June 2022 update SA

June 2022 update SA

*Forecast prepared between June 16th-19th 2022

Review:

G’Day everyone, time for that mid-month update on the proceedings for June, and certainly it has been a wet first half for the most part and we find ourselves on track to get average to above average rainfall with many more frontal systems to come to round out the month, even though we have entered a slight broadscale lull, it is far from the type of lulls we get when there is a much larger broadscale forcing of sinking air like we have had in previous years. Apologies if this is a shorter than usual update, I have injured my eye and not sure how! Bit of a battle to keep them open atm (can’t use the amber fluid as an excuse this time!)

Since the initial June outlook, we have seen a number of systems move through with good rainfall, but especially the 4th-8th even with a series of cold fronts with constantly onshore moisture and upper-level colder air. The long-lived WNW angle allowed quite a lot of head on/perpendicular orographic lift into the Mt.Lofty Ranges (and also a maximised rain shadow behind at first) giving rise to more significant rainfall in the Adelaide Hills. The highest was around 141mm at Uraidla for the event which is most impressive. Numerous other centres cracked the 100mm mark as well nearby including Woodhouse, Ashton and Lenswood. Frosts also occurred, chiefly on morning of Monday 13th over the Lower and Upper North areas. Further east and south, there was enough cloud and moisture to just take the edge off of things although we did see a second burst on the morning of the 18th. Fortunately, most were in the light category with only isolated moderate pockets well inland over.

Meteorological Discussion:

Now onto the proceedings ahead and we will still see a few systems however due to the fact that the MJO is re-emerging out in the Western Indian atm (see climate discussion), we will be favouring more high pressure than low pressure in a broadscale sense. Fronts should still sneak through however with bands of showers, but the totals will be smaller, especially for areas north of about Gawler, things drop off a bit. Looks a fair deal wetter towards the Lower SE overall.

Currently we have a weakening front traversing the state (late 18th) and this will likely deliver only very light patchy rain and insignificant falls during the 19th. The curious thing however is that if you look at the satellite imagery, you will see a large NW cloudband and at first glance would expect a signficant fall but don’t be fooled, it is mostly just jetstream cloud only. There is very little connection to the westerly belt here but note that due to the type of year we are having with the Negative IOD, even the WEAK systems are still getting these cloudbands, the supply of moisture is quite high.

Behind this a slightly stronger front (but by no means a strong front in itself) will cross the state with a series of shower bands from the early hours of Monday 20th and into Monday afternoon before clearing eastwards by the evening. Light falls for the most part here again, however more than the first system. This one also may thicken a little more for Western Victoria if it can gather some extra moisture off the Pacific, but it is a fine line. A weak trough will waffle through on the 21st later on with more showers though no noteable totals, just small ones ticking over and keeping things damp for the most part. Faster moving cold front due 24th attached to a larger Southern Ocean low bringing a band of showers and windy conditions, chiefly ahead as the isobars get squeezed out of the NW but overall, a zonal flow with a lot of west to east and nothing stand up tall. Towards the end of the month, we will likely see some stronger high pressure, but this will also add some blocking to the mix. Quite often in these sorts of years, when you add a block, it breaks down with cut off lows so that will be the next thing to look out for.

Climate Drivers

Onto the Pacific Ocean and we haven’t changed a great deal since the June outlook with a warmer west and cooler east with the Humboldt Current persistent. In the sub-surface though, it must be noted that there has been some warming in the western Pacific and this is beginning to enroach further eastwards. This should be on target to weaken our current La Nina into a cool neutral setup but no further, so that is running to plan at this current stage. The Indian is behaving as expected for a developing Negative IOD with the latest value coming in at –0.3C on June 6th. I’d be expecting this index to lower steadily through the winter peaking sometime in early spring as a traditional negative IOD does, likely in September with values to around –1.2 to –1.4C. That is a moderate to strong IOD just under the 2016 strong of –1.5C but there is a long way to go yet! The warming off Northern Australia and through Indonesia is consistent as is the convective activity with tropical thunderstorms quite rampant for this time of the year. Normally things are much quieter now. Gove is still seeing showers this month in a moist easterly flow with 17.6mm so far this month. Figure 1 below shows the warmth above Australia very clearly and this has been very, very consistent which is a sign for wet conditions ahead.

Moving onto the MJO and this has made a concerted effort to get back into the Western Indian and is now in Phase 1 and beginning to move into phase 2 shortly. It should hold at a moderate strength and slowly move into our window by early to mid-July which should line up closely with the next period of higher potential for cut off lows and rain. Will watch this closely and let you know of course if there are any major changes.

