February 2022 update SA

*Forecast prepared between Feb 16th-18th 2022

Review:

G’Day one and all, that time of the month again for a little update on how things are going. A fairly uneventful first half of Feb after the last update at least (heavy rains across the Pastorals last day of Jan especially and also the 1st Feb but these were before the Feb outlook). A weak trough moved through on the 9th delivering patchy rain and isolated thunderstorms for most districts, though falls were quite light in the order of 1-5mm but nonetheless helped keep that tinge of green we see around the traps. After this ridging dominated with warm to hot days and nocturnal gully winds at times, a standard Feb pattern but true heat has been mitigated by the heavy inland rain over the heat engine of the country. There is a lot of water still flowing into Lake Eyre down the various rivers and creeks from both QLD, NT and locally in SA and these flows should keep coming well into autumn and thus giving the lake it’s best fill since 1989 I would suspect, and we still have one good monsoonal burst to come.

Meteorological Discussion:

Currently as I type this on the 16th there is a nice little sharp upper trough grinding away over the Eyre Peninsula and this is generating areas of rain ahead of it where the uplift is. Isolated thunderstorms are forming closer to the back edge of the rain over the Eyre Pen where the mid-levels are much colder allowing sufficient CAPE (Convection Available Potential Energy) to generate some low topped thunderstorms. With surface heating behind the rain in the clear air through the guts of this upper trough, we will see renewed thunderstorms develop during the afternoon chiefly over northern Eyre Pen and a bit more isolated further south. The upper trough will weaken though as it heads eastwards and largely dissolve by the time it crossed the gulf areas.

Beyond this we will be in a pattern that is an even battle between the slightly stirred up westerly belt below the country and the inland troughing pushing against some strong high-pressure ridging coming out of the western Bight. This will initially drive cooler to mild southern maritime air across the state with high moisture content near the coastal areas with the passes of two weak fronts on the 18th and late 20th/early 21st respectively throwing up some isolated to possibly briefly scattered shower activity. I don’t envisage much in the way of totals from this, but it will keep the low cloud about southern coasts and ranges, especially at night and early morning.

Given we will have the MJO in phase 3 to 4 in the coming week, we will see the inland troughing deepen with fairly strong high-pressure systems once again pushing below the mainland with an easterly flow across much of the mainland, pushing into that main uplift area of the MJO (see climate drivers for more detail on this). With such an easterly regime, this will likely begin to re-activate the eastern trough/easterly dip with Coral Sea moisture later in the month and with westward advection, start to affect areas further inland later in the month with potentially an E/NE infeed into eastern border areas of our state as well. I'm looking at this starting to infiltrate the NE Pastoral eastern border areas from roughly the 23rd or so and linger for a few days so we should see some isolated afternoon and evening showers and thunderstorms develop with at least some afternoon convection visible further west of here given the moisture in the ground as well. The greatest timing for increased rainfall and tropical activity with further monsoonal onset will be very late Feb and into March as uplift across the top end of the mainland will be enhanced to a moderate level. As the MJO moves further east to phase 5-6 we should see Tropical Cyclone activity pick up a little, moreso from mid-March at this stage.

Looking ahead a little further through March I see a reasonably wet month, especially inland before we see a gradual breakdown of this pattern into April or May where drier conditions have a higher chance of presenting, more so later where an Indian Summer may occur. The Eyre Peninsula and likely Yorke should have plenty of sub-soil reserves, but the Mallee and Riverland plus SE districts will have a lot less unless a solid rain occurs there. I can see at least the potential for one good rain for most before the tropical air will lessen.

Winter at this stage doesn’t look hugely wet but reasonably regular frontal activity should keep most areas going but east of the ranges will be on the backfoot a little with these.

