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La Nina over, but 'above average' rainfall could continue

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The La Nina weather system which contributed to severe flooding in NSW and Queensland last month is officially over, the Bureau of Meteorology has announced.

The event was declared on September 29 last year, and above-average rainfall fell in spring and summer across most of northern and eastern Australia.

“This is typical of La Nina systems, which generally bring wetter spring and summer conditions for eastern Australia,” the bureau said.

“The increase in rain reduced the fire risk over the last summer and also contributed to an increased chance of tropical cyclones and an increased risk of flooding as seen in the recent flood events through Queensland and NSW.”

The floods have been declared an insurance catastrophe and insured losses are estimated at $537 million and rising.

In recent weeks, bureau climatologists have noted a steady decline in La Nina indicators in the Pacific Ocean, with the La Nina/El Nino outlook now re-set to “inactive”.

Climate modelling shows few signs of a second La Nina or El Nino developing in the foreseeable future. However, there's always the possibility of significant rainfall.

"We're forecasting above-average rainfall to continue [in April] for northern parts of Australia," Senior Climatologist Naomi Benger said.

Dr Benger says as La Nina recedes, secondary drivers such as the Madden–Julian Oscillation, will play a larger role in influencing rainfall.

"The Madden-Julian Oscillation moving through the tropics is expected to increase cloudiness and rainfall in far northern Australia over the next week or two. This also brings an increased risk of tropical low or tropical cyclone activity."