We are saying goodbye to a very wet 2021 with many areas still very soggy. With a La Nina in play, the wet signal will continue into the first quarter in 2022.

For the short and medium term, a monsoonal break for the end of 2021 over northern areas is likely, the flow is still north of the nation and will remain there until next week. But it will return. The tropical rainfall and heavy falls will ease over FNQ by this weekend. The rest of the nation relatively dry away from the east coast of NSW and QLD.

The longer term offers a wetter signal for January, especially from the second week of the month through to early February. Signals are strong that the rainfall will increase over the north of the nation again and that will spread southwards throughout the nation via troughs. For this to happen, the high pressure belt needs to sink southwards, which is again, likely to happen as we roll through January.



%chance of exceeding median rainfall for next 6 weeks - December 28th 2021 through February 10th 2022.

Enjoy the quieter and drier 10-15 days across the nation as the rainfall is expected to ramp up again and will be in line with the monsoon returning up north, the easterly winds returning and freshening over the eastern states thanks to the high dropping south and troughs combining with the deeper moisture layer to see widespread showers and thunderstorms return. The weather is expected to become more humid as we go. Through this period, the climate drivers being the La Nina peaking and the SAM tending positive again, will work together to bring a very wet second half of January and start to February. The wild card systems, the tropical lows over northern Australia. Northern and eastern Australia very likely to see above average rainfall, as already has been observed in many locations in December.

%chance of exceeding median temperatures for the next 6 weeks - December 28th 2021 through February 10th 2022

No overall change to the guidance with the likely cooler signal persisting for eastern Australia, the monsoon close by the north of the nation for much of this period will lead to more seasonal conditions overall and the west is where you can find the heat, as we have seen this Summer so far, the west is where you will be baking. Though with the high heat levels, the humidity will be infused into this heat and the rainfall will return to the west moderating temperatures as we go through the outlook period. The southeast will see the most variation in temperatures through this period.


%chance of exceeding median rainfall for Summer 2021/22

Make the most of the drier weather in the coming 10 days, as things are likely to shift again as we move into January and more likely later in the month. As we move through the the next 6 weeks, the monsoonal activity will drive the rainfall chances for northern and central as well as eastern Australia. We are seeing that right now in real time with a weak tropical low spreading rainfall over northern and eastern Australia. The monsoon is likely to persist north of Australia for the remainder of 2021 and will increase again over northern Australia for the start of 2022. The MJO is also likely to arrive from mid to late January. Every time you hear that the monsoon is being forecast to be over Australia this Summer, the impacts are likely to be felt far and wide through the nation. The longer the monsoon stays over the nation's north, the longer the elevated rainfall chances remain over Australia. This will lead to elevated flood risks for the north and east of the nation in particular, we have already seen flooding develop over inland parts of the NT and watches are developing for north QLD.. There is growing evidence that February could be the wettest month out of the Summer. The wet weather has a good chance of lingering into March as well.

%chance of exceeding median temperatures for Summer 2021/22

The cooler bias over central and eastern inland parts of the nation will continue into the second half of Summer with a strong chance of below average temperatures persisting into the February. The temperatures over the west trending above average is fair based upon the current strength and depth of La Nina with the easterly winds eventually taking over, these running over land will warm up and dry out so a good chance of higher temperatures over the nation.


%chance of exceeding median rainfall for Autumn 2021/22

With the lingering La Nina from the Summer still influencing the rainfall distribution through the early Autumn, there is a real risk of a repeat of flooding for the east coast in line with the peak of the wet season for the subtropics which is usually March through May. So pay attention to the guidance in the coming weeks over Christmas and New Years (yes I will still be here). The weather looking less wet for southern parts of the nation for now, but the Autumn break may be moot point with the wet Summer running into March before conditions ease through the season. The tropics may have a prolonged wet season with above average rainfall taking us through to May. Cyclone activity peaks in the Feb to April range through the Indian Ocean and this could influence rainfall for the interior and into the northern and eastern inland.

%chance of exceeding median temperatures for Autumn 2021/22

As per last season, the east and north were below average temperature wise with above average humidity values and rainfall across the east and north expected at this time, so the reduction in temperatures is a logical conclusion. The west and south I think will trend warmer, not necessarily drier, that average across these areas. We may have some impacts of late season cyclones running through the northern and western parts of the nation.


ENSO Spaghetti Plot - Model Predictions December Plume.

I will use this update from last month ahead of the new data set coming in from later this week (I will have that data set on Friday with the 6 week outlook). Note the plume generally sits lower that the ACCESS model run - so that means that looking at the data set, the La Nina will not be short lived and could be a stronger than what is being advertised across the Summer before waning in the Autumn. That idea is still probably the right solution at this time, so be aware, looking at the BROADER data sets is crucial to forecasting these major climatic drivers. As we saw with the botched IOD forecasts from mid to late this year, looking at the full data set assisted me in forecasting the very wet Spring and nationally the WETTEST November on record well ahead of time. And I stand by the stronger and longer duration La Nina for this Summer which seems to be verifying against the Australian Model which is forecasting a weaker La Nina than is currently underway. For the record, no one can really see beyond about 6 months as to what will happen into Spring and Summer of 2022, that would be naval gazing fortune telling, there is no skill, just gambling on being right or wrong.

A brief deep dive into the data sets, and I have outlined the international agencies that persist the La Nina into Autumn 2022. And while there are more that resolve the La Nina by then, this highlights that the event overall will be of normal duration, not short duration with a risk of the La Nina persisting into Autumn

More details coming up on Climate on Friday.

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