An update now on Summer 2021/22, Autumn 2022 and a first glimpse of Winter 2022.
The further you go out with the forecasts, the less refined they are, that is how it works. These forecasts will be refined over the coming months and yes I will be around through Christmas and New Years updating this, planning for the seasons ahead is critically important and a lot of you need the information!
Lets have a look at the latest.
The main driver through Summer into Autumn will be the ENSO and the SAM is the partner in crime delivering the impacts of the La Nina. The more positive the SAM is over Summer, the more flooding is expected over the eastern parts of the nation, the negative SAM will save many areas over the inland from excessive flooding and storm risks. So now we have the La Nina in place, we look at the other drivers and how the relate to one another. I cover that off 2 times a week in your 6 week outlook and daily in the medium term forecasts.
Summer Rainfall Outlook 2021/22
% chance of exceeding the rainfall for Summer of 2021/22.
The rainfall guide remains unchanged through the Summer of 2021/22 with the La Nina finally declared, the impacts of the IOD lingering into December and the SAM phase for December looking more positive than neutral. This will set up a wet start to Summer. As we move through the season, the monsoonal activity will drive the rainfall chances for northern and central Australia. The monsoon is likely to arrive earlier than normal with a decent chance that moisture from the monsoon will be drawn southeast and south through the nation. Every time you hear that the monsoon is being forecast to be over Australia this Summer, pay attention to the forecasts with a high chance of rainfall will increase nationwide. The longer the monsoon stays over the nation's north, the longer the elevated rainfall chances remain over Australia. This will lead to elevated flood risks for the north and east of the nation in particular. The further west and south you go through the nation, the chances of rainfall being elevated are reduced. Nationally the wet signal continues for the Summer.
Summer Temperature Outlook 2021/22
% chance of exceeding the rainfall for Summer of 2021/22.
Cooler in the east and perhaps central areas of the nation thanks to prolonged cloud and rainfall coverage which goes hand in hand with La Nina. The dominance of easterly winds supporting the below average temperatures in the east as well as we track a high pressure ridge into southern Australia. The weather over the west seems to be trending warmer than normal now in recent guidance, especially for the back half of the Summer and this could move into SA and VIC throughout the period IF the La Nina weakens a little. At this stage, the temperatures should lean cooler than normal for the east and central parts with the far east of NSW and QLD looking to have a cooler season overall. For the north, the weather relatively seasonal after the brutal build up.
STORM SEASON OUTLOOK
A review of the conditions for the remainder of the season.
Severe Thunderstorm Outbreaks - October through April.
A reminder of the severe weather season expectations.
The season has been above average over the nation's east and we have seen one outbreak of severe thunderstorms through SA and VIC this week gone with some areas trashed. There is likely to be another outbreak of severe weather in the first week of November across SA and VIC and more severe weather expected across QLD and NSW. This season is not going to simmer down all of a sudden. I am afraid that many areas are to impacted by severe weather through the harvest and then into early next year. With the La Nina now here, we may lose the hail risk with more moisture in a saturated warm atmosphere, but the flooding risks go through the roof as we head into the first part of 2022 as we saw with last Summer, the east coast and adjacent inland flooded and severe weather impacts elsewhere further west and north. This has now been observed in the past 2 weeks.
Annual Thunderstorm Days Australia.
This chart represents how many thunder days are reported on average across the nation as you can see the nations north and east gets some stormy weather but as we move through Summer the inland of WA also sees more widespread thunderstorm activity.
Flash Flood Risk Forecast December
This will be the most featured severe weather element as we track through Summer and likely to impact the north of the nation (which is not unusual given it is wet season) but over the eastern seaboard, thunderstorms likely to feature frequently bring up the chance of flash flooding for the eastern states. Deepening troughs of low pressure embedded in the onshore easterly flow also pose a large risk for the east coast with higher rainfall rates forecast. The SSTs are elevated over the Coral and Pacific Ocean and with the higher moisture content, expect the higher rates of rainfall. The west of the nation even if it is at a lower risk, this is quite significant for December and indeed as we track through Summer. After a wet November for many over eastern WA and the inland parts of the nation, flash flooding will be quite a feature with outback rainfall continuing. Remote and rural communities should prepare to be cut off from larger centres during Summer.
Risk of riverine flooding - Summer 2021/22
This chart represents the chance of flooding and potential disruption for outback areas in particular. Now you don't have to see rainfall falling overhead to be impacted by flooding, with the Darling River for example flooding upstream but can impact communities deep into NSW as we have seen throughout this year. The higher values exist over northern and southeast Australia, as has been the expectations since July. The weather over the southeast carries a high risk of disruption, with major river systems at 100% capacity and saturated catchments. These areas are sitting ducks to flooding, especially along the Murray River, even though the catchments have had a break in the past 2-3 weeks which has been a godsend. Over the north, the flooding could start early through the wet season, from December onwards. Elsewhere, excessive convection and persistent unsettled weather could see the flood risk increasing in the next two weeks, especially with near record rainfall for parts of the outback of the NT and WA.
