January 2023 Outlook SA

January 2023 outlook SA

*Forecast prepared between January 2nd-5th 2023

Review:

G’Day everyone, Happy New Year to you all! I value each and every one of you who read and provide feedback for these updates that I do. I hope you all had a wonderful Christmas. This year is when I plan to make some moves on the future of The Weatherman brand and bring out a subscription service with more content both in amounts and frequency than I have been providing in these bi-monthly updates so pleased stay tuned for further developments as the year goes by!

Now a brief look back at December before we nut out the first month of 2023 and to be honest December was a fairly unspectacular month though that is what we expected and hoped for granted so many of you were busy doing the harvest (and some still are).

For the most part we saw more settled conditions across the state compared to spring with a reset in the broadscale pattern. Thunderstorms still occurred however they were less widespread and severe with a focus a little further north with high pressure ridging keeping areas. The main thunderstorm event occurred on the 21st with some fairly strong thunderstorms including supercells across the Lower and Upper North primarily but also the NE Pastoral and Riverland. Flash flooding, damaging winds and low-end large hail were the main threats. A particularly strong storm moved through the Appila to Peterborough area with strong rotation and from what I heard from on ground reports did cause some localised damage.

Heat then made itself known closer to Christmas and after with temperatures into the low 40’s inland but a surface trough on the 26th anchored over the eastern parts of the state was fed a little more moisture than initially expected resulting in afternoon showers and isolated thunderstorms across many areas north of about Gawler, with Owen copping repeat thunderstorms and 26mm with flash flooding in parts.

In terms of the initial outlook rainfall wise this is the recap of the outlook for December:

“But overall, as an outlook for December, I am expecting a very close to average month for most areas, but perhaps with a slight trend to slight below average across agricultural areas such as the Lower and Upper North, Mallee and SE Districts but not a huge amount. Further north across the interior sees the greatest chances of above average rainfall with the upper NW Pastoral fielding the best chance of above average falls being closer to those infeeds from the NT.“

Figure 1: December 2022 rainfall deciles – source BoM http://www.bom.gov.au/climate/

Now above we can see that overall, the outlook rang quite true with average conditions being dominant. The drier trend to slightly below average worked well across the bulk of the agricultural areas and we can see this reflected well in the percentages chart in Figure 2 below. There was however a little patch of above average rainfall for the far N EP to the Southern NW Pastoral mostly due to thunderstorm activity and also a band of rain with a large bulk of the remainder of the NW Pastoral being below average. The expected above average area over the Upper NW Pastoral was there but I think it was clearly more dominant over the Upper NE Pastoral and this is most likely due to the jetstream taking the heavier thunderstorm activity that bit further east than I envisaged. But all in all, a respectable month for those needing to get the harvest done as another November like effort would have been quite devastating.

Figure 2: December 2022 rainfall percentages – source BoM http://www.bom.gov.au/climate/

Meteorological Discussion

The current pattern is now in a typical summer pattern but with no strong biases either way to too hot or too cool. We have an established Monsoonal flow to the north with heavy rain and monsoonal showers and storms with ridging further south interspaced by low pressure troughs with the eastern trough currently delivering severe thunderstorms to NSW and QLD. On the 2nd there were some extremely powerful supercell thunderstorms across VIC triggered from this trough, namely south of Pyramid Hill and Benigo as well as near Clunes. This trough will continue to contract east to NE in the coming days.

A large high-pressure system is moving through the Bight as we speak (4th) and will move eastwards in the coming days. The deep monsoonal low associated with Ex TC Ellie is located near Broome and will remain slow moving for a day or two before speeding up on a SE path across the interior of WA and NT before dissolving. Heavy rain will continue to occur near this low with a lot of flooding and some of this rain is expected across the far northern interior of SA between late 7th and up to the 10th though totals will be feeble in comparison to the NT and WA. Inland QLD will also get good moisture feeding in off both the Coral Sea and the Gulf of Carpentaria which will combine with convergent lift ahead of this low and broad low-pressure trough. It is quite feasible to say that flooding will occur across WA, NT & inland QLD from this system (we already have WA and NT).

