SA - A CHANGE DEVELOPING TUESDAY BEFORE A STRONG TROUGH APPROACHES THE STATE THURSDAY

That trough is very much a system of interest as it may support severe weather in the form of severe thunderstorms developing for northeast areas during the weekend before moving on into NSW and/or QLD.


In the short term, the bulk of the state is looking dry. A little rain developing tomorrow along a southwest change. There could be a few high based storms over eastern Ag Areas during the afternoon before that too clears off into VIC and/or NSW.


Ridging is keeping the bulk of the state in dry stable sinking air, so clearer skies, seasonal to above seasonal temperatures and the risk of rainfall coming back into the medium term away from the northeast this week remains relatively low.


There may be some hope however with the decayed cyclone over WA, that may shear off moisture and it comes down to the timing of a front moving through Bight waters that will determine whether we see rainfall come back into the forecast next week.


We have seen many different solutions over the past week and this will continue as outlined with low confidence.


Lets take a look

FORECAST

Rainfall Next 10 Days

Rainfall is forecast to remain lean through much of the state as high pressure sits over the heart of the nation and a surface high ridges through the Bight, placing much of the state in sinking dry air. We have the chance of a few thundery showers overnight and into Tuesday morning with patchy rainfall spreading along and to the north of a cold front passing over the southeast bringing cooler conditions. The weather remaining dry and fairly hot over the north of the state. Rainfall chances may lift over the northeast of SA during the weekend if a sharp upper trough deepens over the region and taps into moisture being drawn in via the SAM remaining positive and whether we see moisture also coming through the jet stream from the west via TC Charlotte. So the confidence in rainfall forecasting still remains low despite it looking dry. Expect this to change in the coming week.

Thunderstorm Forecast Tuesday

Thunderstorms are a chance across the state during Tuesday but the risk is lower than 10% for central and western areas where the moisture is very much limited at the surface and most areas should remain dry under high and middle level cloud. So I won't draw a risk in as it can be misleading. The higher chance of thunderstorms producing any measurable rainfall is found on and to the east of Adelaide but more pronounced into NSW and VIC where the dynamics are more supportive of rainfall from any thunderstorm that forms. But will adjust if required.

DATA - Refer to the video for further information and it is critical to keep check of the data sets to understand where the next major weather events are emerging from outside of this period. It may be quiet now but I am all about preparation and ensuring that information is shared with you as soon as it is available.


00Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 2 Weeks

The GFS true to form indicates the weather turning volatile over vast areas of the nation but then is the one to pull back while other models now support the weather to volatile over western, northern and eastern areas. It is a common dance that I have seen in my 25 years of doing this. So at the moment, using the GFS, it carries a lower confidence that the other models which are more realistic of the impacts of the troughs over the east in line with the positive SAM phase (which is stronger than the previous event) so rainfall could be heavy at times over the east of the nation, more than what is being shown here. The weather in the west, is dictated by where Charlotte ends up travelling too, at this time, it does appear it is heading towards the Central West or Gascoyne. Now timing is the issue, we could have thunderstorms increasing in coverage from later this week into the weekend, but the GFS below suggests it could be slower on the approach and weaken the system offshore before moving it ashore with a trough and front. An upper level system still appears on other modelling for the eastern inland, but not on the GFS so that system while absent from the charts in the short term still carries a risk of evolving from the weekend with severe weather potential for the eastern inland. All of this weather bypassing SA and VIC where conditions should remain dry. Finally, the GFS still playing with an idea of a tropical low forming northeast of the Top End (other models have had this solution, the model dance continues) and this could produce heavier rainfall for the Top End and Cape York.

00Z GFS - Precipitable Water Values - Next 2 Weeks

Moisture remains unchanged from this morning. Moisture is forecast to sweep through the nation via the jet stream with a port of moisture running through the upper and low levels of the atmosphere leading to a band of rainfall spreading through the country, patchier this week over parts of SA but may increase through the eastern inland with another trough there. There may be another invigoration of the rain band over in the west with the moisture deepening as the tropical low approaches the west coast. Across the north, more of the same with deeper moisture and widespread showers and thunderstorms continuing as the MJO moves through. Drier air at the surface will likely be trapped under the ridge with little rainfall potential in this region for now.

00Z GFS - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z CMC - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z GFS - Rainfall Accumulation - Next 2 Weeks

Refer to the video for more context and analysis

A closer look in - very low confidence in terms of rainfall beyond 5 days! Be aware of that.

More coming up from 8am EDT. There is little use of doing the models and rainfall wrap tonight looking at the spread. So will review that again tomorrow and update that element if required. 6 Week Outlook also due out tomorrow too.

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