Plenty of people wrapping up the harvest season at the moment as we edge towards Christmas, so the obvious shift post Christmas will be to the sowing season. So what are conditions looking like nationally?
Lets take a look
What a significant week of rainfall across the nation, all thanks to the three drivers working together to promote these large scale rain events. The IOD is now resolved. It has contributed to the heavy spring rainfall and early build up over the tropics as well. The SSTs in the Coral Sea suggest that the La Nina has been underway for some time and the monsoonal flow has arrived out east of the nation (thank goodness) with TC Ruby running through the Coral Sea.. The SAM is still positive and expected to remain positive through until mid January at this time.
The MJO has moved into the Coral Sea and Pacific Ocean and the result has been the development of TC Ruby which is now moving southeast. It has meant a break in the above average rainfall conditions. The weather is expected to turn wetter as we go along in the medium term, with daily rainfall increasing. The weather turning monsoonal in early to mid January when the MJO returns to the maritime continent.
DATA - Refer to video for more on these sets of data
Rainfall Outlook - Next 6 Weeks - December 14th 2021 - January 28th 2022
% chance of exceeding the median rainfall for the coming 6 weeks
No real shift in the overall bias towards wetter as we go through the outlook period, with moisture increasing over the north and east. The remainder of 2021 looks fairly seasonal for much of the nation, maybe a little drier over the southwest and southern coasts. Wetter through the east and southeast towards the end of the year and into 2022. The first portion of January looks wet with a persistent trough over eastern and northern Australia. Once the monsoon establishes, then we will get a better idea on how much rainfall spreads across the nation and then I can be more specific about direct impacts from the monsoonal flow.
Temperature Outlook Next 6 Weeks - December 14th 2021 - January 28th 2022
% chance of exceeding the median temperatures for the coming 6 weeks
Still remaining largely unchanged, though as mentioned, we are starting to track a warmer bias in the charts for parts of the central and southern interior, which is linked to this very warm 2 week period. So I have to adjust for that, now we can see the monsoonal flow head east of the nation. The temperatures will moderate once we get the tropical weather up and running again at seasonal values. Usually following a very hot spell over the nation, this helps the troughs build over the nation and with the elevated moisture content to work with, the storm coverage will increase as we go along. The east remains cooler than normal with persistent onshore winds thanks to the positive SAM.
Humidity Outlook - Next 6 Weeks - December 14th 2021 - January 28th 2022
% chance of exceeding the median humidity for the coming 6 weeks
Thankfully the major monsoonal burst that was being modelled over the nation is expected to remain out in the Coral Sea but the monsoon will return in January. The east under persistent easterly winds are expected to combine with warmer weather to make it feel very tropical in the eastern inland extending back to central Australia. With the La Nina building conditions are expected to become more humid as we go through this period for northern and eastern Australia. The west seeing a drier 6 weeks but the values will continue to increase as we move through Summer as the monsoonal weather moves southwards across the country.
Disease Outlook - Next 6 Weeks - December 14th 2021 - January 28th 2022
The wet weather, and now a shift to hotter weather with high humidity increases the risk of fungal diseases to many crops, even as we enter a quieter week nationally. This signal does not change over the coming 4 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 as the monsoon deepens and that will have a high impact on crops and produce in the southeast and east of the nation for the end of December into January.
Riverine and Flash Flood Risk January 2022
The fact we have ongoing flooding for much of December as a flow on effect from the high rainfall, additional rainfall will continue to exacerbate this risk through until early 2022. Many inland rivers could be flooded right through Summer 2022. The risk will return for outback areas once the monsoon starts so the back half of the month into early January which will see new areas come under flood risk.
Riverine Flood Risk Summer 2021/22
The flood risk is ongoing and continues through the remainder of December and January, and with the wet signal peaking in February, the flooding is here for a while. Keep up to date with the medium term forecasts in the east as rainfall could return next week and persist again.. The monsoonal weather expected from this week, thankfully has landed east of the nation but the tropics rebound in activity towards Christmas and beyond so that will be of concern to the flood zones over the east and southeast as that moisture moves southeast. Flooding over the west and central parts of the nation will be connected to the tropical lows/cyclones that move around the north.
