The rainfall event unfolding through QLD this week is forecast to move into northern NSW from mid-week and drift further south now throughout the state, the coverage of the heaviest rainfall now becoming the tricky feature to forecast.

I will mention that thankfully the position of the trough and upper low could now work in favour of seeing the heaviest of the rainfall bypass the disaster zones in the northeast whereas a few days ago, the models were lit up like a Christmas Tree. However, the change in orientation in the system is now forecast to increase rainfall totals on and west of the divide.

The complicating factor for the remainder of NSW when it comes to rainfall is how quick does the weakening front and trough from SA move into the region and do we see a larger rain event form on the southern branch of moisture over the Lower Western through to the Southeast Districts including the ACT? This idea is being floated but forecast confidence is low.

For those keenly watching temperatures, we have said goodbye to the very cold dry air and you will notice that the air will begin to shift in the coming 2 days with a northeast flow by mid week, meaning we say goodbye to the frosty starts for a little while.

Overnight temperatures are forecast to move above the average and day times will remain mostly seasonal, with higher-than-average humidity.

Severe weather risks also exist throughout this week from thunderstorms over the northwest which could pack quite a punch through to the potential for riverine flooding returning with areas of heavy rainfall also featuring.

Let's take a look


Rainfall Next 10 Days

Rainfall is forecast to gradually increase along the coast this week as the winds veer into the east, driving the showery periods and moderate falls. Over the inland, the scattered showers and thunderstorms are forecast to emerge from about mid-week as an upper low deepens over SA and QLD. This system is the driving force behind the spread of rainfall and severe weather potential so it's placement and strength/scale are key to who gets what. Overall, the current idea is for the rainfall to increase in coverage from Wednesday over northern and eastern areas before spreading further south on Thursday and Friday ahead of a trough coming into SA that will move east through VIC, NSW and QLD. That will kick the upper low to the east and clear the high humidity levels out of the inland so the risk of severe weather will wind down from this weekend. Rainfall totals through this week could be well above average for many areas under the current guidance and the risk of severe weather is moderate to high and riverine flooding is currently a low to moderate chance. The forecast rainfall totals will bounce around in the coming days as the modelling begins to align and set the upper low in position

Severe Weather Risk This Week

The severe weather risk continues for a broad area and I will leave in much of the state under risk, as a form of combating complacency to ensure that subscribers understand that the low confidence forecasting means that many areas could cop a smacking while other areas will be spared. The very high levels of moisture through the state is of concern with high rainfall rates to unfold under such guidance.

Flash Flood Risk This Week

Thunderstorms will drive the flash flood risk this week and it is relatively high for areas closest to the upper low in the north and northwest and along the border in the far northeast where convergent rainfall in onshore winds may develop. A low risk extends southwards from Thursday into Friday ahead of a trough moving out of SA.

Riverine Flood Risk This Week

Riverine flooding is possible over broad areas of the state with a soaking rainfall event to develop from the north mid-week. Rainfall along the coast is expected to be come more widespread from this week, but convergent heavy rainfall may be found in QLD this time around but it is a line ball. Areas over the far northeast need to pay attention to the forecasts this week as heavy rainfall is still a moderate risk.

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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