Climate Drivers

The Pacific Ocean still shows a moderate La Nina though this has peaked in terms of oceanic signature but the lag through to the peak in the atmosphere is still present so the next few weeks will still deliver another monsoonal burst across Northern Australia thanks to stronger trades in the west responding to the MJO in the Eastern Indian. Think of it like the water sucking back into a wave at the beach with the wave being the MJO, it just brings that moisture in off the Pacific, shifts it west and straight into the Kelvin Wave approaching. With a mature Walker Circulation, there is already enhanced uplift over Australia so these little waves etc only add to it. The QLD and NSW coast should see an uptick in rainfall as we move towards the end of the month with significant lift into the ranges off the Coral &Tasman Sea from these trades, before this continues further inland with showers, thunderstorms forming in the troughs inland.

Figure 1: Current SST anomalies – source Tropical Tidbits https://www.tropicaltidbits.com/analysis/ocean/cdas-sflux_ssta_global_1.png

The Indian remains unremarkable at this time as the year as the IOD is dormant. Nevertheless, we still have warmer than normal SST’s, especially in the Eastern Basin closer to Australia and Indonesia as you can see in Figure 1 above and this is assisting the moisture available to the approaching MJO and monsoonal burst.

The MJO is in phase 3 at moderate strength and has definitely intensified in the last 2 weeks since the last update. This is an expected occurrence and should help to deliver a solid monsoonal burst across Northern Australia in the coming weeks, though the monsoon itself will meander and ebb and

flow, especially when lows form within the Monsoon Trough itself. As mentioned previously the strong trade winds pushing into the path of the approaching MJO will greatly assist uplift over Northern Australia. Having a moderate strength MJO will keep it mobile and moving steadily eastwards before the signal weakens towards phase 6. This should cause more low pressure troughing to really dominate as we move into early March with moisture starting to come down the middle of the country again and I’ve got no doubt that more flooding will occur in the next 4-8weeks.

The SAM is currently closer to neutral after being strongly positive through later Jan and early Feb. This has allowed a few fronts to sneak up with cooler air but after the 22nd or so, the index should rise once again with high pressure gradually sagging south as the continent gets that burst of trades (it’s like a well-oiled machine with all the cogs and gears interlocked turning together across diff parts of the country).

Districts:

Eyre Peninsula

Weak front passing below state of 18th with isolated light showers, chiefly about the Lower Eyre Peninsula. Secondary front later 20th with more northward penetration yielding isolated to scattered showers, easing through the evening of 21st. New strong ridge extending from Bight after before moving east quickly before another strong high quickly follows up. Trough deepening over eastern border from 23rd to 26th will tight gradient between second ridge leading to fresh to strong SE winds and seabreezes at times, particularly about coasts. Rainfall for period generally less than 2mm and chiefly in the south.

Upper North

Weak front passing below state of 18th with isolated light showers, chiefly about far south and elevated terrain. Secondary front very late 20th or early 21st with more northward penetration yielding isolated to scattered showers, easing through the evening of 21st. New strong ridge extending from Bight after before moving east quickly before another strong high quickly follows up. Trough deepening over eastern border from 23rd to 26th will tight gradient between second ridge leading to fresh to strong SE winds, especially so at night on western slopes of ranges. Isolated afternoon showers and thunderstorms possible in the north and east from 24th though generally remaining fine and warm for the most part. Rainfall less than 1mm, though brief and very localised 10-20mm dumps are possible in thunderstorms.

Lower North

Weak front passing below state of 18th with isolated light showers, chiefly about elevated terrain. Secondary front very late 20th or early 21st with more northward penetration yielding isolated to scattered showers, easing through the evening of 21st. New strong ridge extending from Bight after before moving east quickly before another strong high quickly follows up. Trough deepening over eastern border from 23rd to 26th will tight gradient between second ridge leading to fresh to strong SE winds, especially so at night on western slopes of ranges. Isolated afternoon showers and thunderstorms possible in the far north and east from 24th though generally remaining fine and warm for the most part. Rainfall less than 1mm, though brief and very localised 5-10mm dumps are possible in thunderstorms.