I am particularly concerned about QLD from this point onwards due to the double effect of the Coral Sea and the Gulf of Carpentaria where the combined moisture levels will be extreme. Look out for flooding tropical rains across Cape York Peninsula then extending southwards into the QLD interior as the month goes by and potentially into February as well.

Back over the remainder of SA all we will likely see is some heat from the NE/N flow ahead of the weak trough and new ridge which will then push in bringing a weak wind change before the gradient tightens and S/SE winds freshen on the 8th and 9th. Temperatures before the change will be in the high 30’s to low 40’s across the agricultural area.

The pattern will almost repeat in the same manner after this change with the new high moving east before weakening and sinking SE allowing inland heat to move south again as a trough deepens over the interior. THe ridge in the Bight may get another squeeze as the trough deepens allowing more SE winds to push back from later 12th to 13th bringing a weak shallow change but remaining hot further inland in a SE-E flow.

After this one thing I look for is when we have a large build-up of moisture over tropical QLD both from the Coral and Gulf of Carpentaria is the advection of that moisture back SW into a retrograding easterly dip. I expect this to happen in the second half of this month or start just before with one or two attempts at getting moisture and humidity right down into the agricultural areas. Once the MJO is closer to phase 2 then the easterlies/NE flow may favour that advection with a ridge pushing up the NSW and QLD coastline cradling and steering the surface trough (easterly dip) westwards. The NE Pastoral especially should be a focus for afternoon and evening showers and thunderstorms but I will re-visit this scenario in the mid-month update. 

The outlook overall for January is a below average month over the more southern portions of the state including most of the agricultural areas and west coast. Average conditions are likely into the interior and the far northern to NE border may see average to slightly above average with moreso the eastern half of the NE Pastoral a focus for above average rainfall with regards to the infeed potential from QLD. Should this moisture push hard enough SW then some average to slightly above average localised pockets may appear over the eastern agricultural areas but this chance for now looks slim.

Climate Drivers:

The Pacific has ever so slightly continued its trend away from La Nina with weakening of the Humboldt Current which can be seen by some warming anomalies off South America’s west coastline. In the sub-surface the warming continues to move eastwards and strengthen but only very slowly so this will be a snail's pace for quite some time yet as we move further into 2023. Over the Western Pacific the very warm Coral Sea has also cooled but this can mostly be attributed to convective feedback which has now halted the intense solar radiation with multiple tropical convective blooms appearing in the region.

The Indian has continued to cool slowly, and the Monsoon Trough has now carved a path of cooler anomalies through Indonesia and across the Kimberley and Top End coastlines where strong W to NW winds are churning up the surface as well as a vast multitude of convection limiting solar radiation. This is normal and once the monsoon retreats, we should see a little more warming resume but overall, very much within expected ranges for this time of the year.

Figure 3: Current SST anomalies – source Tropical Tidbits https://www.tropicaltidbits.com/analysis/ocean/cdas-sflux_ssta_global_1.png

The MJO has recently moved through the Australian window at a moderate strength generating a very solid monsoon onset, a little stronger and more consistent than I was expecting, mainly thanks to the positioning and slow movement of the deep monsoonal low formerly known as TC Ellie. The convergence and compression of the flow to the north of this low has caused frequent monsoonal squalls for the Top End. Furthermore, the cross-equatorial flow from a large Siberian high has further enhanced the longevity of this Monsoon boost. Large areas of flooding inland over NT has occurred which was mentioned in the December update however even more extreme flooding has occurred over the Kimberley with some incredible rainfall totals near Fitzroy Crossing and Broome between 300-400mm in about 3-4 days with another 100-200mm at least yet to come. I expect the MJO to move eastwards through Phases 6 and 7 in the coming week before re-emerging into the Western Indian late January and moving closer to the Australian region for another monsoon burst through February which should be similar strength to the current one if not a little stronger.

