Onshore winds developing are expected to lead to showers returning to eastern areas today. The weather is primarily being dominated by the trade winds up north driving the light showers and the high pressure ridge over the south leading to sunny weather with mild temperatures.
But around the state this morning it is clear as a bell! No cloud over the region in dry air that is stuck under a ridge. But there will be cloud developing today with showers later over the far north.
Over the weekend, the moisture in the onshore easterly winds will spread south and west bringing the chance of shower further inland. A weak inland trough may give rise to thunderstorms on and east of the divide, more widespread through the southeast and east of the state. You can see how the trough over the far north becomes the boundary between the drier air to the west and the moist air to the east, this will be where showers and storms form.
The trough should lift offshore as high pressure strengthens over NSW directing a warm to hot northwest flow, that will see a drier picture for much for the state. Some areas scorching into the mid 30s next week.
But we will be watching the change as it rolls through later next week into the weekend as there could be an organised batch of storms that form on the boundary, given the moisture streaming in from the east into this system as it rolls from west to east. So the system is running into favourable air for inland rainfall to develop.
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 that sits over the southeast but hits the ridge and moves out of the region this evening into Saturday. 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 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 WA and then passes through SA Thursday or Friday, with the system’s strength and speed determined by the weather occupying the Tasman Sea which we can see playing a part in the rainfall spread. 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 today, most of the rain over southern NSW and southeast VIC will be connected to the trough. 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. Meanwhile over QLD we have a trough that forms along the coast and becomes active over central and northern areas east of the divide. There may be thunderstorms along the trough, more likely the further north you are east of the divide. Then that system moves away early next week as a high forms to the south. Note the moisture that builds up over inland areas once again in the medium term, the chances of inland rainfall returning is increasing.
12z GFS Precipitable Water Anomalies next 16 days
No real change to the guidance overnight which is nice. 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 and we are seeing that reflected in the temperatures throughout the southern and eastern parts of the nation. 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 and the timing will be crucial to seeing who gets what. 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.
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 today with a low pressure system starting to form over the Bight. The trough over the southeast will bring the wettest weather to the nation, with moderate falls possible in the coming few days. 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. This morning, the front is being analysed to be forced south however the inland moisture coming in from the east and northeast, means that the rainfall potential still exists, it is just a matter of how widespread and how heavy it will be, this determined by the low pressure system moving east or south over the Bight.
12z Euro Rainfall for the coming 10 days
Showers increasing in the short term over the northeast of the state will spread through to the adjacent central and northern inland with a trough nearby feeding off the trough. Thunderstorms will mean rainfall distribution will be uneven and that is to be expected as we move into the storm season. The weather then dries out over the state and heats up with the storms clearing early next week. Showers may continue for the FNQ coast. Then watching the system developing later next week into the weekend which could bring inland rainfall.
12z Euro Precipitable Water Values next 10 days
Very similar to the GFS with the moisture gradually building back up with widespread showers and a few 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. It is still 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. How far west the moisture comes will determine the spread of rainfall with the first system. There is more moisture left behind for the second week of September.
Rainfall for the next 10 days
The most widespread rainfall is early in the period, still connected to the onshore winds which brings showers along the coast and an inland trough which fires off showers and thunderstorms, more scattered in nature so falls patchy and hard to draw in, but know your number will vary. Then dry from Tuesday next week for all of the inland, with the showers staying up over the FNQ coast. Watching that major event passing through WA through SA and into the east next week which could produce showers and storms over western inland areas.
I will have the medium term forecast later this morning looking at the rainfall potential for the nation and the heat building. Then Summer 2021/22 outlook to be issued. PM forecasts to come with updated rainfall and temperature forecasts for the short term.