MEDIUM TERM FORECAST - THE CONVEYOR BELT OF LOW PRESSURE SYSTEMS AND HUMIDITY RAMPING UP.

We have had a taste of what is to come in the next 6 weeks with wild weather lashing the southern and eastern states. I really am hoping that we don't see further severe damage as we did yesterday through parts of SA and into western parts of VIC and wind damage to crops over the inland of VIC


Unfortunately more wild weather is on the way next week with another strong trough to extend from northwest to southeast with a deep moisture profile. This system has more moisture available to it, and as we have just seen with this past system, the weather was high impact.


The difference in the system next week is the absence of a deep low pressure system which may mitigate the high end thunderstorm activity, however the moisture is deeper and the moisture is expected to hang up over the southeast and eastern parts of the nation, rather than being swept out, so that is something to consider. Higher humidity will be of a significant impact to crops without rainfall and thunderstorm activity being present.


Otherwise the tropics are looking very active during this period taking us through to mid November. The southwest of the nation is looking cooler than normal under persisting ridging, seasonal temperatures elsewhere with higher humidity values. The weather is expected to be dominated by persistent easterly winds over the nation.


Climate drivers, the positive SAM and the negative IOD phase are in combination to bring these higher rainfall chances. The Coral Sea is also well above average in terms of temperature and that is a signal that the La Nina is forming in the ENSO region.


A longer term forecast has been prepared taking us through December which is pinned to the top of the page.


Lets take a look

FORECAST

Moisture Watch This Week - October 29 - November 5th 2021

We have had one impulse of moisture work it's way through the southeast and east of the nation in the past 48hrs and that is lifting through NSW and QLD today. The next pulse of moisture will come down from the northern parts of the nation through early next week into a trough which will bring another batch of showers and thunderstorms for SA, VIC and NSW. There is likely to be a large impulse of moisture passing through Indonesia and into NW WA mid to late next week with another band of rain and storms developing from northwest to southeast.

Moisture Watch Next Week - November 6th - 13th 2021

No change for the high moisture content throughout the nation with the troughs over central and eastern Australia leading to high impact showers and thunderstorm activity. The high humidity will continue to deepen through this period and this could lead to issues away from rainfall with the soupy, warm air impacting crops ready for harvest.

Rainfall This Week - October 29th - November 5th 2021

Rainfall is still low confidence as we track through the next week, and again with the position, timing and scale of a trough that is moving in from WA, through SA and then the southeast from mid next week. Severe weather potential exists through mid next week for SA, through VIC and western NSW. The northern tropics are expected to be very humid with showers and thunderstorms increasing in coverage and spreading south and southeast as well simultaneously with the southeast storm outbreak. The east coast seeing showers and storms over the coming days then showers increasing in easterly winds next week.

Rainfall Next Week - November 6th - 13th 2021

Rainfall increasing over northern parts of the NT with scattered to numerous showers and thunderstorms north of a trough that will stall out over the base of the Top End. Deep moisture from the north will surge southeast through SA into the eastern inland with a number of troughs lifting this into showers and thunderstorms. Again high humidity leading to excessive rainfall potential with thunderstorm activity. The west is expected to be drier under the upper ridge extending in from the Indian Ocean.

Rainfall Anomalies - October 29th - November 13th 2021

As you can see on all the data sets, the rainfall is expected to be extensive over parts of northern and northwest Australia with highly anomalous rainfall potential spreading through the outback and into SA and the eastern interior. Some of the falls could break records for some outback communities through the NT and into SA. This is inline with the negative IOD phase peaking and higher than average SSTs across northern Australia.

Temperature Anomalies This Week - October 29th - November 5th 2021

The warm tongue of air is still working it's way through the northeast of the nation today ahead of a trough before the heat gets propelled back through to the NT and then modified under humid air and recycled through the southern and southeast parts of the nation next week ahead of the next system. The southwest of the nation cannot get out of the persistent onshore wind flow, again not COLD, but cooler than normal values expected.

Temperature Anomalies Next Week - November 6th - 13th 2021

The cooler bias continues for large parts of the southwest and through interior parts through to the eastern and southeast inland, under the current guide of widespread cloud cover and areas of rain and thunderstorm development. This does not mean COLD, it means cooler than average and with humidity values running high, the impact will be moot. For northern areas of the nation the temperatures should begin to moderate, though an upper high floating over Cape York may keep things sultry and very hot.

SEVERE WEATHER OUTLOOK NEXT WEEK

Severe Weather Outlook Tuesday

Heads up for the next storm system coming in from the west and linking up with deep moisture profile through the central parts of the nation surging south and another trough running into this moisture and this leading to showers and thunderstorms developing. The moisture and atmospheric instability is deeper, more widespread and this will lead to a good chance of severe thunderstorms returning to much of SA from Tuesday at this stage, clipping the southern NT and the tri state regions. The weather humid and warm over SA and VIC/NSW. Upper ridge of the east keeping the weather fine.

Severe Weather Outlook Wednesday

The lead trough slowly moves eastwards and there is likely to be an active area of thunderstorms develop on and east of this feature over eastern SA and through to western NSW and VIC. Humid air throughout the east and southeast will mean thunderstorms will be excellent rainfall producers and all modes of severe weather are possible, but large hail may be a lesser risk at this stage.

Severe Weather Outlook Thursday

The trough sharpens during Thursday of next week and with a very deep moisture layer in place, storms will be easily able to produce flash flooding and damaging outflow winds. With PW values near 50mm over inland areas, these storms will be dumpers. There is also a chance of thick cloud cover about the eastern and central inland under such an environment which could be a mitigating factor against high end severe weather next week but at this stage, this is a flagged area for widespread showers and thunderstorms with heavy falls possible.

DATA - Refer to the video above for more

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

18z GFS Precipitable Water Anomalies - 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

More details coming up this afternoon