An El Nino climate event is likely to develop in coming weeks, the Bureau of Meteorology said today. 

The Bureau’s latest Climate Driver Update maintained its El Nino Alert, criteria that in the past has seen an El Nino develop 70% of the time.

“The Pacific Ocean and atmosphere have yet to become fully coupled, as occurs during El Nino events,” the Bureau said. 

“The Bureau's El Nino Alert continues, with El Nino development considered likely in the coming weeks.”

After three consecutive La Nina’s, the World Meteorological Organisation and US and Japanese meteorological groups have already declared El Nino is in play.

The Bureau says its models show wind, cloud and broad-scale pressure patterns still mostly continue to reflect neutral El Nino–Southern Oscillation (ENSO) conditions. ENSO is the oscillation between El Nino and La Nina conditions.

Sea surface temperatures in the tropical Pacific are exceeding El Nino thresholds though, and climate models indicate this is likely to continue at least through to the end of the year. 

Models also suggest a positive Indian Ocean Dipole (IOD) is likely to develop in late winter or early spring. That typically decreases winter and spring rainfall for much of Australia, and can exacerbate the drying influence from El Nino, which typically suppresses rainfall in eastern Australia and brings a greater risk of drought and bushfires.

The Bureau’s long-range forecast is for warmer and drier conditions during August to October for much of Australia, based on all ocean and atmosphere influences. 

It says global warming continues to influence the climate, and April-October rainfall in southern Australia has declined by 10 -20% in recent decades.

The term El Nino refers to the extensive warming of the central and eastern tropical Pacific Ocean which leads to a major shift in weather patterns across the Pacific. During El Nino years, the trade winds weaken, or reverse, and warmer surface water builds up in the central Pacific. 

Cloudiness and rainfall north of Australia are supressed, typically leading to below average winter–spring rainfall for eastern parts of the country, and a drier start to the northern wet season.

It occurs every three to eight years and is associated with drier conditions in eastern Australia, the opposite to La Nina.