The SAM has dropped a little more strongly negative over the last week and this has certainly caused a lot of cold and showery conditions over the southern part of the country but moreso the effect has been over the east with Tasmania and VIC copping it as well as huge cold air surges and deep lows into the southern Tasman Sea. This node of the longwave trough has been especially active and has been a reason why the SAM has dipped negative but the overall meridional aspect of our weather pattern this season has bunched up those effects over smaller areas rather than your classic zonal winter flow which is usually void of tropical interactions. So, take the value of the SAM in these scenarios with a grain of salt at times.

Districts:

Eyre Peninsula

Weak cold front moving through early 20th with a few bands of showers at times. Shower activity becoming more isolated and confined to the Lower Eyre Pen by late 20th. Weak trough then due in moist westerly flow late 21st with an increase in showers for a short while, chiefly over the southern half of the Peninsula. NW winds freshening once again ahead of a cold front due early 24th with another band of showers, once again more isolated over the northern half of the Peninsula and also the NE especially. Beyond this there will be some fronts passing below the state with occasional shower activity in a moist westerly flow before high pressure takes hold towards the end of the month. Slight frost risk from 28th potentially increasing by start of July. Rainfall for period 5-10mm, decreasing to 2-5mm in the north and east. Falls to 20mm possible over the bottom of Lower Eyre Peninsula.

Upper North

Weak cold front moving through early 20th with a few bands of showers at times although long fine breaks likely. Shower activity becoming more isolated by late 20th. Weak trough then due in moist westerly flow late 21st to early 22nd with isolated showers in the south, especially near higher terrain and western slopes. NW winds freshening once again ahead of a cold front due in morning on 24th with a broken band of showers, once again more isolated over the northern half of the district towards the Flinders and the far east. Beyond this there will be some fronts passing below the state with occasional shower activity on western slopes in a moist westerly flow before high pressure takes hold towards the end of the month. Slight frost risk from 28th potentially increasing by start of July. Rainfall for period 2-5mm, decreasing to 1-2mm in the north and east. Falls to 10-12mm possible over western slopes and higher terrain.

Lower North

Weak cold front moving through early 20th with a few bands of showers at times although long fine breaks likely. Shower activity becoming more isolated by late 20th. Weak trough then due in moist westerly flow late 21st to early 22nd with isolated to scattered showers, especially near higher terrain and western slopes. NW winds freshening once again ahead of a cold front due in morning on 24th with a broken band of showers, once again more isolated over the northern half of the district towards the Flinders and the far east. Beyond this there will be some fronts passing below the state with occasional shower activity on western slopes in a moist westerly flow before high pressure takes hold towards the end of the month. Slight frost risk from 28th potentially increasing by start of July. Rainfall for period 4-8mm, decreasing to 2-4mm in the far NE. Falls of 12-18mm possible over western slopes and higher terrain.

Yorke Peninsula

Weak cold front moving through early 20th with a few bands of showers at times although long fine breaks likely. Shower activity becoming more isolated and confined to the foot of YP by late 20th. Weak trough then due in moist westerly flow late 21st to early 22nd with isolated to scattered showers, especially over the foot of YP. NW winds freshening once again ahead of a cold front due in morning on 24th with a broken band of showers, once again more isolated in the north. Beyond this there will be some fronts passing below the state with occasional shower activity, chiefly in the southern half of YP in a moist westerly flow before high pressure takes hold towards the end of the month. Slight frost risk from 28th potentially increasing by start of July, chiefly the north. Rainfall for period 5-15mm, decreasing to 3-5mm in the far N. Falls of 15-20mm possible over the foot of YP.

Kangaroo Island

Weak cold front moving through early 20th with a few bands of showers at times before stream showers in a moist WSW flow. Showers becoming more isolated early 21st. Weak trough then due in moist westerly flow late 21st to early 22nd with more frequent showers, easing later. NW winds freshening once again ahead of a cold front due in morning on 24th with a band of showers, with colder air to follow bringing scattered showers. Beyond this there will be some fronts passing below the state with occasional shower activity, more frequent around 26th in a moist westerly flow before high pressure takes hold towards the end of the month. Rainfall for period 10-20mm, decreasing to 7-10mm in the far E. Falls of 20-30mm possible over the western end of the island.

Adelaide Plains

Weak cold front moving through early 20th with a few bands of showers at times although long fine breaks likely. Shower activity becoming more isolated and confined to far southern suburbs by late 20th. Weak trough then due in moist westerly flow late 21st to early 22nd with isolated to scattered showers, especially closer to the foothills where activity may tend to drizzle periods. NW winds freshening once again ahead of a cold front due in morning on 24th with a broken band of showers, once again more isolated in the north. Beyond this there will be some fronts passing below the state with occasional shower activity, chiefly south of about Gawler in a moist westerly flow before high pressure takes hold towards the end of the month. Slight frost risk from 28th potentially increasing by start of July about the outer plains. Rainfall for period 5-15mm, decreasing to 3-5mm in the far N. Falls of 15-20mm possible closer to foothills.

