Bureau of Meteorology declares El Nino watch

The tropical Pacific Ocean is now in a neutral phase - neither La Nina nor El Nino but there are signs of an El Nino forming later in the year.

An El Nino watch means there is a 50 per cent chance of an El Nino forming in 2023.

More and more experts are tipping the wet climate driver will this year be replaced with the drier El Nino.

The US National Weather Service last week confirmed what most agencies, including Australia's own Bureau of Meteorology, have been saying for months.

The third La Nina is over and the climate will bump along under neutral conditions with a fourth La Nina ruled out, and El Nino favoured to form later this year.

The World Meteorological Organisation says the drier El Nino "is considered likely" for Australia.

The WMO says neutral conditions will continue between March and May.

"The chances of El Nino developing, while low in the first half of the year (15 per cent chance in April-June), gradually increase to 35pc in May-July," the WMO forecasts.

"Long-lead forecasts for June-August indicate a much higher chance (55pc) of El Nino developing but are subject to high uncertainty associated with predictions this time of the year."

While declaring La Nina over, the US National Weather Service said the consensus of world forecasters favored "ENSO-neutral" through the Australian winter "with elevated chances of El Nino developing afterwards".

It's monthly summary warned "it is possible that strong warming near South America may portend a more rapid evolution toward El Nino and will be closely monitored".

Overseas forecasters say many computer climate models are predicting a transition into El Nino "sometime later this year".

They all included the same rider "right now is a very tricky time of year for the models".

Bureau of Meteorology technical lead (extended prediction) Dr Andrew Watkins said after three years of La Nina and record-breaking rainfall in eastern Australia, the Bureau's long-range forecast shows drier than average conditions for most of Australia over the coming months.

"Long-range forecasts show there's an increased chance of below average rainfall for most of Australia during autumn 2023," Dr Watkins said.

"But the northern wet season, including the tropical cyclone season, for northern Australia continues during March and April, so there remains the chance of tropical weather systems bringing heavy rain at times to the north."

If these tropical weather systems extend south, there remains the possibility of periods of heavy rainfall, and flooding, particularly in parts of eastern Australia where soils remain wet and rivers and dams are still full.

Dr Watkins said should the chance of El Nino forming later in 2023 increase to around 70pc, the Bureau will change to El Nino alert status.

"Even if El Nino impacts Australia, this does not necessarily lead to drought," he said.

"There have been 27 El Nino years since 1900, and around 18 of those years were affected by widespread winter-spring drought."

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Dr Kimberley Reid is an atmospheric scientist from the ARC Centre of Excellence for Climate Extremes at Monash University.

She agreed that it was "not that unusual" to swing into El Nino after a La Nina event.

"Now is the time to start cutting back the excess vegetation that grew over the last three years," she said.

"All it takes is a dry winter and spring, which is probable with an El Nio, and all that excess vegetation will be fuel for summer bushfires."

La Nina is the cool phase of the El Nio-Southern Oscillation (ENSO), usually bringing more rain to Australia, while El Nino is the warm phase, where our climate is often drier than usual.

ENSO describes a naturally occurring cycle in the climate system, including the location of warmer or cooler than average sea surface temperatures in the central and eastern tropical Pacific Ocean, and its connection with the trade winds and patterns in the atmosphere.

The effects impact weather around large parts of the globe, including Australia.