Chances increase for above-average winter rainfall

24 May 2022

Climate drivers in the Pacific and Indian oceans are pointing to an increased chance of above-average winter rainfall in eastern Australia, the Bureau of Meteorology says.

The bureau says all the climate models it surveys suggest a negative Indian Ocean Dipole (IOD) may develop in the coming months, while two of seven models say La Nina conditions may continue through the southern winter.

“Even if La Nina eases, the forecast sea surface temperature pattern in the tropical Pacific still favours average to above-average winter rainfall for eastern Australia,” the Climate Driver Update says today.

A negative IOD is associated with the chance of above average winter-spring rainfall for much of Australia, as well as warmer days and nights in the north.

“While model outlooks have low accuracy at this time of year and some caution should be taken with IOD outlooks, there is strong forecast consistency across international models,” the bureau says. “Outlook accuracy for the IOD begins to significantly improve during June.”

The IOD is the difference in temperatures between the west and east tropical Indian Ocean, which can shift moisture towards or away from Australia.

Negative phases are more likely to coincide with a La Nina and can have an impact from May to December, the bureau says. Australia had its wettest year on record in 1974 when a negative IOD coincided with a La Nina.

The current La Nina, which has brought heavy rainfall and catastrophic flooding to NSW and Queensland, is the second in two years. Consecutive events were previously seen in 2010-2012.