Mid-May 2022 update SA
May 2022 update SA
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All updates will be between 28-5th of the month and mid-month 14-18th and special updates as needed.
*Forecast prepared between May 16-18th 2022
Review:
G’Day everyone, sorry it’s been a while between the last update and this one, quite a bit has been happening! Firstly, the planned fishing trip out to Fowlers Bay and surrounds went well for a week before tracking back through Elliston for a couple of nights. Then onto some major sinus surgery for myself on the 11th, can’t say that I recommend it, but I know long term it should be good – nothing quite like a new snoz after many years of grief.
Now due to the May outlook being issued before the end of April, I wasn’t able to give you the final charts to discuss how the month performed so I will do this here.
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Figure 2: April 2022 rainfall anomalies – source BoM http://www.bom.gov.au/
And we can see it was a real mixed bag, a tale of two regions with the mostly arid areas doing well with inland moisture feeds but the agricultural areas struggling under ridging holding that moisture out combined with a lack of southern maritime air and onshore moisture. The original outlook is as follows: “Consequently, my outlook for April is below average rainfall for a large swath of the state. Pockets to scattered areas of well below average are likely, especially over the Pastoral Districts once again but even down through the southern coastal districts and into the SE. The best chance of average rainfall at least is over parts of Eyre Peninsula and into the Upper North. “
A real mixed bag on that forecast, Pastorals clearly wrong apart from the far NW and northern portions as well as the Upper North came in below for the southern half at least but better into Flinders. The general drying trend towards southern coastal districts and the SE was much better predicted. It can be challenging when nailing down tropical feeds into the desert, one big event can throw things into the mixer but that is the challenge, and I will never shy away from that.
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Now onto events since that outlook and we have started to see a few cold fronts and general cold air events push further north as expected but without anything significant. A nice little event to start May with a cold pool that slung quite nicely north around the front side of a large high. I expected this for the SE districts but unfortunately didn’t have time for a special update closer to the event, so we did see much greater reach of those showers and small hail across southern and eastern agricultural districts. Out west where I was it was a lot more isolated. Should note though that it was quite green in parts of the Eyre Pen and West Coast, probably the healthiest I have ever seen Mallee scrub in my life. The grass and early crop greenery was noteable around Ceduna as well.
Recently we have seen a large cold pool traverse below the mainland delivering scattered to widespread showers again over the southern to eastern ag areas with small 2-3mm falls per day ticking over, namely more exposed coasts. Have managed 4.6mm and 5.6mm in the last 2 days here in Adelaide.
Meteorological Discussion:
Currently we have just seen the end of a little frontal flurry with a broad field of cold air over the Southern Ocean, the second main intrusion of this for the month. Scattered showers associated with multiple weak to moderate cold fronts have been a feature however northward penetration has been only slight with the bulk of the activity focusing in the south and east. We are now entering the chief crossroads in the seasonal change which is the signal I look for to herald an impending break but I stress this will likely be in many stages rather than one giant band of rain, a progression from west to east where WA scores first before that shifts into the SA longitude.
Dynamic NW cloudbands are beginning to feature and this is expected due to the gradient between the tropics and the westerly belt (will touch again in the Climate section) where mid-level cloudbands stream SE along the jetstream generating a broad rainband. Good falls have occurred with this current band over the Pilbara with Onslow Airport recording 141.6mm in the last 48hours to 9am 18th May. Pretty impressive and a good sign of the potential sitting off our NW coast. This current band will push into the NW Pastoral and Far West of the state through 18th-19th but break down into a patchy rainband and dry out due to no further support, but this is the first proper attempt, and it will take more to get the activity in.
The next step is the broad scale setup and reset. A mammoth high pressure will now plant itself near Tasmania for a number of days in the wake of all this cold air in the last week giving rise to a large scale easterly feed westwards across the country. Convergence will thus be focused fairly and squarely into WA over the next week or two giving rise to an excellent seasonal break there. For SA
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however this means another fine spell and unfortunately not unexpected for this May as we have not seen the the last of these strong highs, there was another just before the most recent cold air blast. It is likely to be the last of the more significant ones however for a while as we come to our final step in the long and mostly dry spell this autumn has delivered over the agricultural area.
So a period of fine and settled weather from 18th-24th classic fine May weather with light airs though the easterly regime will show up giving some light nocturnal downslope on the western slopes of ranges which isn’t that common in the cooler months. There will however be a moisture intrusion from NSW/QLD because of the massive fetch of easterlies tending NE into SA so we may see some convective activity chiefly afternoons creeping across the eastern border, mostly NE Pastoral from the 22nd with some isolated shower activity pushing further SW to the Upper North but really barely anything in it.
