MODELS AND ALL THINGS RAINFALL - THE MEDIUM TERM AS FORECAST HERE - GETTING WET AND HUMID.

And this is why I like to keep these daily updates going for the medium term to show you patterns and to tell you what to watch and what to disregard. The theme of wetter for the start and end of December as forecast here in November is fair and looks to verify quite well.


Now how wet will be determined by the tropical activity over the northwest and northeast of the nation and by how far south the high pressure system will ridge. The further south of the mainland, the more likely the easterly winds will be unstable for most areas of northern, eastern and central parts of the nation.


The two tropical lows could work with each other and produce two deep moisture ports seeing rainfall increasing across the nation.


That said, only a few models are showing this so it is important to recognise that.


The short term remains much drier than the previous 12 weeks which is good news, but that drier signal is set to come to an end around Christmas across the nation.


SHORT TERM

A couple of week troughs with scattered showers and storms across pockets of the country will dictate rainfall distribution over the course of the next 7 days so no widespread heavy rainfall or severe weather events relating to rainfall is expected. Even the tropics remain fairly quiet until the weekend, that is when the rainfall rates increase again for the region.


UKMET - Rainfall Next 7 Days - MODERATE CHANCE

No real change from last night's guidance, but the coverage of rainfall through the weekend over VIC, NSW and QLD could be increasing as will the secondary trough over WA through SA early next week. Something to watch.



MEDIUM TERM

Rainfall chances come up over tropical Australia during Christmas and into NYE. The weather over the central parts of the nation will turn humid first and then into the eastern inland as well, thus seeing the showers and thunderstorms returning daily. The west coast trough also becoming more active with moisture streaming into the feature as well. This will lead to more scattered falls, where dry thunderstorms will feature in the short term. The interesting features to watch will be over the northwest of the nation, whether a tropical wave forms into a cyclone, shearing moisture into the nation's northwest and central areas. The other, a high combining with a trough over the Coral Sea could see showers increasing for much of QLD and NSW. Both of these funnelling moisture into the southeast over this period.


ICON - Rainfall Next 8 Days - VERY LOW CHANCE

No - way off.

CMC - Rainfall Next 10 Days - MODERATE CHANCE

This is now starting to pick up on the moisture building via easterly winds over QLD and NSW and the tropical weather becoming more active as moisture returns as does the development of troughs through the region. The rest of the nation seeing periods of unstable weather but no organised rainfall events expected in this period, but may develop after Christmas.

EURO - Rainfall Next 10 Days - HIGH CHANCE

The rainfall is increasing every run over the northern tropics and the hit and miss showers and storms for the remainder of the nation from time to time is a good solution. The fast flow pattern to the south of the nation supporting the weather becoming changeable over southern Australia and that means rainfall opportunities will move through quickly and the humidity unable to really build up to very high levels over the east and central areas until this pattern relaxes.

ACCESS - Rainfall Next 10 Days - LOW CHANCE

Rainfall is still probably a little too widespread in the short term as compared to other models, but the idea is right that moisture and rainfall will be increasing, the ACCESS maybe a little too quick on that idea. Most of this to fall after Christmas I would think.

KMA - Rainfall Next 12 Days - LOW CHANCE

It has been more volatile in the past few days and offers heavy rainfall for the east. And while that does look to kick off from after Christmas, the coverage of rainfall elsewhere is far too elevated for this period.

GFS - Rainfall Next 16 Days - LOW CHANCE

A low chance with the tropical moisture over the north and east appearing this evening for the first time, after this model ran driest out of the three. What the data is expressing is that there is likely a shift in the weather coming up over the course of the end of the year and the start of 2022.

ENSEMBLE DATA

The broader data sets are getting wetter as we go through the period, some members, not all, do have some robust tropical weather developing across the north but the location, scale and impacts will become clearer as we get into next week. For now, the rest of the short term is looking similar to what we have now with scattered falls. The medium term turns wetter and humid and Christmas for some locations will be very warm and humid and possibly unsettled.


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

Only giving this a low chance due to the high impact weather that has just emerged in the latest run, where it has been running very dry for the past week. Will monitor trends over the days to see how this data stacks up.

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

I do think this is probably closer to the post given the moisture building over the north and east and the signal shifting wetter thanks to the positive SAM and the deepening of troughs over northern Australia. Drier the further west and southwest you go.

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


LONG TERM

I outlined this today in the Longer term forecast, but the wet signal is red hot for January.


CFS - Rainfall Next 6 Weeks - MODERATE CHANCE

The wet spell continues for the east and that will emerge through the end of the month and for the first half of January. The monsoon is expected to return from mid January.

More coming up from 7am EDT.


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