March 2022 Update SA

March 2022 update SA 

*Forecast prepared between Mar 20th--21st 2022 

Review: 

G’Day everyone once again, time for the mid-month update, sorry it is late this time around, extra  shiftwork due to staff illness has certainly been testing! 

We are currently in the midst of a general reset across the tropics after the onslaught into the east  of the country, with some of that moisture filtering west into low pressure troughs inland resulting  in sporadic showers and thunderstorms and locally heavy falls. One notable fall was in Broken Hill,  

a town which has been so dry for many years, and they recorded 72.4mm with a thunderstorm on  the 15th with flash flooding in town. Also, parts of the Upper SE not far from Lameroo had unofficial  but very believable reports of 100mm+ in a little over an hour and a half.  

However, the main dominant feature over much of our state during the first half of March has been  the ridge to the south which has directed a fresh SE flow over most districts, and this is pretty much  expected for this time of the year after all, SA is the ridge state.  

Meteorological Discussion: 

The remainder of the month will see a bit more activity on the east and west of the country but not  a huge amount through SA. Currently moisture is building off the NW coast over the Indian Ocean  and is largely associated with Tropical Cyclone Charlotte which at this stage has been struggling to  organise however I would expect some rapid intensification overnight tonight (21st) with a maximum  intensity in the Severe Category 3 range tomorrow afternoon. There is a good outflow channel to the  poleward side aloft which will help this intensification before it gradually weakens heading SW with  dry air entrainment, cooling SST’s and increasing wind shear. The key is how much influence the next  approaching upper-level trough/westerly belt change will have on a recurve back towards the SE.  This will be critical in determining how much rain parts of WA get, with many being very dry this  summer. At this stage I’d be a little surprised if it did cross the coast at TC strength or above but more so get torn up offshore first with increasing shear with the remnants then being carried back 

across on the strong upper-level winds generating patchy rain areas for the SW of WA. A trough is  then likely to linger down the west coast of WA and pull in a lot of moisture that was channeling into  the system from the north to generate a fair deal of shower and thunderstorm activity, more than  there has been for a fair bit of this summer at least. The core however even as an Ex-Tropical  Cyclone will likely contain damaging winds so take heed to warnings if it gets close and you live that  way or know people who do! 

Back for SA though we are in the midst of generally light airs with no strong ridge influence over the  last two days. That has caused warm to hot and fairly stagnant conditions aside from some nocturnal  gully winds. A trough will cross from the west tomorrow (22nd) with a band of mid-level showers or  patchy rain as it draws on moisture from TC Charlotte. An isolated thunderstorm is possible also,  mostly likely though over the West Coast, Eyre Peninsula and Upper North districts which will repeat  through the afternoon potentially over the Flinders to NE Pastoral in the afternoon of the 23rd with a  surface trough lingering though these may struggle to get up as the trough is very weak. 

Behind the trough will see a stronger ridge establish and push in from the west driving cooler  conditions in from the south with southern maritime air giving light coastal showers to exposed  areas through evening of 22nd and possibly also 23rd. Beyond this the ridge will do it’s usual thing and  progress steadily eastwards. 

An interesting feature however will be tracking the path of an upper-level trough from the 24th-27th.  This should pinch off into an upper low over NSW and will likely lead to another period of severe  weather for areas chiefly ahead of this feature where moisture will once again (sounds like a broken  record atm) feed in from the east and be uplifted. I can see more heavy showers, rain areas, severe  thunderstorms and general damage from flooding caused by this system but not the level we saw  late Feb. 

The main interest no doubt lies in what happens from here on in for April and beyond. I’ve  mentioned I expect one more strong burst out of the tropics into the mainland and this is starting to  show signs of beginning as mentioned above but it would be unfortunate for SA to miss completely  before we go into an Indian Summer like pattern through mid to possibly late April. If it is strong it  could persist into May. We have a lot of warm SST’s but at this stage no significant triggers to really  bring that moisture down hard. It could continue to bake which would make for a strong break when  it finally does come through May and June. I will be tracking the SAM closely through the April May  period as it will certainly give rise to how long we should remain dry or dryish at least with minor  insignificant systems.  