The SAM has been consistently positive since the last update but due to such big inland rains, the heat has struggled a little to really push south and stay there. The index should remain positive in the coming weeks adding to the heat and moisture pressure from the north. I am noting however the ridging through the Eastern Indian west of Perth has been stronger than usual for a positive SAM so the influence of new ridging into the Bight will be more present and thus the weak shallow S/SE changes from the new Bight ridge will have more impact across Southern Ag areas as we move through the remainder of this month. Remaining very hot inland however but with rain events across the far northern interior likely.

Districts:

Eyre Peninsula

Generally dry for the period. High pressure system moving steadily eastwards directing hot to very hot conditions over the district from 6th-8th ahead of a weak change bringing cooler conditions during 8th. New ridge and tight S/SE gradient later 8th and especially 9th bringing fresh to strong seabreezes before the ridge moves east and warm to hot conditions return from 11th tending very hot by 12th ahead of a shallow and mostly coastal change. Ridge briefly pushing back with tighter SE flow freshening winds about exposed coastlines but remaining hot to very hot inland. Heat building once again to potentially very hot mid-month ahead of a slightly stronger trough extending from the west. Rainfall for period less than 1mm to nil.

Upper North

Generally dry for the period. High pressure system moving steadily eastwards directing hot to very hot conditions over the district from 6th-8th ahead of a weak change bringing cooler conditions during 8th. New ridge and tight S/SE gradient later 8th and especially 9th before the ridge moves east and warm to hot conditions return from 11th tending very hot by 12th however a westward moving surface trough from the eastern states may see isolated afternoon and evening showers and thunderstorms from 12th in the east and about elevated terrain/ranges. Nocturnal gully winds may be fresh to strong at times about western slopes on 5th-6th and again 9th-10th. . Rainfall for period less than 1mm for most however local 5-10mm totals may occur in potential thunderstorm activity.

Lower North

Generally dry for the period. High pressure system moving steadily eastwards directing hot to very hot conditions over the district from 6th-8th ahead of a weak change bringing cooler conditions during 8th. New ridge and tight S/SE gradient later 8th and especially 9th before the ridge moves east and warm to hot conditions return from 11th tending very hot by 12th however a westward moving surface trough from the eastern states may see isolated afternoon and evening showers and possible thunderstorms from 12th in the east, far north and about elevated terrain/ranges. Nocturnal gully winds may be fresh to strong at times about western slopes on 5th-6th and again 9th-10th. . Rainfall for period less than 1mm for most however local 3-8mm totals may occur in potential shower or thunderstorm activity.

Yorke Peninsula

Generally dry for the period. High pressure system moving steadily eastwards directing hot to very hot conditions over the district from 6th-8th ahead of a weak change bringing cooler conditions, especially about the foot during 8th. New ridge and tight S/SE gradient later 8th and especially 9th bringing fresh to strong seabreezes before the ridge moves east and warm to hot conditions return from 11th tending very hot by 12th in the north ahead of a shallow and mostly coastal change. Ridge briefly pushing back with tighter SE flow freshening winds about exposed coastlines but remaining hot to very hot towards the north of the Peninsula. Rainfall for period less than 1mm to nil.

Kangaroo Island

Generally dry for the period. High pressure system moving steadily eastwards directing warm to hot conditions over the island from 6th-8th ahead of a weak change bringing cooler conditions during 8th. New ridge and tight S/SE gradient later 8th and especially 9th bringing fresh to strong seabreezes before the ridge moves east and warm to hot conditions return from 11th. Ridge briefly pushing back with tighter SE flow freshening winds once again but remaining mild to warm for the most part and dry. Rainfall for period less than 1mm to nil.

Adelaide Plains

Generally dry for the period. High pressure system moving steadily eastwards directing hot to very hot conditions over the district from 6th-8th ahead of a weak change bringing cooler conditions, especially about the southern suburbs during 8th. New ridge and tight S/SE gradient later 8th and especially 9th bringing fresh to strong seabreezes before the ridge moves east and warm to hot conditions return from 11th tending very hot by 12th in the north ahead of a shallow and mostly coastal change. Ridge briefly pushing back with tighter SE flow freshening winds about exposed coastlines but remaining hot to very hot towards the outer northern plains. Nocturnal gully winds may be fresh to strong at times about western slopes on 5th-6th and again 9th-10th. Rainfall for period less than 1mm to nil.

