The weather is still influenced greatly by high pressure elsewhere through next week, but two rainfall events are likely to make an impact during the last week of September as expected and likely to see rainfall ongoing into early October.

Main points are unchanged from yesterday so lets look at the data at hand this morning.


ICON - Rainfall Next 5 Days - HIGH CHANCE

This illustrates the shift in conditions over the course of the next 5 days, with the high pressure dominance moving on, and the dry air also moving on with a return to humidity sweeping in from the east with onshore winds and through the northwest of the nation with a new trough out west. It is the trough over WA that causes the major rainfall event as it passes into deeper moisture in the east.

UKMET - Rainfall Next 7 Days - HIGH CHANCE

Very similar spread to ICON in the shorter term, you can see impact of the trough over in the SWLD with areas of rain and thunder from tomorrow into next week, then that trough finding the better moisture over eastern Australia with showers and storms breaking out Tuesday. Humid over the north with showers developing.


CMC - Rainfall Next 10 Days - MODERATE CHANCE

Following into the latter part of next week into next weekend the rain and storms continue in the east with another rainfall event expected over in WA to bring widespread rain and storms again. That system will move on into SA with rainfall next weekend and follow up rainfall into the eastern inland with another round of rain and storms. The tropics are expected to turn more active as we go through the latter part of next week with the upper high dissolving. Showers and storms could become more widespread over QLD later next week into the first week of October.

ACCESS - Rainfall Next 10 Days - MODERATE CHANCE

Rainfall heavy at times over the east. The weather is likely to lead to pockets of riverine flooding, with some spots up to 200mm over southeast NSW and northeast VIC. Otherwise the falls are quite widespread from QLD through VIC with the first trough. The second system comes passing through WA and into SA with moderate falls, this will also pass over the eastern inland of the nation with follow up falls later next weekend. The tropics turn active later next week into the weekend.

EURO - Rainfall Next 10 Days - HIGH CHANCE

Good agreement with the CMC in terms of timing of the system in the east next week and the system coming through WA next week as well. The only difference, the system out of WA moves slower and does not reach SA within the forecast window. The tropics turning active later next week into the weekend. Storm coverage a bit more widespread over QLD.

KMA - Rainfall Next 12 Days - MODERATE CHANCE

Widespread rain in the east is ongoing from mid to late next week with the first trough moving eastwards slowly. The weather out west turns wet again with a new trough developing offshore and dragging moisture from the central Indian Ocean, which could produce another 1/2 months worth of rainfall. The north turns stormy from next week with the upper high moving on. Another rainfall event beyond this is possible over in the west.

GFS - Rainfall Next 16 Days - MODERATE CHANCE

Good agreement in the modelling for next week into the following weekend, with broad rainfall over the south and east continuing for much of the period. Rain and storms over SWLD of WA early next week and another event expected through the region later next week. This model has more moisture available through the interior sparking showers and storms next weekend into the first week of October.


GFS - Rainfall Next 16 Days (median of 35 members) - MODERATE CHANCE.

Rainfall numbers have come down from yesterday but this is common with GFS, where it leads the pack, pulls back, and then comes back with each event. This is still excellent rainfall for parts of the nation, especially for the east. But this may also create a problem in terms of flooding for the parts of the southeast. Note the rainfall over the coming 2 weeks is still moderate for parts of Ag SA even though the deterministic shows not as much.

CMC - Rainfall Next 15 Days (median of 30 members) - MODERATE CHANCE

Still unchanged with the heavy rainfall signal for the east and the southwest. The falls have become lighter for the interior, and the tropics have seen a slight reduction in rainfall since yesterday.

EURO - Rainfall Next 15 Days (median of 51 members)

This is likely closest to the post today, so if you are living in the east, there is a risk of flooding next week in areas that have already seen flooding in past weeks/months. Wet over the southwest but the falls are more restricted to the southwest. The numbers are not too bad for Ag SA, again looking at the deterministic single basic data (which populates all your apps) is not good weather forecasting, and you need to dive deeper into the data sets and the Euro is wetter for SA than what is publicly available.

I will prepare my full forecast later this afternoon looking at the rainfall event with my forecast charts and a wrap on the flood potential for parts of the east.

144 views0 comments