Winter at this stage looks fairly stock standard, perhaps with at least warmer SST’s off WA we will  have a greater chance of rainbands rather than just showery fronts but that needs to persist plus the 

SAM needs to launch heavily negative which is always struggle in La Nina events that linger like this  one. It should be gone back to cool neutral then, however.  

Climate Drivers 

We certainly have a Pacific that is refusing to lay down the La Nina signature, compared to last year  we are holding firm which no major changes from the last update – good trades putting in good  amounts of moisture into Australia’s east with a persistent cooler signature in the central to eastern  Pacific. The depth of colder water beneath has eased a little but there is still some down there to rise  and this will keep things lingering on a little longer. 

Figure 1: Current SST anomalies – source Tropical Tidbits  

https://www.tropicaltidbits.com/analysis/ocean/ 

The Indian is warm, no doubt about and if we look at Figure 1, we can clearly see the extra heat  around the western side of the mainland. The entire country is circled by warmer than average  temperatures to be honest and this will be primed for one more assault from the tropics before the  season is largely done as mentioned before. There are signs finally that WA may see more influence  this time from the tropics, we already have TC Charlotte south of Indo and plenty of convection over  the water so moisture should feed S to SSE towards WA, the only question is how much goes below  the mainland and how much actually crosses the coast. The most likely area at this stage is the  bottom corner of WA but with thunderstorms inland.

Moving on to the MJO and it is currently in phase 3 and moving towards the mainland once again  after gathering strength over the Indian in the last week or so. This is no surprise given the increase  convection in this region. It should remain slow moving between phases 3-5 over the coming weeks  before slowly petering out in the Western Pacific. This should open the window for increased  Tropical Cyclone activity as mentioned in the last update from Mid-March onwards and likely to  continue well into April. The next area to watch for a spin up is the Gulf of Carpentaria or Arafura  Sea. 

The SAM is fairly neutral atm, perhaps a slight positive tendency but not like it was and cannot see  any major changes for the meantime. Upper troughing will take hold over the east in the coming  week which is often the case when surface ridging is strong. As mentioned before, the eastern states  will benefit the most from this, especially NSW. 

I thought I’d also quickly touch on the record ‘heat’ recorded over parts of the Antarctic Continent in  recent days with some places being 30C or so above average. The values are no doubt appear much  more significant and to the untrained eye will raise alarm but there is no need. A simple explanation  is due to the fact that a significant fetch of moisture channeled southward on the western periphery  

of strong high pressure ridging in the Pacific due to La Nina. This moisture channeled south in the  form of an atmospheric river in a highly meridional setup which is essentially an opening of a  channel from the tropics to the mid-latitude areas. On occasion these can keep going towards the  poles and in this case, right to Antarctica triggering all those records. Given it is so dry down there,  an increase in moisture will increase the temperature quite significantly due to the higher Specific  Heat Capacity of moisture. It is very likely this event will stand out for many years to come unless we  can get another opening/atmospheric river. 

Districts:  

Eyre Peninsula 

Weak trough passing through the region on 22nd with some mid-level showers or patchy light rain.  Brief isolated thunderstorm or two likely, especially about the West Coast. Stronger ridge pushing in  behind driving light showers in onshore flow to exposed coastal areas overnight 22nd into 23rd. Fresh sea breezes. Ridges likely to dominate for remainder of month with SE/E flow for the most part  however a trough or cold front could impact late from 29th onwards with some shower activity but at  this stage not looking significant. Rainfall 1-4mm mostly falling on 22nd.

Upper North 

Weak trough passing through the region on 22nd with some mid-level showers or patchy light rain.  Brief isolated thunderstorm or two likely, especially about the Flinders. Isolated afternoon  thunderstorm possible on 23rd over northern Flinders. Stronger ridge pushing in behind with milder  conditions and freshening SE/E flow once again and nocturnal gully winds. Ridges likely to dominate  for remainder of month with that SE/E flow for the most part however a trough or cold front could  impact late from 29th onwards but at this stage, nothing significant. Rainfall 1-3mm mostly falling on  22nd. 

Lower North 

Weak trough passing through the region on 22nd with some mid-level showers or patchy light rain.  Brief isolated thunderstorm or two possible, especially towards the north. Stronger ridge pushing in  behind with milder conditions and freshening SE/E flow once again and nocturnal gully winds. Light  shower or two likely about elevated terrain overnight 22nd into 23rd. Ridges likely to dominate for  remainder of month with that SE/E flow for the most part however a trough or cold front could  impact late from 29th onwards but at this stage, nothing significant. Rainfall 1-2mm mostly falling on  22nd. 

