November 2022 Outlook SA

*Forecast prepared between Nov 4th-6th 2022

Review:

G’Day everyone, feels like only a few days ago that I pumped out that quick update for the deep low and associated cold air outbreak. There certainly was some wild weather involved although fortunately the strong thunderstorms were mostly confined to the Lower and Upper North with some strong supercells. I went up for a look and managed to get very close to what was an attempted tornado just south of Mount Bryan. The storm also had numerous large funnels from near Spalding up to half an hour earlier. I am almost certain it may have touched down at some point. There was also a second one further south that hooked up near Auburn to Eudunda. If anyone has any photos or accounts from the day, please inform either Peter or Alex. I must say the crops looked pretty good through much of the areas that I travelled but the enormous amount of rain after must have taken some sort of toll, especially for those with soil that doesn’t drain quite as well. Blyth area especially looked very good. The good news is we are entering a little dry spell with some much-needed warmth which I will explain more about in the next section.

The second part to the system though was the enormous cold outbreak with a couple of strong fronts, especially the second where the cold air really punched in hard. Before this though, showers continuously tending to rain areas over the Lower and Upper North especially with heavy falls and flooding. Significant stream and river rises once again occurred with water still high in some areas. The cold air brought squally showers and small hail as well as some isolated cold air thunderstorms. Some hail falls were quite significant in stronger cores with large ground coverage. There was even snow over the higher ground near Hallet and Mount Bryan with a recording down to 580m which is extremely impressive for any month, let alone the start of November.

Overall though it was a very wet month for a vast majority of the state. Incredibly though at my place in southern Adelaide I received 44mm which is below average of 56mm. Crazy how it goes with the northern suburbs getting anywhere from 80-100mm on average nearly doubling their averages. Huge totals were recorded over parts of the NE Pastoral, Lower and Upper North, Riverland and Mallee districts (refer to figure 1)

Figure 1: October rainfall deciles showing vast areas of well above average to record rainfall – source BoM http://www.bom.gov.au/climate/

Now going back to the October outlook this is what the forecast was:

“All in all, for the month I see nothing but above average to well above average rainfall for the entire state, not many places will miss this month. Especially however the western portions of the NW Pastoral, NE portion of the NE Pastoral will comfortably be pushing well above average. The Mallee, Upper and Lower SE should all do well. Possibly the only regions that may come closer to just average rainfall are Yorke Peninsula and KI, but I wouldn’t be surprised if we have a sea of blue on the deciles chart by the end of the month. See how we go!“

A sea of blue is what we expected, and a sea of blue is what we got! Certainly, a massive month, perhaps a touch more centralised across the Pastorals but otherwise all went very much to expectations with even the closer to average areas over KI and YP which was the most minute risk for near or slightly below average.

Figure 2: October rainfall percentages – source BoM http://www.bom.gov.au/climate/

I don’t think we will be seeing a month that significant both state and nation wide for quite some time to come. It certainly has increased the widespread and devastating flooding over the eastern states, especially over NSW and VIC.

Figure 3: October Rainfall over Murray-Darling Basin – source BoM http://www.bom.gov.au/climate/

We can see above in Figure 3 just how wet it was over the Murray-Darling Basin. So many rivers are now into major flood with the main flood peak on the Darling still slowly rising even though it is above the major level on many gauges. This will take longer to reach SA than the Murray flows however enormous rainfalls in the Snowy Mountains in October (Mount Buller 490mm is one example with many likely much higher), Lake Dartmouth and Lake Hume will keep on spilling vigourously so the flows will remain very high. Factoring in further heavy rainfall, a truly enormous amount of water will continue to enter the system that hasn’t even arrived yet. Flooding will continue well into early next year across the Basin with more immediate flooding further upstream and east in the basin, and slower onset and prolonged flooding further downstream in SA for example. I am still expecting a flood peak very close to the 1974 level, but potentially it could be higher if a pulse down the Murray Co-incides with the main flow down the Darling. Many shacks and even parts of some towns will go under in any case so as mentioned previously, please be ready!

Meteorological Discussion:

Currently we are being blessed by some nice fine and warm weather with conditions even grading to hot inland. This is a rare welcome sight as normally hot and dry weather can be taxing for many but after what we have had, it’s certainly quite welcome to help dry out some very wet and soggy areas. The good news is we have a couple more days left of this with a slow-moving high-pressure ridge directing a relatively dry NE flow across the state although due to the remnant soil moisture content being high across a vast area of the state and especially the eastern states, we will see afternoon convection with even the slight chance of a shower or brief thunderstorm, especially closer to the border and about the ranges of the Upper and Lower North and at best the northern Mt.Lofty Ranges. This will be fairly isolated in nature on both the 7th and just a smidge more on the 8th.

