Conditions are preparing the way for a concerning combination of El Nino and positive Indian Ocean Dipole (IOD) – two weather systems that are likely to contribute to reduced rainfall and potentially severe summer bushfires.

The Bureau of Meteorology today again stopped short of declaring an El Nino event, continuing with its “alert” status. Past alerts have led to El Nino events 70% of the time.

But the bureau says sea surface temperatures in the tropical Pacific are exceeding El Nino thresholds and have continued to warm slightly over the last two weeks. Further warming is likely.

Trade winds last months were slightly weaker than average across the Pacific for the first time since January 2020, and “other atmospheric indicators have also recently shown signs of possible coupling between the Pacific Ocean and the atmosphere”.

“This coupling is a characteristic of an El Nino event and is what strengthens and sustains an event for an extended period,” the bureau says.

A positive IOD is now “very likely”, with the IOD index above the threshold for a positive event for a fourth week.

“If the IOD index continues to remain above this threshold, a positive IOD event will be considered underway,” the bureau says.

“All models indicate this is highly likely and that a positive IOD will be sustained to at least the end of spring.

“A positive IOD typically decreases spring rainfall for central and south-east Australia and can increase the drying influence of El Nino.”

The bureau’s long-range forecast for Australia indicates warmer and drier than average conditions are likely across most of southern and eastern Australia from October to December.

As previously reported by insuranceNEWS.com.au, the bushfire outlook for spring warns large areas of the country face above normal risk.