October outlook 2024 SA
October outlook 2024 SA
*Forecast prepared between October 1st-3rd 2024
Review:
G’Day one and all, October is now here and certainly a
critical time in regard to how things finish. For
some, there has been too much damage done and that is greatly unfortunate and
sad to see. For others, there is still some hope left where a few mm here and
there may end up giving the last finish for what is still growing, albeit at a
very reduced yield. We’ll take a look at what we
can find for the rest of this month and then going forward.
Firstly, though as usual, a look back at the month that
was, or should we say – wasn't in September. The expectation many months out
was that we’d be making a run at a Negative IOD with September showing
improvement compared to July and even August with a building towards a better
finish to the year. Fast forward to the start of September and it was clear
that that was out the window with a much-revised forecast which I will put
below:
“Overall, in terms of a September rainfall outlook
I am expecting a mixed bag across the districts ranging from below average to
above average. The greatest risks of above average are over the Lower SE,
Kangaroo Island and potentially some parts of the outer NW and NE Pastorals.
Activity will drop away to average to below average across most central areas,
and down to generally below average for eastern Districts including the Upper
SE, Mallee, Riverland. The Eyre Peninsula will be around average to slightly
below at this stage but no strong signals either way. So
an improvement on August but not by a great deal”
Taking a look below now at the relevant charts for
September starting with the Deciles in Figure 1:
Figure 1: September 2024 rainfall
deciles – source BoM http://www.bom.gov.au/climate/
Figure 2: September 2024 rainfall
percentages – source BoM http://www.bom.gov.au/climate/
Figure 3: September 2024 rainfall
anomalies – source BoM http://www.bom.gov.au/climate/
As we can see, most of those charts
paint yet another grim picture for the agricultural areas which in the end was
generally expected. The slightly higher chance of above average in the forecast
of the Lower SE KI and NW Pastoral areas, mostly only occurred for the Pastoral
area thanks to tropical infeeds but a slither of the Lower E coastline managed
to get there thanks to being far south enough to get the top edge of weak
fronts, which never had influence further north. But the bulk of the rest were
very dry and if it were not for a reasonable rain event towards the end of the
month with 8-15mm totals, we’d have seen a lot more of the lowest on record
coloured in. All in all, another very poor month in the growing regions with
any moisture completely halted beyond the NW corner of the state.
Now onto that rain event and there was an expectation of
a more significant system around the 24th-27th or so from
the mid-month forecast. The first attempt at a system resulted in a broad and
waffly trigger with no focused convergence and poor connection to the tropics
and as a result only very light patchy rain was recorded and mostly under 1mm.
Fortunately whilst in that window, another front moved in and captured the
moisture that failed to connect and we saw a better broken up series of
rainbands from the mid-levels on the 28th and early hours of the 29th
which generally saw most locations east of the Spencer Gulf receive 5mm or
more. There were some good 15-30mm falls in the Mount. Lofty Ranges thanks to
orographics but the main good news was falls of 5-10mm across the Mallee area
and 8-14mm over the Upper SE. Very much welcome but in the grand scheme of
things, a mere drop in the ocean and more is needed.
Overall, a poor month with significant frost early and a
late rain only the saving grace.
Meteorological Discussion:
Onto current proceedings and we have a strong pre-frontal
trough and cold front blasting across WA with a broad upper trough behind
containing a lot of cold air. This is providing an ideal thermal gradient for
severe weather to form along and ahead of. The system has already given good
falls over WA with severe thunderstorms to boot, tapping into some moisture
lingering over inland WA. The downside is the entire system will dry out and
weaken as it moves through SA (a standard affair for us unfortunately). Nevertheless,
we will see some activity so let's look at what to expect with it as it moves
across.
A broad area of mid to upper-level cloud is crossing SA
generating areas of patchy light rain. Ahead of this unfortunately, fresh to
strong and very dry northerly winds are funnelling south ahead of the system
adding more curing to already stressed crops. The patchy light rain will weaken
out as it crossed the gulf area with no sustaining uplift to keep it going
since it was merely the remnants of strong thunderstorm activity over WA
yesterday. Further west, a cold front is marked by a line of heavier showers
and thunderstorms is moving quickly eastwards however most of the thunderstorm
activity will weaken into a slightly thicker band of rain catching up to the
decaying one ahead. Another weak trough is located just west of the front with
some isolated showers and thunderstorms. All this will extend E/SE across the
agricultural and adjacent pastoral areas on the evening of the 3rd
and early hours of the 4th for the eastern districts. Generally
light falls are expected although with western extent, some totals may be
useful enough across the western and southern/Lower Eye Peninsula up to about
10-12mm potentially. Further east away from the lift of the ranges, most totals
will come in around 1-5mm, perhaps some isolated 6-7mm luckier totals.
