The year began and ended wet, with a long dry patch in the middle really impacting southern Australia. We’re taking a break from the rain over the Christmas week, before it ramps up again in the new year.
Looking back over the past year shows that much of the country had a good year for rain - but there are some standout major deficiencies.
A large area over the southeast, mainly from Adelaide through to Melbourne, experienced an incredibly dry year, with most of the rain not falling from autumn through to spring (which is highly unusual as that is the time of year when it usually rains).
A large part of the southwest was also in the same boat - also lacking rainfall at the time of year when it usually rains.
This is starkly shown in the Drought map - a ‘severe deficiency’ affecting parts of the country that are usually guaranteed rain from cold fronts.
Drought over the past 12 months.
We began the year in an El Nino, with moisture from the Pacific Ocean pushed away from Australia. But that usual drying effect was offset by an incredibly warmer than average Tasman Sea that provided bucket loads of moisture, working with a favourable weather pattern to turn that moisture into heavier than average rain.
That weather pattern shifted for much of autumn through to spring, stopping the cold fronts from hitting the south.
Then we had big feeds of moisture from both the north and east to end the year, and the weather pattern decided to push that in and produce big rains in November and early December.
The current Sea Surface Temperature Anomaly (SSTA - how much warmer or cooler than average the top of the ocean is) has a lot of the yellow and red colours around Australia.
This is a result of extra heat in the atmosphere settling in the top part of the ocean - and these warmer waters make sure there is so much more moisture available in the air above.
That is a critical ingredient in the recipe for rain - and the map indicates that we will have plenty of this moisture in the Australian region as we go through summer.
Sea Surface Temperature Anomaly (how much warmer or cooler than usual).
The other ingredient in the rainfall recipe is instability, found in low pressure, and wind patterns that allow that ocean moisture to be fed into these lows, troughs and fronts.
There is one of these affecting central Queensland now, producing huge rainfalls, because that is where the weather pattern is sending the moisture right now.
Over the next week much of the country takes a break from this, but the break may not last long as the outlook for January to March 2025 shows that much of the country has a higher chance of above average rain.
This is thanks to the moisture available - but it does depend on what the weather pattern will do as to which parts see this enhanced rainfall.
BoM’s latest outlook for January to March 2025.
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