Lets get straight into the next phase of the wet weather for the coming months, the wet weather engine now emanating from the tropical north as the signals from the monsoon are increasing, looking more likely that a pre Christmas burst is developing for northern Australia.
Ahead of that, we still have easterly winds to dominate the east, low pressure running into that deeper moisture which will keep the wet signal going for much of NSW and QLD and at times for VIC.
The high humidity will dominate, though that said, ahead of the monsoon, a nice dry heat will spread from WA, though SA into VIC and NSW which will be welcome, bringing about a period of typical summer weather.
But it will not last long and it is likely that most areas over eastern and northern Australia will turn wet in the week leading into Christmas into the New Year with a good supply of moisture and low pressure bringing back the rainfall.
The west, looking dry for now, but as you know living out there, it takes one event from the northern tropics to bring the rainfall back.
That looks to last until Mid January.
Lets take a look
Rainfall Outlook Next 6 Weeks - Next 6 Weeks - December 3rd - January 17th 2022
% chance of exceeding the median rainfall for the coming 6 weeks
The past few days we have seen more evidence in the medium term that the monsoon is set to descend about 2-3 weeks early over northern Australia, where this flow peaks will determine the heavier rainfall. The further west the flow develops, say over northwest Australia, the more rainfall that will extend across the country from mid month onwards into the end of the year. If the flow is over northeast Australia into the Pacific, then the rainfall will be more widespread for QLD and NSW, drier further west. The remainder of the south and east ahead of this burst will be humid at times with widespread showers and thunderstorms near troughs of low pressure. The rainfall will be patchier the further west you travel through SA through the first half of this period but I do expect rainfall to increase once again from Christmas onwards into 2022. For the west, seasonal weather expected, that means the rainfall will be infrequent. One tropical system moving down the west coast can change this, but I am not anticipating this at this time.
Temperature Outlook Next 6 Weeks - Next 6 Weeks - December 3rd - January 17th 2022
% chance of exceeding the median temperatures for the coming 6 weeks
The cooler signal is expected to remain in place for the eastern inland towards the east coast, but as I mentioned Tuesday, this is not COLD, but more humid, cloudy and wet. The south and west may end up seeing a little bit more hot weather through the first half of this period before the moisture and rainfall returns from Christmas onwards which could tip the period leaning warming than average, but prolonged heatwaves one after the after, not likely away from the SWLD of WA. The monsoonal flow being early could bring periods of cooler weather for the NT and across Cape York with that leaning bias to cooler weather extending through the outback into the east and southeast.
Humidity Outlook Next 6 Weeks - Next 6 Weeks - December 3rd - January 17th 2022
% chance of exceeding the median humidity for the coming 6 weeks
The moisture signals remain very high for the nation, despite a period of drier and hotter weather for southwest and southern areas of the nation in the shorter term, things shift from mid to late month with more rainfall and thunderstorms expected with yet more flooding. The area that will escape the worst of it at this stage is the SWLD of WA but this can all change with one tropical low/cyclone decaying over the region and lifting moisture levels for the region, but the risk is considered low at this time.
Disease Outlook - Next 6 Weeks - December 3rd - January 17th 2022
No change from Tuesday, the wet weather, and now a shift to warmer weather with high humidity increases the risk of fungal diseases to many crops. We have now finally seen that intrusion of warmer air throughout the nations south and east. This signal does not change over the coming 6 weeks. The west may be dry for now, but there will be an increase in humidity returning through this period and with the higher temperatures this could see prolonged periods of above average humidity values.
Riverine and Flash Flood Risk December 2021
No change in the guidance from Tuesday, the data sets have not increased the rainfall as feared for eastern inland parts of the nation but I will review again next week with further rain and thunderstorms increasing over northern Australia. I may increase flood risks for the NT for the period leading into the end of the year especially if a tropical low or cyclone is in the region. Those experiencing flooding should still prepare for a 1/100 year flood with the rainfall signals very high despite a lull.
Riverine Flood Risk Summer 2021/22
The flood risk is ongoing and continues through December and January. Keep up to date with the medium term forecasts in the east as rainfall could return next week and persist again.. The weather should turn wetter over the inland of WA as tropical weather increases with that starting from the second week of December as per some of the guidance. The monsoon should start to have an impact on rainfall for the north from mid December at this stage.
The wet climate drivers are still in play, and to cut through all the content this is what you need to know. The IOD is waning still, but the influence appears to continue for another 2 weeks. I was anticipating the influence to wane by now but there is still more moisture being drawn in until mid December and an early monsoon could provide a decent amount of moisture as well. The ENSO is the driver that is taking over, with a La Nina phase underway and strengthening in the next 4-6 weeks, likely to peak in January before waning through February. The SSTs in the Coral Sea suggest that the La Nina has been underway for some time, thankfully we have now seen all global agencies including the WMO calling it a La Nina. The SAM remaining positive into early December with brief stint back to neutral values at times, but generally positive of normal is likely.
The MJO has passed through to our north in the past week and is now indiscernible with no impact expected over the Maritime Continent. With a La Nina developing and the waning negative IOD phase, the enhanced moisture, build up conditions will persist and the the likelihood of an early monsoon is gaining momentum as the MJO phase may redevelop by mid December which could assist in enhancing rainfall over the tropical north. We have seen mixed signals for the monsoon to emerge over the Indian Ocean, the Timor Sea and over the Coral Sea. This will become clearer during the next week or so.
