The severe weather so far this Autumn has been absolutely insane for areas in the east with records broken and broken again with exceptional rainfall off the back of a waning La Nina, elevated SSTs surrounding the nation and the persistent positive SAM phases bringing the same weather events, delivering the same rainfall potential, to the same areas.
Do we see conditions shifting the rainfall across the nation through the coming 6 weeks? There was evidence on Tuesday in the update that, it will be likely that a shift into a southern focus on rainfall and a cooler shift which is in line with the Autumn Break will be observed through this time.
Lets see what the latest tells us about the strength, speed and scale of the shift in conditions and whether it is a national impact or continuing to be localised to regions as it has been so far this year.
%chance of exceeding or not exceeding the median rainfall expectations for the next 6 weeks
Well the signals from Tuesday has largely remain unchanged with the chance of above average rainfall running very high over the north and east of the nation, in the east, the area from south of Sydney to about Orbost in VIC need to watch and inland to Canberra. The flood risk is running high over northern and eastern Australia, but more likely for the tropical north with the wave of low pressure lingering for about a week over Easter and along the east coast with the positive SAM. Now moisture will spread through remaining parts of the nation leading to rainfall returning to southern and southeastern parts of the nation, but I do think this rainfall will become extensive in May (despite an Autumn Break potential in the short term) with the cooler shift to follow. So really, many areas are leaning bias towards wetter conditions through this period, but that does not mean all areas will get above average rainfall. The climate drivers are supporting more rainfall over the country than not. So pay attention to the short and medium term forecasts for more details on each of the systems as they roll through. These outlooks do not pick severe weather events, but they pick where the higher chances of more active will be found and they have proven useful in forecasting the flooding through Spring 2021. Summer 2021/22 and so far this Autumn 2022.
%chance of exceeding or not exceeding the median temperatures expectations for the next 6 weeks
With the higher moisture content through the atmosphere, this can play two ways. This can suppress temperatures and lead to cooler than average weather for much of the country, but at this time of year, this will help to keep the late season baking weather at bay, so seasonal temperatures for most areas across the nation is fair. Where it will be cooler through to the end of Autumn is along the east coast with the persistent La Nina and positive SAM relationship that refuses to break up and the southwest of the nation with higher than average rainfall possible along cold fronts and troughs that are more active in that region with the placement of the long wave remaining more often than not across the region. For northern Australia, above average night time temperatures and below average day time temperatures likely with significant cloud and rainfall coverage anticipated. But as you can see the forecasts for the nation are conditional on all of that information playing out in reality.
%chance of exceeding or not exceeding the median moisture expectations for the next 6 weeks
This has been the larger change since last update and connected to the shift in the SAM to the persistent positive phase for the east that runs through into May. Then we have this persistent tropical plume of moisture over northern Australia which gets stuck as the upper level winds collapse, resulting in the moisture being stuck over the Top End and Cape York for a fair chunk of April, maybe sweeping into the Indian Ocean towards ANZAC Day. All of that moisture could be spread throughout the interior of the country leading to elevated rainfall chances across the nation but increased cloud cover and possibly ore organised cloud bands via the jet stream interacting with cold fronts and troughs look more likely as we go through this period. So with the extra moisture, that will lead to higher cloud cover, warmer nights mitigating frost chances for now but also leading to higher rainfall chances as well.
Refer to the video for further information on the details below. The Autumn and Spring Outlooks can be quite volatile and change rapidly, so use this product here Tuesday and Fridays with the daily short and medium term forecasts.
Additional Points to consider moving forward into May and June.
I did promise an update on May but with the severe weather coverage and trying to get as much of the short term weather details out, this has been pushed back into Sunday if not early next week.
We have more severe weather issues that are of higher importance at the moment, given we have vulnerable crops, stock and livelihoods to consider.
I will be having this afternoon off to spend time with the family before they divorce me, so next update on Saturday morning and next video update coming up on Sunday with more info on the volatile weather expected in the short term throughout the weekend.