Heat is moving into the eastern states in a big shake up from last week’s weather pattern, while the connection to tropical moisture takes a break, limiting the rain potential in southern Australia.
We’ve just finished a week where the weather pattern pushed heat into the west, and cooler southerly winds into the east.
Next week looks to be exactly the opposite.
No more high pressure over the Bight directing southerlies through the east and northerlies into the west - now we’ll have northerlies as the main feature in the east, directing hot air from the interior right through to the coast, while cool southerlies extend through southwestern parts of the country.
Remember this is the overall pattern. We will still have cool changes affecting the east, but when you add it all up at the end of the week, the heat outweighs the cool.
Next week’s temperature outlook - how much warmer or cooler than average we are likely to be overall
There isn’t a lot of rain to go with this pattern if you’re in southern Australia. Most modelling suggests there will be some rain at times, but it won’t add up to much.
One of the main culprits for this is a weather driver known as the Madden-Julian Oscillation (MJO). This pulse of energy travels around the tropics and when it’s in the green zone Australia has a better connection between tropical moisture and our weather systems that turn that into rain.
We’ve just come out of a stint in Australia’s longitudes and now the pulse is rapidly moving away. Entering the brown zone and strong (as it’s so far away from the inner circle on the chart), means our tropical connection is suppressed.
The forecast doesn’t have it wandering out there for long, coming back towards the centre in the second week of November.
Meanwhile, southeast Queensland and northeast NSW have active sessions of showers and severe storms when a trough is in the area - these are fed by moisture from the Pacific Ocean and Tasman Sea. The troughs ensure those to the east have the potential for rain, while those to the west remain dry.
The Madden-Julian Oscillation (MJO)
The amount of moisture from the Pacific and Tasman will ramp up as we head into summer.
The latest forecasts for the Pacific show the index is close to crossing the USA threshold for La Nina, but still a little way from BoM’s official threshold (the beginning of the green area on the following chart).
BoM won’t declare La Nina until we’ve spent 8 weeks in the green zone. They tell you when something has occurred, not when it is likely to arrive - why they have us in ‘La Nina Watch’.
The ocean is heading towards La Nina, but the atmosphere is yet to follow suit. When it does we’ll see increased moisture coming in from the Pacific - it will be actively pushed towards us - and when that interacts with low pressure we get heavier than usual rain.
So we’re heading into a push of moisture - but as always that’s only one part of the rain equation - you need low pressure to turn that into rain and it’s the day by day weather pattern that is responsible for that part.
Pacific Ocean Index - heading towards the La Nina threshold
Check the full details at Jane’s Weather to keep up to date on what the models are projecting for your spot. If you’d like an in depth analysis don’t miss my weekly video update - perfect if you have 20 minutes to spare!
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