June Update 2024 SA

June update 2024 SA

*Forecast prepared between June 17th-18th 2024

Review:

G’Day everyone, I hope you are keeping well and no doubt busy keeping a very close eye on any emerging crops. I expect many still have no emerged which would no doubt be stressful so this update will take a look at the next 2 weeks and how things are shaping up rainfall wise. We have made some progress finally in some dry districts but there are multiple locations that have received minimal rainfall and need a lot more in these coming weeks to have any chance to get near average rainfall for the month and indeed going forward with their yields.

June so far has been a real mixed bag – a dry and mild to warm start after a little bit of rain at the end of May. Frost was a feature across most districts in the first week and in particular on the mornings of the 2nd & 3rd where many negative readings were recorded, chiefly in the north and east of the state. However, the 5th, 7th, 8th 16th and again especially this morning on the 17th have seen more significant moderate frost areas recorded with –4.8C at Yunta, -2.2C at Keith West, -2.4C at Robe & Padthaway and –1.9C at Renmark. Yunta especially with that temperature will be getting closer to heavy frost.

Now rainfall wise, it took a little while for systems to push east enough and break down the block to finally start to break the season and we saw this come for a second try around the June 11th-14th period where a general infeed of moisture from the NW pushed into a weak cut off low that formed in response to a small upper trough aloft. This system was a little ‘flatter’ in nature meaning that the steering flow was more west to east than NW-SE and this assisted in getting better penetration over the ranges with the mid-level rainband which was semi-convective at times with a focus across the Southern Mallee and Upper SE Districts. The Lower SE however, especially more southern portions really did miss out. Rainfall of 8-15mm from the rainband seemed fairly commonplace, although in that narrowish band. Locations north of Adelaide did not fair so well with patchier 2-7mm totals.

The kicker was once the upper low moved over the top with the low-level moisture leftover from the rain the day before. Once surface heating occurred, showers and isolated thunderstorms developed which were stronger than the typical coldie cells we get in cold air – these were more a hybrid type of warm season storms and the coldie type and thus with greater vertical extent than coldies as well as more moisture. Some training of these cells occurred over the Southern Suburbs of Adelaide during the afternoon of the 14th with localised flash flooding in the Lonsdale to Reynella area with totals of 60-70mm within a couple of hours. Isolated thunderstorms also develop over the Mallee and Riverland with that cold air aloft generating localised 10-20mm totals in a short time so some people did quite well but not all received these localised dumps. High pressure moved in after with further frosty conditions which we have seen this morning.

Meteorological Discussion:

Currently we are in the midst of a developing wetter period which is a nice change from the blocking and relentless dry that have plagued the state since late January, with a gripping autumn dry spell that resulted in severe deficits in many growing and pastoral zones. The longwave trough which is a key driver in breaking rainfall and infeed our winter rainfall has been anchored to the SW of WA for a solid month now and it continues to sit there with various shortwaves breaking off from it and pushing eastwards. Most of these have been beaten down by the high pressure to the east however recently we have seen the influence of that weaken with more frequent NW cloudband intrusions and shortwaves getting to our longitude. This will continue to build over the next 2-3 weeks as the NW flow aloft dominates the region.

A current look at the satellite imagery shows the persistent infeed of moisture from the Eastern IOD measurement area from Sumatra and Java with a NW cloudband of moisture almost semi-permanent in that region at the moment.

Figure 1: Current satellite imagery from 16.06/24 @ 1630hrs ACST showing persistent moisture feeding into WA from Indonesia – source Weatherzone

This is a great sign and although sustained rainfall is not happening right now in SA nor VIC, seeing this at least gives hope that it is feeding down and giving some opportunity. If I did not see this signal/cloud feeding down, I’d certainly be far more bearish on this growing season.

To the east over the Tasman Sea, we have a large low-pressure system which has been driving showers up the NSW coastline as well as generating a very large swell with significant beach erosion from powerful waves. Surfers however have been happy with probably the best swell event of the year.

Further to the SW of WA lies a cold front with a pool of cold air and this is the system that we cast our eye toward for the next rainfall for wed 19th to thurs 20th.

Currently however as of the 17th, a weak trough of low pressure over the west of the state is combining with a slight squeeze on the jetstream aloft to generate areas of patchy light rain across the Western and Northern agricultural districts. This rain is not very significant although Minnipa has managed to record 4mm since 9am however most totals from this have been below 2mm and that is for the most part how it will remain.

