We are already feeling the impacts of what has been a very wet last 2 years across NSW and the signals are for that wet phase to continue further into Winter 2022.
The main climate drivers behind the wet signal are still in place. We have the active ENSO region, resulting in a stubborn La Niña that refuses to resolve, pumping warmer than normal SSTs back towards the east coast.
We have the Indian Ocean Dipole that is forecast to turn sharply negative through July and strengthen further in the August and beyond, that if it comes off, will result in excessive rainfall developing for parts of inland NSW and some of that drifting over the ranges at times. Also any east coast low that forms can feed off moisture being drawn in on the jet stream.
Also as the La Niña wanes, we will see the SAM turning back more neutral to negative, with some longer duration negative events meaning that the westerly winds are more prominent, leading to the drier season taking shape over the coastal areas of NSW.
But on the current guidance, it will be hard pressed to find a community that will be below seasonal in terms of rainfall. The higher chances are likely to be further west along the NSW and QLD border through the northwest. However, with the Indian Ocean Dipole deepening the negative phase, even this region could come in with well above average rainfall, which has been going on for months now in many locations.
Let’s take a look
%Chance of exceeding or not exceeding the median rainfall for Winter 2022
Rainfall is expected to be above average for many areas, with the higher chances of achieving above average rainfall expected over areas along and to the west of the Great Dividing Range as we see the lingering La Nina influence resolve and the Indian Ocean Dipole influence take over. This will see rainfall events stack up over inland areas and given they are running from west to east, this will leave the remains of the systems to peter out over the areas along the east coast. The wettest month of the Winter should be June for the east coast with the remains of the La Nina influence still about but come July and August, some areas could actually see seasonal to below seasonal rainfall as we move into the traditional dry season. But areas over the northern and northwest inland could see above average rainfall thanks to the Indian Ocean influence which looks to strengthen as we go through the season. Note that the peak of the Indian Ocean influence comes in the September and what is reflected here is the influence of the above average SSTs surrounding the nation and the developing IOD. The lingering La Nina should resolve by July. The flood risk for the region is moderate through the season, tending higher further south.
As mentioned, the influence of rainfall shifts from the La Nina to the Indian Ocean Dipole. The rainfall spread could reflect similar values to what we saw in 2016 where flooding developed through the Winter but then increased through the harvest of 2016 where flooding increased and damage to property and much of the harvest was compromised for many inland areas.
%Chance of exceeding or not exceeding the median temperatures for Winter 2022
The temperature guide is looking to support the Indian Ocean Dipole moving into a negative phase and while there is a lot of blue on the board for areas on and west of the divide, this looks to take place from July onwards I would think. June could come in warmer than normal for some areas over the inland with the influence of the lingering La Nina and warmer than normal SSTs around the eastern parts of the nation, that influence being drawn in on the easterly winds. Then we shift influences to the IOD which will likely see the jet stream infused with deep moisture leading to widespread rainfall and cloud bands running through the nation. This will see a trend to below average temperatures across the inland with the higher rainfall signals. Along the east coast, some areas in the northeast and mid-north could see above average temperatures from time to time with westerly winds blowing through during the peak of Winter. But certainly as the rainfall increases over the course of July and August, this may support these below average temperatures. The below average temperature signals are expected to spread throughout the state into Spring. The snow season also looks to be well below average with above average temperatures possible thanks to the above average SSTs and moisture via the jet stream.
Certainly, looking at below average temperatures running up and down the Great Dividing Range as mentioned thanks to the IOD remaining in negative phase. The east coast could see some above average values from July to August. The warmer trend not uncommon through the traditional dry season. The values over in the northwest could be well below average with well above average rainfall. The signals for cooler than average temperatures increase further across the state.
More to come on this as we move through the weeks ahead and break down the months through the 6-week outlooks both Tuesday and Friday.