A period more settled conditions for the majority of the inland of NSW with a broad high pressure ridge passing through the southeast and east today and that is responsible for the drier but windier weather over southern areas of the state today. The onshore flow will result in showers for the coast areas and as far inland as the GDR but otherwise it is looking dry on and west of the divide, plus humid for a wee while.

A trough over SA will form the focus of showers and thunderstorms there, drawing in the moisture from the easterly winds and tropical north resulting in showers and storms migrating mainly west of the state, but it will move back east next week at some stage.

Timing of that is yet to be determined.

So a mostly fine few days on the way and very humid for inland areas and showers for the coast.

Lets take a look


Rainfall Next 10 Days

Rainfall is expected to remain more extensive on and east of the ranges in NSW with the onshore easterly flow supporting the persistent shower coverage. With the ridge being closer to the region, the showers may not be as extensive or heavy, but a shift into a northeast flow and the high skipping 100-200km further south and that may change so will watch those wind bearings along the coast. Inland areas, mostly dry, there is the chance of an isolated afternoon shower or thunderstorm from time to time, the better coverage out west and through SA. That trough over SA will move east next week, maybe by Australia Day, timing has been appalling on the guidance, but a belt of showers and thunderstorms will emerge from the west with many areas seeing at least 25-50mm with that feature. Falls may exceed 100mm along the coast.

Thunderstorm Forecast Thursday

Scattered showers with local thunderstorms over the far northeast during the afternoon and evening. No severe weather is expected though some storms could drop heavy rainfall.

DATA - Refer to video for more information on the daily breakdown

00Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 16 Days

As mentioned in the video above, the features to watch are the trough over SA, does that stay stationary, bringing heavy rainfall for multiple days over central SA through to the NT with flooding a high risk, or does that trough weaken or does it move east? This will dictate weather over the central and eastern parts of the nation and this is what models are struggling with. The GFS keeps it stationary. Very humid air and stable weather for the eastern inland of the nation with above average humidity values will make things feel pretty foul. Showers and thunder for the east coast in onshore winds, some of those could be heavy for NSW and southeast QLD. The tropics, the feature to watch is the monsoon trough and whether a low pressure system forms in the trough. If it does develop, does that form near WA, NT or QLD? Models have diverged on that idea as pointed out today, that too has a major impact on rainfall and moisture forecasts moving forward. Finally, the SAM, does that turn neutral allowing the west of the nation to cool down for a number of days thanks to the westerly wind belt moving north. Does that westerly wind belt flush the humidity north? Plenty of moving pieces and sadly more questions than answers right now.

00Z GFS - Precipitable Water Values - Next 16 Days

As mentioned in the video, a very rich and broadly moist airmass will result in high rainfall chances for the nation, and where troughs form, flash and riverine flooding is possible for many areas through this period. The monsoon over the north looking to crank as well, and that will add more moisture to the nation meaning a wet end to January and start of February.

00Z GFS - Rainfall Accumulation - Next 10 Days

Refer to video for further details

00Z CMC - Rainfall Accumulation - Next 10 Days

Refer to video for further details

00Z GFS - Rainfall Accumulation - Next 16 Days

Refer to video for further details

A closer look in - the low confidence forecast continues for the eastern inland in relation to the movement of the trough over SA. If that system does remain stationary over the central parts of the nation, then the eastern inland will be very humid with only a scattering of showers and storms for the coming week before the trough moves east.

More coming up after 9pm EDT with a look at the models and the rainfall forecasts. Very much a divergent bunch of data right now.

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