SA - BECOMING UNSETTLED OVER THE NORTHEAST AND FAR EAST, DRIER ELSEWHERE

The swing state that is SA in full swing this week, with the trough to the east and northeast as well as a trough and front in WA set to peak before impacting the region, however it is not clear how both systems will work with each other this week.


That makes the forecast packages for the eastern and southern sides of the state very challenging, with the severe weather running along the eastern border with NSW and QLD. The other element is the front and trough spreading through the southern districts later this week, does that pull moisture in from the east and/or does the moisture out of the west stay intact leading to more widespread rain developing than what is being advertised.


There are many ways to describe what is going on and all the possibilities, but it is best to look at the video for that to explain the latest weather information for you.

So many variables at the moment so let’s take a look.

FORECAST

Rainfall Next 10 Days.

Rainfall remains a very tricky element to forecast for the state. A betting person would place the bulk of the heaviest rainfall around the state and on the current guide that is the right call. However, with the upper low component over the northeast, this low only needs to deviate about 100-300km from its current projected location through the northeast of the state to be further west or south, and the rainfall increases dramatically for the eastern parts of SA. Conversely if the low moves further north and east, then less rainfall is forecast. At this stage, I am placing the falls in the northeast. A weakening cold front passing through the south of the state will bring a band of patchy rain and a cooler change with some evidence that this system will bring better rainfall to the west of the nation, weakening as it comes through SA. This means that while there are good rainfall opportunities for large chunks of the country, we may sit in between it all. Another event looks to be stirring over WA through the medium term which may offer the next chance of rainfall for the state towards the 21st.

Severe Weather Watch - Tuesday through Thursday

A low-end threat of severe weather over the northeast of the state with the chance of heavy rainfall leading to flash flooding with slow moving thunderstorm clusters and severe thunderstorms themselves, initially producing all modes of severe weather in the same highlighted region. There is a chance that the system is too far east, and this watch area contracts out of the state but for now, the risk is modest (30%).

MEDIUM TERM - May 15th-22nd 2022

Rainfall Anomalies

Rainfall anomalies continue to signal above average falls persisting about QLD and southwest and western parts of WA with seasonal weather most elsewhere. There are no drier signals present on the global modelling for this time, with forecast confidence moderate at the moment. The positive SAM potential for the east has one eyebrow cocked for QLD, where additional heavy rainfall could occur and slip into NSW. The southwest may see moisture from the decaying tropical cyclone Karim come into a front and bring widespread rainfall into the medium term. Either way the remainder of the nation should see seasonal rainfall expectations for this time.

Temperature Anomalies

A cooler bias persists for the west as conditions are set to shift from this week and continue into the medium term with the westerly wind regime impacting the area. The north of the country will return to more muggy and dry weather with temperatures reflecting the above average SSTs in place across northern Australia, so this dry season will be warmer and humid than normal. In the east, a weak signal for cooler than normal weather, but this could be increased if a positive SAM phase develops, and we see more cloud and rainfall come onto the forecast. Seasonal weather conditions are forecast elsewhere with no sign of brutally cold dry weather in the coming 2 weeks.

DATA - Refer to the video for more information.


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

The nation is dominated by high pressure for the week, but it does not translate to fine weather for all. The upper low over inland NT and then into QLD will bring a severe batch of weather through. The west, your dry spell is coming to an end and there is plenty to watch out there as well. And can SA get some follow up rainfall to the light and patchy attempt at the last week? Refer to video for more information on the day-by-day breakdown.


00Z GFS - Precipitable Water Values - Next 2 Weeks

Certainly, very moist air over the eastern inland of the country which dominates the proceedings in terms of rainfall opportunities, drier air can be found closer to the high pressure, but the moisture from the north and northeast will eventually override that dry air so expect to see more cloud and rainfall spread across the country. Out west, more moisture surging in after a drier week with the remains of TC Karim needing to be watched as that could influence rain band potential through the jet stream. The north is enjoying the first proper dry surge, but it does not last that long with a more humid northeast flow developing as we go through the outlook period. The pattern is expected to relax a little mid month as the atmosphere resets and the threat for above average rainfall and higher humidity is still well and truly on the cards for many locations.


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 - the rainfall generally falls in the short term but with a disorganised pressure pattern over the region in the medium term, there is potential for this forecast to become much wetter given the moisture profile out of the Indian Ocean and the cold fronts returning.

More coming up from 8am EST and there is a lot happening in the coming week so make sure you check back in morning and night, and I will have more details for you giving you the very latest on what you need to know.



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