Moving forward, the aforementioned cold front and pool of cold air will move NE during the 18th and by the 19th will cross the state with a band of showers initially. A small cut off low will form as the system moves NE causing the cold air to spiral into some banding, the backside of this should then fling back up around the West Coast to Eyre Peninsula before gradually petering out as the centre of the low is most likely to track up the gulf areas approx. Isolated thunderstorms are possible across any agricultural areas however more likely though just offshore as the system comes in and around Kangaroo Island. The Upper North and general northern agricultural areas will not see substantial rainfall from this system, but perhaps something to ward off the dryness for a short while. Not a deep soaker by any stretch. Some parts of Eyre Peninsula from the combination of the frontal band and wrap around occlusion on the back side should see over 10-15mm which will be most welcome with some reasonable penetration on the wrap around band.

Beyond this we quickly see a moderate sized high pressure move in and with that comes a frost risk. At this stage I will be anticipating the greatest risk on the morning of the 22nd where we should see widespread moderate frost in the eastern to northern agricultural areas however there should still be a slight risk in the western as well. The 23rd sees the risk continue, chiefly more in the northern and eastern once again but perhaps not quite to the level of the night before. I should also make note whilst on the topic of frost that the morning of the 18th looks similar in mostly the eastern to SE Districts away from cloud and into Western VIC where the risk increases to a moderate to potentially heavy frost in some locations including the 19th as well.

As the longwave to the west continues to spawn smaller shortwaves, the next one due will be around the 24th give or take a day. Now the good news is we have a mobile pattern, with no upstream blocking however there is enough meandering in the jetstreams with a meridional flow to induce cut off lows with a majority of the systems. We are yet to see a steady zonal winter pattern which typical comes with a more strongly negative SAM. I see only a weak negative to neutral levels at the current point in time but more on that in the climate driver section. The system around the 24th should bring a band of showers but will likely weaken on the way in as the jet aloft slackens letting the shortwave slide and lift although a more substantial large shortwave should spawn off the longwave trough under WA and bring a potential NW Cloudband in ahead of a broader low pressure and cold air field from around the 26th to 27th give or take a day again - something I am watching closely as the moisture feed will be ready, the alignment is the issue. Granted the position of the longwave, this system will still have a sliding tendency but with that NW-SE flow aloft, tending more W-E potentially. A rainband tending to showers and isolated cold air thunderstorms, chiefly over southern agricultural areas is my current thinking with this final system of the month. A special update will be issued to nail specifics should the need arise.

Climate Drivers:

A rather lax Pacific in the last couple of weeks has seen no real changes in the SST pattern with the development of La Nina no further progressed since the last update and this is normal as nothing forms at a steady rate. We currently sit smack bang in neutral conditions as far as the SOI goes but with that tendency towards La Nina as the colder sub-surface waters slowly begin to surface. I do expect trade winds to pick up a little in the coming week or so which may begin to get the ball rolling again.

Figure 2: Current SST anomalies – source Tropical Tidbits https://www.tropicaltidbits.com/analysis/ocean/cdas-sflux_ssta_global_1.png

The Indian has moved slowly in the last 2 weeks however the latest reading of the IOD is –0.02C. Negative side of 0 but well within neutral territory but the trend has been towards negative for a number of weeks now which is backed up by the constant presence of NW cloudbands feeding into WA and the ever present convection and thunderstorm activity right over the Eastern IOD box. I fully believe this ‘false’ positive IOD is going to be the case as mentioned in previous updates where there was a lot of noise about it and although we may push back a little into positive territory in July, I expect the broader tendency as we move towards Spring, especially mid spring to be much closer to a weak negative IOD than anywhere near a positive one. But this means however that for the bulk of the growing season we will be sitting in neutral territory which I know doesn’t bode well for some but the negative side of neutral at the crunch time of the season. The Indian influence is strong now, but it is not getting into our state enough and I expect that presence to remain there more or less

throughout the season, but especially in September to November. There will be a slow ebbing and flowing till then of the moisture levels presenting into mainland Australia out of the Indian.

The SAM is slowly expanding a little to negative territory but we still are broadly in a neutral zone. Not the strong positive we saw in April and May. I expect a negative finish to June before back to neutral in July with some more positive moments as high pressure returns for a while.