Yorke Peninsula

Weak front passing below state of 18th with isolated light showers. Secondary front very late 20th or early 21st with more northward penetration yielding isolated to scattered showers, easing through the evening of 21st. New strong ridge extending from Bight after before moving east quickly before another strong high quickly follows up. Trough deepening over eastern border from 23rd to 26th will tight gradient between second ridge leading to fresh to strong SE winds and seabreezes. Rainfall less than 2mm generally.

Kangaroo Island

Weak front passing below state of 18th with isolated light showers. Secondary front through afternoon and evening of 20th with more northward penetration yielding a band of scattered showers, easing through the evening of 21st. New strong ridge extending from Bight after before moving east quickly before another strong high quickly follows up. Trough deepening over eastern border from 23rd to 26th will tight gradient between second ridge leading to fresh to strong SE winds and seabreezes. Rainfall less than 2mm generally.

Adelaide Plains

Weak front passing below state of 18th with isolated light showers. Secondary front very late 20th or early 21st with more northward penetration yielding isolated to scattered showers, easing through the evening of 21st. New strong ridge extending from Bight after before moving east quickly before another strong high quickly follows up. Trough deepening over eastern border from 23rd to 26th will tight gradient between second ridge leading to fresh to strong SE winds, especially at night on western slopes of ranges. Rainfall less than 2mm generally.

Mt.Lofty Ranges

Weak front passing below state of 18th with isolated light showers, scattered about southern coasts and ranges. Secondary front very late 20th or early 21st with more northward penetration yielding isolated to scattered showers more frequent about the southern coasts and ranges with drizzle periods at times, easing through the evening of 21st. New strong ridge extending from Bight after before moving east quickly before another strong high quickly follows up. Trough deepening over eastern border from 23rd to 26th will tight gradient between second ridge leading to fresh to strong SE winds, especially at night on western slopes of ranges. Rainfall 2-5mm generally.

Riverland/Mallee

Weak front passing below state of 18th with isolated light showers, chiefly about far SW of Mallee. Secondary front very late 20th or early 21st with more northward penetration yielding isolated light showers, easing through the evening of 21st. New strong ridge extending from Bight after before moving east quickly before another strong high quickly follows up. Trough deepening over eastern border from 23rd to 26th will tight gradient between second ridge leading to fresh to strong SE winds. Isolated afternoon showers and thunderstorms possible, most likely in the north and east from 24th though generally remaining fine and warm for the most part. Rainfall less than 1mm, though brief and very localised 10-20mm dumps are possible in thunderstorms.

Upper SE

Weak front passing below state of 18th with isolated light showers, chiefly about the Coorong coastline and southern border. Secondary front during afternoon/evening of 20th with more northward penetration yielding isolated to scattered showers, easing through the evening of 21st. New strong ridge extending from Bight after before moving east quickly before another strong high

quickly follows up. Trough deepening over eastern border from 23rd to 26th will tight gradient between second ridge leading to fresh to strong SE winds. Isolated afternoon showers and thunderstorms possible, most likely in the north and east from 24th though generally remaining fine and warm for the most part. Rainfall less than 1mm, though brief and very localised 5-10mm dumps are possible in thunderstorms.

Lower SE

Weak front passing below state of 18th with isolated light showers, chiefly about the coasts. Secondary front during afternoon/evening of 20th with more northward penetration yielding a band of showers, easing through the evening of 21st. New strong ridge extending from Bight after before moving east quickly before another strong high quickly follows up. Trough deepening over eastern border from 23rd to 26th will tight gradient between second ridge leading to fresh to strong SE winds, especially about the coast leading to cold water upwelling. Isolated afternoon showers and thunderstorms possible, most likely in the north and east from 24th though generally remaining fine and warm for the most part. Rainfall less than 2-4mm, though brief and very localised 5-10mm dumps are possible in thunderstorms.

Finals Notes:

· La Nina matures, with one more burst of rainfall for the mainland, generally through March and into early April possibly

· Increasing moisture from east as trades pump moisture in through later Feb

· Dry spell after La Nina breakdown through mid to later autumn becoming a little more likely though will review on subsequent outlooks

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Happy farming and cheers from The Weatherman

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