El Niño unlikely this year

30 Jun, 2017 04:00 AM
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THE BUREAU of Meteorology (BoM) says an El Niño weather event, which correlates with drier than average conditions in Australia, is unlikely this spring.

But it warned a sustained ridge of high pressure is playing a part in stopping rain delivering in low pressure systems and shows no immediate signs of abating.

The block of high pressure is remarkable, some five hectopascals higher than average for June in southern Australia

The BoM predicted the likelihood of a dry winter in southern regions in its latest three month forecasts, issued in late May.

It rated some parts of Western Australia’s cropping belt as having a 20 per cent chance of exceeding median rainfall.

So far, the prognosis has been accurate, with most of WA, South Australia and Victoria experiencing lower than average June rainfall.

BoM senior climatologist Catherine Ganter said warming in the eastern tropical Pacific Ocean had eased.

“In the atmosphere, the trade winds and Southern Oscillation Index are well within the neutral range and sea surface temperatures near Peru cooled during March and April,” Ms Ganter said.

She said forecasting models used by the BoM had also eased off their predictions.

“In April, seven out of the eight models were suggesting a possible El Niño, that is back to zero,” she said.

Focus is turning to the other key driver of rainfall in the Australian spring, the Indian Ocean Dipole (IOD), which Ms Ganter said offered mixed news.

“Three out of the six models suggest an IOD positive event, consistent with drier conditions in Australia, could develop,’’ she said.

In terms of current weather patterns, which have seen areas in the northern Wheatbelt and SA’s Eyre Peninsula in particular not receive sufficient rain to germinate crops, she said a positive Southern Annular Mode (SAM) had played a role.

Much of southern Australia’s winter rainfall comes from constant cold fronts pushing through, with frequent, relatively low volume bands of rain.

Higher totals, associated with tropical moisture, are more likely in the spring.

“We will still get some frontal systems hitting southern areas but they just might not be so frequent,” Ms Ganter said

FarmWeekly
Gregor Heard

Gregor Heard

is the national grains writer for Fairfax Agricultural Media

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