The MJO is currently weak and largely not influencing weather patterns however there is a potential for it to emerge in the Indian at a moderate strength although I suspect it will be on the weaker end. This at least will help keep convection firing near Indonesia and possibly some cooler water to surface over the Western IOD box. The stronger the pulse the better that outcome is for us.

Districts:

Eyre Peninsula

Weak trough with mid-level showers or patchy light rain clearing on the 18th. Cold front and associated low pressure system moving through on morning of 19th with a band of showers and an isolated thunderstorm or two. Colder air showers to follow throughout the afternoon and evening, chiefly for the Lower and Western portions of the Peninsula with strong and squally NW-SW winds developing as low tightens and moves NNE up the gulfs, gale force at times about exposed western coasts. Secondary showery band wrapping around back side of low on 20th with slightly more northern penetration with strong and squally SW winds tending S throughout the day and moderating with showers becoming isolated. Sheep graziers alert is likely for the wet and windy conditions. High moving in quickly for 21st-23rd period with fine conditions. Slight frost risk in prone locations on morning of 22nd. Weakening shortwave and cold front due around 24th with a band of showers before a stronger system with NW Cloudband potential pushes in from the west from the 26th to 27th. Rain areas tending to showers with colder air to follow in a fresh to strong NW-W flow are likely, especially over western and southern portions of the Peninsula once again. Rainfall for the period 20-30mm over southern and western portions of EP. Scattered totals to 35mm and isolated 40mm falls possible closer to the Lower Western EP coastline. Totals decreasing towards the N and NE with 8-15mm likely with isolated areas down to 5mm about far NE EP.

Upper North

Weak trough with mid-level showers or patchy light rain clearing on the 18th. Cold front and associated low pressure system moving through during late afternoon of 19th with a band of showers and an isolated thunderstorm or two. Showers much more isolated north of about Jamestown. Shower activity clearing overnight as a fresh NW-W flow established behind the front bringing drier air in. Secondary showery band wrapping around back side of low during afternoon 20th with showers extending up from the SW before becoming isolated and clearing during the late evening. High moving in quickly for 21st-23rd period with fine conditions. Moderate frost risk in prone locations on morning of 22nd and 23rd. Weakening shortwave and cold front due around 24th with a band of sliding isolated showers before a stronger system with NW Cloudband potential pushes in from the west from the 26th to 27th. Rain areas tending to showers with colder air to follow in a fresh to strong NW-W flow are likely, however much more likely with southern extent. Rainfall for the period 8-15mm. Scattered totals to 20mm and isolated 25mm falls possible in the south and about higher terrain. Totals decreasing towards the N and E of the ranges with 5-8mm expected.

Lower North

Weak trough with mid-level showers or patchy light rain clearing on the 18th. Cold front and associated low pressure system moving through during late afternoon of 19th with a band of showers and an isolated thunderstorm or two possible. Shower activity clearing overnight as a fresh NW-W flow established behind the front bringing drier air in. Secondary showery band wrapping around back side of low during late morning to early afternoon of 20th with showers extending up from the SW before becoming isolated and clearing during the late evening. High moving in quickly for 21st-23rd period with fine conditions. Moderate frost risk in prone locations on morning of 22nd and 23rd. Weakening shortwave trough and cold front due around 24th with a band of sliding showers before a stronger system with NW Cloudband potential pushes in from the west from the 26th to 27th. Rain areas tending to showers with colder air to follow in a fresh to strong NW-W flow are likely, however much more likely with southern extent. Rainfall for the period 12-18mm. Scattered totals to 25mm and isolated 30mm falls possible in the south and about higher terrain. Totals decreasing towards the N and E of the ranges with 7-12mm expected.

Yorke Peninsula

Weak trough with mid-level showers or patchy light rain clearing the north on the 18th. Cold front and associated low pressure system moving through on the afternoon of 19th with a band of showers and an isolated thunderstorm or two. Colder air showers to follow throughout the evening and overnight into the 20th about the foot only with strong and squally NW-SW winds developing as low tightens and moves NNE up the gulfs. Secondary showery band wrapping around back side of low on 20th with more northern penetration with strong and squally SW winds tending S throughout the day and moderating with showers becoming isolated later. High moving in quickly for 21st-23rd period with fine conditions. Slight frost risk in prone locations about the Central and northern portions of the Peninsula on morning of 22nd and again on 23rd although a lower risk. Weakening shortwave and cold front due around 24th with a sliding band of showers before a stronger system with NW Cloudband potential pushes in from the west from the 26th to 27th. Rain areas tending to showers with colder air to follow in a fresh to strong NW-W flow are likely, especially with southern extent. Rainfall for the period 18-28mm over the foot. Scattered totals to 30mm and isolated 35-40mm falls possible here. Totals decreasing towards the N with 15-18mm about Central portions and 12-15mm about the north.

