The odds of a drier than average winter period across the nation's agricultural regions continue to strengthen.
Farmers in southern and north-western regions in particular are concerned at an emphatic set of Bureau of Meteorology (BOM) numbers in its recent climate outlook.
The sobering report found that parts of southern, taking in much of Victoria, southern NSW and south-west WA, and north-western Australia are at least twice as likely as usual to receive unusually low rainfall of Decile 2 or below for the critical June to August period.
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Odds of seeing below median rainfall in these areas have risen to above 80 per cent, the maximum confidence in BOM outlooks.
In other key farming areas such as northern NSW and southern Queensland there is a 60 to 80pc chance of below median rainfall for the period, while in the tropics, where winter rain is only sporadic, there is no clear trend for drier or wetter conditions.
While there is good stored moisture across many areas that received heavy rain last spring, such as SA, Victoria, NSW and Queensland the forecast will inspire nerves, especially from the grains sector where farmers are midway through the autumn planting period.
Chances of rainfall for June are slightly better than the later two months in winter.
The BOM is becoming increasingly confident in the outlook.
While long-term accuracy in the autumn is generally not high, past accuracy of winter long-range forecasts has generally been moderate to high for much of Australia, increasing to high accuracy for south-east Queensland and inland NSW.
Climate drivers in both the Pacific and Indian oceans are moving towards phases correlated with drier condition in Australia.
BOM senior climatologist Zhi-Weng Chua said his organisation was monitoring the potential development of both an El Nino in the Pacific Ocean and an Indian Ocean Dipole positive event.
"We continue to see things like the Southern Oscillation Index in the Pacific push closer to El Nino levels, while we are also monitoring colder than average sub surface sea temperatures in the eastern Indian, which could lead to an IOD positive," he said.
"The accuracy for the IOD is not great at this time of year so we will put out our estimates next month with a lot more confidence."
Dr Zhi-Weng said there was a tangible connection between the Indian and Pacific oceans.
"Scientific work found a third of the variability of the IOD came from what was happening in the Pacific Ocean, with two thirds natural variability, so it is definitely a factor.
"An El Nino does not guarantee an IOD positive but it will mean it is more likely."
"It is easy to think of in real terms, some of that cold water in the western Pacific flows through the Maritime Continent (Indonesia) and into the eastern Indian Ocean."