NSW - SHOWERS AND THUNDERSTORMS DECREASING TOMORROW - WARM WEEKEND. SIGNS FOR AN AUTUMN BREAK?

The weather is certainly volatile across the western parts of the state with a near stationary trough getting a kick along today by an upper feature running over the top of this surface feature, lots of humid air has lead to widespread showers and thunderstorms.


The activity will begin to settle down as the trough weakens and the air begins to stabalise. Still looking warm and humid through much of the week before we see a drier airmass coming in from the southwest with a westerly change, but this cooler drier air may fail to reach the northern inland.


Overall, once we lose the storms over the west of the state, most areas should be dry for a while. There will be a few showers at times through the east and few thundery showers about parts of the inland but it is so random and disorganised the forecast of mostly fine for all of you is the best forecast.


Next week we are seeing some indications of the easterly winds returning as the SAM tends back positive, this may allow for showers to increase as we head towards the end of the month and a trough may establish over the inland leading to scattered showers and thunderstorms at the very end of the period.


There has also been rumblings of moisture streaming out of the Indian Ocean into a jet stream and being propelled across the nation into the southeast and eastern inland. Will watch those trends in the coming days but the overall forecast confidence is low at the moment beyond the weekend.


Lets take a look

FOREACST

Rainfall Next 10 Days

Rainfall is scattered and uneven in distribution with thunderstorms this evening easing and clearing to the east tomorrow. Isolated showers and thunderstorms over the state tomorrow and a few showers along the coast in northeast to southeast winds. The weather remaining mostly dry over the state into the weekend. There is another weak front rolling through the southeast with the southerly winds rolling up the coast during the weekend. This may trigger a few showers and storms for the east which will stall out over the northeast. Next week dry start for the inland with warming temperatures but we do see some evidence of a fast flow pattern emerging south of the nation which will help to draw in moisture from the northwest of the nation into the south and east. Thick cloud and patchy rain and storms may develop in association with the moisture meeting a weak trough in the east but the confidence is not especially high so I am placemaking the higher % chance of further rainfall developing next week rather than the actual totals being accurate at this time. That is normal during the shoulder seasons.

Thunderstorm Forecast Wednesday

Thunderstorms this evening, locally severe in the west will ease overnight but a few may linger into Wednesday. Storms unlikely to be severe on Wednesday but there could be the very isolated heavy fall and gusty downburst but overall the coverage is less extensive than today. Storms if they form may be in the very far southwest.

DATA - Refer to the video for more information about the short and medium term breakdown details. Really important to gain context to the charts and forecasts here!


00Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 2 Weeks

The pattern as outlined this morning and as I have touched on in recent days, the confidence beyond about Sunday is quite low as the pattern continues to respond to the climate drivers. The SAM has been very hard to pin down. What was looking like a negative phase of the SAM for next week is now turning positive and therefore the models are playing catch up and adjusting from run to run, hence your forecasts keep changing erratically. That will continue. The weather over the north a little more settled into a routine, which is wet with late season heavy falls and severe storms. That moisture may creep southwards through the nation and help to prop up the humidity and rainfall levels into the medium and longer term. So that is something to watch. Over the west, watch the Indian Ocean, the first widespread falls of the seasonal shift may be approaching next week and consequently may move across the remainder of the south of Australia into the end of the month. East coast areas should remain seasonal with warm weather but the rainfall may increase in coverage if the positive SAM strengthens. There is a large scale severe weather event on the GFS this evening that I talk through in greater detail in the video at the top of the page.

00Z GFS - Precipitable Water Values - Next 2 Weeks

Moisture values remain higher than normal for the southern and southeast inland but that should be eroded during the next few days. The drier airmass over the south of the nation will spread northwards over the weekend, though temperatures will remain above the average. Northern tropics under above average moisture values through the coming week to two weeks with an approaching MJO. That MJO may set up a large moisture in feed across the country as I have outlined in recent days, setting up a rain band from WA, through Central Australia and if the fast flow pattern allows, through to the southeast inland.

00Z GFS - Rainfall Accumulation - Next 10 Days

Refer to video for further details and model context

00Z CMC - Rainfall Accumulation - Next 10 Days

Refer to video for further details and model context

00Z GFS - Rainfall Accumulation - Next 2 Weeks

Refer to video for further details and model context

A closer look in - this forecast is volatile and will change. So be aware of that, anything beyond 5 days is poor confidence.

More in the models and rainfall wrap coming up after 9pm EDT tonight to see what is lurking out in the medium term, are we seeing the Autumn Break becoming a fixture on all data or is it just a GFS thing!?!


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