Kangaroo Island

Weak trough with a possible mid-level shower or two clearing on the 18th. Cold front and associated low pressure system moving through around lunchtime to early afternoon of 19th with a couple of bands of showers and an isolated thunderstorm or two. Colder air showers to follow throughout the evening, with strong and squally NW-SW winds developing as low tightens and moves NNE up the gulfs, gale force at times about exposed western coasts. Showers becoming isolated on 20th as low weakens and moves away to the NNE. Sheep graziers alert is possible for the wet and windy conditions, especially towards the western end of the island. High moving in quickly for 21st-23rd period with fine conditions. Slight frost risk in prone locations near centre of island on morning of 22nd. Weakening shortwave and cold front due around 24th with a band of showers before a stronger system with NW Cloudband potential pushes in from the west from the 26th to 27th. Rain areas tending to showers with colder air and isolated thunderstorms to follow in a fresh to strong NW-W flow are likely. Rainfall for the period 30-40mm generally with scattered totals to 45mm and isolated 50mm falls possible closer to the western end. Totals decreasing towards the E with 20-30mm likely there.

Adelaide Plains

Weak trough with mid-level showers or patchy light rain clearing the northern suburbs and outer plains on the 18th. Cold front and associated low pressure system moving through later on the afternoon of 19th with a band of showers and an isolated thunderstorm or two. Colder air showers to follow about the far southern suburbs during the evening and overnight into the 20th. Secondary near stationary band of showers (at first) wrapping around back and top side of low on 20th with fresh NW-S winds moderating with showers becoming isolated later. High moving in quickly for 21st-23rd period with fine conditions. Slight to moderate frost risk in prone locations about the outer northern plains on morning of 22nd and again on 23rd although a lower risk on the 23rd. Weakening shortwave and cold front due around 24th with a sliding band of showers before a stronger system with NW Cloudband potential pushes in from the west from the 26th to 27th. Rain areas tending to showers with colder air to follow in a fresh to strong NW-W flow are likely, especially with southern extent. Rainfall for the period generally 20-30mm with scattered totals to 35mm in the south and near foothills with isolated 40mm falls possible here also. Totals decreasing towards the outer N plains with 15-20mm expected.

Mt.Lofty Ranges

Weak trough with mid-level showers or patchy light rain clearing the northern ranges on the 18th. Cold front and associated low pressure system moving through later on the afternoon of 19th with a band of showers and an isolated thunderstorm or two. Colder air showers to follow about the southern ranges chiefly during the evening and overnight into the 20th with orographic effects playing a big part. Secondary near stationary band of showers (at first) wrapping around back and top side of low on 20th with fresh NW-S winds moderating with showers becoming isolated later. High moving in quickly for 21st-23rd period with fine conditions. Slight to moderate frost risk in prone locations about the Barossa and low-lying hills valleys on morning of 22nd and again on 23rd although a lower risk on the 23rd. Weakening shortwave and cold front due around 24th with a sliding band of showers before a stronger system with NW Cloudband potential pushes in from the west from the 26th to 27th. Rain areas tending to showers with colder air to follow in a fresh to strong NW-W flow are likely, especially with southern extent. Heavy falls possible about known wet spots and highest peaks. Rainfall for the period generally 30-40mm with scattered totals to 45-50mm. Isolated 50-70mm falls possible about those known wet spots. Totals decreasing towards the Barossa and outer northern ranges down to 20-30mm and the lee side of the ranges down to as low as 10-20mm.

Riverland/Mallee

Weak trough with mid-level showers or patchy light rain clearing the Riverland on the 18th. Cold front and associated low pressure system moving through during late afternoon of 19th with a band of showers and an isolated thunderstorm or two. Showers more isolated towards the Riverland. Shower activity clearing overnight as a fresh NW-W flow established behind the front bringing drier air in. Isolated to scattered showers re-developing during the afternoon of 20th before easing and largely clearing during the evening. High moving in quickly for 21st-23rd period with fine conditions.

