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The Bureau of Meteorology yesterday issued an “alert” warning for a La Nina event to form over the coming spring.
In the Bureau’s own words, weather conditions that reach “alert” status go on to form a La Nina 70 per cent of the time.
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Weatherzone meteorologist Andrew Schmidt told nine.com.au that a third consecutive La Nina would be very uncommon, but wouldn’t quite break the laws of nature.
“Climate change is probably one of the bigger drivers,” he said.
La Ninas are driven in large part by warming sea surface temperatures in the Pacific, which the Bureau noted were increasing in yesterday’s release.
Schmidt said climate change could contribute to this effect, but there were a range of other factors as well, making it difficult to pinpoint a single cause.
La Nina events historically bring more wet weather to Australia’s east coast, with the Bureau predicting higher falls than normal through spring and summer.
However, Schmidt said that trends seen in global models showed that if the La Nina formed in spring, it could retreat by January next year.
Nonetheless, that brought a “major risk” of flooding, particularly to previously affected areas such as Queensland’s south-east and northern New South Wales.
More rain is also a consequence of a negative Indian Ocean Dipole – measured by sea surface temperature differences between two points.
Schmidt confirmed the IOD was currently in the negative.
Could it bring a cyclone?
Typically, La Nina events bring an increased risk of tropical cyclones, as those Queenslanders who battled through Yasi’s landfall in 2011 have good cause to remember.
Curiously, however, Schmidt said recent reports suggested that the region would see fewer cyclones in the coming season – but they would likely be more severe.
“At this stage, it’s close to an average forecast,” he said.
“In the past couple years, we haven’t seen too many make landfall, but you can’t always count on that happening.”
Australia’s cyclone season, as determined by the Bureau, runs from November 1 – April 30.