SA - FINE AND COOL TODAY - LIGHT RAIN OVER THE WEEKEND - BETTER RAIN NEXT WEEK.

A cold start inland today as a weak ridge of high pressure begins to move over. Areas of frost are currently melting away, a settled day of weather with light winds becoming northwesterly. Frost has been reported in scattered pockets along the Flinders through the Mid North into the eastern districts.

There is a front passing through WA today and that will make it's way into the Bight, where it will slow down and cut off into a low pressure system. The moisture not especially deep on its northern and eastern flank so rainfall really limited to coastal areas.

From Friday the showers will remain offshore for most of the day, before they spread through the region by Saturday morning. Light falls are expected for southeast areas of SA and that should clear by Sunday.

Next week, heating up, some areas could record 30C or more next week for a number of days before a strong cold front arrives. That system carries cold air and those airmasses clashing with moisture in the region, could result in a widespread rainfall event once again.

But again the strength of the system will be determined by the Tasman Sea weather and I post this image again to refer to the blocking pattern impacting the weather moving from west to east.

12Z GFS Surface Pressure Pattern for the coming 16 days

The pressure pattern is largely unchanged this morning with the modelling good surrounding the movement of low-pressure system slowly passing southeast. There will be a trough that rotates around this low later today and moves north over the southeast and combines with a cold pool, moisture and bringing widespread rainfall to the southeast of NSW and VIC. There will be a few showers about the southern parts of VIC and NSW this weekend as a trough passes through from SA. That trough is expected to remain fairly inactive over SA but once it finds the moisture over the east, we see the rainfall increase. Otherwise, the region dries out and warms up next week ahead of a cold front that delivers well above average temperatures. A band of rain will develop from the west during Wednesday afternoon over SA and then passes through the southeast and east during Thursday and Friday, with the system’s strength and speed determined by the weather occupying the Tasman Sea. Medium term, there are more weather systems rolling through the southern parts of the nation, moisture building up over the northern and eastern parts of Australia, this lending the forecast trend to turn more spring like and move away from the winter weather associated with the westerly winds.

12z GFS Rainfall for the coming 16 days

Rainfall continues to dominate over the southeast of the nation, so southern NSW and southeast VIC during the coming few days with a trough leaving the southeast later Friday and another rolling through during Saturday and Sunday. The system coming through on Saturday over VIC will have more isolated showers, before the coverage turns scattered during Sunday as the trough runs into better moisture over the east and into eastern NSW. The chance of thunderstorms over eastern VIC and southeast NSW could bring further moderate falls. Next week it dries out and then we see another stronger system on the approach and how that performs is determined by weather in the Tasman Sea. More rainfall can be seen beyond this, but the pattern is looking spring like and that will lend itself to more productive rainfall events, models won’t see it this far out.

12z GFS Precipitable Water Anomalies next 16 days

The drier air over the nation is starting to be overrun through northeast part of the nation with trade winds and with another impulse over the southwest of the nation. This will start to erode the dominance of the drier air under high pressure and by next week, we will have widespread moisture passing through from the easterly winds and then being pumped into the eastern and central inland of the nation. The trough over eastern inland QLD will bring showers and storms as the moisture is lifted through the region. A signal of the seasonal shift underway. A strong cold front and trough then runs into this moisture, you can clearly see this being drawn in from the north and northeast, this is where the rainfall begins to break out over Central and Eastern areas. But where that occurs is still being ironed out. Through the medium term we will be watching the north of the nation where moisture increases and whether the Indian Ocean will decide to wake up and play a part in introducing rainfall through the north and west of the nation. There are signals that this could occur from the middle of September, about 4 weeks later than what I have been indicating, and what the models have been suggesting for months. So this shows the modelling is quite fallible and now we adjust the forecasts in line with the observed weather.

12z Euro Surface Pressure Pattern for the coming 10 days

The Euro in good agreement with the GFS showing the rainfall over the southeast of the nation in the coming days, a weak cold front over the west will bring light falls to WA today and into Friday, that system wraps into a low over the Bight. The trough over the southeast will bring the wettest weather to the nation, with moderate falls possible. Then you can see the impact of the moisture seeping south through QLD, combining with a trough and onshore winds to bring showers and storms through the weekend and into next week. A strong cold front, is expected to move through WA and into the southeast state from later next week, running into moisture and widespread rainfall likely to develop. The clash in temperatures is where will see rainfall most widespread and as per this previous system, a low is likely to form along the front. The models will likely see this in greater confidence next week, likely a few days out from the event taking place.

12z Euro Rainfall for the coming 10 days

Rainfall very similar to the GFS this morning with widespread falls expected over the southeast of NSW and VIC. The falls greater through VIC and far southeast NSW. Then showers and storms breaking out over QLD could be heavy at times over central and northern parts of QLD just inland of the coast. However that should stay north of NSW for now and sweep out with a trough next week and high pressure developing over the eastern inland of QLD and NSW. Then the next wave of widespread rainfall comes through the south and east with a strong cold front and you can see the impacts moving around with that feature from run to run. That is normal for spring. So 2 systems to watch, one coming through on the weekend and another mid to late next week.


12z Euro Precipitable Water Values next 10 days

Very similar to the GFS with the moisture gradually building back up with widespread rainfall and storms developing first in QLD thanks to the trough in the region combining with onshore winds before that weather turns south to spread the rainfall down to about the Wide Bay and Sunshine Coast. A series of troughs out over the west tries to bring in modest moisture through the southern and eastern inland of the nation this weekend but the drier air looks to win out there. Next week, once a high has re-established itself over the east, a stronger longer fetch easterly wind will propel the moisture inland to the NT and SA and this is swept up by a strong front which leads to the most interesting system on the board over the coming 10 days, that will likely introduce widespread rainfall for the nation.

Rainfall for the next 10 days

Showers about the southern coastline will bring light falls through Friday into the weekend, with the better rainfall again likely over the eastern states where moisture is a little deeper. Then we warm up dramatically next week with a long fetch northwest flow. Then widespread rain is possible throughout the nation from mid to late next week with moderate to heavy falls possible as the airmasses clash over the south and southeast and moisture gets pulled into the system as well from the east and north. So this could be quite a dynamic system regardless of the rainfall bouncing around from run to run.


I will have another medium term update later this morning with a look at that rainfall event next week in greater detail as well, as the impacts are widespread across the nation from temperatures through rainfall and possible severe weather.

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