages | The Outlook

Climate indicators sending mixed messages | The Outlook

Weather
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There remain no clear indicators either way for 2020, but the positive signs are the negative rainfall indicators all appear to be fading at this stage.

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ALTHOUGH the principal drivers of the extremely dry weather pattern that dominated the latter months of 2019 have now mostly faded, there are still some unusual happenings with the long-term climate indicators that reduce the confidence level of any predictions for the coming months.

One reason is that the oceans around the continent (indeed around much of the world) are holding more heat (energy) than at any time in recorded history, and there is uncertainty on how this will play out in the immediate future.

Looking for analogous years in the past as a guide is impossible.

To consider some of these aspects, we might start with the Indian Ocean. Although the Indian Ocean dipole is back close to zero, its effects on Australian rainfall in the first four months of the year are minimal at the best of times, but its importance will return later in autumn.

Next, the pulses of tropical activity that circle the globe every 30 to 60 days, known as the Madden-Julian Oscillation, are important in the coming months.

A recent strong MJO has moved away to the east and as a result, more stable weather is favoured in the tropical part of the continent in the coming weeks.

The next pulse is not expected in the Australian region until mid-February, but this has the potential to change as the MJO can be variable.

Therefore as a long-term forecasting tool, it is not great.

Thirdly, the Southern Annular Mode refers to the north-south movement of the Southern Ocean westerlies.

Recently, a negative SAM has pushed the westerlies further north than normal at this time of year, bringing dry, hot conditions in NSW and Queensland. After briefly returning to zero, it is again slightly negative but - hopefully - this won't last long.

A positive SAM in February and March would be good news for eastern NSW and Queensland, but its fluctuations recently have been unusually inconsistent.

Finally, let's look at the Pacific Ocean.

The El Nino Southern Oscillation is the main indicator and this has been neutral for some months.

Neutrality is favoured to continue so this decreases its use as a predictor in months ahead.

The Southern Oscillation Index - a simple guide to how ENSO is performing - is neutral between -7 and +7.

Currently the SOI is around -5, so within range but towards the "drier" part of it.

So in summary, there remain no clear indicators either way for 2020, but the positive signs are the negative rainfall indicators all appear to be fading at this stage.

So, near average rainfall is favoured for a lot of the coming year.

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