The nation, in the grips of the La Nina Summer, classic wet phase for the east in relation to the positive SAM phase and the two combining to produce not only wild weather, but a lot of rainfall and below average temperatures for the east coast, as advertised back in November.
This forecast is only going to get wetter for the north and east of the nation as we go through the month. The west and south, particularly SA and WA, will remain hot for the most part over the coming week, but even there, humidity values will be creeping up and more showers and thunderstorms will return to the forecast than what we have previously seen in recent weeks, if not the past month.
With the slack pressure pattern and persistent ridging to the south of the nation, this allows for the forecast to remain fairly stagnant for many areas, but the other element for you all in the south and east that you need to pay attention to is the tropics. The tropical weather is set to become more active with a deepening set of heat lows, followed by the emergence of a monsoonal trough. The heat trough and lows help to drag in that monsoon and we will see that unfold in the medium term.
Lets take a look at the latest data.
Rainfall Next 10 Days
No real change to the spread in rainfall across the nation with the bulk over the east and north. You will notice the intensity coming down in the forecasts as storms conclude and the rainfall numbers will then pick up further west through SA and interior parts of the nation back towards the NW of WA as we move through the medium term. The wildcard in the sequence as we know the coverage of the rainfall well in the short term, is that tropical feature up north. Models still all over the place with the regards to placement and timing and that will have major implications on any specific forecast moving into mid month onwards, I will not be doing that here at this stage. So for now, areas over inland NT, through northern and central QLD, through southern QLD into NSW, the ACT and central and eastern VIC need to pay close attention to the system as it will likely run over the areas impacted by the rainfall in the coming 10 days. There is a lesser chance for that tropical mischief to come through northwest WA and SA, but it is not a 0% chance, it is just a lot less likely.
Thunderstorm Forecast Thursday
A reminder for those about this evening, avoid non essential travel through southeast NSW and eastern VIC with the risk of damaging and high end flash flooding continuing to be a problem on all major roads and arterials and back roads.
Thunderstorm Forecast Friday
Thunderstorms continue for the same areas into Friday with severe weather continuing over the east and southeast with the trough stationary. Heavy rainfall leading to flash flooding and damaging winds are the main issues. The highest risk once again over inland areas of NSW and VIC. The storm coverage over the north remaining unchanged with a deep trough developing over the northern states. The trough will snake back into WA with a chance of gusty storms but mainly light rainfall totals for now through to the Pilbara and Gascoyne.
Thunderstorm Forecast Saturday
Thunderstorms will slowly contract out of the southeast and move into Central NSW and points north and east near to the east of a trough that will once again pull up stumps somewhere over northern NSW Sunday. The storm focus continues with routine expectations over northern Australia for a monsoonal break period.
Thunderstorm Forecast Sunday
Thunderstorms will likely regenerate along the same trough over the eastern inland and snake into another heat trough and low over the Central interior where strong to severe storms are possible. Damaging winds and heavy rainfall the main concerns still with high levels of atmospheric moisture. Over the tropics, the thunderstorm coverage still thinner than normal but where they form, could pack a punch. Storms through interior parts of WA near a heat trough advancing east, could be gusty with moderate falls.
Tropical Depression Forecast - Next Fortnight.
Just because it is shaded in over northern Australia, do not think that the impacts of any tropical weather will remain up north. We are already feeling the impacts of the short lived monsoon from Christmas now entrenched over the southeast and east of the nation for the next few days. So this area is critical to seeing how much more rainfall is to come through the next 2-4 weeks and then February which is still looking like the wettest month for Summer. This forecast will be updated again during Friday.
DATA - Refer to the video for more guidance on the data sets below
GFS 00Z - Surface Pressure Pattern and Rainfall Distribution - Next 16 Days
More information in the video but in the day 6-16 range, the confidence is very low nationally and we have to see what happens with the monsoonal weather up north and what impacts that will have on the weather down south and east of the tropics.
GFS 00Z - Precipitable Water Values - Next 16 Days
Remaining unchanged through the short term with excessive moisture coupled with low pressure producing above average rainfall and flooding for the south and east of the nation. The weather over the north is a little more subdue but the moisture values are still very high. Eventually most of the nation becomes engulfed in high moisture levels, that is a high chance, the lower confidence portion of the forecast is placing the low pressure systems/troughs on the board to locate the heavier rainfall, which models are struggling with.
GFS 00Z - Rainfall Accumulation - Next 10 Days
More information in the video
CMC 00Z - Rainfall Accumulation - Next 10 Days
More information in the video
GFS 00Z - Rainfall Accumulation - Next 16 Days
More information in the video
12Z Euro Ensemble - Rainfall Next 15 Days
More weather coming up tomorrow morning, stay weather aware and safe out there in the southeast and inland parts of NSW and QLD.