Climate indicators show a La Nina system has emerged, according to the Bureau of Meteorology.

“Trade wind strength and cloud patterns have been indicative of La Nina since at least mid to late September,” the bureau said. “Latest assessments of the El Nino–Southern Oscillation indicate La Nina is under way. There are clear signs the tropical Pacific Ocean and atmosphere are now coupled, meaning they are acting to reinforce and sustain the La Nina pattern.”

The bureau says tropical Pacific Ocean temperatures are likely to remain at La Nina levels until early next year, before returning to neutral.

The El Nino–Southern Oscillation is a natural cycle in the Pacific Ocean that affects global weather, including Australia. It has three phases: El Nino, neutral and La Nina.

In a La Nina phase, trade winds strengthen and warm water builds up north of Australia, while water in the central to eastern Pacific cools.

La Nina typically leads to above-average winter and spring rainfall for eastern and central Australia; an earlier start to the northern wet season; and lower daytime temperatures south of the tropics.

The climate pattern has been blamed for the catastrophic 2022 floods – Australia’s costliest insurance event and the second-largest worldwide that year. Three consecutive La Ninas, a rare triple dip, culminated in that year, causing the record flooding in the eastern states.

The bureau’s senior climatologist, Lynette Bettio, says this La Nina is likely to be weak and short-lived.

“Sea surface temperatures are forecast to remain above average in the Australian region, especially to our east,” she said. “Warmer oceans can provide increased moisture and energy that can enhance the severity of storms, cyclones and rain systems.”