Mt.Lofty Ranges

Weak cold front moving through early 20th with a few bands of showers at times although long fine breaks likely. Shower activity becoming more isolated and confined to southern half of ranges by late 20th. Weak trough then due in moist westerly flow late 21st to early 22nd with isolated to scattered showers, tending to drizzle periods at night. NW winds freshening once again ahead of a cold front due in morning on 24th with a broken band of showers, once again more isolated towards the northern ranges. Beyond this there will be some fronts passing below the state with occasional shower activity, chiefly south of about the Barossa in a moist westerly flow before high pressure takes hold towards the end of the month. Slight frost risk from 28th potentially increasing by start of July about low lying valleys. Rainfall for period 10-20mm, decreasing to 5-10mm in the far north of the district Falls of up to 40mm likely about higher peaks of ranges, possibly higher depending on northern extent of frontal series. If they are a little more north, then this could easily get closer to 75mm.

Riverland/Mallee

Weak cold front moving through early 20th with a few bands of showers at times although long fine breaks likely. Shower activity becoming more isolated by late 20th and clearing the eastern border by early hours of 21st. Weak trough then due in moist westerly flow late 21st to early 22nd with isolated showers in the southern to SW Mallee, but little or no impact over the Riverland with lee drying/rain shadow effect. NW winds freshening once again ahead of a cold front due in morning on 24th with a broken band of showers, with more isolated activity over the Riverland as band breaks up. Beyond this there will be some fronts passing below the state with occasional shower activity towards southern and SW Mallee in a moist westerly flow before high pressure takes hold towards the end of the month. Slight frost risk from 28th potentially increasing by start of July. Rainfall for period 3-6mm, decreasing to 1-3mm over the Riverland. Falls to 5-10mm possible over southern to SW Mallee.

Upper SE

Weak cold front moving through early 20th with a few bands of showers at times although long fine breaks likely. Shower activity becoming more isolated by late 20th and clearing the eastern border by early hours of 21st though onshore flow near Coorong will maintain nocturnal shower activity. Weak trough then due in moist westerly flow late 21st and through 22nd with an increase in shower activity. NW winds freshening once again ahead of a cold front due in morning on 24th with a broken band of showers, with more isolated in the far N. Beyond this there will be some fronts passing below the state with occasional shower activity, more frequent towards the Lower SE border in a moist westerly flow before high pressure takes hold towards the end of the month. Slight frost risk from 28th potentially increasing by start of July. Rainfall for period 10-20mm, decreasing to 5-10mm towards the N. Falls to 20-30mm possible towards the Lower SE border.

Lower SE

Weak cold front moving through early 20th with a few bands of showers at times. Shower activity becoming more isolated by late 20th and clearing the eastern border by early hours of 21st though onshore flow near western coasts will maintain nocturnal shower activity. Weak trough then due in moist westerly flow late 21st and through 22nd with an increase in shower activity. NW winds freshening once again ahead of a stronger cold front due in morning on 24th with a band of showers, heavy at times with a possible embedded isolated thunderstorm, chiefly about the coast. Scattered stream showers to follow in colder air with possible small hail in the far south. Beyond this there will be some fronts passing below the state and also clipping the district with showers on and off in a moist westerly flow before high pressure takes hold towards the end of the month. Slight frost risk from 28th potentially increasing by start of July. Rainfall for period 20-30mm, decreasing to 15-20mm towards the N. Falls to 30-40mm possible towards the SW/S portions of the district.

Western VIC

Weak cold front moving through on 20th with a few bands of showers at times, possibly increasing to areas of rain south of the Wimmera. Shower and or rain activity contracting eastwards by early 21st. Weak trough then due in moist westerly flow late 21st and through 22nd with an increase in shower activity, chiefly over the SW district. NW winds freshening once again ahead of a cold front due on 24th with a band of showers, with more isolated towards the Mallee, but heavier towards the southern coasts with isolated thunderstorms possible. Beyond this there will be some fronts passing below and over the bottom of the state with occasional shower activity, more frequent towards the coast in a moist westerly flow before high pressure takes hold towards the end of the month. Slight frost risk from 28th potentially increasing by start of July, especially further north. Rainfall for period 10-20mm, decreasing to 5-10mm towards the Mallee. Falls to 25-40mm possible towards the coastal strip of the SW District.

Finals Notes:

• · No major changes to outlook for rest of winter, generally average to above average with greater chances of a peak in activity from July to September


• · La Nina getting a good beat down, but it will take a lot more to finish it just yet


• · Broadscale reset with MJO emerging in Western Indian causing more high pressure over Australia for the short term


• · Resumption of more significant cut off lows and events from early to Mid-July

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Happy Farming and Cheers from The Weatherman

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