NSW - A RUN OF SETTLED DAYS BEFORE A THUNDERY CHANGE THURSDAY INTO FRIDAY.

That sets the scene for a challenging forecast with signals diverging as we track into the weekend and into next week. Some have persistent low pressure, some global models clear us out with a run of westerly winds under high pressure.


Lets take a look

Rainfall next 10 days

Rainfall is likely to be reserved for far southern areas of the state as we track through the early part of this week, thanks to the westerly wind profile to the south of the nation. The weather over the north and east should remain dry for now. The tricky portion of this forecast will be from Thursday into Friday, a trough passing through helped along by a cold front over VIC, will drive a band of rain and storms, but the modelling is not clear with some driving more rainfall than others. The weather for the period following this then becomes dependent on what happens with this system, so the low confidence strap applies from later this week into the weekend. I will draw the regional charts once we have a bit more confidence in the modelling through the week so stand by for that.

Thunderstorm Forecast Monday

A cold front racing through the southeast will bring unstable colder air and the chance of thunderstorms during the afternoon and evening, mainly through VIC, where the dynamic support is greater and the timing of the front with the day time heating process also helping out. These may creep into southeast NSW later in the day but weaken in the evening, but watch closely for damaging winds and small hail in the Ag areas.

Damaging Winds Forecast Monday.

Scattered showers and thunderstorms through the region will be capable of dragging down a strong jet aloft, winds to 100km/h is possible with thunderstorms over the western inland of VIC and these may spread east. Strong gradient winds over elevation in the east could also see gusts in excess of 100km/h.

DATA


Euro 00z - Surface Pressure Pattern and Rainfall Distribution - Next 10 days

The pattern has resolved, the moist and unstable airmass that brought the storms is now well off to the east. We have a series of fast moving cold fronts passing through the southeast, one sliding over VIC tonight, another through SA and VIC on Monday and through the SWLD of WA on Monday night. That front will pass through southern Australia by mid week, and link up with moisture to produce scattered to numerous showers and storms through Thursday and Friday. That thundery weather may clip southern QLD and northern NSW. Then moisture hangs back with part of the trough over inland Australia and moisture from the northwest will feed into the deep trough over central Australia producing widespread rain and storms. Part of the change rolling through the southeast on Thursday will become stalled out over southeast QLD this weekend coming with more rain and storms developing. The tropics, looking soupy with increased showers and storms about.

Euro 00z - Precipitable Water Anomalies - Next 10 days

The Anomalies are what you would expect to see during October with higher values rotating through the inland of the nation with the source of this moisture coming in from the tropics and the easterly winds that will return through this period. The impact of that moisture won't transition into rainfall until the back half of the weekend over eastern parts of the nation and through Central Australia. The rainfall over southern Australia won't be heavy to start this week, the values are not impressive but they do improve with the system on Thursday and again note how the moisture sitting over the eastern inland of the nation is then picked up by the trough, the better rainfall sits back over in VIC and NSW once again. That is not uncommon in any year. For you in SA, watch the moisture over Central Australia, even though it is expected to pass east through to QLD, other models (as per the GFS) place it over the southeast and south, so that is one area to watch this week. The west is likely to dry out a little as ridging takes place.

Euro 00z - Rainfall Accumulation - Next 10 days

Rainfall is bias once again for the southeast and east of the nation through this outlook period which is in line with seasonal expectations, but due to the moisture content being higher than normal, the rainfall is likely to be more productive over the eastern and southeastern states. The inland likely to see rainfall come back during next weekend, and southeast and southern QLD could also start to see a storm outbreak with that central Australia moisture working its way east into a developing trough over NSW and QLD. Over the north, pop up random scattered showers and thunderstorms and the west, numbers coming down, as they should during October with the seasonal shift continuing.

A closer look in (you can see the video for GFS comparison).

The next update coming up on Monday morning and I will be looking at the Medium term forecast again daily from mid morning this week and how is this potential La Nina tracking for summer? All that and more coming up.

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