The disruption and pockets of destruction to crops in SA, VIC, NSW and QLD I am afraid is a sign of what is to come for the coming 6 weeks or so. There is no way of telling if YOU will be impacted heavily or not, but stay close to forecast trends. As we have seen the atmosphere is volatile and is willing to throw everything at us through this coming period.
We have one system that has already caused havoc from large hail to destructive winds and heavy rainfall through the southeast, severe weather expected through parts of NSW and QLD today and tomorrow and then we repeat the cycle next week with more moisture and low pressure combining to bring more rain and storms.
I have touched on Summer and Autumn 2022 as well very briefly. More on that next week.
Lets look beyond that now.
Rainfall Outlook Next 6 Weeks - October 28th - December 13th 2021
% chance of exceeding the median rainfall for the coming 6 weeks
Wet. Wet wet wet, highly disruptive rainfall signal for the harvest period. The further east and southeast you are, the wetter you are likely to be, but also the severe weather risks are running high too. The tropics very wet with near record rainfall possible through the northern and eastern parts of the nation with this deeper moisture profile. The further south and west you go, the less likely you will be to record above average rainfall, however we saw SWLD of WA under a low chance of exceeding the rainfall for October and scattered pockets saw record rainfall for October. So these charts are a guide and not the rule, but the signal as you can see underpinning the forecast is very wet. Finally with thunderstorms, your number will vary.
Temperature Outlook Next 6 Weeks - October 28th -December 13th 2021
% chance of exceeding the median temperatures for the coming 6 weeks
The data sets have trended colder in recent days and I am leaning towards that given the amount of moisture, cloud and rainfall forecast during this period. We have multiple ports of moisture coming from the Coral Sea through the northern tropics and from the Indian Ocean, all diving south this seeing the rainfall signals increasing and thick cloud cover persisting for days at a time. The weather is not expected to be cold over central and eastern areas, but more likely humid and unsettled with rainy skies more often than not. The southwest of the nation is expected to see cooler and drier air with onshore southwest winds thanks to persistent ridging. The northern tropics will see temperatures moderate over the coming 2 weeks.
Humidity Outlook Next 6 Weeks - October 28th -December 13th
% chance of exceeding the median humidity for the coming 6 weeks
Higher humidity values against the average continues to be observed throughout the north of the nation and is now spreading south and southeast this coming week. The moisture on some of the modelling coming through is expected to hang up over large parts of the nation's northern and eastern states. This will contribute to showers and thunderstorms becoming widespread as mentioned above, however the impacts to crops in the humid and warm weather with the rainfall could be quite high as many farmers wait to get them out of the ground. The further south and west you go through the nation, there will be breaks in the humidity. The further north and east you go, the longer duration of humidity and warmer weather with rainfall frequent.
No change to the guidance in the climate models in the past two weeks, the Indian Ocean is peaking in it's negative phase and we are seeing that impact on the overall short and medium term forecasts with moisture streaming in from the northwest into the tropics and then southwards into the interior. This influence will continue for the coming 4-6 weeks across the nation. The SAM is currently positive and expected to stay that way, increasing rainfall chances along the east coast as you can see in most data sets below. Finally the ENSO is likely to shift into La Nina during the latter part of November into December, HOWEVER, the shift into the La Nina and the impacts felt in Australia, usually has a lag of about 4-6 weeks and so this is likely to be experienced after Christmas at this stage over the continent. We will have new data coming in next week on that and more details Tuesday or Wednesday with that.
DATA - Refer to video for more on these sets of data
Euro Rainfall Accumulation Ensemble Data - Next 6 Weeks - October 26th -December 10th 2021
Rainfall bias has not changed for the nation. The northern and eastern areas of Australia to experience the wettest weather through this period. We have been talking about the early onset tropical weather over northern Australia leading to higher than normal rainfall values for central, southern and eastern portions of the nation. This is a very wet look for the period and this will have heavy impacts on crops and yields this year. We have already seen the impact from the severe weather events in recent weeks and this will continue to impact large parts of the nation. The southwest may see easing conditions.
Euro Rainfall Accumulation Control Data - Next 6 Weeks - October 26th -December 10th 2021
The control member is one data set with heavy falls being shown through QLD and the NT still and extending south and southeast through the nation. There is also evidence that data is spreading the rainfall into northern WA which could feed the heat trough out west, with showers and storms becoming more frequent over the outback.
