EVENING RAINFALL UPDATE FOR SA AND VICTORIA

Like the guidance in other states, no real change to the overall pattern coming this week with the westerly flow to dominate proceedings for the southern and eastern parts of the nation. Lets get into the latest data.


00Z GFS - Surface Pressure Pattern and rainfall next 16 days - Valid Monday 12th of July 2021.

The pressure pattern is largely unchanged on the GFS tonight with the fast flow pattern looking rock solid over the coming days interacting with moisture streaming out of the west and northwest. Where the model gets interesting is over the weekend, with some of the colder air in the upper atmosphere hanging back and creating an upper low over the southeast which would keep the showery weather going. But also creating a low off the NSW coast as it moves on by. The system would then slow the progression of the weather up stream, meaning that the follow up rainfall event that was slated to go more south than east, may go more east than south, placing the southern parts of the nation in with a chance of rainfall next week, not just WA. So that is something to watch. Otherwise, good totals for most of southern SA and into VIC this week. Even some good falls popping up over the outback.

00Z Euro - Surface Pressure Pattern and rainfall next 10 days - Valid Monday 12th of July 2021.

The Euro is largely unchanged tonight, still has widespread rainfall developing from the west Tuesday with moderate falls over the central and eastern districts. Then a real showery mess Wednesday and Thursday with again light to moderate accumulations in the moist westerly airstream. A follow up front later Thursday could spice up the shower activity bringing more moderate falls to the southern coastlines. Then it keeps the westerly flow in tact and places high pressure over the state, that is not in line with GFS. Has the follow up rainfall event scooting into the Bight at the end of the run with moist air coming in on it's northern flank over the continent.

00Z GFS - Precipitable Water Values and pressure pattern next 16 days - Valid Monday 12th of July 2021.

The PW values and anomalies are running pretty high for this time of year, which is traditionally the driest time of the year nationally. Elevated PW values can be seen in the cloud cover building over WA and the subsequent rainfall that has been observed. That mass of cloud will continue to drift eastwards as the front moves into Bight waters bringing moderate rainfall to large parts of the nation. A shot of dry air will accompany the colder shift Thursday with moderate falls along that boundary, before showers ease briefly. But then as per the synoptic charts, you can see that moisture comes back through the weekend and next week introducing more rainfall and some bigger falls for the region which would be handy for SA and western VIC.

00Z Euro - Precipitable Water Values and pressure pattern next 10 days - Valid Monday 12th of July 2021.

The PW values like GFS are elevated and signify a shift to a wetter period across much of SA and VIC. This first band will be rather productive in terms of the spread of rainfall through the southern and eastern inland. The second feature again providing some more showery period and moderate falls. Then you note the dry air surging in with the colder shift Friday before the moisture reboots along with that next major low coming through WA next week. That system moving more east than south this evening which is a positive sign for SA and VIC.

00Z GFS - Rainfall for the coming 10 days - Valid Monday 12th of July 2021.

Not much change in the rainfall guidance this week, anywhere exposed to the westerly wind regime doing the best, so you know if you are in one of those zones. The rainfall widespread Tuesday and Thursday before it contracts back to the coast during Friday afternoon and clears the inland by the weekend. Next week all eyes on the west with low confidence in predicting rainfall totals with the system not well handled. And that will continue to be the case until it is initialised in real time south of Java which won't happen until Friday or Saturday this week.

00Z Euro- Rainfall for the coming 10 days - Valid Monday 12th of July 2021.

Like GFS not much change in the rainfall spread, it is lighter on than GFS but my forecasts reflect the spread of models and not just one data set that is offered here. So looking at the evening data set I am placing my forecasts in the middle of all the solutions. Euro has the spread of rainfall correct, the intensity will be varied in real life compared to this guidance.

And a closer look for our friends out west in SA bordering eastern WA, you can see the moisture influence from the northwest, repeats itself next week with that heavier rainfall shield moving closer to the state line with each run, lets hope it continues for communities out west.

Starting with SA


Rainfall for the next 10 days - Valid Monday 12th of July 2021.

Rainfall numbers have hardly changed from this morning even though the modelling bounces around a bit. I am not introducing the rainfall analysed by the GFS into the forecast package yet as it is the first time I have seen that on the data sets. Otherwise decent rainfall accumulation over the coming days will begin to impact the region Tuesday afternoon until about Saturday. The inland dries out from about Thursday north of Coober Pedy and Saturday from north of Hawker.

Rainfall for the next 10 days - Valid Monday 12th of July 2021.

Rainfall guidance for the region largely unchanged, a slight increase to include Mildura in the red zone and expand the 40mm shield into Hamilton. Otherwise it is largely unchanged. The best of the rainfall coming later Tuesday into Wednesday morning and again Thursday afternoon through Saturday for this region. The rainfall eases later Wednesday for inland areas north of Peterborough to Port Augusta to Mildura but then returns Thursday night with a front and then eases again in this region later Friday into Saturday morning. The southeast coastal areas could stay showery until Sunday morning from Port Lincoln through Adelaide down to Mt Gambier.

FOR VIC


Rainfall for the next 10 days - Valid Monday 12th of July 2021.

Widespread rainfall develops from Tuesday night in the far western districts spreading to eastern areas by Wednesday morning. A strong northwest flow may develop rain shadows south of the divide, the most acute around the Melbourne Metro area. Good rainfall between Trentham and Lake Eildon with the initial band and over the northeast highlands. The showery periods will follow in a moist unstable airmass with light to moderate falls expected to continue Wednesday and Thursday for much of the state, with possible thunderstorms. Another front and colder shift may deliver a severe weather event for the region on Friday with showery squally weather extending statewide with areas that were rain shadowed expected to get the better rain here. Moderate to heavy falls east of Melbourne into the Yarra Ranges likely and through West Gippsland with this southwest to westerly flow. GFS wants to keep the showery weather going over the weekend and the Euro not so interested so watch this space as there could be some changes.

Rainfall for the next 10 days - Valid Monday 12th of July 2021.

A closer look at the impact of the rain shadowing around Melbourne and surrounds. The secondary rainfall event with that feature looks to be much more productive and the cold air with the bay effect in a southwest flow means the rain belt east of Melbourne will be in full swing through to Sunday morning. So a wet period for this region, may start out a little slow in and around Melbourne but will catch up quickly later this week.

Later in the period we have got the chance of another rainfall event, that comes into the picture about mid next week. That system is very tricky to pin down so I will have an update after 9pm on that feature and more analysis through the days.


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