We’ve crossed into a new phase of weather - a Negative Indian Ocean Dipole, and the Pacific Ocean may be undergoing changes too.
The main things to note this week are: significant rain for eastern NSW and southwest WA this weekend, as high pressure crosses the southeast letting conditions warm up. The Indian Ocean crossed the threshold into a Negative IOD earlier this week, while there have been some changes in the Pacific Ocean too that are worth keeping an eye on.
Upper atmosphere energy is letting a low form just off the northern NSW coast, bringing significant rain to those near and to the south of the low.
There is lighter rain inland over northern NSW too, easing as it all moves eastwards. Much of Queensland only sees a little, on the 'dry side of the low'.
Here is the pattern of where the heavier falls should be, before it all eases on Monday as the low moves away:
Potential rainfall in NSW has falls over 50mm through a large area near the coast and ranges.
A series of fronts peak in the west this weekend, producing a widespread 25 to 50 mm of rain, and 10 to 25 mm further inland.
This rain comes with gusty winds and the risk of storms, and eases on Monday:
Potential rainfall over the weekend, into Monday from cold fronts passing through
A feed of tropical moisture comes down from the northwest next week, and this will be picked up by a low/trough/front and delivered as significant rain to those in its path.
The first wave of this is likely to take the same path as this week’s: across NSW and southern Queensland. Due at the end of the week.
Again, high pressure blocks this from reaching the southeast, but the high may move over the Tasman Sea (between Australia and New Zealand) letting that moisture slide down into the southeast beyond the end of next week.
The following guidance from the Euro model shows the spread of rain across NSW and Queensland, then how in the next week it could spread down into the southeast. This is on the horizon and one to keep an eye on.
Potential rainfall in week's 1 and 2 shows the rain affecting a large part of the country
Earlier this week we crossed an important threshold. The Indian Ocean went down into a Negative phase. It will need to be there for 8 weeks to officially be a Negative IOD, and we are at week one - but the forecasting shows it is likely to stay there.
What this does is encourage feeds of tropical moisture to spill down across the country from the northwest.
All we need is for those to run into low pressure to produce significant rain.
Indian Ocean Index - crossing the threshold into a Negative IOD
The Pacific Ocean has also recently taken a turn.
Still very Neutral, but there are signs of a slight veer in the direction of La Nina - and the Japanese model likes it coming closer to the threshold than the rest of them.
We also have a pool of warm water off the coast of Queensland, that helps send moisture our way too.
So that's two oceans that are trying to increase the rain chances for Australia over the next few months.
Pacific Ocean Index - remaining Neutral, but some modelling has it nearing the La Nina threshold
For the full in depth update (around 16 minutes this week), don't miss my video:
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