July 2022 Outlook

*Forecast prepared between July 1st-4th 2022

Review:

G’Day everyone, I hope you are all keeping well as we now have winter upon us! A time of good hearty roasts, warm fires and red wine (I must say it’s not just winter I’ll enjoy those). A fire though wouldn’t be a bad idea with the frosty period we have had recently as high-pressure systems take hold. 

A look back since the last update has seen a gradual drying trend with less significant systems with more limited inland penetration which has been caused by purely onshore moisture only without proper connection to the tropics. A series of weak fronts did most of the rainfall, with extra orographic assistance into the Adelaide Hills giving better totals there. The Mallee and Riverland as well as the Upper North and Northern Eyre Peninsula generally came up short from these shallow fronts. The most significant period was between the 20th-27th where many districts recorded at least 0.2mm on each day with damp and drizzly conditions at times. A final front with showers and a weak upper cold pool came through on the 29th with 3-5mm totals for most districts but some isolated 20-30mm totals about the Adelaide Hills helped catchments there as well as 8-10mm about the foot of Yorke Peninsula being most welcome.

Frost also started to have an influence with moderate frost on the 27th and 28th with some –1 to –3C temperatures occurring over the Riverland, parts of the Mallee and Upper North Districts. Further light frost has been reported since although cloud this morning (1st) has limited some of the minimums. More frost is expected which I will expand on further below.

A final review of the June outlook shows some mixed results but the overall pattern fairly correct.

A quick recap is as follows:

“Overall, June is likely to be an average to above average month for many districts. The greatest chances of above average rainfall is in the Central regions of the state including Adelaide, Mt. Lofty Ranges and down into the SE Districts and possibly also the southern Mallee. The greatest

chance of not meeting average may be in the northern portions of the upper North and in the far West”

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

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

Analysing the two charts above with respect to the outlook the net result was overall a little unders for the Pastorals and certainly the Upper North, the latter was reflected in the potential for below average, albeit northern portions (Flinders chiefly). However, Northern EP and the Riverland also were subject to some below average totals which were not in the forecast. The above average bullseyes certainly were over the Mt.Lofty Ranges and towards the SE Districts due to frontal action so the trend of drier north and wetter south went roughly ok with most other areas coming close to average give or take 10mm across the agricultural districts. But more is needed and will expand on below.

Meteorological Discussion:

An important period in the season looms as we start July and as you may have already worked out, it won’t be starting with much rainfall, and I will explain why below.

In June I alluded to the fact that we will have high pressure and frosts to finish the month and also, I the forecasts with frosts potentially increasing in the start of July as this signal was starting to show its hand. I also expected blocking but that to break down from early to mid-July with a return to cut off lows. What we are seeing unfold now is a strong block caused by a persistent atmospheric river between the tropics and the mid latitude westerlies with repeat tropical moisture flowing down in a trough off the east coast of the mainland. To the west of this massive uplift area is downlift with high pressure (fuelled by a positive SAM). The high meridional aspect of this pattern has seen upper troughs and colder air push up with the surface ridging but then interact with that tropical moisture to our east and form repeat cut off lows and East Coast Lows (ECL’s) over the Tasman Sea. The highs to the west then cannot move but by staying stationary, colder air keeps pushing up aloft and once more, further cyclogenesis offshore will continue. This pattern will hold until we see weaker upper troughing and colder air move up to form these east coast lows or the atmosphere becomes so overturned that the next systems forming will become weaker. All blocks break down and let the traffic move through and I expect this time it will start to flow from mid-month. That’s a long time to wait however and a good week or more than expected from the last update. It is certainly one of the better and more persistent blocks that I have seen from the Tasman Sea and can mostly be attributed to the large amounts of tropical moisture feeding down and supplying this setup.

So, I will keep it brief but strong surface high pressure systems dominating through much of the first half of the month. From the 4th till 6th approx the first high will move through, initially with fresh SE winds which are quite rare for July. This will then weaken as it moves east allowing a weak front to slide up and pass below the state before the second large high develops to the west from the 7th, renewing the S to SE flow once again with onshore isolated light showers mostly in the Lower SE District and about the Southern coasts and Ranges of the Fleurieu Peninsula and possibly KI too. Aloft another strong upper trough will wander NE and induce a secondary broader East Coast Low (ECL) and dominate the weather pattern through the Tasman Sea for a further 4-5 days.

