The storm activity yesterday across parts of VIC and NSW were as expected nasty with a pre frontal trough passing through southeast areas, with a very hot and unstable airmass producing those elevated severe storms.

Damage has been reported from many locations in the east, mainly due to strong gusty winds and large hail across the ACT as well as flash flooding. Cooma saw flash flooding as well.

The weather has become more unstable overnight and this morning with rain and storms across SA, VIC, NSW and parts of QLD. This weather is set to become more widespread this afternoon and sweep the east of VIC, NSW and QLD with warnings likely to spread east.

Once the cooler southwest to southerly flow is through, your storm risk diminishes and that should be for most southeast areas by tonight, though storms over the east of NSW and QLD may persist into Monday.

For the north, storms back this afternoon but the coverage is set to increase this week with a monsoonal flow developing to the north of the nation. For the time being, a heat low drives not only the heat but the severe weather risks.

For the south and west, this week, benign weather developing as we head into Christmas, with a large high sitting close by controlling the weather.

Lets take a look at the most important bits today

Rainfall Next 10 Days

Rainfall remains very much focussed over the north and east of the nation with a series of troughs and low pressure born out of the heatwave conditions, causing showers and storms most days this week. The trough responsible for the showers and thunderstorms over southeast Australia today will contract north and clear the south by tomorrow. The trough becomes slow moving and will trigger showers and thunderstorms for northern NSW and much of QLD for the week ahead. The remainder of this week for southern Australia looks dry and seasonal and for the east and north of the nation, humid unsettled with showers and thunderstorms increasing. The monsoonal flow north of Australia is expected to freshen with moderate to heavy falls developing around Christmas if not shortly after with the region becoming the focus of heavier falls nationally as we move into the end of the year.

Rainfall Next 16 Days

Rainfall is expected to increase further over northern and eastern parts of the nation with a significant burst of tropical weather. Rain, becoming heavy at times with local flooding possible as the monsoonal weather begins to move southwards, a tropical low is also likely to form across the northern tropics enhancing the northwest flow and rainfall for some areas. For the east, rainfall likely to increase as a trough deepens over the inland of QLD and NSW and pulls moisture southwards from the tropics and feeds off the easterly winds to see the showers and storms increase further. A trough passing through the southeast during the end of the year may bring a more organised batch of showers and thunderstorms but the signals are not suggesting heavy falls for now, that looks to be happening more for NSW and QLD. The west looking drier, especially the southwest.

Thunderstorm Forecast Sunday

Thunderstorms, locally severe, are underway this morning but the coverage of thunderstorms is contracting eastwards this morning into NSW and VIC. Thunderstorms will be severe in many locations this afternoon with damaging winds and heavy rainfall the main issues, but large hail about the southeast of NSW will be featuring once again.

Thunderstorm Risk Monday

Thunderstorms along a weakening trough are expected to return during Monday afternoon and evening, with damaging winds and heavy rainfall possible. Thunderstorms will extend back through the Outback into the Top End and Kimberly with damaging winds and heavy rainfall leading to flash flooding. The rest of the nation under stable air.

Thunderstorm Risk Sunday

Thunderstorms are forecast to become more widespread today, we have thunderstorms active over many areas in the shaded zone and this will continue to move east and northeast as we go throughout the day, clearing from the south and west later today.

Flash Flood Risk Sunday

Flash flooding is a high risk over the southeast of the nation with thunderstorms training over the same region for several hours. Catchments are wet and will respond quickly to heavy rainfall. We saw flash flooding in Cooma yesterday and about the ACT.

Large Hail Risk Sunday

Large hail is a moderate to high chance over the southeast of NSW where forcing is greatest as a fast moving front kicks a trough along later this afternoon. Golf ball sized hail was reported on Saturday in a few locations and the coverage increases in the southeast today.

Damaging Winds Risk Sunday.

Damaging winds remain a very high risk with thunderstorms passing through the eastern inland and southeast of the nation. Thunderstorms will bring damaging to locally destructive wind gusts, as seen yesterday, with some locations seeing extensive damage north of Canberra. The risk contracts east with the trough.


12Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 16 Days

The fast flow pattern is responsible for the volatile weather through southeast Australia today, a trough is expected to push north and east today, meaning storms and showers will ease from the west, with a lovely, drier southerly flow sweeping that heat out. The north will see showers and thunderstorms increasing most days this week with a trough deepening and the monsoon flow sinking from the north. The eastern inland will see an increase of showers and thunderstorms through this week with troughs and onshore winds combining for the humid and unsettled weather. The west and south of the nation are anticipated to be drier and more settled as we move towards Christmas this week with seasonal conditions and we will lose that heatwave conditions over interior parts. The moisture from the tropics will become a major feature throughout the period between Christmas and New Years.

12Z GFS - Precipitable Water Anomalies - Next 16 Days

Very deep moisture over the north will spread southwards and eastwards into the inand through this week and where that moisture goes, the rainfall chances follow. So not a surprise with the coverage of showers and thunderstorms increasing for the eastern and central interior. As you move south and west, the weather remains dry and settled near high pressure. The tropical monsoonal flow increases as we track through the outlook period and this will see rainfall chances comes up with heavy falls developing, but where it goes determines the rainfall spread. Last night it had a cyclone over the Top End, today it is putting it over the Gulf. The signal remains the same, increasing rainfall chances as we track into the end of the year and into 2022 throughout much of Australia but drier weather for now for much of SA and WA.

12Z GFS - Rainfall Accumulation - Next 10 Days

The GFS is having a real rough time with the monsoonal weather, it will do this, see the approach of the monsoon, then back off and then come back with heavier rainfall totals a few days out from commencement. It plays havoc with your rainfall prognostics, but you see this every year. The higher confidence in the forecast is drier and warmer for the west and south with hit and miss showers and thunderstorms becoming more widespread for QLD and NSW as we get close to Christmas.

12Z CMC - Rainfall Accumulation - Next 10 Days

This model is placing a deep tropical/monsoonal low over the Top End, and while it is a possibility it is a very low chance given that this is the only model showing it. Showers and storms increasing across the nation's north and east with humidity increasing in line with the troughs deepening. The west too wet compared to other models at this time.

12Z Euro - Rainfall Accumulation - Next 10 Days

The Euro consistent in it's approach to rainfall, has the sharp system today and tomorrow through the southeast clearing but follow up rainfall expected from mid to late this week with another trough that will linger into Christmas with humid weather. Over the north, it sees the increase in rainfall but the single run data set does not bring in the monsoon, the broader data set does. Much of SA and WA dry for a while.

12Z GFS - Rainfall Accumulation - Next 16 Days

Rainfall increases through the outlook period, the GFS placing the monsoonal burst somewhere different every run, the idea is the same, the weather turning wetter as we go. The weather in the east over the eastern seaboard expected to turn unsettled with onshore winds feeding troughs, more storms forecast in the medium term. The falls could turn heavier as we get closer to NYE. The west and much of the south seeing less rainfall.

12Z Euro - Rainfall Accumulation - Next 15 Days

The Euro ensemble data and the control data set (not adjusted) is wetter than the deterministic data above. So expect more changes to northern and eastern area forecasts. The west and south look dry and that carries a higher confidence at the moment.

More details to come this afternoon. A reminder that I will be travelling tomorrow with an update expected later today and then again tomorrow afternoon/evening once I settle in Darwin.

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