Northwest cloudband set to spread rain over the southeast

We're ending the week with a surge of heat, and a trough that produces showers and severe thunderstorms. That is only for Queensland and NSW on Friday, it has cleared the southeast. 

This is followed by milder conditions (but still cold enough for snow in southern Tasmania - see how the speckled cloud only comes half way up the apple isle this time, not right into the mainland).

Meanwhile, we're starting to see cloud building over the Indian Ocean. This is the precursor to the next big weather system.

Satellite and radar on Friday morning.

Up next is our next widespread rain system. The Negative Indian Ocean Dipole (see further down in this article) is doing its job to push moisture in from the Indian Ocean. Low pressure is meeting up with this to turn it into rain, and the pattern should spread that rain from the west through to the southeast.

This occurs from later in the weekend to mid next week (very slow moving), and I have here the latest guidance from this morning. Keep in mind that the path of the low pressure may change as it gets closer, so keep up to date with these rain maps. ‍

Potential rainfall over the next week.‍

Day by day rainfall potential as per the modelling on Friday morning.

‍So, that is a big sweep of rain heading across the country, as shown in the week one summary/anomalies. There may be another surge to follow, but the guidance for week 2 (beginning Monday, October 27) has the rain signal confined to the tropics in the NT and Queensland:

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Weekly anomalies has next week's rain sweeping across the country, then confined to the north in week two.

The US has declared a La Nina in the Pacific, but the Americans work on a lower threshold to the Australians - we need the signal to head further negative for BoM to call it:

Pacific Ocean: La Nina declared by USA, not quite at the Australian threshold.

Meanwhile we've been across the negative Indian Ocean threshold since late July (in a Negative Indian Ocean Dipole [IOD], the 'La Nina' of the Indian Ocean - quite a strong one). The huge cloudband that we'll see with the next significant rain is a textbook example of this in action.

Indian Ocean Dipole (IOD): We have been Negative since late July.

In simplest terms, what these two graphs tell us is that both the Indian and Pacific Oceans are keen on sending excess moisture towards Australia. We also have warmer than average water around the majority of the country, further enhancing this.

So, the moisture part of the rainfall equation has a big tick.

Whenever that runs into low pressure it is turned into heavier than usual rain. But it is only for those that are in the path of the low pressure who get to see it.

As always I take you through all these charts and more in my weekly update video. If you have 14 minutes to spare, settle in as I discuss the latest:

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