Next a cold front will try to push in from the west as the large high begins to weaken but I do expect this front to only drive some scattered showers across the agricultural areas and move fairly swiftly through on Monday 11th. After this another high will move in from the west as the block begins to break down over the Tasman although there is a possibility if the front is stronger on the 11th that the cold air aloft will actually act to enhance a third East Coast Low event. I will watch the shape of the system carefully as this will be important. Beyond this expect more fronts to start to make their way in from the west with a better chance of a cut off low developing as it is commonplace to see them form after bocks break down upstream before finishing with a flurry of fronts later in the month. 

Frost will absolutely be front and centre with so much higher pressure. The main periods of interest are the mornings of 5th-7th (especially the 6th as winds really drop out) a lesser risk then till 9th with cloud at times before increasing again on 10th as it could be quite crisp ahead of the freshening winds from that front. Post front I expect a return with the next high increasing the risk around 13-15th especially but that’s getting a little far off at the moment to be accurate on. 

This time wasted with dryness is going to come at the cost of an average to above average month with a much greater chance of generally finishing in the average to below average bracket for most districts despite the activity picking up from mid-month. I can see especially trying times for the Riverland, Northern Mallee, Northern and parts of the Upper North District and into the Pastorals with below average rainfall a greater chance there. Northern Eyre Peninsula is also within this risk though they will at least have some more room to move than the aforementioned districts. Above average odds look far less for most but if there is going to be anywhere that manages to get close it will be Kangaroo Island to Lower Yorke Peninsula and possibly southern portions of the Fleurieu but this will be an uphill battle. If I didn’t expect the pattern to come back in the second half of the month then I would certainly expect very much below average. Fortunately, some areas have had a good start but no doubt by mid-month, they will be after more.

The good news is there is still persistent convection off Java to the SW with active thunderstrorms as well as a much larger area of convection south of Sri Lanka. This moisture will eventually channel towards Australia when it all lets go upstream giving better odds for August through to September to get some good rainfall and wetter conditions.

Climate Drivers

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

Figure 4: Vertical profile anomalis of sub-surface Pacific Ocean – source BoM http://www.bom.gov.au/climate/enso/#tabs=Pacific-Ocean

Now looking up at Figure 3 here we can see there has been some changes since the last outlook. The BoM have firstly declared that the La Nina has ended, and this is more reflected in the sub surface as well with warmer water sitting just below (see Figure 4). Whilst the very surface still shows some much colder water in the very far east thanks to the Humboldt Current, that cold water is shallow and will run into the increasing warmth in the sub surface. Having said all that, I am still confident that conditions will remain as forecast in the cool neutral zone before having yet another crack at a third La Nina next summer. Trade winds are still blowing strongly through the Central Western Pacific and cloudiness near the date line is low which are La Nina indicators.

Now the most important basin for us in South Australia is the Indian ocean and at this time of the year, it plays the most critical role of any time in the season – winter and spring rainfall. The initial influence late May and into June was significant with a flurry of NW cloudbands and rainfall meeting fronts causing cut off lows and heavy falls for many areas. However, there has been some cooling off the NW shelf of Australia in response to two things. Firstly, the increased cloudiness caused by the warmer seas themselves and secondly, the current large spike of the SAM into the positives which has caused large high pressure to throw a burst of SE-E trades across the Indian. The cooling has been over the East but also the west, so the net result is the IOD reading still remains around –0.49C which is below the threshold of –0.4C although we know that weak negative IOD’s do not do much for us rainfall wise. We need to see it get below about –1.2C to really make a strong difference and this will be a work in progress as we drop the values into August with a peak sometime in September at a moderate strength. I still expect it to come in short of 2016 levels so no changes there. So, in short, despite this brief cooling in the eastern Indian, there will be more warming ebbing and flowing with further cooling in the west setting up that classic west to east gradient and driving the overall circulation with an expectation of above rainfall in the July-September bracket as a collective but for July itself as per above, the start will be hampered by the dominant cut offs.

The MJO has moved into the Eastern Indian and is approaching the mainland near phases 3 to 4 but the signal has weakened since it was moderate to strong over the African and Western Indian region. That strong signal has caused the response in the SAM to some degree with strong highs and trades piling west into the vigourous uplift that was out there. I expect the signal to move eastwards and steadily weaken as it goes through Phase 5 and 6 with no significant westerly wind burst (WWB) into the Pacific.

