The latest data sets are coming in for the remainder of Autumn 2022 and conditions are still forecast to shift from the warmer and settled interior with the late season rainfall over the north, to cold front and rainfall increasing for southern and western areas of the nation and potentially less severe weather for the eastern seaboard.
But, looking across all the latest model data in recent days and the hundreds of data sets, we may have more above average rainfall to deal with over many areas where they don't want it. The good news, it does appear that rainfall will come in time for those planting through the southern and western Ag areas of the nation which would be welcome.
Tropical weather is forecast to remain very active for this late in the season which could enhance rainfall prospects for some northern inland areas. At this time (and this could still change) that moisture is likely to be out of phase with frontal/trough weather over the south and we could lose the opportunity for an Autumn Break through Southern Australia via this expression of weather.
Lots of moving pieces as is always the way during the shoulder seasons. Tricky forecasting which is enjoyable but annoying all at the same time. Lets take a look
%chance of exceeding or not exceeding the median rainfall for the remainder of Autumn 2022
Rainfall is still forecast to turn wetter for many areas of the nation. It does appear that the influence of the tropics will be a key role in this shift for southern and western Australia. We are already seeing the influence over WA with the moisture streaming in from the Indian Ocean into an upper low in recent days bringing above average rainfall. This type of weather will play out throughout the west over the next 6 weeks with frontal weather likely to take over from May. SA, VIC and western NSW through southern NSW, the weather is forecast tend wetter as we go. One of the branches of tropical moisture, whether it comes via the current expression of above average rainfall through northern Australia in the current forecast or whether it comes via the Indian Ocean into early May, the idea is the same, influence from the north and northwest is forecast to unfold through this period and we should see further widespread cloud band development as a result. in the east, we cannot rule out further severe weather but the pattern does become more zonal, that meaning that weather is moving more from west to east with frontal weather and this can offset the ECL season a little bit but we have to be on watch. With the zonal flow, this will see the dry season start to unfold up north and the wet season for southern and western Australia increasing. So overall it is all as you would expect under the current climate drivers.
%chance of exceeding or not exceeding the median temperatures for the remainder of Autumn 2022
Temperatures are forecast to adopt the same theme as recent weeks with much of the interior looking to be above average for much of the next 3-4 weeks with the warmer air staying in place thanks to the absence of strong cold fronts (we are seeing a positive SAM for the coming weeks helping to keep easterly winds in place) so expect a warm end to April and possibly beginning of May. The weather likely to be cooler than normal in the southwest of WA with the persistent cloud cover and rainfall in the region. Along the east coast, we will likely see more cloudy skies and cooler than normal weather in the short and medium term, but the pattern should flip by the longer term, so through May, warmer days should start to develop with more sunshine about with some luck. Up north, the weather is forecast to be seasonal overall, cooler with the persistent rainfall in the short term but in the longer term, the air dries out and with elevated SSTs up north, I do think we see temperatures remaining above normal. The elevated SSTs not a good sign for the snow season for those wanting a big early start to the season, but all it takes is one rogue system to change all that. At this time, I wouldn't be betting on early snowfalls.
%chance of exceeding or not exceeding the median moisture content for the remainder of Autumn 2022
Looking very much above average over northern Australia with the lingering wet season in line with the waning and lingering La Nina. That will play out also for eastern coastal areas of QLD and NSW, but the impacts likely to be less than what we have seen in previous months. The moisture over the northwest is likely to be seasonal but we could see more moisture influence the southwest of WA thanks to the placement of the long wave trough and this helping to propel moisture out of the region south of Indonesia and into the jet stream. This could begin to influence the moisture content over the central and southeast inland of the nation during May but I am leaning more away from this happening earlier than previous update, this due to the synoptic scale out of phase with the moisture content over the north of the nation. So I do think for areas such as SA, VIC and much of inland NSW and QLD, moisture returns from ANZAC Day onwards, but I am tipping more likely into May. So growers hold on through the southern and southeast inland.
CLIMATE DRIVERS FOR THE SHORT TERM
SAM - Next 8 Weeks
Looking at a positive phase over the coming 2 weeks and that should start to shift back to neutral by the time we reach early May. So expect rainfall numbers to come up over the east yet again across the forecast products. For the following 4 weeks, it is much more tricky to forecast, but there is a shift towards a negative phase as we move into June which may increase frontal activity, but the confidence is never especially high this far out. This the latest forecast models blended this morning and the zone at the end of the period shows the range of possibility.
CLIMATE DRIVERS FOR THE LONGER TERM
Indian Ocean Dipole Forecast - Next 9 Months
We are seeing the downward trend in the Indian Ocean towards that negative phase into Winter 2022. The waters are already fairly warm across large chunks of the Indian Ocean Basin and this will lead to a general increase of moisture and rainfall across the nation from northwest to southeast from July onwards. Like the ENSO, there is a lag from the event developing, peaking and waning to the response felt via the atmosphere. So I do expect a wetter back half of the year as a result. And data supports that. The forecast confidence on the IOD is now moderate and will improve through May and into June. I do think the strength of the negative phase will soften a little bit as we get better data sets into the next 6 weeks.
ENSO OUTLOOK - Next 9 months
The latest data sets support a slow waning of the La Nina that is present and a return to neutral conditions. The overall trend is for the ENSO phase to turn cool neutral through the winter with minimal impacts forecast for the period into early Spring. But some of the models diverge as we head into Spring with a few more now indicating La Nina will redevelop in the Spring into Summer 2022/23 where other modelling supports the cool neutral phase to continue. For now, the preliminary forecast is for cool neutral here and this will continue to refine as we go through the coming 3 months. The longer the La Nina lingers, the more likely we will see another develop in the coming Spring and Summer. This year so far is very much following last year's trends.
Additional Points to consider
I was going to update this on Good Friday but given that many people are away, this forecast will be updated again on Tuesday next week. I have a climate bite during the next week but it gives us all a chance to take a breath. More this afternoon in the short and medium term forecasts and make sure you take advantage of those forecasts to cross check the details in these longer term forecasts.