NSW - A WARMER SPELL DEVELOPING TODAY BUT WHAT ABOUT THAT RAINFALL?

A cold morning across much of the state, the high pressure is sitting right on top of us and combining with that drier airmass over the region, not much way in fog this morning, so severe frost has returned to pockets of the GDR and widespread frost over the plains. Down to -5C in Canberra and widespread -2 to -4C up the GDR.

The satellite imagery shows that dry airmass with sinking air throughout the nation with little rain bearing systems, which was expected for this period of August many weeks ago.

A warmer spell is developing today with a broad scale northwest flow developing, the high pressure that has given us a frost this morning, is expected to pass to the east and southeast bringing a warmer northwest flow. That will see a warmer end to the week, the front that is expected Friday is now not as far north (the model madness continues which is fun)

Temperatures are expected to reach the mid to high 20s over the northern and northwest inland well to the north of the frontal weather from Thursday into the weekend, while temperatures after being mild to warm over southern areas, will moderate under cloud and patchy rainfall.


The big feature this week is the warming temperatures throughout the nation it seems, some hot values over the inland of SA sweeping through the northern inland of NSW and into southern and western QLD.

The warmer air may play a part in adding some atmospheric dynamics into play, steepening the lapse rates as the cold front on Sunday into Monday moves through, this could see shower activity turn more numerous and thunderstorms be involved.

The medium term still remains up in the air - the Euro and GFS continue to split, however in the recent runs from last night, it has started to ping perhaps of some rainfall returning to the east coast and the eastern third of NSW and into QLD. The forecast still remains low confidence.


12Z GFS Surface Pressure Pattern for the coming 16 days

The pressure pattern is looking settled for the coming few days, not too much change in the forecast from overnight until about Sunday. The only difference we need to monitor is how far north are the fronts going to travel this week, which will determine how much of an influence it has on the weather over SA, NSW, VIC. This morning, the modelling has decided to drop the cold fronts south by about 200km which is why you are seeing less rainfall, but that could easily wobble back north. I spoke about that last night being a risk. Then we keep an eye on that stronger front passing through during Sunday into Monday, which does move more east northeast, driving a colder southwest wind with showers and rain spreading further over the southeast inland. This colder air may help promote rainfall over the east coast as winds veer into the east next week. As you can see more rainfall opportunities exist into the end of the month.

12z GFS Rainfall for the coming 16 days

Rainfall totals are more lean this morning for the coming couple of days due to the fronts being further south and somewhat decoupled from the moisture coming through from the northwest. We can see that moisture activated into showers and thunderstorms overnight over inland WA with isolated moderate falls. That moisture can still activate into heavier rainfall if the fronts stand up in future runs over SA, and VIC, but very wet for western TAS. The wettest weather is still attached to the front passing through later this weekend over the southeast. That system likely to bypass the west, so we will see widespread rainfall for the southeast states Sunday into Monday, that may extend further north through NSW and rainfall could return to the east coast IF the winds veer into the east, but we will keep watching. Also keeping an eye on the moisture over inland QLD which could turn into showers and storms if the colder unstable airmass lifts north through NSW. The system exhibits more spring like properties.

12z GFS Precipitable Water Anomalies next 16 days

The chopping and changing in the modelling regarding the moisture content in the air continues. On the weekend, this model showed significant signals for deep moisture sweeping the nation, now it has swung back to drier air dominating, that is in parts thanks to drier air coming in behind the front that came through Monday. And that will be the case behind the front that passes through later Sunday into Monday, so that will snuff the rainfall chances over north and northwest of the nation. Keeping an eye on the weather over the east where moisture still wants to pool over QLD and NSW through the medium term. That could see showers developing for the eastern parts of the nation IF the winds veer into the east. There are too many variables for me to carry a high confidence in the forecasts after Sunday at this time. Also in the medium term, the moisture does return through WA and then into SA from later next week. That also needs a lifting mechanism.

12z Euro Surface Pressure Pattern for the coming 10 days

Very similar spread in the Euro model this morning with this also pinging the frontal weather just a little further south over southern Australia from later this week, the first front should still bring a burst of rainfall to WA, but it is not as heavy as previous forecasts. The moisture profile is unchanged with the weather coming in from the northwest through the southern states but the frontal weather is further south this morning in modelling, hence the rainfall totals are less. Still wet for western TAS with the sequence. A stronger front still expected later Sunday but the system is not as strong as GFS. That could send up a pool of colder air and interact with moisture mainly offshore QLD and NSW and see a low form, that is why we are seeing showers developing over eastern QLD and NSW, but it carries low confidence and I would not be surprised if it disappeared from the next run.

12z Euro Rainfall for the coming 10 days

Rainfall remains lean for much of the inland of the nation, with dry and and high pressure causing sinking air motion, so the heat continues to build over northern Australia. The weather expected to be changeable for the south with showers from time to time but not widespread heavy rainfall expected. With the frontal weather though moderate accumulations are possible through the southern coastal areas, lighter falls for the inland. Two systems to watch for the nation that offer the most rainfall, the front passing through Sunday into Monday and then possibly seeing rainfall developing over southeast QLD and eastern NSW next week.

12z Euro Precipitable Water Values next 10 days

The moisture distribution continues to be very inconsistent run to run, and this morning the moisture has returned into the second half of this outlook for parts of the nation, where last night it was gone. The north of the nation could see a reprieve from those early build up conditions that were forecast a few days ago, with a drier southeast to easterly flow returning next week pushing the moisture out. Moisture may deepen over the east coast with the onshore winds deepening thanks to a low sitting offshore. That is certainly low confidence as it is a new feature on the charts. Otherwise another pulse of moisture comes in from the northwest of the nation later in the outlook, but needs a lifting mechanism to be useful and see rainfall spread over the southern parts of the nation.

Rainfall for the next 10 days

Rainfall is moving around a bit between the models, I will show you more of that later this morning in the medium term forecast update as some want rain, many do not. At this stage I am still not willing to change the forecast of rainfall too much as it is inconsistent forecasting. There are 3 fronts to watch in the outlook period, one that comes through Friday, one that comes through Sunday into Monday and another that will roll up the NSW coast during mid next week with a low possibly forming offshore. This is still a low confidence forecast.

Your medium term forecasting coming up later this morning and a look into early September too.

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