MODELS AND RAINFALL - AS PROMISED THE RAINFALL WITH STORMS DRIVING BIG FALLS OVER THE EAST.

That is a sign of what is to come this season with the high risk of flash flooding and ongoing riverine flooding. Many of you who have been here for a while have seen the charts posted back in October for this period and I dare say they have verified well Just because it is happening in the east at the moment, if you are living in SA and VIC through to WA, your time will come a number of times this Summer too.


This weather will be featured many times over the course of the longer term.


Lets look at the short and medium term regarding rainfall.


Flash Flood Risk December.

Just a reminder on the risk areas for the flash flooding potential throughout the coming month and we have already finished November with flash flooding in many areas of NSW and QLD today. The risk extends throughout as we see the monsoon get involved in the weather pattern for the back half of December while it continues over the east.

Riverine Flood Risk

The riverine flood risk is very high over many areas at the moment and is expected to expand to other regions throughout December and through Summer. Some areas could see a 1/100 year flood scenario in the coming months over QLD and NSW.

To the data sets

SHORT TERM

The short term offers no real change to the guidance, the west remaining largely dry and settled with ridging. So southern WA through SA and into the southern NT, relatively dry for now, though watching a mid level trough over the weekend which may bring a few showers and storms. The next major rainfall for SA and VIC will likely be next week with a sharp trough and low For the short term out east, the heavy rainfall will ease to showers and thunderstorms throughout the course of the next few days with a southerly change and trough then stalling out over QLD next week kicking off the next storm event for the flood zones. The northern tropics, rainfall increases from this weekend with a couple of tropical waves passing through.


UKMET - Rainfall Next 7 Days - VERY LOW CHANCE.

Has lively thunderstorm activity for NSW and QLD in the coming days dipping down into eastern VIC. Then has another trough coming into the east next week with yet another round of showers and storms. But otherwise it is way too dry for the north.

MEDIUM TERM

The medium term is messy, as outlined in the evening weather video, the monsoonal flow is heading south from the equator and the MJO is over the western Pacific through this period. We may start to see the models enhance rainfall over the tropical north with a westerly flow developing for the NT and QLD, northern WA may be a little too far south. That said, the impact is the same with more rainfall coming into the northern parts of Australia and potential cyclone activity. For the remainder of the nation, a deeper trough over QLD, NSW and VIC will drive showers and storms and heavy rainfall is once again possible. The western interior will have moisture increasing down the axis of a trough line. Moisture will get to SA but as is common at this time of year, the moisture can avoid the region with high pressure in the region keeping things settled.


ICON - Rainfall Next 8 Days - VERY LOW CHANCE.

No...

CMC - Rainfall Next 10 Days - MODERATE CHANCE.

The uneven distribution of rainfall is likely throughout the nation but it is spreading out the rainfall gradually over SA, the NT and back through the eastern states with each run. So that is something to watch. This model has the monsoonal flow in the ensemble data set.

EURO - Rainfall Next 10 Days - MODERATE CHANCE

The Euro showing the rainfall over the east in the coming 2 days and then again next week and the moisture from the north is increasing in line with the tropical waves passing through from the weekend into next week. The west is dry but this could easily change with the trough moving around the western interior.

ACCESS - Rainfall Next 10 Days - MODERATE CHANCE

This has the rainfall distribution right and is picking up the developing tropical increase in weather as a low near Darwin, classic signalling from the models that the wet season is about to ramp up. The east is wet with deepening low pressure again next week.

KMA - Rainfall Next 12 Days - LOW CHANCE

Significant rainfall for the northern and eastern parts of the country but I do believe that this model has got the distribution wrong at this time.

GFS - Rainfall Next 16 Days - LOW CHANCE.

It is a lot drier than the ensemble data set which suggests to me that this is under doing the rainfall potential for the nation as a whole and expect more changes in the coming days and erratic rainfall patterns.


ENSEMBLE DATA

Ensemble data starting to pick up on the monsoonal flow potential, but also noting the rainfall bias is unchanged for the east. Drier conditions west, but some of the data sets below now recognising the moisture from the tropical north may indeed shift further south throughout the outlook period, so your numbers will bounce around.


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

The wet signal continues to build but the GFS is slower than the other models.

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

CMC sees the monsoon flow coming into Australian waters during this period and that is why numbers are increasing over Australia. I am leaning with this solution.

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

Wet and the monsoon is now starting creep into the medium term forecast on this particular product.

LONG TERM

The wet weather continues as I outlined in the longer term forecast today, numbers are increasing and becoming quite concerning for flood zones. For the northern tropics, the monsoon is getting closer and we may see an early burst and another burst in early January.


GFS - Rainfall Next 5 Weeks - HIGH CHANCE

Northern and eastern areas of the nation should remain on alert with the monsoon on the approach in the coming weeks and the persistence of low pressure and deep moisture over the eastern states. Interior parts can expect more rainfall than what is advertised here.

More details coming up from 7am EDT.




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