NSW - A COLD START BUT WARMING UP FRIDAY AND THEN HOT FOR SOME SATURDAY AHEAD OF RAIN

The yo yo weather continues as we track a series of waves throughout the southern parts of the nation, this likely the last in the four week sequence of winter weather that has brought above average rainfall for the month for many areas


Rainfall Percentages - Month to date.

The persistent westerly wind regime is clearly evident in the rainfall distribution.

The weather is set to end of a soggy note for southern parts of the nation including NSW with these two long wave troughs to push through bringing bursts of rainfall.


Temperatures are expected to warm today after the morning frost clears. The northerly winds starting to increase over the west, that will bring in the very warm air from the interior. That sets up a warm to hot Saturday with temperatures well above the average.


Temperatures as of 6am EST.

Frosts and even a freeze down through the southeastern inland of NSW, with severe frosts reported through most of the GDR and through western plains. But note the temperatures through western NSW and SA this morning.


The temperature clash with the cooler air coming in from the west with the warmer air over the eastern inland, combining with modest moisture supply will allow rainfall to break out. The rain band likely to be mostly light to moderate Saturday night into Sunday.



The rain band will come north through Sunday into Monday, getting another kick along with a secondary front marching through the southeast. That will allow the rainfall to become moderate over the northeast of the state, running up the GDR. Some areas about the region from Glen Inness through Inverell to Nundle may see 20-40mm from the event.


The moisture and rainfall will clear north Tuesday with a drier airmass surging northeast. A new high pressure system will begin to clear the inland.


So two systems over the next 4 days will lead to the wettest weather for the period, then we wait until the second week of August where rainfall is likely to return.


That will begin the shift in the surface pattern as we lose the westerly wind regime by the end of next week with signals that up north, the moisture is set to return to kick off some rainfall for QLD. That may drift further south.


Precipitable Water Anomalies next Sunday 8th of August.

GFS for the same period - starting to get good agreement, though GFS is more aggressive. However this will be the focus of medium term forecasting over the weekend with clearly two rainfall events on the board with these areas of higher PW values and troughs nearby.

Lets look at modelling


12Z GFS Surface Pressure Pattern for the next 16 days

The pressure pattern is largely unchanged over the coming 4 days with moisture sweeping northwest to southeast with the pattern dominated by the long wave coming in from WA. The weather then trends colder through the southeast as the long wave trough passes through and then into the east with a southwest flow developing. All the moisture ahead of the frontal weather will lift into areas of rainfall through inland NSW, VIC and most of coastal SA. We may even see rainfall come into parts of southern QLD which is the first meaningful rainfall since early July. The weather the trends drier mid to late next week with the weather set to be dominated by high pressure. That high will reset the moisture over the nation with easterly winds redeveloping over QLD sending in a moisture plume through the north and central areas, which may continue to track southwest through the eastern inland. This may lift into widespread areas of rain. Out west there will be a separate long wave out west which may produce a widespread rain band if a front can be in phase with that feature. So these will dominate the medium term forecasting.

12z GFS Rainfall for the coming 10 days

Rainfall is largely unchanged from overnight with the rainfall connected to the westerly wind regime, two frontal passages and the deepening moisture supply streaming in from the northwest ahead of the fronts as they rush through. The weather is expected to ease from mid to late next week as high pressure comes in so you can see no more additional rainfall under stable air, that carries through next weekend.

00z GFS Precipitable Water Anomalies for the coming 16 days

This product again shows the shift in the conditions after we get through the last of the frontal weather. The nation begins to be dominated by high pressure as it digs into the southern states. The more settled weather expected from Thursday for several days next week. As that happens, the whole pattern resets and we see easterly winds strengthen over the north and east and finally gives the eastern inland a chance to see moisture return, coastal showers return to the east coast, giving the south a chance to dry out. It is looking more likely that a rainfall event may get going over QLD next weekend. Then out west we watch the moisture surging southeast into frontal weather approaching next weekend which may bring a separate rainfall event to the west later next weekend Another rainfall event may develop over the northeast with a deeper moisture plume over much of QLD. That is the second time this model has shown this today for mid month, that event would be more widespread if it verifies.

12z Euro Surface Pressure Pattern for the coming 10 days

The pattern largely unchanged from last night with two frontal waves tapping into large amounts of moisture streaming out of the northwest and extending over VIC and NSW, then into QLD this weekend into early next week. Then we see the last of the fronts move through Tuesday with a colder southwest flow redeveloping. The weather will clear under that high pressure system moving in as the westerly winds retreat south. Note the upper trough over QLD later in the outlook and another long wave building off WA next weekend, these two areas will be the focus of medium term forecasting over the weekend and may provide the next batch of rainfall into the second week of August.

12z Euro Rainfall for the coming 10 days

Rainfall again largely confined to the next 2 systems rolling through the southeast, one on Saturday and Sunday and another burst of rainfall coming through on Monday through Tuesday before we see clearance. Some lingering showers possible during Wednesday over the southern inland however the weather should clear out during this time next week with more sunshine and milder weather developing as a northwest flow develops around the high moving to the east. So drier weather expected from Wednesday onwards through next weekend for most locations. If the winds turn more easterly, then I may reintroduce showers to the east coast.

12Z Euro Precipitable Water Anomalies Next 10 days

The Euro is similar to the GFS with moisture likely to reset under the new high pressure system next week. We can see a good supply of moisture coming in ahead of frontal weather over the southern and eastern states over the coming few days, leading to once again light to moderate follow up rainfall. The northern inland of NSW and southern QLD could surprise during Sunday and Monday as an upper trough deepens with the second system surging northeast bringing a colder southwest shift to the southeast state. In the later part of the next week into the weekend, we can see moisture developing over QLD and WA, where this will be the focus of the medium-term forecasting as two large cloud bands could develop in response to the moisture and troughs combining. Rainfall coverage next weekend is hard to pin down and better clarity will come Sunday night with the forecast packages and during early next week once the long wave over the southeast moves east.

Rainfall for the next 10 days

Rainfall largely unchanged for the coming 4-5 days with the weather dominated by those two long waves, but we see rainfall reduce mid next week with a drier period expected this time next week ahead of a milder spell with plenty of sunshine into next weekend. That is when the rainfall moves to parts of QLD and back to WA as high pressure moves the moisture away from the southeast inland, but rainfall likely to come back in the second week of August.


More weather details to come today including another August Climate Update



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