The weather over the east is starting to ease after what was a significant period of rain and thunderstorms this week. Many areas will remain in flooding for the coming week or two with the residual peaks moving downstream, so if you are living in southern, western QLD be aware of this and northwest NSW and northeast SA could feel the impacts of this as well moving into June.
Overall, the pattern is starting to relax. We have a cold front crossing through southern SA tonight and tomorrow, this moves onwards into VIC and southern NSW during the weekend with a few showers and windy weather, but drier air is to follow which will bring the more settled patch of weather for much of the country into early next week.
Persistent showers, maybe some thunder for the east coast of QLD can be expected throughout the period but overall, the weather is looking more settled, with the long wave trough clipping southwest WA, southern SA and southeast Australia with mainly light falls.
After some solid falls in the west yesterday where many got over 30mm including the Pilbara and Gascoyne (a sign of things to come this cool season) the weather will turn drier with high pressure moving in, but the jet stream is still active and likely to see widespread cloud develop and the risk of further patchy rainfall developing early next week is quite high through this region. An upper trough is still forecast to meet the moisture over the Pilbara and Gascoyne, possibly spreading more widespread rainfall through the region which could spread south into the Central West and Goldfields. So further follow up is possible here, the rainfall may bypass the SWLD to the north at this time.
That rainfall over WA may continue the journey through to northern and western SA but become blocked by a developing inland trough over QLD and NSW again. There are growing signals we could see another burst of widespread rain and thunder for the eastern inland of the nation with the weather reflecting the continuation of the La Nina and positive SAM phase in place during later next week that will play out after the Election weekend.
Northern Australia, fairly typical weather after some rogue storms dumped 50mm in some communities overnight, that is 10x the May average. While this may seem inconsequential to most, it most certainly is not to me. It indicates that we have the elevated SSTs playing a huge role in increasing the moisture content across all corners of the nation, and so for those who are missing out on the rainfall in the south, it is bad luck that you have not seen rainfall. Just like it is bad luck that the same areas keep getting hit with flooding.
Overall, the pattern is expected to gradually adopt the cooler season distribution of rainfall, and we will see that take place once we have a more persistent negative SAM phase. When we get a more persistent negative SAM phase, then we know the La Nina is also waning further. So, there are plenty of areas to watch in the weeks ahead. Hopefully this offers some of the methods to the forecasting madness.
Let's take a look
Rainfall Next 10 Days
Rainfall numbers are coming way down as forecast, with the severe weather event off the east coast this evening with showers lingering, the rainfall is forecast to become more scattered. In the west we have seen gusty showers along the south coast of WA with light to moderate rainfall, but the large cloud band that has been traversing east across the state into SA is weakening further and rainfall numbers are coming down with this band too. The front over SA is forecast to move towards the southeast states tomorrow with patchy rainfall and windy weather but a drier airmass will follow and this is where you will note the change in conditions from that real soupy air. Over northern Australia we are dealing with dry season showers and thunderstorms about, but they should become more widely separated over QLD with some areas seeing sunny weather for the first time since last September. During next week, the moisture over the northwest will continue to deepen, so cloud is expected to thicken over inland WA with widespread rainfall chances for the Pilbara, Gascoyne, Central West and Goldfields, then spreading east to Northwest and Western SA. Some chances of above average rainfall through these areas. At the same time, an inland trough over QLD and NSW is forecast to deepen with the chance of showers and storms increasing, moisture once again being fed into this system from the easterly winds but also thanks to the jet stream spreading through the heart of the nation. Depending on the location of the trough, this could spread fairly widespread rainfall over the same areas as this week. SA, you currently look to sit in between it all, but as mentioned, many are using single data sets like yr.no and apps. No, that is not weather forecasting, and there is more meat to the bones in some of these systems. Sure, rainfall is going to be lighter than other areas, but there is the chance that rainfall numbers could come up over some locations in the coming days for southern and southeast areas. So keep watch.
