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Unsettled today over the southeast and east with a weakening trough over the southeast and a developing trough over inland areas of QLD. Moisture levels deeper over QLD will see showers increase over inland areas this afternoon as well as along the coastal fringe.
Then we take a look at the developing heat next week, well above average temperatures are expected to spread throughout the south and east of the nation and that headlines the forecast this week.
A developing cold front over the SWLD of WA will bring showers from mid to late week and that will cause temperatures to fall well below average! Those temperatures could be up to 12C below average in some locations while some areas east of the front will drag temperatures up to 12C above the average. That sets up a battle ground between the hot air and the colder air.
The location still seems to be over SA through to VIC where this battle will play out, but we need to add in moisture, and that looks to race in during the middle of the week from the east once the high pressure system develops east of NSW.
In the medium term, there have been follow up events on all models ranging from widespread rain and storms over QLD through to rain and storms over SA and VIC, to dry weather in a stable airmass. Lets have a look at the latest data.
Rainfall for the next 2 weeks
The main rainfall event is over QLD during the coming few days with a coastal trough with that system expected to move off the coast during mid week. The bigger event for the nation comes through from the west during mid week with the frontal weather expected to be the feature to watch for SA, VIC, NSW and southern QLD. Some areas could record one month's worth of rain with this feature, that will become clearer as we get closer. Also watching the chance of showers and thunderstorms over the north of the NT once again mid to late this week with another impulse of moisture. Medium term rainfall, split camp exists, where models have significant rainfall over inland areas of NSW and QLD where others are not as keen. I will keep the map dry for inland areas for now and add rainfall when the guidance becomes clearer.
Temperature Outlook - August 30th-September 6th 2021.
This week - Dominated by the well above average temperatures from the northwest wind flow with a strong cold front expected to plunge the southwest into much colder weather from mid to late this week.
Temperature Outlook - September 7th-14th 2021
A marked shift in the pattern over the southwest and southeast east of the nation, with a set of cold fronts passing over the southeast - some chance of cold air surging north into QLD and NSW further, but I am keeping the outlook conservative for now. Warmer days return to the southwest of the nation with the northeast flow returning there as a high moves over the Bight. Hot over the north, with burst of humidity and drier air from one day to the next.
GFS 12Z - Surface Pressure Pattern - Next 2 weeks
No change since the last update on Friday where we have the well above average temperatures coming into the east and southeast of the nation through this week and below average temperatures moving into the southwest and west of the nation. All thanks to a cold front standing up and passing eastwards through southern parts of the nation. That will be linking into moisture as you can see over SA and then a thundery rain band forms in central and eastern SA and that passes off to the eastern inland of the nation next weekend.
There is a colder shift on the charts for the second week of September over in the east where the west returns warm and sunny, and drier air on this current run would clear out moisture from much of the inland of the nation.
GFS 12Z - Rainfall - Next 2 weeks
Again no real change from previous days with the main rainfall events ongoing today for the southeast with a weak system passing over NSW and VIC and a developing trough over QLD which is triggering showers and storms. The QLD event will be updated in the evening forecasts. The main system to watch is again that front passing over southwest WA on Wednesday which will bring a burst of rainfall for manly SWLD, that spreads through southern coastal areas and then begins to increase in coverage at this time over SA, most likely from the EP up through Central Australia eastwards and then slowly moving through the eastern states. The heaviest falls of the southeast inland areas of the nation. A drier and colder southwest flow is expected to sweep in behind the frontal system. A follow up cold front is likely to reinforce that cold spell over the southeast, however some modelling take that colder air over the eastern inland and combines that with moisture and sees rainfall break out over QLD and NSW in the medium term, the GFS below says no to that idea.
GFS 12Z - Precipitable Water Anomalies - Next 2 weeks
The moisture clearly running through the nation today is elevated and leading to scattered showers and thunderstorms, again mainly high based and light. The weather over eastern QLD is supported by deeper moisture in the low levels and that will increase over the coming 24hrs. That will see the rainfall increase from tomorrow into Tuesday over the northeast. A weakening cold front over the southeast with again a good supply of moisture in the upper atmosphere will see thick cloud over southeast areas from Tuesday. Moisture will continue to stream in from the northwest and feed the frontal weather passing over SWLD of WA. The moisture from the northwest will meet the moisture from the NE of the nation and converge over SA, with a front lifting this into a large scale rainfall event. The weather slowly progressing east with colder dry air to follow and the surge north. Again some modelling in the medium term into the second week of September suggests that moisture may pool again over eastern inland areas of QLD and NSW and produce rainfall with the cold air aloft, though the GFS is going with the colder wintry outlook with dry air surging north.
CMC - Surface Pressure Pattern - Next 10 days
Just wanted to add the CMC showing the potential for follow up rainfall which is connected to the large event mid to late this week. There is a follow up system that all models do see in a cold airmass, some surge that front through within the westerly wind belt and allow the high pressure ridging in. Some models such as CMC suggest the cold air moves north and cut off the cold air into an upper low pressure system over QLD. We will see how that stack up.
Euro - Rainfall - Next 15 days
Last night the Euro also suggested the cold air over inland portions of QLD and NSW with further rainfall developing in the second week of September. So something to watch this week as we track the first feature through the nation. This is likely to come and go off all charts in the coming days.
Overall the weather is typical for spring with variations in temperature and 1-2 rainfall events spreading through the nation which is normal for this time of year.
I will have another update on the medium term tomorrow and update the state based forecasts this afternoon.