The pattern is fairly typical for what you see in early January nation wide. But interest is building for next week.
AREAS TO WATCH
The remains of tropical moisture being drawn into an east coast trough that will dig through the eastern inland of NSW and into VIC with a fairly robust storm event to take off from mid week into the weekend.
The tropics are set to become more active this week with a few severe storms about, but this heralds more widespread rainfall returning to the north which will see moisture run south through the nation, via troughs in the west and over in the east.
The monsoon may redevelop over the north of the nation mid to late month which would then add more energy into the mix, more moisture to work with and this could see elevated rainfall chances over the nation beyond the short term.
18Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 16 Days
The pattern is shifting this week from that dry hot airmass over the interior remaining in place but the airmass is becoming more unstable, thanks to high pressure leaving the nation’s south and this allowing for moisture and instability to drift further south through the nation from the north and east, you will notice in coming days, your rainfall forecasts will increase, especially in the east. Southern Australia will see light falls if anything and that is thanks to the flow being easterly and the trough axis sitting over the eastern states. But you will feel the humidity. The weather then trends more active over the northern parts of the nation, again, the location of the tropical low/cyclone activity will act like wild cards for those looking for rainfall. This will then become the focus for major rainfall event coverage across Australia from mid month onwards. Wetter as we go through January is the theme.
18Z GFS - Precipitable Water Values - Next 16 Days
This illustrates the point that the moisture is building this week across the north and east with that moisture being transported throughout the east first with troughs lifting that into maximum potential. The west of the nation, coastal areas dry, but inland areas will see elevated showers and storms on most occasions but not much rainfall. The moisture takes it up a step in the second week of the outlook with tropical waves deepening and low pressure redeveloping within a developing monsoon trough with weather turning much wetter across the nation’s north and then sweeping south with any landfalling tropical feature. That could be anywhere and there is no skill in forecasting where there is just yet. But that is the idea that is on the table for now and is supported well by other agencies.
REGIONAL RAINFALL IMPACTS
SOUTHEAST AND EASTERN AUSTRALIA
Showers and thunderstorms about today are scattered and elevated with moderate rainfall. The storms will meander about through the early part of the week before redeveloping near a new trough mid week that emerges from SA. That will be where you will see more widespread rainfall for VIC, NSW and southern QLD with heavy falls possible. In the medium term, you can see that surge of tropical moisture coming down from the north of the nation into SA with heavy falls developing. This will move around from run to run with moderate to heavy falls aLao moving around so there is no specific forecasts, just a place mark of areas to watch over the coming week. The east would then see another burst of heavy rainfall once again with the surge of moisture in the medium term, by mid to late month, some areas could have seen 1-3 months worth of rainfall. It can change that quickly.
EASTERN AND NORTHERN AUSTRALIA.
Scattered random showers and thunderstorms will lead to more build up conditions for the first half of this week. The remains of Seth will be absorbed into the northeast flow and that moisture will be propelled into the deepening trough over inland NSW and QLD during the middle to latter part of this week. This will set up a fairly damp, humid and cooler week for the east coast. Up north, the showers and thunderstorms will increase as a trough and developing heat low whips up more instability with moderate to heavy falls returning. The weather becoming more unstable this time next week over northern Australia with heavy falls moving inland further over the NT and QLD, some tropical low development is possible. The moisture is expected to move southwards through the outback with rainfall increasing by mid month. The east coast wet most days throughout the outlook period. That is La Nina Summer.
The tropics are the area of interest to watch, and while the numbers bounce around, are impossible to forecast ahead of time, given the nature of rainfall is convective, the overall trend Is increasing falls, frequency of rainfall and deepening of low pressure over northern parts of the nation.
Fairly dry across much of the SWLD and the west and south coasts with high pressure close by. Inland areas are expected to see showers and thunderstorms most days near a heat low and heat trough, these will be elevated and possibly gusty with not much rainfall, but these will continue to increase during the next week. The Ag Areas of the west should see hot and humid weather but not much rainfall. Keep a watch on the tropical weather building mid month as this could begin to shift moisture south and southeast through the state and bring up the chances of above average rainfall for interior parts.
La Nina is yet to peak across Australia and this will likely take place during the next 4-6 weeks before that phase wanes, however rainfall will continue to be above average at this time through March.