The focus of the heaviest rainfall has been parked over the east for weeks, with a significant area of moisture constantly being lifted by low pressure troughs that are propelled east and west via high pressure sitting to the south of the nation, cradling the troughs and the moisture, leading to this daily dose of rainfall.
The troughs are causing heavy rainfall tonight and at times through next week with the risk of flooding ongoing as mentioned in your updates this evening.
The drier bias over the west and southern parts of the nation will eventually be over ridden by moisture seeping south as you will see below with that flaring into showers and thunderstorms. The low pressure will help to push the high pressure further south leading to the rainfall coverage coming up into the medium term.
Lets take a look
The short term offers the heaviest rainfall once again over northern NSW and central and eastern QLD with multiple rounds of showers and storms (some are underway this evening). The remainder of the south and west are looking quite a lot drier with the ridge in place for much of this week and fresh easterly winds. The tropics getting active but nothing too outrageous just yet.
UKMET - Rainfall Next 7 Days - MODERATE CHANCE
A little more generous on the rainfall front for the eastern parts of NSW and VIC but has the heavy rainfall smear through QLD and northern NSW. Note the position of the trough is everything. If you are to the east of the trough you are likely to see some rain and a thunderstorm. If you are west of the feature, dry for a while.
The medium term forecast remains wet and unsettled for northern areas of the nation with the usual build up of thundery weather most days. The moisture from the tropics will start to feed the trough developing down the west coast so the coverage of thundery weather will increase inland areas of WA, maybe as far southwest as the SWLD and the southern coastal areas. The moisture will also run into eastern QLD with scattered showers and thunderstorms developing once again for western and central areas. Along the east coast of QLD extending down into NSW, there is likely to be another trough combining with easterly winds leading to more showers, heavy falls possible on and east of the divide and the moisture eventually will spill into VIC sparking unsettled weather in the easterly flow. For SA, you will be the last to see the thundery weather develop but it comes towards the end of the first week of December.
ICON - Rainfall Next 8 Days - VERY LOW CHANCE
Way too dry for the period nation wide.
CMC - Rainfall Next 10 Days - MODERATE CHANCE
This is a complex set up on the CMC and has one system this week which clears through but another system to follow next week with further rain developing over the interior of NSW and QLD. Has the trough running down the west coast of WA with storms and showers developing and moisture increasing over the interior.
EURO - Rainfall Next 10 Days - MODERATE CHANCE
Has the trough in the right spot and is increasing rainfall as per UKMET for the eastern third of NSW with this feature coming through later this week. Widespread storms for QLD and storms and showers building for WA which is the right call as that moisture spreads south into SA. The upper level winds may carry the moisture back towards the east away from the west coast.
ACCESS - Rainfall Next 10 Days - MODERATE CHANCE
Heavy rainfall through QLD is quite likely under the current synoptic scale, but who gets what in QLD remains to be seen. The showers and storms also increasing for parts of VIC and southern NSW with the feature later this week. Also has the storms and showers descending through WA and into SA at the end of the run.
KMA - Rainfall Next 12 Days - MODERATE CHANCE
Also has heavy rainfall for QLD extending into northern NSW with the feature this week and another east coast trough next week which needs to be watched. Tropics active with again that idea of the moisture spreading throughout WA and then into SA gaining momentum. That will likely spawn a rain event nationwide mid month.
GFS - Rainfall Next 16 Days - LOW CHANCE
The nation trending more unsettled as we go through the period. Not as amplified in the short term for VIC and southern NSW/ACT with the system later this week. Has the rainfall heavy in places through QLD this week and again next week. Moisture running down through WA and SA develops later than the other models, but the idea is the same in that spread southwards. Tropics too dry.
It has been non stop in predicting the wettest weather over the east of the nation and this bias continues for the coming 15 days which is just remarkable. The flooding at this rate may be with us until Christmas.
GFS - Rainfall Next 16 Days (median of 35 members) - MODERATE CHANCE
Similar to the CMC and wetter than the deterministic for the same period.
CMC - Rainfall Next 15 Days (median of 30 members) - HIGH CHANCE
Much wetter than the other two but it has picked the rainfall events of October and November well ahead of the others.
EURO - Rainfall Next 15 Days (median of 51 members) - MODERATE CHANCE
Has more widespread falls than the deterministic, and spreads more rainfall over northern and eastern Australia and down the west coast in the medium term.
And the very wet weather continues into New Year and early 2022
GFS - Rainfall Next 5 Weeks - MODERATE CHANCE
Taking us to the end of the year and it is looking wet for many of us.
CFS - Rainfall Next 6 Weeks - MODERATE CHANCE
Wet through to mid January as well with this smoothing out the rainfall but there will be some very wet locations in the NT, QLD and NSW through the coming 6 weeks.
More tomorrow from 7am EDT.