QLD - SHOWERS AND STORMS DEVELOPING THIS WEEKEND FOR THE EAST.

It has been cold this morning through southern inland areas of the state with areas of frost about some locations, but the day should warm up fairly well this morning.

A trough is expected to form this weekend over the eastern parts of QLD with a moist onshore flow feeding the trough leading to showers and thunderstorms developing. The shower and thunderstorms may kick off some early season falls for the sub tropics, a sign of the wet season ahead.

For now the weather is expected to remain dry further southeast, and most likely remaining dry for the western two thirds of the state.

The cooler than average weather is expected to continue for the south until the weekend, when the moisture is expected to deepen and that will filter into most of the east, lifting overnight temperatures. Across the inland we will likely see the winds tend westerly introducing a warmer airmass.

A major frontal passage is expected to sweep through the southeast of the nation during mid to late next week and that could bring showers and storms later in the outlook along a colder change.


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 will increase over the FNQ coast this weekend with light to moderate rainfall passing over the region in easterly winds. That moisture then will be drawn southeast and east over the northern and central inland and showers and storms are likely to break out across large parts. Some moderate to heavy falls are possible with thunderstorms in random and scattered pockets. The rainfall will ease off next week as a high takes over. There will be some further showers about the region from mid September.

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

Since starting this site, I have not said this once, but the better rainfall in the short term is over QLD in the short term with widespread showers and storms developing along a trough that will be anchored inland of the tropical coast through the Coalfields into the Highlands. Now picking who gets the heaviest rainfall ahead of time in these situations is impossible with thunderstorms in the mix. The showers will be widespread along the coast with general moderate falls, but inland is a wild card, some areas copping 50mm+ and some areas 5mm. But the shift in season is upon us. The weather dries out mid next week as a warmer and drier northwest flow develops.

I will have a medium term update and another look at the stormy outbreak later today as the data becomes a bit better in the coming days, impacts will be easier to forecast.

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