MEDIUM TERM FORECAST - THE NATION IS WARMING UP - THE STORMS ARE BECOMING MORE WIDESPREAD.

We are in another transition period through to the warmer season now, with the weather starting to turn over northern areas this past week, we have seen the uptake in showers and thunderstorms over the northern tropics. We have seen an uptick in the severe storms over QLD and NSW which is always a sign of the season shifting and we are losing the westerly wind profile during the coming week as well.


All signals leading to a warmer nation, a much more stormy nation where rainfall is now derived out of the tropics, inland troughs and moisture streaming in from the warmer waters surrounding northern Australia. The frontal weather is now having lesser impact, meaning the moisture cannot be swept out as efficiently as say 6 weeks ago.


That means that rainfall intensity is going to increase as we go through the weeks ahead with more storms involved and a warmer airmass can hold more moisture resulting in more productive rainfall and vigorous thunderstorm development, which have experienced in the past 10 days.


Lets take a look

Moisture Watch This Week - October 20-27 2021

Watching the ongoing troughs over the east and the trough coming through SA today collapse but leaving some moisture behind, but an upper high and ridging will suppress that moisture until it emerges over the the GDR in NSW and QLD with showers and thunderstorms again this weekend. A deeper pulse of moisture will pass through the NT into WA and then swing southeast in upper level winds and begin the journey into the southern states next week.

Moisture Watch Next Week - October 28-November 4 2021

That moisture from the previous week will be over the southeast and eastern inland with showers and thunderstorms ongoing. The tropics are hot and humid and unsettled. Another pulse of moisture will be drawn in from the Indian Ocean ahead of a southeast moving cold front which will drag that moisture throughout the nation with another rainfall and storm event for southern and eastern Australia. Storms and showers will continue in humid air for much of QLD.

Rainfall This Week - October 20-27 2021

A weakening trough over SA will bring spotty showers and high based storms, this trough will emerge over the southeast and east this weekend and fire off storms in better moisture. Easy to pick out the region of stable air over the east with rainfall chances on the periphery of this high pressure system. Moisture being projected into coastal troughs will see showers continue with thunderstorms for the east coast with uneven distribution of rainfall. Tropics unsettled in northeast to easterly winds with showers and storms. That moisture will be moving southwards on the western side of a strong ridge and being propelled into SA later in this outlook period before turning southeast. After showers over the southwest today, things dry until Monday when another batch of showers passes through.

Rainfall Next Week - October 28-November 4 2021

Tropics expected to get wetter with a deepening trough over the NT and extending through northern WA and Cape York. Has been hints for an upper trough over QLD which may increase rainfall chances there. Moisture from SA turning southeast from the previous week will be picked up by a trough and see more widespread rainfall for VIC and southern NSW as the trough moves through, scattered falls for SA. Another pulse of moisture will emerge at the end of the month through early November which may be captured by another trough passing over southern WA, this bringing another burst of showers and thunderstorms for SA and then into VIC and NSW. Storms continue off and on for much of QLD with the inland trough oscillating west to east.

Rainfall Anomalies - October 20-November 4 2021

I have removed the drier bias over the eastern inland through this period because we have two systems to watch which will bring uneven rainfall distribution, so at this time, it is a flip of a coin as to whether you get above or below average rainfall, but more likely that values will be closer to seasonal expectations. The west is trending drier now with another 2 systems for the SWLD with light rainfall at this time. The northern tropics and over the east coast, damp, storms and showers appearing most days through this outlook period which is above normal activity for October.

Temperature Anomalies This Week - October 20-27th 2021

Temperatures are expected to be running above average for much of the north and we are likely to experience that warmth moving south and east during the coming weekend ahead of a trough and again next week as the high consolidates over in the east. Over in the southwest, your temperatures warming up but another cooler shift expected next week with a new high ridging in following a front. Seasonal conditions for the east coast.

Temperature Anomalies Next Week - October 28-November 4 2021

Heat levels will increase for inland areas of the nation, with near certainty of above average temperatures for the heartlands. The eastern inland warm to hot and becoming humid with a northeast to northwest flow. The southwest remaining cool for now with persistent ridging and the tropics may start to see some reduction in the high heat levels with more rainfall about.


DATA - Refer to the video for more details


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

Note the repositioning of high pressure further south over the course of the next week or so. That will assist in bringing the moisture and warmer weather further south so prepare for more warmth nationwide, away from the SWLD.

18z GFS Precipitable Water Anomalies - Next 16 Days

Higher moisture values over the north as mentioned will be moving south over the course of the next 10 days - note the drier air trapped under the ridging keeping rainfall chances low for much of the eastern and central inland - normal, nothing to worry about. The thing to worry about is the Indian Ocean influence and tropics being active, flooding risks will be elevating through the run into Christmas.

18z GFS Rainfall Accumulation - Next 16 days

Rainfall numbers are coming up and will bounce around - so stay tuned.

12z CMC Rainfall Accumulation - Next 15 days

12z GFS Rainfall Accumulation - Next 15 days

More details to come throughout the day.

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