The Bureau of Meteorology's latest climate driver update suggests La Niña will hang around until early 2023, but the negative Indian Ocean Dipole (IOD) is on track to collapse at the end of spring.
The negative IOD in the west and La Niña in the east have been helping to fuel the ongoing wet conditions across eastern Australia over the last few months.
This update confirms the wet conditions are likely to remain for at least a while longer.
The update comes as a low pressure system lingers off the southern New South Wales coast, causing yet more rain in the south-east.
The system is expected to move down over Tasmania tonight.
Showers and storms are expected to continue for the rest of south-east and eastern Australia with potentially severe thunderstorms for coastal areas between Townsville and Wollongong.
The BOM is predicting that heavy rainfall will be the primary risk, but warns damaging winds and large hail are possible.
La Niña set to last
As we have experienced time and again recently, La Niña conditions encourage rainfall over northern and eastern Australia.
The latest update suggests the La Niña is likely to persist through to early 2023.
All seven of the climate models monitored by the BOM suggest the La Niña will last through November.
Five of the models are predicting the phenomenon to persist until at least the end of the year.
A few have the likelihood of its presence above or borderline in January, but all suggest we will be below La Niña levels by February.
Its life span can differ greatly between events, but a typical La Niña would be expected to break down at about the end of summer or in autumn.
This La Niña is looking like it could be relatively short, but because it is the third in a row the impacts are compounded.
Conditions are primed for widespread flooding even beyond what we have already seen over the last few weeks.
Saturated catchments mean it is taking relatively little rain to trigger flooding.
During the summer wet season heavy rainfall would be expected for northern Australia, south-east Queensland and northern NSW, regardless of when the La Niña technically ends.
Indian Ocean Dipole
The update shows all but one climate model indicates that negative IOD conditions are likely to continue through November.
The Indian Ocean Dipole typically breaks down as the monsoon moves south at the beginning of summer.
It is therefore not surprising that all the models predict the IOD will be gone by December.
This update reconfirms we are likely to continue to have extra moisture supplied from the north-west for at least the next month.
Southern Annular Mode
The climate driver update also signals that the Southern Annular Mode (SAM), which helps determine how high up the prevailing weather systems sit, is expected to return to a positive phase.
In a positive phase the westerly wind belt sits lower, meaning less rainfall for the south-west facing coastal regions in southern Australia.
But it means more rain for Australia's east coast as more southerly high pressure systems direct more winds onshore.
SAM has been in positive phase for most of October but is expected to drop down into a negative phase at the end of the month.
The outlook suggests it will get back up into the positive territory at the beginning of November.
Madden Julian Oscillation
Speaking of short-term drivers, the update suggests the Madden Julian Oscillation (MJO) is at moderate strength over the western Pacific Ocean.
It is expected to track slowly eastwards across the western Pacific over the next fortnight.
Unlike the other drivers, the MJO pulses around the equator, fuelling and reducing the effects of the monsoon when it swings down over northern Australia during summer.
The update suggests this moderate pulse over the Pacific may contribute to above-average rainfall for parts of eastern Australia, particularly northern Queensland, and temporarily weaken the trade winds over the tropical Pacific.