Moderate frost risk in prone locations on morning of 22nd and 23rd. Weakening shortwave and cold front due around 24th with a band of sliding isolated showers possibly clipping the Southern Mallee before a stronger system with NW Cloudband potential pushes in from the west from the 26th to 27th. Rain areas tending to showers with colder air to follow in a fresh to strong NW-W flow are likely, however much more likely with southern extent towards the southern Mallee. Rainfall for the period 5-10mm about the Mallee with scattered totals to 12mm and isolated 15mm falls possible in the far south/SE. Totals decreasing towards the Riverland with 4-7mm the general idea there.

Upper SE

Weak trough with mid-level cloud on the 18th. Cold front and associated low pressure system moving through during mid to late evening of 19th with a band of showers and possibly an isolated thunderstorm. Shower activity clearing overnight as a fresh NW-W flow established behind the front bringing drier air in. Isolated to scattered showers re-developing during the morning of 20th before easing and largely clearing during the evening. High moving in quickly for 21st-23rd period with fine conditions. Moderate frost risk in prone locations on morning of 22nd and 23rd. Weakening shortwave and cold front due around 24th with a band of sliding showers, chiefly near the Coorong coastline only before a stronger system with NW Cloudband potential pushes in from the west from the 26th to 27th. Rain areas tending to showers with colder air to follow in a fresh to strong NW-W flow are likely. Rainfall for the period 8-15mm with scattered totals to 20mm and isolated 25mm falls possible in the far west towards the Coorong coastline. Totals decreasing towards the Mallee down to around 6-8mm potentially.

Lower SE

Weak trough with mid-level cloud on the 18th. Cold front and associated low pressure system moving through during mid to late evening of 19th with a band of showers and possibly an isolated thunderstorm. Isolated to scattered showers re-developing during the morning of 20th before easing later though a moist onshore southerly may keep drizzly light showers ongoing. High moving in quickly for 21st-23rd period with fine conditions. Moderate frost risk in prone locations on morning of 22nd and 23rd. Weakening shortwave and cold front due around 24th with a band of sliding showers, chiefly near the SW coastline only before a stronger system with NW Cloudband potential pushes in from the west from the 26th to 27th. Rain areas tending to showers with colder air to follow in a fresh to strong NW-W flow are likely. Rainfall for the period 12-22mm with scattered totals to 25-30mm and isolated 35-40mm falls possible. Totals decreasing towards the Upper SE down to 10-12mm.

Western VIC

Weak trough with mid-level cloud on the 18th. Cold front and associated low pressure system moving through during the late evening of 19th with a band of showers and possibly an isolated thunderstorm with the band becoming slow moving early on the 20th over the SW district. Isolated to scattered late morning to afternoon showers re-developing further north of this band across the Wimmera and possibly the Mallee too before clearing for the most part during the evening. High moving in quickly for 21st-23rd period with fine conditions. Moderate to possibly even heavy frost risk in prone locations on morning of 22nd and 23rd. Weakening shortwave and cold front due around 24th with a band of sliding coastal showers only before a stronger system with NW Cloudband potential pushes in from the west from the 27th to 28th. Rain areas tending to showers with colder air to follow in a fresh to strong NW-W flow are likely. Rainfall for the period 8-15mm with scattered totals to 20mm over the SW District and about the Grampians with isolated localised 25mm totals there. Totals decreasing towards the Mallee down to 4-8mm.

Final Notes

• The long, drawn out and frustrating break continues for many, especially areas north of about Clare however as we enter a period of regular systems, these areas will eventually become wetter but through small accumulations only
• Strong to gale force winds W-SW winds across the Western coasts of Eyre Peninsula especially with system later on 19th, a sheep graziers alert would be warranted there
• Good rainfall towards more southern portions of the agricultural areas especially with multiple fronts and systems in general making use of Indian Ocean moisture but the impacts drop off markedly to the east and north
• Frost risk quite evident around 22nd-23rd so please take heed
• Initially a frontal period to start July before activity tapers off with more high pressure and frost developing
• August to November a slow build from below average rainfall into average to above average as a weak negative IOD attempts to form in conjunction with a weak La Nina however much of the growing season looks to be neutral on both the SOI and the IOD till quite late.

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Happy Farming and Cheers from The Weatherman

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