MEDIUM TERM FORECAST - THE TROPICS TAKING OVER THE NATION

The forecast lead in for this long duration humidity and storm outbreak has been well modelled in the past week and now it is starting to unfold with many areas now starting to feel that humid air coming in today, coupled with the warmer weather too. That will start to be lifted into showers and storms by a trough through much of the NT through SA and into western QLD, NSW and northwest VIC tonight with a soupy and humid unsettled day expected over the southeast tomorrow.


The showers and storms will re fire once again along the trough through NSW during Wednesday and Thursday with heavy rainfall leading to flash flooding the main risks at this time.


The trough looks to get stuck over the east of NSW and QLD during later this week into the weekend being fed by an onshore northeast flow, that could surprise with extensive rainfall more than what modelling is showing and the potential for severe thunderstorms this weekend over NSW, the ACT and southern QLD.


Another trough comes through this weekend over SA with more rain and storms, thanks to that soupy airmass lingering over the eastern two thirds of the nation. That will see scattered moderate falls and isolated heavy falls with thunderstorms with severe weather also possible. This trough likely to merge over the eastern inland of the nation with the lead trough.


Another trough will form early next week with yet another band of rain and thunderstorms to pass through Central Australia, perhaps bypassing the southern coastline, but don't write that off just yet, but more likely to see further humid weather, showers and thunderstorms from northern SA through to NSW and QLD with above average rainfall.


Another trough is expected to form mid month with similar rainfall expectations for the areas mentioned above.


The southwest of the nation, settled under persistent ridging, that ridge will eventually pass south of the nation mid month, and how far south that sits will determine how wet the nation will be under a broad scale easterly flow.


Lets take a look

FORECAST

Moisture Watch This Week - November 2nd-9th 2021

No change in the guidance. The moisture impacts are now starting to increase and note that this afternoon over the nation, widespread convection will develop in the day time heating process. Tomorrow, the showers and thunderstorms will develop over the southeast and eastern inland as low pressure lifts the moisture into productive rain and thunderstorms.

Moisture Watch Next Week - November 10th-17th 2021

No change, the nation under the influence of moisture though stable air over the southwest of the nation will keep things dry for now, however as explained, the moisture could easily be drawn southwest into the SWLD with a westward moving upper low, will watch that trend. Otherwise no change elsewhere from yesterday.

Wildcard Systems - November 10th-17th 2021

Keep an eye on these regions beyond the weather systems we have on the board in the short term, these could pack a punch, especially over the eastern inland of the nation. The SWLD of WA carries a lower risk.

Rainfall This Week - November 2nd-9th 2021

The nation is under a very humid airmass and many over the east and north have felt that in recent days, now SA, VIC and NSW are starting to feel that in combination in the rise in temperatures. The rain expected to break out over SA today through VIC and NSW tomorrow and QLD from today but eastern areas from Thursday and Friday. Rainfall over the outback through WA and the NT will be near record levels through this week, with some locations possibly picking up 6 months worth of rainfall from thunderstorm activity.

Rainfall Next Week - November 10th-17th 2021

Rainfall is expected to be widespread, moderate to heavy near troughs as the soupy airmass lingers over northern and eastern parts of the nation. As mentioned, SA sits on the edge of where the troughs deepen and then link into moisture to produce widespread rainfall but storms will still bring some a month's worth of rainfall. The west is dry under ridging but this could change if an upper level system emerges. The tropics continue to run very wet and humid.

Rainfall Anomalies - November 2nd-17th 2021

Rainfall bias to the wetter phase is continuing to expand over much of the continent. Near record values of rainfall possible over parts of the NT and through this period. That deeper moisture profile will be sheared east through upper level winds and lifted into above average rainfall chances through the eastern and southern states The configuration of the synoptic scale lends itself to being very wet over the eastern two thirds of the nation, where the west coast under ridging and drier air supported to be near seasonal. Values over eastern NSW may increase further and extend into QLD.

Temperature Anomalies This Week - November 2nd-9th 2021

The heat values over the interior will start to decrease as we see more cloud and rainfall emerge near inland troughs and deeper moisture profile leading to the temperatures struggling to rise freely. Persistent onshore winds over the southwest coupled with inland cloud leading to cooler weather. Onshore winds over the east coast with cloudy skies keeping things humid, but the day time temperatures may be below average. Heat levels may decrease over northern areas from this weekend.

Temperature Anomalies Next Week - November 10th-17th 2021

No change from yesterday for this period with a very cool spell expected for much of the nation, no necessarily cold, but certainly a humid, cloudy and wet phase is likely to unfold for much of the nation. We will see cooler weather back in the SWLD due to ridging that will slowly move through during the first half of November and the north of the nation will have a reduction in temperatures with more rainfall developing.

DATA - Refer to 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

Your number will vary with thunderstorms. I cannot highlight that more.

12z CMC Rainfall Accumulation - Next 15 days

12z Euro Rainfall Accumulation - Next 15 days

More details to come this evening in your state based forecast and later tonight in the rainfall wrap and looking at the data across all agencies with my quick fire analysis of each.