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Flood fears rise as La Nina looms

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The Bureau of Meteorology says there is now a 70% chance of a flood-inducing La Nina weather system developing this year.

La Nina typically results in above-average winter-spring rainfall for Australia, particularly across the eastern, central and northern regions.

The last significant La Nina event was in 2010-11, which was Australia’s wettest two-year period on record. Devastating floods in Brisbane and other parts of Queensland resulted in insured losses of more than $1.5 billion.

Bureau background documents confirm the presence of La Nina “increases the chance of widespread flooding”.

“Of the 18 La Nina events since 1900 (including multi-year events), 12 have resulted in floods for some parts of Australia, with the east coast experiencing twice as many severe floods during La Nina years than El Nino years,” the bureau says.

Manager of Climate Operations Andrew Watkins says La Nina also typically brings “cooler and cloudier days, more tropical cyclones and an earlier onset of the first rains of the wet season across the north”.

The cooling of surface temperatures in the tropical Pacific Ocean and an increase in the strength of the Pacific trade winds are clear indications the chance of a La Nina has risen, the bureau says.

“When these two changes occur at the same time, at this time of year, we see a greatly increased chance of a La Nina forming and persisting through spring,” Dr Watkins said.

The 70% chance of a La Nina developing is three times the normal likelihood.