MODELS AND ALL THINGS RAINFALL

The model madness continues for the short and medium term with divergence in the guidance, not unusual when you have a rather amplified pattern and a deep layer of moisture across the nation. The guidance will become very volatile from run to run as we are dealing with 2-3 events sweeping the nation as well as the event currently in play over the east.


Lots on the board so lets take a look at each of the global models and my ranking of plausibility is next to each so you can see where I am going with my forecasts for your region.


Riverine Flood Risk - Next 6 Weeks. November 5th through December 21st 2021

I will have more on this in tomorrow's Harvest Outlook from late Friday morning

SHORT TERM

Extensive rain over the eastern parts of NSW and into VIC will continue to fall overnight and into Friday. The moisture is deep through areas west of a trough, which itself is moving west overnight and into Friday through central VIC and NSW into southern QLD by morning. This will kick off showers and thunderstorms once again with flash flooding a risk through mainly inland NSW and southern QLD. The weather along the east coast will be humid with showers and some isolated thunder with moderate falls. The trough over in SA and WA tonight will continue to move east with showers increasing as this trough not only drags down deep moisture from the northwest as outlined in the medium term forecast package earlier today, but it runs into residual moisture and the trough lingering over the east during the weekend. So more widespread rainfall with scattered heavy falls for northern and eastern SA, through much of VIC, NSW and QLD. The NT wet through this period as well and into next week. Now next week, the models differ and this is impacting rainfall into the medium term. From Tuesday it is a LOW CONFIDENCE FORECAST nationwide away from the tropics


UKMET - Rainfall Next 7 Days - MODERATE CHANCE

MEDIUM TERM

The weather modelling splits with some models disrupting the flow pattern of that third trough and upper low from WA moving into SA, with a system riding out of the southern ocean and moving towards southeast Australia. This would deflect the moisture north and east through the nation, so the NT and QLD would see the bulk of the heavy rainfall and thunderstorms with this feature. The weather over the southeast would be wet and a period of stormy weather would develop later next week but the pattern would not be as wet under that scenario. The other modelling suggests that the low pressure system comes into SA and moves southeast into the low moving north over the southeast, seeing a large scale severe weather event unfold for SA, VIC, TAS, NSW and QLD extending into southern and eastern NT. This would be a one in 20 year event if it were to verify, but some of the modelling that support this idea are very wet with high end severe weather so we need to watch carefully in the coming days.


ICON - Rainfall Next 8 Days - LOW CHANCE

CMC - Rainfall Next 10 Days - MODERATE CHANCE - The east coast needs to pay attention to the trends for a deepening east coast trough too.

EURO - Rainfall Next 10 Days - MODERATE CHANCE

ACCESS - Rainfall Next 10 Days - MODERATE CHANCE

KMA - Rainfall Next 12 Days - LOW CHANCE

GFS - Rainfall Next 16 Days - VERY LOW CHANCE

ENSEMBLE DATA

Again I think these are most useful to see where the rainfall bias lay and where we can expect to see the rainfall forecasts remain fairly active and where other areas see less rainfall so these remain a better product than the above in this sequence.


GFS - Rainfall Next 16 Days (median of 35 members) - LOW CHANCE

CMC - Rainfall Next 15 Days (median of 30 members) - HIGH CHANCE

EURO - Rainfall Next 15 Days (median of 51 members) - MODERATE CHANCE

LONG TERM

Wet and unstable weather right through to Christmas looks like a fair forecast for the northern and eastern areas of the nation, with less frequent rainfall further south and west, but all points of this nation will feel the impacts of the higher moisture content during this next 6 weeks in the form of severe thunderstorms and heavy rainfall.


CFS - Rainfall Next 6 Weeks - MODERATE CHANCE

More weather details coming up from 7am EDT.

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