The SAM has rocketed into strongly positive territory right when it is not needed. Values like this in July do not do any favours for rainfall with large high pressure systems holding fronts and regular winter triggers below the mainland. This is not unusual in any year for a one off or twice occurrence but repeat instances like this over the period of winter always result in below average rainfall. As I have said before, in years such as these where moisture from the tropics is still in abundance, (see eastern seaboard at the present time), a balance of positive and negative SAM is important with neutral values serving the bulk of the southern agricultural areas the best. This positive phase will last roughly to mid-July (about a week or so longer than previously expected) and thus dryness and frosts will be common in this period.

Districts:

Eyre Peninsula

Generally dry conditions with dominant high pressure from 4th till 10th. Light coastal showers or drizzle patches about Eastern Eyre Pen possible on 8th with moisture off Spencer Gulf in low level

SSE flow ahead of new high but not much at all. N to NW winds freshening ahead of cold front 11th with scattered showers and a fresher WSW flow clearing mostly on 12th. High likely again behind this once more before transition to more rain bearing systems after. Frost risk slight to moderate through 5th-7th, with moderate more likely on 6th. Slight to moderate risk again 9th-10th and 13-15th under new high. Rainfall for period around 3-6mm about Lower Eyre Peninsula and also 1-3mm about Eastern Eyre Pen coastline fringe. General 2-4mm with less than 2mm in far north. Isolated falls to 10-12mm still likely about Lower Eyre Pen.

Upper North

Generally dry conditions with dominant high pressure from 4th till 10th. N to NW winds freshening ahead of cold front 11th with isolated to scattered showers, chiefly in the south and a fresher WSW flow clearing mostly on 12th. High likely again behind this once more before transition to more rain bearing systems after. Frost risk slight to moderate through 5th-9th, with moderate more likely on 6th. Slight to moderate risk again up till 10th and 13-15th under new high. Rainfall for period around 1-3mm only, though isolated 5mm totals possible from front on 11th but not a lot in it. Sone locations further north and east may not see any rain at all in the first half of the month.

Lower North

Generally dry conditions with dominant high pressure from 4th till 10th. N to NW winds freshening ahead of cold front 11th with isolated to scattered showers, chiefly in the south and about higher terrain with a fresher WSW flow clearing mostly on 12th. High likely again behind this once more before transition to more rain bearing systems after. Frost risk slight to moderate through 5th-9th, with moderate more likely on 6th. Slight to moderate risk again up till 10th and 13-15th under new high. Rainfall for period around 2-5mm only, though isolated 5-8mm totals possible, mostly from front on 11th but not a lot in it.

Yorke Peninsula

Generally dry conditions with dominant high pressure from 4th till 10th. Light showers or drizzle patches on 8th in moistening SSE flow ahead of new high. N to NW winds freshening ahead of cold front 11th with isolated to scattered showers, chiefly about the foot in a fresher WSW flow clearing mostly on 12th. High likely again behind this once more before transition to more rain bearing systems after. Frost risk slight through 5th-9th, with moderate more likely on 6th in north. Slight risk again up till 10th and 13-15th under new high. Rainfall for period around 2-5mm only, though isolated 5-10mm totals possible about foot, mostly from front on 11th but not a lot in it.

Kangaroo Island

Generally dry conditions with dominant high pressure from 4th till 10th. Light showers or drizzle patches on 8th in moistening SSE flow ahead of new high. N to NW winds freshening ahead of cold front 11th with scattered showers in a fresher WSW flow clearing mostly on 12th. High likely again behind this once more before transition to more rain bearing systems after. Frost risk slight on 6th about centre of island. Slight risk again 10th and 13-15th under new high. Rainfall for period around 4-8mm only, though isolated 8-12mm totals possible, mostly from front on 11th.