Euro Rainfall Accumulation Ensemble Data - Next 6 Weeks - December 14th 2021 -January 28th 2022
The models remain unchanged, for the wet signal to build further over northern Australia during this period and over the eastern seaboard. The early monsoonal burst from a few weeks ago lands in the Coral Sea but will likely return in early January. The east is expecting further rainfall and flooding issues as we go through the latter part of this month but more likely in January in line with the monsoon returning and the bulk of the nation looks to record at least seasonal to above seasonal rainfall values.
Euro Rainfall Accumulation Control Data - Next 6 Weeks - December 14th 2021 -January 28th 2022
The heavy rainfall guide continues for the southeast, east and northern parts of the nation with flooding being renewed through January over inland NSW and QLD. Northern Australia will get a good monsoonal burst in January and when that happens, expect rainfall chances to increase nationwide, not just the east. Some areas can expect flooding to develop in areas that have been spared so far, especially over eastern inland areas and through central interior locations. The far south may see seasonal conditions.
Euro Rainfall Anomalies - Next 6 Weeks - December 14th 2021 -January 28th 2022
The numbers over the south and east remain elevated. But now we see the strengthening of the monsoonal signal mid January and that will likely sweep south and east through the nation with increasing rainfall and humidity.
The Euro Control Anomalies for the coming 6 weeks shows that tropical weather is the wild card of Summer rainfall and where the tropical lows go is where you find the rainfall. But the persistent excessive rainfall signal for southeast NSW, the ACT and Gippsland of Victoria continues and now seeing the impact of that mid January monsoon activity.
GFS Rainfall Accumulation - Next 5 Weeks - December 14th 2021 -January 16th 2022
Significant rainfall signals continue for eastern Australia and tropical rainfall expected to increase over the coming weeks, with a larger impact on tropical rainfall expected from near Christmas onwards into January. The remainder of the nation relatively seasonal rainfall expected through to early January. I do think we will tend much wetter than this as per the Euro.
GFS Rainfall Anomalies - Next 5 Weeks - December 14th 2021 -January 16th 2022
The model is now showing a dry bias over the northern and western parts of the nation with the monsoon being analysed over the Pacific Ocean. That remains very low confidence. The high confidence is over the east and southeast of the nation where the rainfall is expected to remain well above normal. I am of the belief that the nation will be wetter than this.
CMC Rainfall Accumulation - Next 4 Weeks - December 10h 2021 - January 12th 2022
Additional rainfall to come over northern and eastern Australia is excessive and this will support further flood potential after the dry week coming up. Watching the tropics closely as we head into Christmas and beyond with tropical weather increasing for the end of the month and into January.
CMC Rainfall Anomalies - Next 4 Weeks - December 10th 2021 - January 10th 2022
The wet phase is easing for a week over the southeast and east but it will return as we get towards Christmas as the moisture profile deepens and the low pressure deepens. So for southeast areas and much of eastern QLD, rainfall will remain above average. Mixed odds for the north with the tropical rainfall still in build up phase but note the first burst of monsoonal weather thankfully has landed in the Coral Sea, that burst would have put the east under the 1/100 year flood risk which has thankfully eased for now.
Euro Temperature Anomalies - Next 6 Weeks - December 14th 2021 -January 28th 2022
The east is looking very much below average with a decent supply of rainfall, cloud cover and this will suppress temperatures. The moisture may return frequently (after this drier period) to bring cloud cover through southern WA and into SA and then the southeast. Certainly are seeing that right now. The tropics seasonal and the west coast is above normal.
GFS Temperature Anomalies - Next 5 Weeks - December 14th 2021 -January 16th 2022
It is persisting with the warmer signal for northern Australia which is interesting, as the other models have been running cooler and the tropics indeed have been running hotter through this season, so certainly merit to this forecast.
January 2022 - Rainfall Anomalies
The model has turned a bit drier for January which I am not totally convinced about, the shorter and medium term forecasts support a deepening of the low pressure over the north of the nation, but for now calling it seasonal for the north and west, with drier spots here and there over the outback and possibly through the south, wetter over the east.
February 2022 - Rainfall Anomalies
The wet signal increases over the tropics which is in line with the La Nina in place and the impacts of that being felt from late January into February. The nation as a whole responding to that, with a very wet end to Summer possible.
Summer - Rainfall Anomalies
But looking at the Euro, the impact of La Nina is evident. I would not read too much into that brown shading over WA as it takes one system from the tropics to see that drier bias disappear. The wet Summer continues for the east and north.
Another update on La Nina coming up soon - I am waiting on another 2 data sets to come through, they are yet to arrive so I will update most likely tomorrow or Thursday.