The first one will see a deepening broad trough of low pressure over the west and NW of the state move eastwards. As it does so, it will weaken due to the fact that the supporting upper shortwave becomes quite small and weakens away. Nevertheless, isolated showers and thunderstorms are expected to develop from the 7th out over the Far West and gradually ever so slowly extend eastwards to reach most Central and agricultural areas by the 9th and eastern areas east of the ranges specifically by the 10th. It will become a little humid with this trough.

I should note that a weak trough will remain present over the eastern states from the 6th and 7th resulting in isolated afternoon and evening showers and thunderstorms caused by solar heating.

The trough will weaken further and clear to the east by the 11th contracting most shower and thunderstorm activity (there may be some lingering activity still remaining on afternoon of 11th) with it briefly however a more significant upper trough will likely snap off from the westerly belt and become cut off over the western Bight by later on the 11th and into the 12th. In response to this cooling air aloft, a new broader and deeper surface trough with associated low-pressure system will deepen over the interior of WA/Far West SA during the 11th and extend quickly SE. Isolated showers and thunderstorms will once again re-develop with this second system. By the 12th the surface low will begin to deepen further and curl back towards the cold air aloft situated further west and this should result in more scattered showers and thunderstorms developing, chiefly afternoon and early evening with a focus across the Lower and Upper North, Flinders, Riverland, Mallee and a vast swath of the Pastoral areas east of about the Stuart Highway. I will issue a special update for this system closer to the date to nail down the true specifics of the activity, but overall, not many will miss.

This system will contain greater quantities of tropical moisture and as a result greater instability causing a risk of severe thunderstorms with flash flooding, large hail and damaging winds once again.

By the 13th, the main trough will start to work eastwards causing showers and thunderstorms to begin to contract towards most districts east of the ranges and into the NE Pastoral. However, due to the head of the upper low closing in from the west, further scattered showers and isolated thunderstorms are likely to form as it pushing in during the 13th but these will be less electrically active and significant than the storms on the trough further east.

During approx the 14th-15th will see scattered to widespread showers as the upper low with cold air aloft moves eastwards. It will become much cooler and quite windy as the surface low moves eastwards, directing a fresh to strong and much cooler SW airstream across most districts, especially the agricultural areas.

Beyond this I can see another small lull in activity with high pressure having an influence before stronger troughs and lows become dominant towards the end of the month and this activity is likely to kick on into early December.

So overall it will come as no surprise that I am expecting another above average month for most districts, that hasn’t changed for some time now. The greatest chances of above average to well above average will be across the Lower and Upper Nort, Eyre Peninsula, Mallee, Riverland and into the Adelaide/Mt.Lofty Ranges region. The NE Pastoral closer to the Flinders also should do well. The greater pastoral area further north and west may become a little patchier due to the highly convective nature so there is a risk out here of some below average holes as well as the far western border portions but certainly a lot of blue again for this month. I don’t envisage the wetness of October however but still be context, it will be a frustrating month for harvest preparations and keeping crops from going rotten or sprouting in the head. Let's hope these dry days can really do some good in the meantime!

Climate Drivers

The Pacific has doubled down with the current La Nina with some cooling in the east and further warming in the west with the Coral Sea a main focus. It would easily be the warmest that I can ever remember it in my time following the weather. The expected weakish westerly wind burst from the MJO being in phases 6 and 7 has done nothing to weaken the overall La Nina. Further cold upwelling from the Humboldt Current with heating over the Coral has strengthened the gradient and as the sun works its way south towards the Tropic of Capricorn, the power of heating will increase further across the shallow waters north of the country and hold firmly in the Coral. There is a solid and well-established Walker Circulation at the moment and I think now with this doubling down through late October to now, that we will see the La Nina hang on that bit longer than it looked like a month or two back, with the eastern states firmly in the firing line.

Figure 4: Current SST anomalies – source Tropical Tidbits https://www.tropicaltidbits.com/analysis/ocean/cdas-sflux_ssta_global_1.png

Now the Indian has finally shown signs of the breakdown of the Negative IOD, and this has come right on time. It has been fuelling a lot of these strong systems through October, but the overall influence will linger in November before warning more in December. We shouldn’t have to worry about it until next year but that is a fair bit early as to which way the index will lean in 2023.

