NATIONAL WEATHER UPDATE - MOISTURE WATCH....AND THE PATTERN FLIP?

We are starting to see the modelling come into agreement, digging the high pressure belt southwards next week, giving a little break to the constant frontal barrage that has been in place for the past few weeks.


The current pattern is very much dominated by the westerly wind regime as you can see below with the westerly waves passing over the southern states, while high pressure continues to sit over the mid section of the nation, keeping much of QLD, through northern SA, NT and central and northern NT drier with hot weather in the north.


GFS 18z Pressure Pattern from 18000ft through to the surface - Thursday 29th of July 2021.

It will take the best part of the next 10 to 12 days to see the weather shift, that meaning high pressure sets up over the eastern and southern states, the wavy westerly flow moves south with the SAM trending neutral or positive. That will allow moisture to build up over the northwest of the nation and be able to be drawn down into the next front that arrives through WA mid month (timing will chop and change).


But the overall point of showing you these two images is the pattern flip that is taking place slowly during this period.


GFS 18z Pressure Pattern from 18000ft through to the surface - Wednesday 11th of August 2021.

GFS 18z Pressure Pattern from 18000ft - Next 2 weeks.

The best way to show the shift is in the flow pattern over the coming 2 weeks, and you can see the heights recovering to above average with high pressure over the southern states after the last week of westerly wind dominance. That will mean the pattern can flip and allow a reset on moisture pooling through the nation, especially over the northwest of the nation. The pattern flipping will introduce warmer air into the southern parts of the nation, allowing for the jet stream to reconfigure and align itself more northwest southeast, as opposed to the west to east trajectory, again opening the door for the moisture to draw through the northwest of the nation, via the interior and then into the southeast or eastern inland. This is more inline with the rainfall chances increasing for the second half of August. We need to see the pattern flip first and we are now starting to see hints of that occurring.

The repositioning of the high pressure system into the east will see easterly winds redevelop for the first time in a long while, since the beginning of this month which lead to the heavy winter rainfall for inland QLD. This will allow the moisture over the east track west and lift heat levels over Cape York, NT and WA. That is very important for rainfall for the eastern, southern and central parts of the nation.


With a cold front drawn in where GFS has it in the second week of August, this could be where we see the pattern flip taking shape, with rainfall increasing for inland areas, in line with the moisture drawn southeast through the interior.


But it is the second impulse that is now showing up on the modelling, this conneted to an easterly wave that is drawn over the tropics, which could see a much larger rainfall event take place for areas of northern, central and eastern Australia if that verifies.


Bottom line we are seeing the weather shifting away from the fast flow pattern.


GFS 18z Precipitable Water Anomalies for the next 2 weeks.


The temperature roller coaster will also continue with bursts of heat rolling down the western flank of high pressure that moves through at speed, followed by frontal weather and colder air, that is leading to the squally weather at the moment with a tight thermal and pressure gradient.


Rainfall for the next 10 days

The rainfall is retreating further south and decreasing in the coming days, as the frontal systems have less of an impact on the nation. They will still be skirting through, but do anticipate a drier picture coming up in the next week to ten days of southern inland parts of the nation as the pattern slowly flips and high pressure moves in over the southern parts of Australia.

State based updates coming up later this afternoon and this evening.

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