A cold front ahead of a cut off low extending from the west will drag down a NW cloudband from WA into it before weakening into a trough as it slides SE. Areas of patchy rain and isolated thunderstorms will mark this feature with a reasonably convective type of system but weakening from around late 24th to 25th at this stage. This will open the door for a potential secondary and third system a few days behind with another NW cloudband attempt and areas of rain tending to showers with a third colder system due right near the end of the month or very early June leaping out of the SW around a potentially complex Southern Ocean Low. But more specifics on this closer to the time for a special update.
Climate Drivers
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Figure 3: Current SST anomalies – source Tropical Tidbits https://www.
A very important section to talk about this month with some strong changes noted in the Pacific and Indian and general waters north of the mainland. Taking a look at the Pacific and once again despite lessening at the last update we have found even more cold water to upwell from the ever reliable Humboldt Current off Peru and this has now extended back west again near the equator. This back and forth oscillation has been going for months now as the La Nina refuses to give in. Further west in the Pacific trade winds continue to pile moisture into Eastern Australia and it’s been no surprise that many May records have been broken with heavy rainfall. If you look closely off Brisbane, you will see a cold water ‘scar’ from the low pressure churning of the surface in the previous week. I still expect the overall Pacific La Nina to weaken to a cool neutral through winter and spring but no further, but the current persistence is impressive and will have impacts as the IOD develops.
Now onto the Indian and here too we see mass changes compared to the last update and they are for the better. Overall, this growing season has been off to a very lacklustre and patchy start with no true seasonal breaking rain. Some areas may have stacked together enough totals to be off to a bit of a start but we haven’t seen that consistent strong system with a good rainband for most districts but that shouldn’t be far away now with the current SST structure. Rapid warming over the waters north of Australia and immediately off the NW coast, it is like a pot of warm water ready to boil, it just needs to get a decent system out of the SW. This warmth to the north combined with the increasing winter action from the south will set up more frequent baroclinic cloudbands (NW Cloudbands) that shoot rapidly ESE off the Indian into the mainland along the jetstream. These will come in a series or sequence of events, with each successive system having a bit more penetration than the last. As I type this, we already have a cloudband delivering tremendous rainfall to the Pilbara and parts of inland WA. Multiple fronts associated with numerous strong cut off lows will stand up one after another for SW WA and deliver some very good falls in the coming week there. This is a proper pattern shift, the next step is getting that further east which should develop for us
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more so into June with many good events through winter and into Spring of that cut off low nature. That is, large multi-day events with multiple directions of rain around broad low-pressure systems and deep SW winter flows. Overall, there is no change to the forecast negative IOD with the early stages starting to develop now, the warming north of Australia coupled with some cooling in the waters of NE African and the Middle East.
The MJO is currently in phase 2 moving closer to the mainland, in a weak to moderate form. This will give a further little kick to any events that start to stream out of the Indian however at this time of the year, the MJO overall has less influence on what happens over the mainland with the exception of strong up welling or downwelling events.
The SAM has been positive for quite some time with brief bursts towards neutral but no negative shift yet. In these years as mentioned it’s better to be closer to neutral where we have a balance between the tropical feeds off the Indian and the fronts to the south allowing them to combine. I can see more negative activity towards winter, but this strong positive SAM will still feature for a little while yet allowing easterlies into the mainland across the interior and tropics allowing Pacific moisture to penetrate inland.
Districts:
Eyre Peninsula
A fine and settled period under the domination of a 1037hPa high centred near Tasmania till approx 24th. Freshening N winds ahead of a cold front with a thickening band of mid-level showers and isolated thunderstorms tending to patchy rain areas at times on 25th. Front will weaken to trough and slide away to SE though follow up system from the NW then SW likely at end of month or very early June with rain tending to showers with much colder air to finish. Rainfall for period likely 8-15mm but potential 20-25mm falls about Lower Eyre Pen.
Upper North
A fine and settled period under the domination of a 1037hPa high centred near Tasmania till approx 24th. Isolated showers, chiefly afternoon likely from the NE on 21st/22nd. Light nocturnal gully winds on western slopes through period. Freshening N winds ahead of a cold front with a thickening band of mid-level showers and isolated thunderstorms tending to patchy rain areas at times on 25th. Front will weaken to trough and slide away to SE though follow up system from the NW then SW likely at
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end of month or very early June with rain tending to showers with much colder air to finish. Rainfall for period likely 5-10mm but potential 10-20mm falls over more elevated terrain later in period with likely far wetter pockets beyond 30-35mm.
Lower North
A fine and settled period under the domination of a 1037hPa high centred near Tasmania till approx 24th. Light nocturnal gully winds on western slopes through period. Freshening N winds ahead of a cold front with a thickening band of mid-level showers and isolated thunderstorms tending to patchy rain areas at times on 25th. Front will weaken to trough and slide away to SE though follow up system from the NW then SW likely at end of month or very early June with rain tending to showers with much colder air to finish. Rainfall for period likely 7-15mm but potential 15-25mm falls over more elevated terrain later in period with likely far wetter pockets beyond 30-40mm.