The MJO is now firmly over the other side of the world with the downwelling wave of the pulse now over the mainland of Australia. This has suppressed the tropical feeds for a short period (refer to Figure 5 below )

Figure 5 - Current MJO showing red downwelling air over the Australian/Indo region – source Mike Ventrice http://mikeventrice.weebly.com/mjo.html

However, I do expect the next upwelling phase of the MJO to push into the Australian region from late November and that is when we may see another uptick in tropical infeeds into the mainland although there will be slow increase from roughly the 10th onwards given the negative IOD is still having some form of influence albeit waning.

The SAM shot into negative territory at the end of October which was not unexpected given the MJO was in phase 6 to 7 from the last update though given the overwhelming power and influence of the La Nina, this will quickly revert back positive again in the coming days and weeks and to be honest

for a vast majority of the year with perhaps only brief spurts to neutral range and maybe negative however I don’t expect such strong cold polar surges anymore, only moderate strength ones or strong wrap around cut off lows.

Districts:

Eyre Peninsula

Warm to hot throughout and tending to very hot in the far west ahead of a deepening trough developing over the western border from about the 7th. Isolated showers and thunderstorms will be associated with this trough and will develop during the afternoon, although these will weaken through the evening reaching the Eyre Peninsula by the early hours of the 8th. Renewed isolated showers and thunderstorms will develop on 8th along the trough over the west coast with more easterly impact later in the evening. There may be a severe thunderstorm with damaging winds out amongst these over the far west and west coasts and associated interior. The trough weakens as it crosses the Peninsula on the 9th but still generating some isolated showers and thunderstorms and messy patchy rain areas. Storms again may be severe towards the NW Pastoral or far N of the Peninsula. A deepening and more significant low-pressure system from 11th to 14th will see conditions become humid and unsettled with stronger showers and thunderstorms with severe potential, especially in the north. Rainfall for the period highly variable due to thunderstorm activity. Totals generally between 8-15mm with isolated totals to 30mm in thunderstorms, especially in the N.

Upper North

Warm to hot throughout, tending to very hot towards Port Augusta although afternoon cloud will develop along the ranges with a slight chance of a shower and thunderstorm on 7th and more likely 8th. Deepening trough from west there after with isolated showers and thunderstorms extending from the west on the 9th with re-development on the 10th, chiefly in the east of the district. A deepening and more significant low-pressure system from 11th-14th will see conditions become humid and unsettled with stronger showers and thunderstorms with severe potential, especially on the 12th. Rainfall for the period highly variable due to thunderstorm activity. Totals generally between 15-25mm with isolated totals to 50mm in thunderstorms, especially in the far N and NE.

Lower North

Warm to hot throughout although afternoon cloud will develop along the ranges with a slight chance of a shower and thunderstorm on 7th and more likely 8th. Deepening trough from west there after with isolated showers and thunderstorms extending from the west on the 9th with re-development on the 10th, chiefly in the east of the district. A deepening and more significant low-pressure system from 11th-14th will see conditions become humid and unsettled with stronger showers and thunderstorms with severe potential, especially on the 12th. Rainfall for the period highly variable due to thunderstorm activity. Totals generally between 10-20mm with isolated totals to 40mm in thunderstorms, especially in the N and E.

Yorke Peninsula

Mild to warm in the south grading to hot in the north although afternoon cloud will develop along the Peninsula with a slight chance of a shower and thunderstorm on 7th and more likely 8th in the far north. Deepening trough from west there after with isolated showers and thunderstorms extending from the west on the 9th clearing on the 10th. A deepening and more significant low-pressure system from 11th-14th will see conditions become humid and unsettled with stronger showers and thunderstorms with severe potential, especially on the 12th. Rainfall for the period highly variable due to thunderstorm activity. Totals generally between 10-15mm with isolated totals to 20-25mm in thunderstorms, especially in the N.

Kangaroo Island

Mild to warm although afternoon cloud may develop on seabreeze convergence with a slight chance of a shower on 7th and more likely 8th if the seabreeze balance is correct. Deepening trough from west there after with isolated showers and thunderstorms extending from the west on the 9th clearing on the 10th. A deepening and more significant low-pressure system from 11th-14th will see conditions become humid and unsettled with stronger showers and thunderstorms, especially on the 12th. Rainfall for the period highly variable due to thunderstorm activity. Totals generally between 8-15mm with potential to 20mm if the low wraps around with more vigour.