DATA - Refer to video for more on these sets of data
Euro Rainfall Accumulation Ensemble Data - Next 6 Weeks - December 3rd - January 17th 2022
The rainfall guide continues to be excessive over the north and east of the nation with the general consensus for above average rainfall and flash and riverine flooding to feature through to early January though numbers have come down just a little bit in this run which is good news for the east, but still well above average. The remainder of the nation runs a decent chance of above average rainfall with severe thunderstorm events continuing. The monsoonal flow is expected to pass through northern Australia earlier than normal and may see 2 bursts in this period, at this time, the NT and WA into Cape York the wettest part of the nation. The east coast, watch closely.
Euro Rainfall Accumulation Control Data - Next 6 Weeks - December 3rd - January 17th 2022
Thankfully the numbers have come down a tad from last weeks and this weeks run but still well above average through much of the nation. The north seeing enhanced tropical activity. The rest of the nation at the mercy of where that moisture goes. I will mention that one run does not a pattern/trend make, the overall trend is unchanged for further heavy rainfall for much of the nation during the next 6 weeks with some areas getting clobbered and others getting spared, but those areas being spared will be few and far between. Head to the far west and south if you need some heat.
Euro Rainfall Anomalies - Next 6 Weeks - December 3rd - January 17th 2022
The rainfall anomalies remain excessive and are increasing over northern Australia. The numbers will adjust further in the coming period. Outback flooding is also likely cutting off major arteries at times through the nation so freight/logistics be aware and the monsoonal weather up north could spark some torrential early season rainfall. Very humid air coupled with the warmer persistent easterly winds nationally will increase the chance of disease to summer fruit crops and vingerons.
The Euro Control Anomalies for the coming 6 weeks - December 3rd - January 17th 2022
This has major flooding all over it, it does move it from QLD through to NSW from run to run, but the idea is still the same, FLOOD ZONES NEED TO BE ON ALERT THROUGHOUT THIS TIME. I will be here right through Christmas and New Years keeping you up to date, especially if this verifies. The first installment of this event for the east may emerge in the short term forecasts later this week. The tropical weather will dictate who gets what.
CFS Rainfall Accumulation Ensemble Data- Next 6 Weeks - December 3rd - January 17th 2022
No real change with very wet weather for the north and east and potentially tropical weather sending rainfall through the northwest to the southeast of the nation. Ignore the drier weather over interior parts, storms will fire in this area and there will be heavy rainfall potential for SA and the NT.
GFS Rainfall Accumulation - Next 5 Weeks - December 3rd - January 10th 2022
Significant rainfall signals continue for eastern Australia and tropical rainfall expected to increase over the coming weeks. The GFS adjusting to factor in the early monsoon now and the eastern seaboard is looking very wet again. The west seeing less rainfall spread but where it rains it will be heavy. There will be pockets that will be hot and dry over southern and southwestern parts of the nation.
GFS Rainfall Anomalies - Next 5 Weeks - December 3rd - January 10th 2022
The model is now showing a dry bias over the northern and western parts of the nation with the monsoon being analysed. That remains very low confidence as per last week. The high confidence is over the east and southeast of the nation where the rainfall is expected to remain well above normal and that signal is increasing as we go along. The short and medium term GFS products are wetter for northern Australia than this climate output.
CMC Rainfall Accumulation - Next 4 Weeks - December 3rd - January 3rd 2022
Significant moisture incursion in the coming 4 weeks may contain 1-2 cyclones over northern Australia with some areas with flooding potential. As you can see the moisture shears south and east through the nation and this is not good news for the remainder of 2022 with flooding potential to persist. The south and southwest of the nation will see less rainfall.
CMC Rainfall Anomalies - Next 4 Weeks - December 3rd - January 3rd 2022
The excessive wet phase is expected to continue as we run into Christmas, this has not changed since this updated last week, and what is more concerning is the fact this is additional rainfall anomalies above what has fallen over the east.. Blue shadings in a time when the north is wet spells trouble for further flooding rainfall across the nation and cooler weather. I would ignore that drier signal inland of Darwin as that is conditional. This is only the next 4 weeks which shows you how wet the phase is.
Euro Temperature Anomalies - Next 6 Weeks - December 3rd - January 17th 2022
Cooler than average signals continue for the east and that is a fair forecast. The north under monsoonal weather likely to see seasonal conditions and the west is where you will find the warmer weather through this period. The monsoon is likely to be in place during this period over northern areas which will support thicker cloud cover over northern and eastern Australia.
GFS Temperature Anomalies - Next 5 Weeks - December 3rd - January 10th 2022
The warmer signal continues to grow for the north and interior parts, this is suggesting the monsoon would not arrive but I am not siding with this solution, I do believe we will have a monsoonal flow up north reducing temperatures up north. But the interior may be warmer than first thought. The east cooler with persistent rainfall.
CMC Temperature Anomalies - Next 5 Weeks - December 3rd - January 3rd 2022
The coolest set at the moment and has been consistently cooler than other modelling with this model indicating the monsoonal weather will persist for the best part from mid month onwards. This will lead to prolonged periods of cloudiness and rainfall.
I will have fresh notes on the Summer Outlook again on Sunday afternoon and next week will take a look at the state of the ENSO and see how this La Nina is tracking.