General scattered mid-level showers and isolated
thunderstorms will clear the E/SE of the state by sunrise as a low moves in
from the west south of the state with onshore shower activity. Aloft an upper
trough will result in showers increasing with some daytime heating during the 4th
before clearing again during the evening. Another cold front in the onshore
flow will move in from the WSW reaching Kangaroo Island just after 12am on the
5th with a band of showers. These will arrive in the Adelaide area
by about sunrise with showers then extending across much of the southern
agricultural area, more frequent about the ranges. Given the timing, there
should be reasonable penetration across the Mallee this time around with the
band moving through, although isolated towards the Riverland. I suspect this
band will give better totals than the activity the night before for nearly all
areas east of the ranges. Falls will still be light but perhaps 1-4mm from the
shower activity is a reasonable expectation with some 5-6mm localised totals
possible closer to the Upper SE and more over the Lower SE.
On the 6th still embedded in a moist onshore
WSW flow another weak front will clip the SE of the state – weaker than the one
the day prior but enough to bring another broken band of showers to chiefly the
SE Districts and the southern coasts and ranges including KI. A repeat will occur again on the 7th,
a weak sliding front clipping the Lower SE.
A clearance will occur ahead of a weakening front from WA
with a decaying band of mid-level showers around the 10th but don’t
expect much here. Beyond this high pressure will temporarily take hold ahead of
some trough activity deepening out of inland WA towards mid-month but it is too
early to tell if this will connect with any colder air out of the SW.
Overall, my outlook for October is for average to slight
below average rainfall across most agricultural districts. The greatest chance
of average rainfall or slightly above again is the Lower SE which like
September will just be south enough to receive fronts. The greatest chance of
above average again will be the western border areas up to about Western Eyre
Peninsula but moreso into the NW corner of the state.
Climate Drivers:
Now the Pacific has seen a stall in any movement
towards La Nina which November and December really the final window to get one
declared. It may be a case of NOAA declaring but the BoM not it is that much of
a knife edge and in that case a cool neutral will be the final call for 2024 by
the BoM. There is still cooler water to upwell but not a great deal, the
Humboldt Current remains steady with no changes. Trades have dropped back to
near average again so despite a good burst, the final levels have not been
reached. In any case, a good amount of warmer water remains to the north of PNG
and generally NE of Australia (see Figure 4).
Figure 4: Current SST anomalies –
source Tropical Tidbits https://www.tropicaltidbits.com/analysis/ocean/cdas-sflux_ssta_global_1.png
The Indian unlike the Pacific has continued its trend
towards a negative IOD, the ever pulsing and flipping values that have plagued
the 2024 season so far. As expected through spring, we are now dropping with
the latest value coming in at –0.39C at the start of October, a hairs breath
away from negative values once again. This time I expect those values to hold
around –0.4C maybe even lower before moving back to neutral. I don’t quite
think we hold there long enough to make it officially negative but like it has
done on both the positive and negative side earlier this year, hold for a few
weeks then shoot back the other way except this is the last move in the IOD
window which closes once the monsoon season approaches, destroying the surface
wind patterns that generate the anomalies we see. This will increase moisture
feeding into the NW of Australia through spring, but chiefly November and
December. It won’t be huge but an improvement from what we have seen. The key
for me is getting heat in first, once we get heat in then the moisture will
have a much easier path into those troughs. Trouble is, that will be harvest
time for those that do have something to reap or hay bailing time. Frustrating
but I am sure anything will be taken.
Now moving onto the SAM, we have a decent dip into the
negatives which is at least getting some fronts into the area but not too
strong like late August to early September so at least it is allowing some WSW
flow with onshore flow but not strong enough to make it a flat westerly flow
with big wind which does nothing to help the situation rainfall wise. The SAM
is expected to move back to neutral ground as we nudge through October but
perhaps with a negative flavour lingering aloft as I can see a lot of meandering
of the jetstreams thanks to some very strong solar activity from the sun in the
last few days so watch this space for some ‘random’ or unorthodox systems.
The MJO is currently on the other side of the world
around the African region at a moderate strength. It is expected to move
towards the Australian region by mid-month at a similar strength but may lose
steam once it moves into the Pacific. Look for increased tropical thunderstorm
activity by mid-month. This will be well timed to enhance any potential
negative IOD influence albeit a shortened one.
Districts:
Eyre Peninsula
Trough and cold front will combine to generate areas of
patchy rain during the afternoon and evening of the 3rd with a line
of showers and isolated thunderstorms to follow, gradually tending to areas of
rain over the Lower Eyre Peninsula. Weak upper trough on 4th with
scattered showers. Cold front early 5th with a band of showers,
becoming much more isolated towards the NE corner of the Peninsula. Another
weaker front clipping the coast on the 6th with isolated light
showers in the far south followed by a repeat third weak front on the 7th
with similar conditions. Remaining mostly fine further north. Weak trough around
10th though generally remaining dry. Increasing instability likely
through the mid-month period from 13th-19th or so with a
couple of potential stronger systems with showers and thunderstorms extending
from the NW. Rainfall for the period 5-12mm generally, increasing to 12-18mm
about Lower to Western coastal Eyre Peninsula. Totals decreasing towards the
N/NE corner down to 3-5mm.
