AN UNUSUAL climatic event which is linked with freezing conditions in the northern hemisphere is likely to play a role in retaining hot and dry weather in Australia.
Sudden Stratospheric Warming (SSW) is rare in the southern hemisphere, with just two confirmed cases in the past 60 years, but Bureau of Meteorology (BOM) climatologist Andrew Watkins, said it was not a good sign for those looking for rain.
"It is correlated with drier than average conditions in mainland Australia, especially eastern Australia.
"Western Tasmania, at a more southerly latitude, even possibly far southern Victoria are a chance to receive higher than average rainfall as a result of the event but other places will be hotter than drier."
In bad news for those looking for rain Dr Watkins said there was a SSW event in the Antarctic in 1967 and something around the threshold in 2002.
Both years were among the worst droughts in living memory through much of Australia.
However Dr Watkins said the SSW had already been factored into BOM seasonal outlooks, which are for a dry spring.
"It is not going to swing the odds further in favour of lower than average rainfall, it has already been in the models, so it does not mean that we are even more chance of drier than average conditions."
An SSW occurs when pulses of warm air get into the normally freezing Antarctic stratosphere, 30-40 kilometres above the earth's surface.
"Normally at this year the air at that levels is very cold, it has been in darkness with no sunlight," Dr Watkins said.
"It is not exactly clear what pushes the warm air there, big weather events or the air hitting mountain ranges at exactly the right angle."
He said the warm air slowed down the high winds that normally move over the stratosphere at 200kph and then the slower winds come down to the surface and the normal weather patterns push further north.
"It is great for Tasmania and even perhaps southern Victoria, although the further we move into spring, where the weather patterns are changing, less so, but for large parts of eastern Australia instead of getting cool and moist air from the Tasman Sea instead we could see hot and dry air brought in from central Australia.
"I think we've got some sort of a harvest already with the moisture we've got and
Dr Watkins said once the Antarctic winds began to slow down the SSW was fairly traceable.
"The event started during August into early September, so the fires we are seeing in south-east Queensland and NSW are not due to this.
"We are likely to see its effects from late September, potentially right through to January, depending on how strong it is.
"From there we are still likely to revert to neutral weather patterns by January at the latest," he said.
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