Over the course of the next week we have the potential for widespread soaking rain over much of southeastern Australia, fuelled by rain crossing the north and interior.
All the climate drivers are lining up to feed moisture into Australia from the oceans to our northwest and the east, and whenever that can run into low pressure it is converted into heavier than usual rain.
The next week is a perfect example of that in action, and there may be several follow up events as we go into summer.
The last of the coastal Queensland heavy rain dries up today (Friday) and this area enters a generally dry spell. Much of northeast NSW is also quite sunny and warm - a marked difference from recent weather, and all the action that is occurring further west and south
In the southwest the rain system has now moved on, and there isn’t much left over across the next week.
The focus is firmly on the north down into the southeast.
Potential rain from Friday 22nd to Friday 29th November
Our sources of moisture can be seen by looking at the Sea Surface Temperature Anomaly (SSTA) chart. The orange-red areas show well above average temperature, and that means there is extra moisture available to the atmosphere in these parts.
The waters off the northwest coast are incredibly warmer than average - this is a huge source of moisture (and you can literally see it pouring down from the northwest into the southeast in the above rain map).
The waters of the Tasman Sea (in between southeast Australia and New Zealand) are also significantly warmer than average. This was one of the main sources of moisture last summer, and should have a similar impact this year (depending where the low pressure goes).
The blue in the Pacific box is in contrast to the weak warmth off Queensland, and that combination acts as a weak push of moisture into Australia from the Pacific Ocean.
Sea Surface Temperature Anomaly (SSTA) - how much warmer or cooler than average the top of the ocean is. Tells us which areas have more moisture to play with
These all work together to provide the moisture part of the rain equation. But there is a second, very important part - low pressure - and this is essential if we are to turn that moisture into rain.
It will all depend on where the low pressure moves as to who will see the rain, but these ‘moisture drivers’ are reflected in BoM’s latest outlook for rainfall potential this summer:
BoM’s forecast for summer rain potential: Green areas show an increased chance of exceeding the median (or average) rain for this time of year
So, the focus of rain shifts to a large area from the northwest down into the southeast over the next week, as that is where the low pressure is lingering. Keep checking in to see which areas have the low pressure trigger next.
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