Risk of Heatwaves - Summer 2021/22
The eastern inland carries a very low risk of heatwave activity thanks to expected rainfall and cloud cover. The humidity values however have certainly make things feel very uncomfortable through QLD and this is likely to expand throughout the nation at times as the temperatures increase. The temperature's over northern Australia have begun to moderate under more cloud cover and rainfall frequency. The Mediterranean Climate allows for hot weather in the west and a low to moderate risk of heatwave conditions can be expected through this period but I suspect this won't be observed or be a risk until later December if not January. Finally we have seen a swing to more traditional weather for the west.
Bushfire Risk - December
The higher humidity with elevated rainfall chances for much of the nation will decrease the risk of fire danger throughout the east and southeast. Though lightning risks will always start fires in the nation so be weather aware, even in the rare chances of the dry thunderstorm activity during this period. The west drying out and with excessive undergrowth underway with the very wet year will spark an elevated fire risk especially into the New Year.
Bushfire Risk - January
The bushfire risk remains fairly low for the nation with the continuing wet weather over the east with higher humidity engulfing large parts of the nation. The elevated risks remain over the west and pockets of TAS where drier weather is more likely than not. This will be reviewed in about a month, but the confidence is high on the chances of a lower impact bushfire season.
Bushfire Risk - February
The bushfire risk traditionally peaks during February but this coming season looks to be suppressed due to ongoing rainfall and higher humidity values across the nation as the peak of the wet season unfolds. Will have to watch the SWLD of WA and the coastal areas through Margaret River down to Augusta and the southeast of Tasmania. Higher fuel loads are building this Summer and next season and the following season into 2024 look nasty if we dry out.
CYCLONE OUTLOOKS - NO CHANGE IN THE GUIDE
The number of named storms through the north of Australia has remained unchanged since the last guidance with expectations the season will be some what above normal in most regions. This does not mean that each of these systems will cross the coast. The green symbols indicate at least 1 tropical depression making it down into the lower latitudes which could pose some serious weather in of itself as we saw with TC Seroja in March of this year. These systems can be post tropical and also pack a punch through this time period. I am expecting one system off the SE QLD coastal area or even NE NSW and one that is likely to turn post tropical from the north running down the west coast during the latter parts of the season, say February or March.
Cyclone Risks - Usual expectations of the impacts from cyclone activity.
This chart represents the areas that have major direct impacts from cyclone activity, whether they are passing by over the north in open water or through the inland with rain and storms with flooding potential. The impacts seasonally are far reaching. This year with the amount of cyclone activity being forecast by global agencies suggests we could see quite a bit of rainfall as the main issue to deal with this year. We have to watch the tropical lows as well as these can drop more rainfall than the cyclone activity, especially in the sub tropics down to areas such as Exmouth in the west and Coffs Harbour in the east.
December will continue in the same vain as much of Spring, the wet bias over the southeast inland, through the eastern inland and over the tropics. The residual impact of the Indian Ocean Dipole negative event continuing to stream moisture in from the northwest will be in place until about Christmas and then that impact will begin to ease. For the north and east, the tropical waters around Australia are well above average presently and this will continue into Summer. The Coral Sea of great interest, already indicating the La Nina phase, the waters east of QLD are well above normal and are forecast to remain this way and spread south to be off the NSW coast during Summer. Every time the winds veer into the east over NSW and QLD, the showery weather will be productive and heavy. We saw this last Summer, the inability to dry out between major rainfall events and the flooding was therefore more extensive and severe because of the persistent rainfall. For the southeast of the nation, December will be humid, unsettled and this may extend into parts of Ag SA, but once again the better rainfall odds are over in the east. For the west, seasonal conditions, but as we see this week coming, it takes one event of rainfall to push many areas above the average, so the above average rainfall while impressive is not as significant as above average rainfall in areas where it is the wet season, like the tropics, which look very active from now onwards.
The nation generally wet and humid, unsettled with persistent troughs through inland areas of the nation. The troughs lifting areas of deep moisture over QLD, NSW and VIC. The wet bias over in WA could be an expression of the above average wet season and potential tropical activity, that element no model can forecast ahead of time. The NT has brown over it, I would not read too much into that, again one tropical cyclone/low and the average for the month is taken care of. For much of the nation, high humidity, more rainfall than normal is a fair chance in most states and this will offset the high heat potential for many inland areas.
Wet weather increasing from January to February. The wet signal thanks to the monsoon over the north of the nation and the peak in the easterly wind dominance over the nation causing the rainfall chances to be elevated over much of eastern and northern Australia, stretching down into the southeast, helped along by weakening frontal weather from time to time. We average about 1-2 fronts per month in summer for southern areas. For WA, it is near seasonal and that is normal, however a rogue tropical system can cause this forecast to be quite useless. Otherwise the trend of the wet Summer getting wetter as we go is in line with what occurred last season.