Adelaide Plains

Generally dry conditions with dominant high pressure from 4th till 10th. Some isolated light showers or drizzle patches late 7th and into 8th chiefly about southern suburbs and foothills. N to NW winds freshening ahead of cold front 11th with isolated to scattered showers, chiefly about foothills in a fresher WSW flow clearing mostly on 12th. High likely again behind this once more before transition to more rain bearing systems after. Frost risk slight to moderate through 5th-9th, with moderate more likely on 6th over outer plains. Slight to moderate risk again up till 10th and 13-15th under new high. Rainfall for period around 2-5mm only, though isolated 5-8mm totals possible in the south, mostly from front on 11th but not a lot in it.

Mt.Lofty Ranges

Generally dry conditions with dominant high pressure from 4th till 10th. Some isolated light showers or drizzle patches late 7th and into 8th chiefly about higher peaks and S/SE slopes or windward slopes as low-level moisture streams pile in. N to NW winds freshening ahead of cold front 11th with isolated to scattered showers in a fresher WSW flow clearing mostly on 12th but lingering light showers persisting in onshore S flow. High likely again behind this once more before transition to more rain bearing systems after. Frost risk slight in low lying valleys through 5th-9th, with moderate more likely on 6th.. Slight risk again up till 10th and 13-15th under new high. Rainfall for period around 5-10mm though isolated 10-20mm totals possible about higher peaks, mostly from front on 11th.

Riverland/Mallee

Generally dry conditions with dominant high pressure from 4th till 10th. N to NW winds freshening ahead of cold front 11th with isolated showers, chiefly in the south/SW of the Mallee and a fresher WSW flow clearing mostly on 12th. High likely again behind this once more before transition to more rain bearing systems after. Frost risk slight to moderate through 5th-9th, with moderate more likely on 6th. Slight to moderate risk again up till 10th and 13-15th under new high. Rainfall for period around 1-3mm only, though isolated 5mm totals possible mostly from front on 11th in far SW Mallee but not a lot in it. Sone locations in Riverland and Northern Mallee may not see any rain at all in the first half of the month.

Upper SE

Generally dry conditions with dominant high pressure from 4th till 10th. N to NW winds freshening ahead of cold front 11th with scattered showers, heavier towards the Lower SE border, in a fresher WSW flow clearing mostly on 12th. High likely again behind this once more before transition to more rain bearing systems after. Frost risk slight through 5th-9th, with moderate more likely on 6th. Slight to moderate risk again up till 10th and 13-15th under new high. Rainfall for period around 3-5mm only, though isolated 5-8mm totals possible mostly from front on 11th closer to the Lower SE District border.

Lower SE

Generally dry conditions with dominant high pressure from 4th till 10th. Light coastal showers or drizzle patches from 7th-9th potentially in onshore S/SSE flow but minimal totals. N to NW winds freshening ahead of cold front late 10th or early 11th with scattered showers, heavy at times, in a fresher WSW flow clearing mostly on 12th though some lingering onshore showers are likely. High likely again behind this once more before transition to more rain bearing systems after. Frost risk slight through 5th-9th, with moderate more likely on 6th. Slight to moderate risk again up till 10th and 13-15th under new high. Rainfall for period around 8-15mm, though isolated 15-25mm totals possible mostly from front on 11th.

Western VIC

Generally dry conditions with dominant high pressure from 4th till 10th. Light coastal showers or drizzle patches from 7th-9th about the SW coastline potentially in onshore S/SSE flow but minimal totals. N to NW winds freshening ahead of cold front or early 11th in the SW with scattered showers, heavy at times, in a fresher WSW flow clearing mostly on 12th though some lingering onshore showers are likely. Frontal impact reducing significantly with northern extent with only isolated showers for the Mallee District. High likely again behind this once more before transition to more rain bearing systems after. Frost risk slight through 5th-9th, with moderate more likely on 6th. Slight to moderate risk again up till 10th and 13-15th under new high. Rainfall for period around 6-12mm about the SW District with isolated totals to 25mm about the coast. Totals decreasing with northern extent with 3-5mm over the Wimmera and less than 1-2mm over the Mallee. Parts of the NW corner of the state may not see any rainfall at all.

Finals Notes:

• Tough period to navigate, most years do have these, but this will be quite dry for July
• Once signifiant block caused by East Coast Lows breaks down, a resumption of moisture and cut off lows can occur for later half of month
• August and September should still bring good rainfall with Negative IOD
• Spring to summer should see a greater ramping up of thunderstorms compared to last year with greater moisture available

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Happy Farming and Cheers from The Weatherman

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