MEDIUM TERM FORECAST - THE INLAND RAINFALL EVENT GATHERING CONFIDENCE THIS WEEKEND ONWARDS.

That seems to be the most impressive system on the board to produce inclement weather over the nation during the coming week, but what about any follow up potential?


The tropics set to see more moisture and potentially an increase in rainfall coverage from mid month onwards as the upper high dissolves aloft. That will support more convection and use of that moisture profile. The upper level winds will help to feed moisture south and southeast through the nation.


Now I know many have probably already seen the deterministic data for GFS this morning and you may see some wild forecasts on social media in the coming days, all I say is to ignore that and keep the expectations conservative and make sure you get the professional assessment of that data and curated forecasts.


Lets take a look.

Moisture Watch This Week - October 5-12 2021

The moisture is still streaming in on the mid latitude westerly wind regime with cold fronts picking up some of that moisture and producing widespread showers through southern areas. Another front, the last in the sequence is passing through WA today and into SA and VIC through Wednesday and Thursday. Then the moisture coming through the tropical north is expected to turn southeast, the average of all members wants to turn it into NSW and southern QLD. The deterministic data that is freely available is pushing through QLD.

Moisture Watch Next Week - October 13-20 2021

Models want to keep moisture through QLD and NSW as well as parts of the Central interior through to the tropics, with troughing in the region lifting the rainfall chances. Some modelling cranks the rainfall up to severe thresholds, but caution is advised on that idea.

Rainfall This Week - October 5-12 2021

The first part of the rain event that is of note this period is over the Central interior from the weekend and could drift south into much of inland SA before shearing eastwards into QLD and NSW with moderate to heavy rainfall potential, but as mentioned position, timing, intensity and scale are still to be determined. Once there is a low pressure centre identified in real time, then the guidance from the models improves.

Rainfall Next Week - October 13-20 2021

A wet bias for the eastern third of the nation with persistent low pressure, some models have much more widespread falls than this, some have a lot less, this is the split between all the solutions on the table. The west remains dry under ridging.

Rainfall Anomalies Next 2 weeks - October 5-20 2021

Higher chance of above average rainfall through this period over the northern tropics, over the outback (that could expand further south and east if the GFS solution this morning does get more traction) and through the southeast inland of NSW.

Temperature Anomalies This Week - October 5-12 2021

The cooler bias starting to ease over the southeast but the cooler bias persists over the SWLD with a southwest flow for much of this week, marginally cooler the further inland you go. The north under the presence of an upper high expected to be baking.

Temperature Anomalies Next Week - October 13-20 2021

The upper high remains in place for the northern tropics, but weakens, however leaves a warm and very soupy airmass in place. Cool bias continues for the west with a strong southwest change mid next week and the east is a flip of a coin, the chance of a large scale rainfall event could swing the weather cooler than normal for large parts of the east, but if it is less extensive then it could be warmer than normal. The guidance is poor.

DATA - Refer to Video for more details at the top of the page.


18Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 2 Weeks

Compare the pair - the morning runs - note the difference in moisture and rainfall distribution through the eastern parts of the nation. Refer to the video for more guidance. THIS WILL CHANGE!

Comparing run to run.

18Z GFS - Precipitable Water Anomalies - Next 2 Weeks

18Z GFS - Rainfall Accumulation - Next 2 Weeks

18Z GFS - Temperature Anomalies - Next 2 Weeks

More details on the first of the rain events over the nation coming up from after 6pm EDST.



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