CLIMATE OUTLOOK - SUMMER 2021/22

Well it is coming to the pointy end of the year and we are now working towards the warmer season, as expected and discussed throughout the year, we are staring down the barrel of another wet summer for much of the nation.


The discussion of La Nina back in July is seemingly coming to fruition this Summer. This is not uncommon after one La Nina Summer that another follows. The second event can sometimes have a heavier impact on rainfall nationally and an increase in tropical weather, in particular cyclone activity.


For eastern areas of QLD and NSW, flooding once again is a big risk. We saw last year a lot of the naysayers on social media on my page saying there is no La Nina because it was not raining and then it all came at once and record rainfall was achieved. Not one event is ever the same, but if the La Nina does indeed form, expect rainfall to be acute, heavy, and potentially severe in eastern areas of the nation from December through March.


I will have more to say on La Nina during Tuesday with a more detailed look and commentary then, but seeing it is the weekend, let me stop talking and give you the details - no video for this post - I will add the video on Tuesday with my La Nina update.


HEADLINES


  • Summer, likely wetter than normal for most areas of the nation, with a bias over the north and east.

  • February likely to be the wettest period for the nation with an increased risk of flooding for the eastern portions of NSW and QLD.

  • Flooding likely over outback areas of WA, NT and QLD with more rainfall than normal.

  • Above average storm season leading to more disruptuion to farming operations, especially over the east and southeast.

  • Above average cyclone season in line with a La Nina Summer may influence rainfall for areas of WA with more rainfall over the ouback regions, especially from January.

  • Monsoon more active than normal

  • Higher humidity for many southern and eastern states may cause brown rot and downey mildew etc for many people.


FORECAST


RAINFALL

%chance of exceeding median rainfall for Summer 2021/22 - December 2021-February 2022.

The residual impact of the weakening IOD through December will offer more widespread rainfall chances over inland areas from northwest through southeast and keep the increased build up conditions going from Spring into Summer. The weather over the east will begin to get more humid and wetter through November, we have seen the storm season potential this year and I suspect that will continue onwards into December and January. But the real widespread rainfall is expected to kick off nationwide in line with the monsoon getting underway up north. We saw that as the trigger for widespread rainfall events over the nation earlier this year, the moisture from the north being drawn south into a persistent easterly flow and this lifting rainfall over central and eastern parts of the nation. The rainfall bias again, like for much of this year, over northern and eastern areas of the continent, but areas over the south can also expect widespread rainfall from time to time. This will be helped along by cyclone activity decaying over the continent. As we saw with earlier this year, the wettest part of the Summer for the nation likely to be January through February with the peak of humidity values through this time, the lowest air pressure over the nation is from January to February, this leading to widespread inland rainfall. For coastal areas of NSW and QLD, every time we go into a positive SAM phase, expect an absolute bucket load. This was experienced earlier in the year under the weak La NIna phase and under the current guide this is to be expected again. The wet bias continues for much of the nation into Autumn. The forecast confidence is MODERATE at this time.

TEMPERATURES

%chance of exceeding median temperatures for Summer 2021/22 - December 2021-February 2022

The cooler bias is expected persist through much of the nation with widespread cloud cover, higher humidity values and significant rainfall potential to exist through much of the season. The blues on this chart does not mean it won't be hot at times. Heatwaves will still occur, there will be 40C days in the capitals, but the overall trend for the season is cooler than normal, especially through outback areas and across the tropics, which are expecting an active wet season (through tropical outlooks are very poor as they use a different set of parameters and data sets - too complicated to go into here). The continent is expected to continue the cooler bias into Autumn at this stage but we are going out 5-6 months now, however all models do see the cooler bias continuing.

STORM SEASON OUTLOOK - REMAINDER OF SPRING - The Summer Outlook Updated November 7th 2021

In light of the recent week I thought it important to place this information surrounding severe weather risks over the nation for the remainder of Spring. There will be disruption to your harvest over eastern and southern Australia and in the short term to WA as well. SA may sit in a comfortable position where the bias of severe weather is around the region, but with thunderstorm activity expect the unexpected.


Severe Thunderstorm Outbreaks - October through April.

Looking at an above average season for severe thunderstorm outbreaks through VIC, NSW and QLD as well as over parts of the outback through to the Top End. The storms are likely to be efficient producers of rainfall, so the highest risk from thunderstorms through this period will be heavy rainfall leading to flash flooding and damaging winds. There is also a fair chance of large hail, but as the season carries on, the risk will reduce, especially from December. For SA through WA near normal expectations for severe thunderstorm outbreaks this year on current guide.

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.