SEASONAL OUTLOOK - SUMMER 2021/22
So you can the nation is in green with pockets of heavier rainfall opportunities for the east and north. Significant risk of wet season flooding for the north is likely, over Cape York, the NT and through inland WA and the outback. Flooding risks increase for areas of eastern Australia with the wetter signal kicking off from January but more likely through February. The remainder of the nation, seeing more frequent rainfall events that normal which will see more humidity mixed in with the warmer weather, it is going to feel fairly tropical this Summer. Storm season active, severe storm outbreaks also higher than normal for much the north and east of the nation. This will pose an issue for a range of industries and has already caused some issues in the form of flooding and loss of crops etc. This may continue through to March.
Cooler bias from Spring, it continues in the east for December as the higher than normal rainfall continues to dominate the north and east. We have lost that bias of warmth over northern Australia thanks to more rainfall and cloud cover by December. The rest of the nation, normal conditions are expected, that will see warm to hot weather, interspersed with periods of milder weather with onshore winds as systems move through west to east over the southern states. If you are living in the east and north, the humidity will be off the charts at times so be aware, you may be under blue, that does not mean comfortable values.
The cooler bias over the east wanes a little bit, but increases over in the west of the nation and this could be due to tropical activity and perhaps persisting ridging or troughing, a range of reasons for this. Given the rainfall bias being above normal through the region, I would be thinking it is more to do with the moisture increase coupled with inland low pressure. For the remainder of the nation, seasonal, values could be below average over the north with the above average wet season so that is conditional. Otherwise if you don't like heat and want rainfall, this is looking good for you. With the La Nina developing and likely to peak, the rainfall should increase as will the cloud cover so these numbers may be downgraded.
The cooler bias is back for much of the nation as the wettest period of Summer gets underway. The increased cloud cover across the nation coupled with more rainfall and humidity leading to a cooler month. The warmest parts of the nation may well be over the west coast and Tasmania. With the La Nina peaking and beginning to wane, the temperatures may be downgraded further.
Seasonal Outlook - Summer 2021/22
The nation is looking fairly seasonal for the majority of Summer. Once again the bias of cooler weather linked to where the rainfall is more frequent, the cloud cover more extensive and where onshore winds dominate. That does appear to be the east still and through portions of the west and possibly up across the northern tropics. The rest of the nation, a humid and seasonal Summer. The forecasts may be revised downwards further in terms of temperatures with the increase of rainfall and thundery weather over northern and eastern Australia.
SEASONAL OUTLOOK - AUTUMN 2022
The seasonal outlook for Autumn is looking wet as well, and this could be a hangover like we saw last season from the wet summer. I am leaning towards March being wet and then things starting to dry out as we go through April and into May. We are getting way out there, but thought for forward planners and those wanting to know what is lurking out there, yes there is further wet weather into Autumn with a prolonged wet season thanks to a lingering La Nina. Some of the modelling suggests the La Nina may continue into March or April but we will know more in January.
Rainfall Outlook - Autumn 2022
% chance of exceeding the rainfall for Autumn 2022
With the lingering La Nina from the Summer still influencing the rainfall distribution through the early Autumn, there is a real risk of a repeat of flooding for the east coast in line with the peak of the wet season for the subtropics which is usually March through May. So pay attention to the guidance in the coming weeks over Christmas and New Years (yes I will still be here). The weather looking less wet for southern parts of the nation for now, but the Autumn break may be moot point with the wet Summer running into March before conditions ease through the season. The tropics may have a prolonged wet season with above average rainfall taking us through to May. Cyclone activity peaks in the Feb to April range through the Indian Ocean and this could influence rainfall for the interior and into the northern and eastern inland.
Temperature Outlook Autumn
% chance of exceeding the median temperatures for Autumn 2022
As per last season, the east and north were below average temperature wise with above average humidity values and rainfall across the east and north expected at this time, so the reduction in temperatures is a logical conclusion. The west and south I think will trend warmer, not necessarily drier, that average across these areas.
Rainfall Outlook - Winter 2022
% chance of exceeding the rainfall for Winter 2022
The wet bias from the La Nina through Autumn will wane during the May next year and winter should resolve to near seasonal over eastern areas but coastal communities may still see prolonged colder southeast winds with showers for June before things dry out. At this time, seeing a drier bias for the west of the nation with a persistence of high pressure and a neutral IOD at this time. HOWEVER, there are some models that support the La Nina not quite resolving into winter and there are some models that support the reformation of the IOD into a negative phase. Lets just say this, not El Nino and positive IOD phase is low at this time. Will review this in early January.
Temperature Outlook Winter
% chance of exceeding the median temperatures for Winter 2022
Temperatures at this time, this far out, are leaning warmer than normal, there is not bias towards colder weather at this time, with a few members trending warmer through interior areas, so will placemark this for now. But being this far out, the forecasts will refine during January and February regarding this.
I will have another look at the seasonal outlook the Sunday before Christmas with further details and I will be still here through the Christmas period with all the planning information to take us through into Autumn 2022.