Climate models monitored by the Bureau of Meteorology (BOM) are indicating that an Indian Ocean driver of wet weather will form this year, following the end of the recent Pacific Ocean La Nina.

A negative Indian Ocean Dipole (IOD) reflects differences in temperatures between the tropical west and east that can shift moisture towards Australia.

The IOD index has been very close to, or exceeded, negative thresholds over the past four weeks, suggesting a negative IOD is “increasingly likely”, the BOM says in its latest update last week.

“All climate model outlooks surveyed indicate a negative IOD event is likely for the coming months,” the update says.

A negative IOD raises the chances of above average winter–spring rainfall for much of Australia, and increases the likelihood of warmer days and nights for northern Australia.

The BOM says this month’s torrential rainfall in NSW has been influenced by IOD trends and a positive Southern Annular Mode, which refers to the north-south movement of the strong westerly winds that blow almost continuously in the mid-to-high latitudes of the southern hemisphere.

The Pacific Ocean La Nina has ended, but a “watch” remains in place as some climate models indicate an event may re-form later this year.

Four of seven models surveyed suggest La Nina could return in spring, with the remaining three persisting at neutral levels.