MEDIUM TERM FORECAST - PATTERN FLIP ON THE WAY.

An upper high has been parked over much of the north and northwest of the nation suppressing rainfall, well that feature is now likely to set up camp over in the central and eastern inland of the nation with a firm ridge to keep things settled and rainfall chances suppressed for the coming 7-10 days for a good chunk of SA, NSW and VIC.


This will allow the pattern to flip, increasing the moisture and thunderstorms chances over northern Australia. The western interior of the nation will see their first belt of thunderstorms and showers, thanks to an upper trough and heat low passing over the region with moisture streaming into the feature from the north.


That will see the high nudge east and warm up the southeast and eastern inland of the nation. Some areas over SA, VIC and NSW could see their warmest run of weather so far this Spring. NSW and VIC likely to see their driest spell so far this Spring. I might add, it could be the only dry spell for the remainder of Spring on current guidance. More on that in the Harvest Outlook


Lets take a look at the medium term

FORECAST


Moisture Watch This Week - October 19th - 26th 2021

The moisture distribution largely unchanged from yesterday as the pattern begins to flip this week. We have that large ongoing plume of moisture through the SWLD of WA today and that sweeps eastwards as we track into the back half of this week, but it will be shunted south by the blocking over the Tasman. That is influencing moisture content for the east coast with troughs lurking about, that will activate into showers and storms. Obviously deeper moisture running through the northern tropics with the usual build up noise.

Moisture Watch Next Week - October 27th - November 3rd 2021

No change from yesterday, still watching the shift in the pattern continue through the end of the month, and this will bring moisture into WA and feed a trough producing showers and storms, some of the models introduce this into SA and then the eastern inland for the end of the month and to kick off November. That would be the more likely time for rainfall chances to pick up for the east and southeast inland once again. Over the north, hot and humid with a deeper moisture layer in place.

Rainfall This Week - October 19th - 26th 2021

Can pick the upper high over the central and southeast inland suppressing rainfall chances for much of this period. The rainfall chiefly coastal in the east and southeast. The better rainfall is expected over the southwest of the nation with the front passing through today and once that is off the board, the rainfall chances look best over the northern tropics through the outlook for now.

Rainfall Next Week - October 27th - November 3rd 2021

Rainfall chances then increase from the tropics through northern and central WA as a trough deepens over the western interior of the nation. A heat low may carry that moisture and rainfall chances into SA and then onwards into the southeast of the nation as a trough snakes east. With a positive SAM, I am expecting more rainfall to develop along the east coast with showers and thunderstorms throughout this period, this may also feed a trough moving out of WA.

Rainfall Anomalies - October 19th - November 3rd 2021

No much change from yesterday, still have the drier bias over the southeast and eastern inland with an upper high. The rainfall chances will be below average for this week over the eastern and southeast inland. You will find better odds on the periphery of the upper ridge through northern Australia. The rainfall chances begin to extend south through the NT and into WA with a northeast to northerly flow in the upper levels This may begin to increase rainfall chances for southern and eastern inland parts of the nation after the dry spell from the end of the month into early November.

Temperature Anomalies This Week - October 19th - 26th 2021

Below average temperatures over the west for much of this week, but not freezing just onshore winds keeping the temperatures below the norm until about Thursday then a nice warm up. The cooler weather over the southeast and east will also recover by the end of the week with a period of warmer than average weather developing. The northern tropics, stifling under an upper high for this week with humidity values through the roof.

Temperature Anomalies Next Week - October 27th - November 3rd 2021

The tropics remain foul. That warmer and humid weather will begin to move south through the nation. The cooler than average bias will continue over the western parts of WA with persistent ridging and over the east with onshore winds developing and perhaps an increase in rainfall chances. Warmer weather continuing for much of SA and into western NSW and northern VIC.



DATA - Refer to the video for more details


18Z GFS Surface Pressure Pattern and Rainfall Distribution - Next 16 Days

18z GFS Precipitable Water Anomalies - Next 16 Days

18z GFS Rainfall Accumulation - Next 16 days

12z CMC Rainfall Accumulation - Next 15 days

12z Euro Rainfall Accumulation - Next 15 days

18z GFS Temperature Anomalies - Next 16 days

More details to come soon.