Weird weather on the cards

Bureau of Meteorology weather insights from unusual year


National Issues
Picture: Glenn Corrigan.

Picture: Glenn Corrigan.

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From El Nino to La Nina and more in between, 2017 was an interesting year

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From the brink of a dry and dusty El Nino to a nearly-there La Nina, the weather in 2017 did not run to script.

Now some parts of eastern Australia are eyeing forecasts of above average rainfall in coming months, but the good fortune does not extent to where it is needed most.

Last year’s run of unusual weather included Australia’s third warmest year on record, prospects of an El Nino event, followed by declaration of a La Nina in December.

And in the middle of it the Southern Annular Mode (SAM) kicked into gear and delivered ill-timed frosts to southern cropping regions in November.

Eventually decent rain fell in December on southern cropping regions but winter and spring were generally dry in the eastern half of the continent. 

There is a 50 - 50 chance of higher than average rain in inland eastern farming regions. Image reproduced with permission of the Bureau of Meteorology.

There is a 50 - 50 chance of higher than average rain in inland eastern farming regions. Image reproduced with permission of the Bureau of Meteorology.

Bureau of Meteorology climate services manager Dr Andrew Watkins said in the next couple of months north east NSW, south east and Far North Queensland have above average prospects of exceeding median rainfall.

Its dry in western Queensland, central and northern NSW (including the Hunter Valley and unusually the North Coast). 

But unfortunately in the most parched region, “the odds for western Queensland of above average rain are not strong,” Dr Watkins said.

Despite climate markers triggering an official declaration, the La Nina event has been weak and is forecast to fizzle out in autumn.

“We got a taste of it early in December with rain in NSW, South Australia and Victoria, but La Nina never really got going into a moderate to strong event with cloud cover and cooler Summer temperatures,” Dr Watkins said.

From February through to June the Bureau’s alert went to ‘watch’, the second-highest level for El Nino, typically associated with hot and dry conditions in eastern Australia.

July brought several months of neutral conditions and by October we slipped into ‘watch’ for a wetter than average La Nina year. 

Dr Watkins said the unusual patterns cast new light on the SAM, which is classed as a secondary climate driver, behind El Nino and Indian Ocean Dipole.

A positive SAM delivers dry weather to southern Australia.

It occurs as variable westerly winds contract towards the South Pole and high pressure systems brood over the bottom half of the continent.

“In June and July we had a long period of high pressure over much of southern Australia, which lead some energy experts to talk of a wind energy drought,” Dr Watkins said.

“We learnt you don’t need an El Nino to get a period of very dry conditions with clear skies and frost risk. SAM can act on its own.”

Dr Watkins said bushfires risk was increasing as dry conditions persist for more than six weeks across large areas of eastern Australia.

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