The shift in the weather over the course of the coming days will start to reflect the positive SAM phase that has now peaked through the Southern Ocean and this will now help to promote an easterly flow over the southern and central coastal areas. The onshore winds are forecast to feed a trough over NSW which will start to lift into southern QLD on Thursday seeing the showers and thunderstorms developing and then persisting into the weekend.

The weekend looks wet over the southeast and southern inland with the trough sharpening up over the region. Severe storms are possible over the southeast and southern districts with the risk of heavy rainfall with thunderstorms over the border with NSW. Showers may also be heavy at times with the onshore northeast to easterly flow along the coastal areas.

Heading up the QLD coast, the showers should feature in most towns up to Thursday Island. There will be heavier rainfall found north of Bowen through to the top of Cape York, as the MJO approaches. This will be in association with the freshening trade winds and the deepening of a trough over Cape York. Some areas could see falls over 100mm per day.

Over the weekend and into next week, I am keeping an eye on the risk of tropical low development nearby the NT if not over the Gulf which could raise the bar for showers and thunderstorms increasing across the region. There is a low to moderate chance of a cyclone forming in the region.

Elsewhere, the bulk of the west and northwest should be dry for now, this will extend into the central districts for now, but the confidence in this region is not especially high at the moment.

Once a high moves southeast of NSW during next week, this will assist in winds turning into the north over the state and the weather should begin to dry out over coastal areas, but not clear completely. The temperatures inland look to remain above the average.

Lets take a look


Rainfall Next 10 Days

Rainfall remains of low confidence forecasting, only due to the showers and thunderstorms being spread across the south and southeast of the state. You will see a rainfall guide across the region but some areas may exceed or not exceed these values, so it is useful as a guide rather than the absolute. The heaviest of the rainfall will be found over coastal areas in the southeast and up over the northern tropics where the instability and forcing is much more aggressive. The drier spots, back over western interior parts of the state with drier air and ridging passing through the state. There may be some spillover of moisture from the tropical system over the NT or Gulf that could change rainfall prospects for the interior, but at this time it is considered very low. Overall the next 5-7 days look damp over the east coast and next 2-5 days for inland areas adjacent to the coast but many areas west of Charleville to Longreach to Mount Isa should be dry.

Thunderstorm Forecast Thursday

Thunderstorms are forecast to develop over much of northeast NSW during the day and spread into southern QLD by afternoon and evening. Some of the storms through the Darling Downs and Granite Belt may turn severe with damaging winds and heavy rainfall leading to flash flooding. Thunderstorms will also develop around the Gulf and through Cape York with a small chance of flash flooding in the region. Damaging winds over the tropics should stay over in the NT for now.

Damaging Winds Risk Thursday

Damaging winds will be a low to moderate risk running along the NSW/QLD border as the storms tap into the low level jet.

Flash Flood Risk Thursday

Flash flooding is a moderate risk with thunderstorms pushing northeast from NSW during the afternoon and evening.


Severe Weather Watch - Friday through Tuesday

Watching very closely the emergence of the upper level low moving into western NSW during Friday and how that interacts with the moisture and the existing trough sitting over the northeast of NSW and southeast QLD. Could see a rather expressive period of convection and given the dynamics, the chance of severe weather with storms is elevated over inland areas. Along the east coast, in east to northeast winds feeding the system, we could see heavy showers and flash flooding initially, and deepening on the rainfall coverage and the performance of the troughs together, there may be intense rainfall returning to parts of the coast. The most likely areas would be the extreme coastal fringe between Sydney and Yamba at the moment. The severe weather contracts into the northeast and east of the ranges by next week. The most active severe weather will be over areas south of about Chinchilla in QLD.

Riverine Flood Risk - Friday through Tuesday

The catchments are still very wet even though we have seen an absence of rainfall in recent weeks. The rainfall forecast will be moderate to heavy over a number of days and over time, the catchments will respond to this rainfall. Falls of 100-200mm are possible in the coming period in scattered pockets along the extreme coastal fringe and falls of 50mm an hour with thunderstorms are possible in all areas highlighted here. This may trigger minor to moderate flooding to redevelop along the coast. At this stage the amplification of the event is no where near the levels of the previous event but once again, riverine flooding is a significant risk for catchments devastated by the early March event. Remain weather aware through this region.

Flash Flood Risk - Friday through Tuesday

Flash flooding is a significant risk with thunderstorms with the upper level system moving in from Friday if not Saturday, into the moisture and stalled boundary over the north and east of NSW. The two will combine to bring scattered storms, some severe, with heavy rainfall leading to flash flooding a significant risk. From Thursday, there may be thunderstorms along the coastal fringe and streams of heavy showers floating about between Batemans Bay to Yamba that could see some coastal areas net 50mm in a couple of hours. Thunderstorms over the weekend across central, northern and northeast NSW could drop 30-40mm in an hour with the coverage contracting eastwards during the weekend into early next week.

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

We are still seeing the model madness from run to run and between weather agencies and this will make backing the right horse, hard to do. There are many people out there backing a model to bring them comfort, but the weather does not care about your intuition or what model has the best track record. These periods are low confidence for a reason and we have to look to the broader data sets and the observed weather to get a sense of where the weather is trending to be most active. At this time, the guidance on the modelling is suggesting the weather in the west is looking more unsettled over the weekend with severe weather potential from thunderstorms developing or with the passage of the remains of Charlotte and then a fairly moist and unstable airmass sitting over the western interior through next week. Over the eastern seaboard and into the GDR, the weather looking very wet with flooding become more of a concern as we move through the weekend and into next week with the positive SAM phase playing out over the days ahead. Over northern Australia, watching the evolution of the next tropical depression. This sits in one of the hardest areas to forecast tropical weather and will be very hard to pin down, but the rainfall and severe weather risks are increasing from run to run across most weather agencies. Over the south and southeast Australia extending back into the Central portions of Australia, the weather is forecast to remain dry and settled for about a week.

00Z GFS - Precipitable Water Values - Next 2 Weeks

The moisture profile continues to remain unchanged essentially from run to run, but what is changing in association with the moisture is the placement of low pressure which is what will drive rainfall. For now the driest weather near the upper and surface ridge over the central parts of the nation and extending through southeast areas and adjacent inland regions of NSW and into QLD. The wettest and more humid weather, in the west, western interior, through the northern tropics and over the east coast and coastal escarpment through to the dividing range with onshore winds via the positive SAM. We could see the weather shift during later next week as the high controlling the weather over SA moving into the east and then southeast of the nation. That may promote a deeper moist northeast flow lifting above average rainfall chances once again for NSW and QLD.

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 totals will shift around in the east. When you have upper level systems in play at this time of year, they can cause some rather high impact weather, but for now the confidence is low on both systems, in the short and medium term. So it may be dry for a while in the western and central areas of the state but this could easily change with lots of moisture floating around. Also watch that tropical system up north.

More coming up from 9pm EDT with a look at the models and rainfall, I will only share information that is in reasonable agreement as too much is too confusing and I only want to share what is plausible at this time, so stay tuned for that.

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