MEDIUM TERM FORECAST - MORE FLOOD POTENTIAL IN THE EAST, MORE HEAT FOR THE WEST , MAYBE A MONSOON?

Lots going on in the medium term taking us through to mid December which does not bode well for the flood zones, some locations are looking at another month of potentially record rainfall. We have seen 200-300mm of rainfall so far for December!


In the north we have got more rainfall developing as the monsoonal flow begins to develop north of the continent. The weather is running ahead of schedule IF the monsoon does descend into the north by mid December, with that meaning the monsoon is around 2-3 weeks early.


This will mean excessive moisture will be propelled south and east of the tropics with more rain and thunderstorm activity developing.


In contrast, the west of the nation is looking hot and dry with an easterly flow persisting, the ridging remaining slow moving offshore the SWLD. SA and remaining areas of the NT will sit in the swing zone, where the weather will pass through the region, but become more amplified over the eastern states, resulting in scattered showers and storms at times for SA, the heavy rainfall potential remains to the east.


Lets take a look

FORECAST

Moisture Watch Next Week - December 8-15 2021

Moisture movement remains largely unchanged from yesterday with a very deep moisture supply passing through northern Australia and then being propelled south and east, bringing up rainfall chances for the eastern and southeast states and possibly down the west coast and into interior parts of the nation. The main influence as to how far south the moisture will come is the ridge to the south of the nation. The further south the high is located, the further south the deeper moisture will go, and so that will be the feature to watch. Overall it is not looking good for those who want to dry out, but looking great for those who want more rainfall.

Rainfall Next Week - December 8-15 2021

The rainfall as mentioned in recent days will remain erratic on the global agencies, this is due to the monsoonal influence coming and going from the charts, the ridging and where that sits over southern waters of Australia and how strong the positive SAM phase gets. The ingredients are there for a rain event for the east or southeast that may eclipse what we have seen so far through this period, if not, running into Christmas. This may lead to more excessive rainfall and flooding potential.

Rainfall Anomalies - December 1-15 2021

Remaining a good chance of above average rainfall over the east and north of the country with that risk also leaning above average over the southeast, but that risk becomes near seasonal through southern SA and back over WA, where ridging will feature more often than not bringing the drier weather to these regions.

Temperature Anomalies Next Week - December 8-15 2021

Temperatures also largely unchanged in the guide, the onshore winds, rainy skies and high humidity leading to below average temperatures overall for the period over the east, this will not mean COLD, it will mean below average. Out west, the above average temperatures are a good chance through this period with persistent easterly winds, dry air heats efficiently and the ingredients are there for even a low to moderate heat wave.

DATA - Refer to video for more information.


12Z GFS Surface Pressure Pattern and Rainfall Distribution - Next 16 Days

More details in the video above.

12z GFS Precipitable Water Anomalies - Next 16 Days

Deep moisture up north will move further south, and as the south gets hotter, the more moisture that will be able to be supported by the unstable atmosphere.

12z GFS Rainfall Accumulation - Next 16 days

The driest out of the the three through the 2 weeks, and more erratic from run to run.

12z CMC Rainfall Accumulation - Next 15 days

Rainfall numbers are becoming more widespread nationwide and I am leaning with that solution. This model also has the monsoonal flow in the Pacific Ocean.

12z Euro Rainfall Accumulation - Next 15 days

I will use the control member here to show you, as per yesterday, that members underpinning the mean data sets are wetter and some are drier. The majority lean wet and this is one scenario. The east coast needs to watch carefully through December 8-15 for heavy rainfall potential.

Remain weather aware today with the ongoing flood risks over the east and plenty of thunderstorms likely this afternoon through multiple areas.