Euro Rainfall Anomalies - Next 6 Weeks - October 26th -December 10th 2021
Rainfall anomalies are running very much above the average throughout the nation with again the drier bias over the southwest which is normal. But the weather cooler under the persistent ridging. The humid and rainy weather will have huge impacts over the central and eastern parts of the nation thanks to a persistent trough and low pressure coming through southeast and eastern parts of the nation lifting the deep moisture profile into frequent showers and thunderstorms. There could be record rainfall values through November in some locations of Northern, Central and Eastern Australia.
CFS Rainfall Accumulation Ensemble Data- Next 6 Weeks - October 26th -December 9th 2021
The bias of the rainfall is over the southeast and east of the nation and again note the tropical connection of rainfall extending through the NT into SA and then into the southeast. The drier bias is over the far west and southwest.
CFS Rainfall Accumulation Control Data- Next 6 Weeks - October 28th -December 12th 2021
Significant rainfall over the east and southeast of the nation in response to the tropical activity, however this model does not cope well with tropical rainfall forecasts. But the bias of heaviest rainfall over the southeast and east of the nation continues as well over the Central parts of the nation where moisture will become stagnant and be lifted into widespread showers and thunderstorms.
GFS Rainfall Accumulation - Next 5 Weeks - October 28th - December 1st 2021
Significant rain and thunderstorm activity is expected to develop over the northern third of the nation, especially from the NT and spread south and east via upper level winds, favouring above average rainfall chances for central and eastern states, with lighter rainfall over the SWLD of the nation. Severe weather risks are running high.
GFS Rainfall Anomalies - Next 5 Weeks - October 28th - December 1st 2021
The GFS is running drier than the other data sets and has been all year, so this remains the outlier, but I will point out, even as it is running drier, look at how active the tropics are with that early onset rainfall smear of 5-8 inches above the normal rainfall values. That will impact rainfall chances and totals further south and east. So the idea is the same in the spread of rainfall, just not in agreement with the widespread intense rainfall that other modelling has.
CMC Rainfall Accumulation - Next 4 Weeks - October 28th -November 29th 2021
The latest data set off the CMC for the coming 4 weeks is very wet, these values are higher than what we saw last year heading into a La Nina year with the waning negative IOD, so there is some cause for concern if you are looking for dry and settled weather to get the crops out, you will be hard pressed to find a stretch of dry weather over central and eastern Australia. Better luck exists back in the SWLD of WA but even there, it is wetter than normal.
CMC Rainfall Anomalies - Next 4 Weeks - October 28th - November 29th 2021
The anomalies over the coming 4 weeks very much above the average, the blue shading is 2-4 inches (50-100mm) above the normal rainfall you would see during this time frame! So that is going to place some areas under significant humidity, rainfall and storm impacts, especially those harvesting through central and eastern Australia. The west cooler and damp but not as wet. The tropics, very active fueling the wild weather.
Euro Temperature Anomalies - Next 6 Weeks - October 28th - December 13th 2021
A cooler trend in the modelling and this particular run has turned colder than the earlier data sets this week. This is in line with the higher than average rainfall forecast for much of the nation, northwest to southeast movement of rainfall through the interior, to suppress the temperatures exceeding the values.
GFS Temperature Anomalies - Next 5 Weeks - October 27th - December 1st 2021
This is running a little warm and is the outlier for the east and southeast. It is running warmer in the shorter and medium term data as well. Something to watch but more unlikely in coming off. The southwest and west of the nation, cooler.
CMC Temperature Anomalies - Next 5 Weeks - October 28th - November 29th 2021
The temperature values over the north will begin to moderate over the coming 2 weeks with increased rainfall but the remainder of the nation under this guide, not only wet, but humid and cooler with thick cloud cover and rainfall frequency remaining high. The southwest not necessarily wet, but onshore winds providing cooler than normal weather.
CFS Temperature Anomalies - Next 6 Weeks - October 29th - November 28th 2021
The CFS running cooler than normal for the west of the nation which is in good agreement with the data above and that extends into the central and eastern inland of the nation thanks to the persistent rainfall, cloud cover and onshore winds over the west of the nation as well. The north will see a reduction in the heat levels.
I will have more details on this coming on Tuesday. PAY ATTENTION TO THE SHORT AND MEDIUM TERM FORECASTS DAILY - IF YOU ARE LIVING IN A HARVEST ZONE!