Jane's Weekly Update: 5th September 2025

Who is ready for rain?

A new widespread weather system is kicking off in the west today with a big band of showers and thunderstorms.

This is part one and will move eastwards, reaching the eastern states on Sunday into Monday (after it warms up in the southeast after the latest cold outbreak).

Part two involves a feed of tropical moisture coming down from the northwest - a juicy, northwest cloudband - meeting up with the second wave of low pressure. Depending on where the low moves, we are set for a widespread soaking rain event, with rain across most states and territories, persisting for a few days.

This is most likely to be a system that affects the western side of the ranges - it is not an east coast system.

If the low moves across the southeast then eastern SA, Victoria, western NSW and parts of Tasmania will do very well.

Look for the guidance to show a tighter spread of rainfall potential as it approaches, for higher confidence in the actual path of the low.

This weather system is yet another great example of what can occur when we are in a Negative Indian Ocean Dipole (IOD).

We've now been in one for six weeks, and BoM declares it a Negative IOD year when it has been eight weeks.

The index is incredibly negative, ie very strongly negative:

The IOD naturally ends as we go into Summer, and our focus shifts to what the Pacific is doing.

This index has also been heading southwards. A few models like La Nina (all from USA) but others keep it in Neutral. A tighter spread here would give us better confidence that the Pacific will also encourage moisture to pour in as we go through Spring and Summer - but the warmer than average water off eastern Australia also plays a big role in providing that moisture.

So, we have lots of moisture, and the question - as always - is do we have the low pressure to turn that into rain?

For an indepth look at all of these graphics and more, if you have 8 minutes to spare, don't miss my video:

In this series I'll take you through the drivers of our weather, highlighting any changes over time and things to watch out for (generally every Friday). It covers weather elements like temperature and rainfall, and how they are driven by moisture from the Pacific and Indian Oceans, as well as bursts of energy from low pressure (SAM and MJO).

See and hear my commentary as I take you through the weather pattern's effects on our rain and temperatures in detail over the next week, with a brief look at week 2 and beyond as well.

Plus what is driving our weather in the weeks and months ahead, with the latest on El Nino/La Nina, the Indian Ocean Dipole (IOD), the Southern Annular Mode (SAM controls our weather systems), and the Madden Julian Oscillation (MJO connects tropical moisture to our weather systems).

I update this commentary each week, generally on Friday's. Make sure you are signed up (free or a subscription) so you don't miss an update.

Stay up to date with the forecast specifically for your area in our hour by hour outlook for the next 10 days. Download our app for iPhone and Android.

As always, you can see each of these graphics as soon as they update, as well as more information about them under our Rain Outlook and Seasonal Outlook pages within Jane's Update, along with our Snow Forecast in the snow season.