The weather is looking very busy for northern and eastern Australia with the presence of troughs and a tropical system keeping the moisture and rainfall chances where they have been for the past 4-6 weeks. For our friends in SA and WA, the weather is the same ole song and dance. SA particularly unlucky this time of year with the storms flaring up literally, along the eastern border in two waves this week.

One wave is already on by and you will see that flare up later today with showers and thunderstorms increasing for VIC and NSW, some of these will be severe with all modes of severe weather possible. The next trough comes through on Thursday and deepens into a low pressure system Friday. That once again, finds the moisture over in VIC and NSW with severe weather once again likely for this region. SA on the dry and stable side of the trough.

The weather up north is very busy, TC Tiffany has regained her composure overnight and is looking better organised with her onward journey towards the west. This system is expected to quickly intensify to a 2 then a 3 tomorrow with a nasty core of winds likely to scoot close to Groote Eylandt and points south. Very heavy rainfall and dangerous flash flooding forecast to evolve in the coming days for the Top End as well.

The heavy rainfall will stay up over the Top End, with better guidance coming in on the track for this system to stall out over the central Top End, this posing a dangerous threat of high end flooding for the region. That is still on the table.

Beyond then, what happens to the moisture remains the million dollar question. And as pointed out last night, there are some similarities in the guidance but it is not convincing just yet and so more time is needed to interpret the data and observations to formulate a better forecast. With time, we will know more.

For now if you were a betting person in a La Nina Summer, you would think southeast and east would be the right solution, but this is weather, there are no rules so we wait and watch.

Lets take a look at the information this morning.


Rainfall Next 10 Days

Rainfall forecasting is a nightmare still nationally, this is again relating to the tropical system, so be aware that as you move further into the forecast, the confidence drops off, especially for the north and east of the nation. The west is looking more likely of seeing the drier weather and that is carried into SA. For those along the path of Tiffany and the eventual weakening low, very heavy rainfall is expected of 200-500mm through the sequence, some areas getting more. The northern Top End also likely to see heavy rainfall in onshore winds and a trough near to the north. The moisture from Tiffany is likely to veer off to the south and then southeast seeing heavier rainfall moving southeast through the NT and likely back into western QLD and northern NSW. The timing of a front or trough through the southeast may assist in deflecting the moisture out of the southeast for now. In the short term, we still have two troughs over the southeast and east that will spark scattered showers and thunderstorms, that will be today and tomorrow, the next trough is Thursday through Saturday/Sunday.

Tropical Cyclone Tiffany

Tiffany has remained as a remnant low off the west coast of Cape York which has surprised me, but is expected to regain cyclone status today and strengthen to a Cat 2 or 3 by the time it reaches the eastern Top End. The impacts, very heavy rainfall leading to dangerous flooding and destructive winds for the eastern Top End and dangerous flooding for much of the Central Top End over the weekend and into next week.

Flood Watch Northern Territory

As mentioned a very high risk of flooding is likely to continue for areas around Cape York but transfer that risk now with Tiffany through to the NT where severe flash flooding and riverine flooding is possible, especially about central NT.

Severe Weather Alert - NSW and VIC - Thursday through Saturday.

The risk of severe storms develops on Thursday through western VIC and NSW before slowly translating eastwards on Friday with the most potent weather expected to be over northern VIC and on and west of the Great Dividing Range including the ACT. All modes of severe weather possible on Thursday and Friday with the passage of the deep low and trough, including isolated giant hail and tornado activity. The risk contracts eastwards on Saturday with the main storm focus sitting over the eastern half of NSW, the ACT through to southern QLD. The risk eases by Sunday, severe storms still possible in pockets throughout northern and eastern NSW but would have cleared VIC and southern NSW by Saturday afternoon. More defined risks and forecast charts will be issued in advance of this event.


Thunderstorm Forecast Tuesday

Thunderstorms capable of producing heavy rainfall leading to flash flooding possible over the northern and eastern interior of the nation thanks to a slow moving trough over the eastern interior and a middle level trough moving over the southeast during the day. Storms will clear SA early in the day. TC Tiffany may also produce thunderstorms, some with intense rainfall and destructive wind gusts. Severe storms also possible about the Top End and Kimberly during the afternoon with the approach of a gravity wave off the tropical feature moving west through the north.

Thunderstorm Forecast Wednesday

Thunderstorms continue for the southeast and eastern inland of NSW and VIC with storms likely turning severe over much of NSW west of the divide and through northern VIC. Heavy rainfall and gusty winds likely the issues with thunderstorms, though the coverage not as widespread as Tuesday. Thunderstorms may also develop in eastern SA near the next trough forming over the state. Severe thunderstorms with dangerous conditions as Tiffany, a likely severe tropical cyclone, passes through the Gulf and into areas near Numbulwar to Borroloola with destructive wind gusts and a few isolated tornadoes. The damaging wind threat with storms will be felt right across the NT in the spiral bands rotating around the centre of the storm.

Thunderstorm Forecast Thursday

Thunderstorms likely to continue right across the north with dangerous thunderstorms with destructive winds over the NT quite possible. Thunderstorms expected to turn more widespread over the southeast with a trough deepening through SA. This trough is expected to bring a risk of severe storms, with all modes of severe weather possible.

DATA - More weather information in the video above.

Euro 12Z - Surface Pressure Pattern and Rainfall Distribution - Next 10 Days

Dynamic pressure pattern today with a severe storm outbreak for the southeast already in progress with the upper trough arriving and combining with deep moisture to lift it into scattered thundery clusters this morning. That will be the theme this week with storms over the east and southeast, enhanced by upper troughs, the next Thursday into the weekend, poses a significant threat of severe weather once again for VIC and NSW. For the north it is all about Tiffany and where the remains of her go. She is going to bring significant tropical rainfall to the NT and maybe even the Kimberly now, there has been a slight push back to the west but we will know more on how far west she goes. The models want to keep her up there for much of the next 10 days so some areas could see torrential falls and flooding. The models then want to bring her southwards and the moisture from her southwards into the central and eastern interior with more heavy rainfall into the medium term. For SA and WA, more of the same, dry and warm to hot weather.

Euro 12Z - Precipitable Water Values - Next 10 Days

The deep moisture over the east and north of the nation is clearly where we are finding rainfall at the moment. Severe storms already underway through the east with that upper trough lifting moisture is a cycle likely to be repeated again and again through the next week. This is leading to above average rainfall, thanks to above average moisture content. The north, very rich moisture being drawn in via Tiffany, but as she moves southwards over the NT, she will pull the moisture and the entire kitchen sink with her from the equatorial regions so a very large blanket of deep moisture will remain in place for the period with further widespread heavy rainfall and thick cloud cover over much of the north and northwest. This is La Nina weather, you find the drier air over the south and west of the nation in these climate periods, and that is what you see in the short term. In the medium term, things shift and we see moisture flooding through much of the nation bringing up rainfall chances for a wetter second half to January.

Euro 12Z - Rainfall - Next 10 Days

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GFS 12Z - Rainfall - Next 10 Days

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CMC 12Z - Rainfall - Next 10 Days

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Euro 12Z - Rainfall - Next 15 Days'

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GFS 12Z - Rainfall - Next 16 Days

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More information coming up this morning including a look at the 6 week outlook and the information for the remainder of Summer and answering a few questions filtering through about what happens after La NIna this year.