Adelaide Plains

Warm to hot throughout although afternoon cloud will develop along the foothills and northern plains with a slight chance of a shower and thunderstorm on 7th and more likely 8th. Deepening trough from west there after with isolated showers and thunderstorms extending from the west on the 9th before contracting east and clearing on the 10th. A deepening and more significant low-pressure system from 11th-14th will see conditions become humid and unsettled with stronger showers and thunderstorms with severe potential, especially on the 12th. Rainfall for the period highly variable due to thunderstorm activity. Totals generally between 15-25mm with isolated totals to 30-40mm in thunderstorms, especially over the outer plains.

Mt.Lofty Ranges

Mild in the south grading to warm to hot elsewhere although afternoon cloud will develop along the ranges with a slight chance of a shower and thunderstorm about the central to northern ranges on 7th and more likely 8th. Deepening trough from west there after with isolated showers and thunderstorms extending from the west on the 9th before contracting east and clearing on the 10th. A deepening and more significant low-pressure system from 11th-14th will see conditions become humid and unsettled with stronger showers and thunderstorms with severe potential, especially on the 12th. Rainfall for the period highly variable due to thunderstorm activity. Totals generally between 20-30mm with isolated totals to 50mm in thunderstorms, especially in the N.

Riverland/Mallee

Warm to hot throughout, although afternoon cloud will develop, chiefly in the far west towards the ranges and again over the eastern border with a slight chance of a shower and thunderstorm on 7th and more likely 8th. Deepening trough from west there after with isolated showers and thunderstorms extending from the west late on the 9th with re-development on the 10th, chiefly during the afternoon. A deepening and more significant low-pressure system from 11th-14th will see conditions become humid and unsettled with stronger showers and thunderstorms with severe potential, especially on the 12th. Rainfall for the period highly variable due to thunderstorm activity. Totals generally between 20-30mm with isolated totals to 50mm in thunderstorms, especially in the N of the Riverland.

Upper SE

Warm to hot throughout, although afternoon cloud will develop, chiefly closer to the eastern border with a slight chance of a shower and thunderstorm on 7th and more likely 8th. Deepening trough from west there after with isolated showers and thunderstorms extending from the west late on the 9th with re-development on the 10th, chiefly during the afternoon. A deepening and more significant low-pressure system from 11th-14th will see conditions become humid and unsettled with stronger showers and thunderstorms with severe potential, especially on the 12th. Rainfall for the period highly variable due to thunderstorm activity. Totals generally between 20-30mm with isolated totals to 40mm in thunderstorms, especially in the N and E.

Lower SE

Mild about the coast but grading from warm to hot inland, although afternoon cloud will develop, chiefly closer to the eastern border with a slight chance of a shower and thunderstorm on 7th and more likely 8th. Deepening trough from west there after with isolated showers and thunderstorms extending from the west late on the 9th with re-development on the 10th, chiefly during the afternoon. A deepening and more significant low-pressure system from 11th-14th will see conditions become humid and unsettled with stronger showers and thunderstorms with severe potential, especially on the 12th. Rainfall for the period highly variable due to thunderstorm activity. Totals generally between 25-35mm with isolated totals to 40mm in thunderstorms, especially in the NE/E.

Western VIC

Warm to hot throughout with isolated to scattered afternoon and evening showers and thunderstorm on 7th becoming less likely on 8th as instability shifts west towards SA. Deepening trough from west there after with isolated showers and thunderstorms extending from the west very late on the 9th or early on the 10th, with activity increasing during the afternoon. A deepening and more significant low-pressure system from 11th-14th will see conditions become humid and unsettled with stronger showers and thunderstorms with severe potential, especially on the 12th. Heavy falls and flash flooding are likely. Rainfall for the period highly variable due to thunderstorm activity. Totals generally between 25-40mm with scattered totals to 60mm in thunderstorms, and isolated 80-100mm heavy flash flooding type falls especially in the E to NE.

Finals Notes:

• Marked shift in temperature with warmth now finally here however this increases the instability when moisture returns
• Humid and unsettled period coming up with multiple deep troughs with showers and thunderstorms for remainder of month, chiefly mid month and again later
• December looking hot, humid and very thundery for the eastern states with a tempering of that in SA however average to above average rainfall and thunderstorms are still expected
• January-Feb will bring the heat, however a focus for more inland flooding towards the Lake Eyre Basin can be expected and this may continue into March
• Historic slow onset flooding of Murray Darling on track as expected with multiple high peaks in the 1974 vicinity
• Special update for 11th-14th deep/broad low to contain more precise detail

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Happy Farming and Cheers from The Weatherman

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