Yorke Peninsula 

Weak trough passing through the region on 22nd with some mid-level showers or patchy light rain.  Brief isolated thunderstorm or two possible, especially towards the north. Stronger ridge pushing in  behind with milder conditions and freshening SE/E flow once again and fresh sea breezes. Light  shower or two likely in onshore flow overnight 22nd into 23rd. Ridges likely to dominate for  remainder of month with that SE/E flow for the most part however a trough or cold front could  impact late from 29th onwards but at this stage, nothing significant. Rainfall 1-3mm. 

Kangaroo Island 

Weak trough passing through the region on 22nd with some mid-level showers or patchy light rain.  Stronger ridge pushing in behind with milder conditions and freshening SE/E flow once again and  fresh seabreezes. Scattered light showers likely in onshore flow overnight 22nd into 23rd. Ridges likely  to dominate for remainder of month with that SE/E flow for the most part however a trough or cold  front could impact late from 29th onwards but at this stage, nothing significant. Rainfall 1-3mm. 

Adelaide Plains

Weak trough passing through the region on 22nd with some mid-level showers or patchy light rain.  Stronger ridge pushing in behind with milder conditions and freshening SE/E flow once again and  nocturnal gully winds. Light showers in onshore flow overnight 22nd into 23rd especially about the  southern suburbs. Ridges likely to dominate for remainder of month with that SE/E flow for the most  part however a trough or cold front could impact late from 29th onwards but at this stage, nothing  significant. Rainfall 1-3mm. 

Mt.Lofty Ranges 

Weak trough passing through the region on 22nd with some mid-level showers or patchy light rain.  Stronger ridge pushing in behind with milder conditions and freshening SE/E flow once again and  nocturnal gully winds about western slopes. Scattered showers in an onshore flow, more frequent  about exposed southern coasts and ranges overnight 22nd and into 23rd. Ridges likely to dominate for  remainder of month with that SE/E flow for the most part however a trough or cold front could  impact late from 29th onwards but at this stage, nothing significant. Rainfall 1-6mm mostly falling on  22nd and about those exposed southern coasts and ranges of the Fleurieu Peninsula. 

Riverland/Mallee 

Weak trough passing through the region on 22nd with some mid-level showers or patchy light rain.  Brief isolated thunderstorm or two likely, especially in the evening and about the northern  Riverland. Stronger ridge pushing in behind with milder conditions and freshening SE/E flow. Light  shower or two possible late on 22nd to 23rd morning also in onshore flow in far SW of Mallee. Ridges  likely to dominate for remainder of month with that SE/E flow for the most part however a trough or  cold front could impact late from 29th to 30th onwards but at this stage, nothing significant. Rainfall  1-2mm mostly falling on 22nd. 

Upper SE 

Weak trough passing through the region on 22nd with some mid-level showers. Stronger ridge  pushing in behind with milder conditions and freshening SE/E flow once again. Scattered light  showers overnight 22nd into 23rd chiefly in the W/NW. Ridges likely to dominate for remainder of  month with that SE/E flow for the most part however a trough or cold front could impact late from  29th to 30th onwards but at this stage, nothing significant. Rainfall 1-2mm. 

Lower SE 

Weak trough passing through the region on 22nd with some mid-level showers, more isolated in the  south, however. Stronger ridge pushing in behind with milder conditions and freshening SW to SE  flow once again. Scattered light showers overnight 22nd into 23rd chiefly about the coast. Ridges likely 

to dominate for remainder of month with that SE/E flow for the most part however a trough or cold  front could impact late from 29th to 30th onwards but at this stage, nothing significant. Rainfall 1- 2mm. 

Finals Notes: 

• La Nina is not done yet and the tropics remain active with renewed Tropical Cyclone activity  for the coming weeks. 

• Upper low to combine with Pacific moisture to bring more wet weather and flooding to parts  of Eastern Australia. 

• Drier period still firming after last tropical burst with Indian Summer like conditions mid to  later April or early May. 

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Happy farming and cheers from The Weatherman 

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