Yorke Peninsula
A fine and settled period under the domination of a 1037hPa high centred near Tasmania till approx 24th. Freshening N winds ahead of a cold front with a thickening band of mid-level showers and isolated thunderstorms tending to patchy rain areas at times on 25th. Front will weaken to trough and slide away to SE though follow up system from the NW then SW likely at end of month or very early June with rain tending to showers with much colder air to finish. Rainfall for period likely 8-15mm but potential 12-20mm falls over the foot later in period with likely wetter pockets beyond 25mm.
Kangaroo Island
A fine and settled period under the domination of a 1037hPa high centred near Tasmania till approx 24th. Freshening N winds ahead of a cold front with a thickening band of mid-level showers and isolated thunderstorms tending to patchy rain areas at times on 25th. Front will weaken to trough and slide away to SE though follow up system from the NW then SW likely at end of month or very early June with rain tending to showers with much colder air to finish with small hail and local thunder likely as well as squally conditions. Rainfall for period likely 10-20mm but potential 20-30mm falls over the western end of the island later in period with likely wetter pockets beyond 35mm.
Adelaide Plains
A fine and settled period under the domination of a 1037hPa high centred near Tasmania till approx 24th. Light nocturnal gully winds on western slopes through period. Freshening N winds ahead of a cold front with a thickening band of mid-level showers and isolated thunderstorms tending to patchy
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rain areas at times on 25th. Front will weaken to trough and slide away to SE though follow up system from the NW then SW likely at end of month or very early June with rain tending to showers with much colder air to finish. Rainfall for period likely 7-15mm but potential 15-25mm falls over foothills and southern suburbs later in period with likely far wetter pockets beyond 30mm.
Mt.Lofty Ranges
A fine and settled period under the domination of a 1037hPa high centred near Tasmania till approx 24th. Light nocturnal gully winds on western slopes through period. Freshening N winds ahead of a cold front with a thickening band of mid-level showers and isolated thunderstorms tending to patchy rain areas at times on 25th. Front will weaken to trough and slide away to SE though follow up system from the NW then SW likely at end of month or very early June with rain tending to showers with much colder air to finish. Rainfall for period likely 15-25mm but potential 30-40mm falls over more elevated terrain later in period with likely far wetter pockets beyond 50mm.
Riverland/Mallee
A fine and settled period under the domination of a 1037hPa high centred near Tasmania till approx 24th. Isolated showers, chiefly afternoon likely from the NE on 21st/22nd. Light nocturnal gully winds on western slopes through period. Freshening N winds ahead of a cold front with a thickening band of mid-level showers and isolated thunderstorms, possibly tending to light patchy rain areas at times on 25th but not a lot in it. Front will weaken to trough and slide away to SE though follow up system from the NW then SW likely at end of month or very early June with rain tending to showers with much colder air to finish. Rainfall for period likely 4-8mm but potential 10-15mm falls over western portions of the Mallee closer to the back of the ranges and in the far SW later in period with likely isol wetter pockets beyond 20mm.
Upper SE
A fine and settled period under the domination of a 1037hPa high centred near Tasmania till approx 24th. Freshening N winds ahead of a cold front with a thickening band of mid-level showers and isolated thunderstorms tending to patchy rain areas at times on 25th but not a lot in it. Front will weaken to trough and slide away to SE though follow up system from the NW then SW likely at end of month or very early June with rain tending to showers with much colder air to finish. Rainfall for period likely 5-10mm but potential 10-15mm falls over the western portions closer to the Coorong and also southern border later in period with likely wetter pockets beyond 25mm.
Lower SE
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A fine and settled period under the domination of a 1037hPa high centred near Tasmania till approx 24th. Freshening N winds ahead of a cold front with a thickening band of mid-level showers and isolated thunderstorms tending to patchy rain areas at times on 25th but not a lot in it. Front will weaken to trough and slide away to SE though follow up system from the NW then SW likely at end of month or very early June with rain tending to showers with much colder air to finish with small hail and local thunder likely and squally conditions. Rainfall for period likely 10-20mm but potential 20-30mm falls over the Southern and western portions later in period with likely wetter pockets beyond 40mm.
Finals Notes:
- · Dry spell with high pressure before the start of the main switch in the season begins but it will come in many stages of increasing systems
- · Negative IOD will also start to develop through early winter and become established to a moderate strength
- · Likely best winter rainfall since 2016, main target months/period at this stage is July-September with large cut off low events
- · Will add some more interstate thoughts in June outlook, including Western Victoria
- · Watch the sun in the coming few weeks, quite a bit of instability to play out (we had an M class flare on 17th)
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Happy Farming and Cheers from The Weatherman
*Note – For interest only, all thoughts are of The Weatherman and may not be reproduced without my consent.
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