Mt.Lofty Ranges

Generally dry for the period. High pressure system moving steadily eastwards directing hot to very hot conditions over the district from 6th-8th ahead of a weak change bringing cooler conditions, especially about the southern suburbs during 8th. New ridge and tight S/SE gradient later 8th and especially 9th bringing fresh to strong seabreezes before the ridge moves east and warm to hot conditions return from 11th tending very hot by 12th in the north ahead of a shallow and mostly coastal change. Ridge briefly pushing back with tighter SE flow freshening winds about exposed coastlines but remaining hot to very hot towards the northern ranges. Afternoon convection may be present about northern ranges from 12th as moisture feeds in from QLD into a surface trough but no rainfall is expected at this stage. Nocturnal gully winds may be fresh to strong at times about western slopes on 5th-6th and again 9th-10th. Rainfall for period less than 1mm to nil.

Riverland/Mallee

Generally dry for the period. High pressure system moving steadily eastwards directing hot to very hot conditions over the district from 6th-8th ahead of a weak change bringing cooler conditions during 8th to early 9th. New ridge and tight S/SE gradient later 8th and especially 9th before the ridge moves east and warm to hot conditions return from 11th tending very hot by 12th however a westward moving surface trough from the eastern states may see isolated afternoon and evening showers and thunderstorms from 12th towards the Riverland or far eastern Mallee with general afternoon convection elsewhere. Rainfall for period less than 1mm for most however local 3-8mm totals may occur in potential thunderstorm activity.

Upper SE

Generally dry for the period. High pressure system moving steadily eastwards directing hot to very hot conditions over the district from 6th-8th ahead of a weak change bringing cooler conditions during 8th to early 9th. New ridge and tight S/SE gradient later 8th and especially 9th before the ridge moves east and warm to hot conditions return from 11th tending very hot by 12th however a westward moving surface trough from the eastern states may see isolated afternoon and evening showers and thunderstorms from 12th towards the far eastern border or just north of with general afternoon convection elsewhere. Rainfall for period less than 1mm for most however local 2-5mm totals may occur in potential thunderstorm activity.

Lower SE

Generally dry for the period. High pressure system moving steadily eastwards directing hot to very hot conditions over the district from 6th-8th ahead of a weak change bringing cooler conditions and isolated light coastal showers during 8th to early 9th. New ridge and tight S/SE gradient later 8th and especially 9th before the ridge moves east and warm to hot conditions return from 11th tending very hot by 12th however a westward moving surface trough from the eastern states may see isolated afternoon and evening showers and thunderstorms from 12th towards the far eastern border or just north of with general afternoon convection elsewhere. Rainfall for period less than 1mm for most however local 2-5mm totals may occur in potential thunderstorm activity.

Western VIC

Generally dry for the period. High pressure system moving steadily eastwards directing hot to very hot conditions over the district from 6th-8th ahead of a weak change bringing cooler conditions and isolated light coastal showers during 8th to early 9th. New ridge and tight S/SE gradient later 8th and especially 9th before the ridge moves east and warm to hot conditions return from 11th tending very hot by 12th however a westward moving surface trough may see isolated afternoon and evening showers and thunderstorms from 12th chiefly over the Mallee and Wimmera district. Rainfall for period less than 1mm for most however local 5-10mm totals may occur in potential thunderstorm activity.

Finals Notes:

• Classic January pattern for the most part with mix of heat inland and weak coastal changes
• Big tropical rains for WA, NT & especially QLD for this month with flooding
• Murray flood peak now moving past Morgan and should be into about Mannum within the week to just beyond 1931 levels
• More heat likely for February as inland WA heats up with advection into SA
• Tropical Cyclones will become more frequent in Feb and March with a number of strong systems likely
• Drier later autumn still on the cards with warm neutral to possibly weak El Nino developing with a cooler tha normal eastern Indian another contributing factor but a long way to go yet.

Link to temporary blog website: https://farmweathersa.blogspot.com/