Thunderstorm Forecast Saturday
Thunderstorms are possible over a few pockets of the country, but severe weather is low. Storms have the highest chance of producing some heavier rainfall over central coastal QLD during the afternoon and evening with a trough stalled out. A weak trough over northwest WA through the Pilbara may produce a thundery shower or two and there may be a few thunderstorms inland of Darwin east to Jabiru through the afternoon and evening
Thunderstorm Forecast Sunday
Thunderstorms are only really a moderate chance in scattered for near a weak trough over Central Coastal QLD during the afternoon and evening. Small chance that thunderstorms may kick off across the north of the NT and some possible over sparsely populated areas of the WA Outback.
Thunderstorm Forecast Monday
Isolated showers and thunderstorms are possible along a weak trough near the Border Ranges north to the Coalfields into QLD but no severe weather is expected.
Thunderstorm Forecast Tuesday
Thunderstorms could develop once again over the eastern third of QLD inland of the coast during the afternoon and evening, but they are not expected to be widespread or severe. There may be some thunderstorms during the afternoon and evening over the Pilbara or Gascoyne as a trough deepens.
Southern Annular Mode - Briefly negative but turning back for a modest duration positive phase.
The SAM is tending briefly negative during the early part of next week, but it is the shift back to positive that has my eyebrows raised with a few very strong signals there, but a few are also showing a negative phase. Under the current guide I would be inclined to side with the positive stance given the state of the ENSO.
Medium Term - May 20-27th 2022
Rainfall is forecast to remain above average over the east coast of QLD, extending inland with onshore winds feeding a trough that is forecast to be in the region. Moisture running through the jet stream that will likely bring moderate rainfall, with totals above normal for this time of year, is forecast to feed troughs in the east leading to the heavier rainfall spread. Leaning bias towards wetter conditions over the central areas of the nation but it will come to the placement of inland troughs and the moisture running through the jet stream. Mainly seasonal rainfall odds elsewhere with light to moderate rainfall at this time for southern parts of the nation.
The warmer bias remains unchanged over the north of the country with higher humidity values and low-level moisture combining for pretty filthy weather for this time of year. The eastern inland more humid and warmer than normal, not by a huge margin (similar weather we have seen behind this rain band over the east and southeast) The west, under the cloud band moving in via the jet stream is forecast to keep temperatures lower than normal.
DATA - Refer to the video for further information and context. Next video update due out on Sunday afternoon.
00Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 2 Weeks
More information can be found in the video at the top of the page but the features to watch, the slow clearing of the heavy rainfall off the QLD coast, has been slower today (upper lows/troughs are very hard to pin down). Then we see another cloud band develop over the southwest and western parts of the country with the development of the widespread rainfall event from Tuesday onwards for the west and then lingering. Will that moisture make it to SA? The GFS says no but other models are keener on rainfall returning to the central parts of the nation. Then we have another rainfall event for the eastern inland of the nation dominating QLD and NSW into the ACT with above average rainfall. The weather over the west in the medium term may see further rainfall developing over the eastern inland and another strong cold front rolling through WA with yet another cloud band to form.
00Z GFS - Precipitable Water Values - Next 2 Weeks
Notice the very warm and soupy airmass is set to remain over the northern 2/3rds of Australia with the heavy rainfall linked to the trough over QLD set to ease as the trough leaves the region. Another strong pulse of moisture is forecast to come into the northwest interior of WA and the modelling is struggling to pin down the impacts from that. Overall, the northern third of the nation looks humid and unsettled through the medium term with the risk of this moisture spreading southwards into the interior and the southeast inland. Watching the moisture rolling through the Indian Ocean and feeding the frontal weather moving east towards WA in the medium term.
00Z GFS - Rainfall Accumulation - Next 10 Days
Refer to the video for more context and analysis
00Z CMC - Rainfall Accumulation - Next 10 Days
Refer to the video for more context and analysis - note the difference between the GFS and CMC, highlighting the difference in the guidance for next week relating to the upper level systems.
00Z GFS - Rainfall Accumulation - Next 2 Weeks
Refer to the video for more context and analysis and the state-by-state fly around.
Next video due out on Sunday afternoon with the state-based forecasts so have a wonderful weekend. The next update due out on Saturday morning.