Large Hail Risk Forecast - October.

There remains a high risk of large hail for the remainder of October through eastern inland Australia, in line with the seasonal shift into storm season. The risk is elevated further south through into southern NSW and VIC against averages with the upper atmosphere likely to be more unstable on current climate guides. Watch this weekend's low pressure system through the interior of the nation and as that moves into the eastern inland of QLD and NSW, there could be a risk of hail given the wind profiles. These types of events are likely to continue off and on for the remainder of the month. The remainder of the nation out of the risk, but as always expect the unexpected when it comes to thunderstorms.

Large Hail Risk Forecast - November

This will be the peak risk period for hail issues across the nation, where we see all the ingredients come together. Higher heat values coupled with deeper moisture and higher instability levels will lead to elevated risks of hail through the east, particularly the storm corridor of NE NSW and southern QLD. The risk extends back through much of NSW and southern and central QLD but reduces to very low values back into the Outback. Up inland of Darwin, there is the risk of hail with some of the stronger build up storms, that could cause some issues for any remaining crops in the region. And a very low risk exists over the SWLD of the nation with the heat trough building through the month. The rest of the nation is relatively seasonal in terms of hail expectations.

Flash Flood Risk Forecast - October.

Flash flooding remains a moderate to high risk over much of the east and extending back through the central inland of the nation, thanks to deep moisture, inland troughs and saturated catchments over the southeast and east of the nation. Heavy rainfall coming up this weekend for example, carries a risk of flash flooding over the interior parts of the NT and through the northern NSW and southern QLD, especially with thunderstorms. The risk of flash flooding remains high with any larger scale rainfall events that do take place during the remainder of this month as the ground will not be allowed to dry out. Over the tropics and through the north, the usual seasonal thunderstorm activity could be more widespread than normal.

Flash Flood Risk Forecast - November

The risk of flash flooding increases through November with more moisture being held by a warmer atmosphere. The thunderstorms that develop through the eastern and northern parts of the nation will be efficient rainfall producers but even widespread rainfall events in the absence of thunderstorms could produce flash flooding, especially in areas bound by elevated sea surface temperatures. Over the north, the usual risk of thunderstorms carries the flash flood potential, again activity is higher than seasonal values. And over the southwest, with the waning negative Indian Ocean Dipole, thunderstorm activity that forms along the heat trough and adjacent inland areas could see heavy falls develop, especially over the Goldfields and Wheatbelt. Elsewhere, seasonal expectations at this time, through SA and back through central and northern WA.

Risk of riverine flooding - October through December

This chart represents disruption as a result from riverine flooding. Now you don't have to see rainfall falling overhead to be impacted by flooding. 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. 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 increase from November onwards.

Risk of Heatwaves - October through December

Low intensity heatwaves could feature through this period. The eastern inland carries a very low risk of heatwave activity thanks to expected rainfall and cloud cover. The humidity values however could certainly make things feel very uncomfortable. Higher than normal temperatures over much of the north will continue but offset by the rainfall activity, however there could be periods of suppression in the afternoon storm activity that could lead to low grade heatwaves there. 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 December.

Bushfire Risk - October

A low risk fire season continues for the east and north, with the values over the north still elevated, but the afternoon storms and the higher humidity is starting to mitigate the risks over the NT now, so conditions improving in the rural and remote areas over the north.

Bushfire Risk - November

The low end fire risks continue into November, no change since the last update, with rainfall and higher humidity helping to offset the risks for the early part of the season.

CYCLONE OUTLOOKS - This will be updated November 3rd 2021

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. 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.

DATA


RAINFALL ANOMALIES

December 2021

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.

January 2022

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.

February 2022

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. How wet it gets will become clearer as we go through the next 6 weeks as more data comes in.

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 thus far, early into the season.

SEASONAL OUTLOOK - INTO 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.

TEMPERATURE ANOMALIES

December 2021

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.

January 2022

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.

February 2022

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.

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.

Seasonal Outlook - Autumn 2022

The cooler bias will persist into Autumn with more rainfall through the March keeping things cool. Sometimes March can be a blistering month of weather but at this stage, it could be that we get an early break under the influence of more tropical moisture and the return of cold fronts moving north, picking up that moisture, as we saw this past Autumn. Something to watch. The tropics being wetter than normal for the end of the wet will impact the temperatures over the nation with more cloud cover passing over inland areas, snuffing the heat engine from getting too hot and sending the hot air southeast. I will review the Autumn Outlook in greater detail in December.

I will have a detailed look at the La Nina chances on Tuesday lunchtime. We are getting to a critical time of forecasting this Summer so stay tuned.





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