We have had round after round of flooding rains in recent months, so what is causing it and when is it going to end?
As thousands continue to recover from inundation and the tropics get their round of rain this weekend, the weather continues to be a hot topic of conversation from bowls clubs to bars.
Here's an illustrated crash course in what's going on and why.
Underlying conditions
The reason why it just keeps raining is because the atmosphere is primed full of moisture, looking for any excuse to fall as rain.
The main underlying climate driver setting up those wet conditions has been La Niña — a phase of the El Niño-Southern Oscillation (ENSO).
The ENSO is a circulation that occurs over the Pacific Ocean.
The La Niña phase occurs when stronger-than-usual trade winds cause warm water to accumulate over the western Pacific around northern Australia.
This encourages moisture to evaporate and rise, meaning there is more moisture available in the atmosphere. A bit like steam rising from a kettle.
When this moist air combines with weather patterns or the right topography, it can rise and condense (like the steam from your kettle condensing on the cold kitchen window), causing bucketloads of rain.
The persistently strong south-easterly trade winds also help to push this moist air over Australia — as we've experienced time and time again of late.
There are other climate drivers lurking around, but La Niña has been the big influencer.
It has also helped that this has been the second La Niña year in a row, meaning that many catchments were at least partially primed heading into the season.
Having two La Niña years in a row is not uncommon — some of the wettest periods in Australia's history have been double La Niña summers, such as 2010-12, and 1973 to 1976 was a triple whammy.
It is difficult to tell at this stage if climate change is also a factor.
It is true that with every one degree of warming, the atmosphere can hold 7 per cent more moisture, but with prolonged rain events like we've seen this summer, it is harder to find a climate link, as the factors behind rainfall are incredibly complex.
With or without climate change, eastern Australia has a long history of diabolical flooding, going all the way back through to colonisation and beyond with Indigenous accounts and sedimentary records.
Weather patterns
With La Niña, the atmosphere has been primed so that when individual weather patterns come through, there has been plenty of moisture for them to tap into.
Significantly along the eastern seaboard a series of blocking highs in the Tasman Sea have generated easterly winds, pushing moist air onto the coast.
When that moist air is then lifted by topography or another weather system like a trough or a low, it then condenses and falls.
The high then blocks the low or trough and prevents it from moving out to sea, causing the heavy rain to hang around for days.
These surface-level systems have then been further enhanced by low pressure further up in the atmosphere, which has helped to further enhance the lift and rain.
Atmospheric rivers have also helped to stream moisture into specific areas along the coast, helping to determine where the heaviest falls are recorded.
What's going to happen next?
The tropical wet season traditionally ends at the end of April.
We would usually expect the La Niña to break down during autumn, but it remains active so it wouldn't be a huge surprise if the wetter weather hangs around late this season.
While the La Niña may still technically be in play, it has been weakening and is expected to drop into neutral territory around the beginning of winter.
We would expect the influence of the La Niña and the moisture provided by the tropical wet season to reduce as winter sets in.
We may be near the end of the season, but with catchments so full on the southern east coast in particular, it won't take much more rain to trigger renewed flooding.
Looking forward, winter is traditionally when southern Australia gets the majority of its rainfall, as the westerly winds deliver cold fronts.
It is looking like the ENSO will remain in neutral over winter, so it is unlikely to push factors one way or another.
It's difficult to forecast much in autumn as the climate patterns shift, but across the Indian Ocean it appears we can expect a strong negative Indian Ocean Dipole (IOD).
A negative IOD is much like the La Niña, but instead it occurs across the Indian Ocean.
So again, warm waters near Australia encourage evaporation and lift, creating a moisture-rich atmosphere that the westerly winds can tap into as they move across the country.
If this occurs, it could encourage a wetter-than-average winter for parts of Australia — the last big negative IOD was during the winter of 2016, a phenomenally wet year for parts of the country.
Those with long memories will recall it was a bumper year for cropping but also the winter when a series of tornadoes plunged the whole of South Australia into darkness.
As usual, we will have to wait and see how it plays out.