Upper North
Trough and cold front will combine to generate
areas of patchy light rain during the late afternoon and evening of the 3rd
with isolated showers and thunderstorms to follow, more likely with southern
extent. Weak upper trough on 4th with isolated showers. Cold front
on 5th with a band of showers, becoming much more isolated towards
the back side of the ranges and north of Port Pirie. Another weaker front
clipping the coast on the 6th with isolated light showers in the far
south followed by a repeat third weak front on the 7th however no
rainfall is expected. Weak trough around 10th though generally
remaining dry apart from a possible mid-level shower. Increasing instability
likely through the mid-month period from 13th-19th or so
with a couple of potential stronger systems with showers and thunderstorms
extending from the NW. Rainfall for the period 2-4mm generally, increasing to
5mm about elevated terrain in the south. Totals decreasing towards the back
side of the ranges and the Flinders down to 1mm or so.
Lower North
Trough and cold front will combine to generate
areas of patchy light rain during the late afternoon and evening of the 3rd
with isolated showers and thunderstorms to follow, more likely with southern
extent. Weak upper trough on 4th with isolated to scattered showers.
Cold front on 5th with a band of showers, becoming much more
isolated towards the back side of the ranges and the northern portions of the
district. Another weaker front clipping the coast on the 6th with
isolated light showers followed by a repeat third weak front on the 7th
with further light showers only in the south. Weak trough around 10th
though generally remaining dry apart from a possible mid-level shower.
Increasing instability likely through the mid-month period from 13th-19th
or so with a couple of potential stronger systems with showers and
thunderstorms extending from the NW. Rainfall for the period 3-6mm generally,
increasing to 8mm about elevated terrain in the south. Totals decreasing
towards the back side of the ranges down to 1-3mm or so.
Yorke Peninsula
Trough and cold front will combine to generate
areas of patchy rain during the late afternoon and evening of the 3rd
with isolated showers and thunderstorms to follow, with rain more likely down
the lower half of the Peninsula with thunderstorm activity more likely to the
north. Weak upper trough on 4th with isolated to scattered showers.
Cold front early 5th with a band of showers. Another weaker front
clipping the coast on the 6th with isolated light showers followed
by a repeat third weak front on the 7th with further light showers
only about the foot. Weak trough around 10th though generally
remaining dry apart from a possible mid-level shower. Increasing instability
likely through the mid-month period from 13th-19th or so
with a couple of potential stronger systems with showers and thunderstorms extending
from the NW. Rainfall for the period 5-10mm generally, increasing to 10-18mm
about the foot. Totals decreasing towards the far north around 3-5mm.
Kangaroo Island
Trough and cold front will combine to generate
areas of patchy rain during the late afternoon and evening of the 3rd
tending to areas of rain at times. Possible thunder. Weak upper trough on 4th
with isolated to scattered showers. Cold front early 5th with a band
of showers. Another weaker front clipping the coast on the 6th with
isolated light showers followed by a repeat third weak front on the 7th
with further light showers. Weak trough around 10th though generally
remaining dry apart from a possible mid-level shower. Increasing instability
likely through the mid-month period from 13th-19th or so
with a couple of potential stronger systems with showers and thunderstorms
extending from the NW. Rainfall for the period 8-15mm generally, increasing to
15-25mm about the western end. Totals decreasing towards the eastern end down
to around 7-8mm.
Adelaide Plains
Trough and cold front will combine to generate
areas of patchy rain during the late afternoon and evening of the 3rd
with isolated showers and thunderstorms to follow. Weak upper trough on 4th
with isolated to scattered showers. Cold front early 5th with a band
of showers. Another weaker front clipping the coast on the 6th with
isolated light showers followed by a repeat third weak front on the 7th
with further light showers only about the outer southern suburbs. Weak trough
around 10th though generally remaining dry apart from a possible
mid-level shower. Increasing instability likely through the mid-month period
from 13th-19th or so with a couple of potential stronger
systems with showers and thunderstorms extending from the NW. Rainfall for the
period 5-10mm generally, increasing to 10-15mm about the foothills and southern
suburbs. Totals decreasing towards the outer northern plains down to around
3-5mm.
Mt.Lofty Ranges
Trough and cold front will combine to generate
areas of patchy rain during the late afternoon and evening of the 3rd
with isolated showers and thunderstorms to follow. Weak upper trough on 4th
with isolated to scattered showers. Cold front early 5th with a band
of showers, with showers more frequent and heavier over the southern Fleurieu.
Another weaker front clipping the coast on the 6th with isolated
light showers followed by a repeat third weak front on the 7th with
further light showers, chiefly about the southern coasts and ranges. Weak
trough around 10th though generally remaining dry apart from a
possible mid-level shower. Increasing instability likely through the mid-month
period from 13th-19th or so with a couple of potential
stronger systems with showers and thunderstorms extending from the NW. Rainfall
for the period 5-12mm generally, increasing to 12-18mm about the southern
Fleurieu. Totals decreasing towards the northern ranges and in the lee side
down to around 3-5mm.
Riverland/Mallee
Trough and cold front will combine to generate
areas of patchy light rain during the evening of the 3rd and into
the early 4th with isolated showers and thunderstorms to follow,
more likely with southern extent across the Mallee. Weak upper trough on 4th
with isolated showers again more likely over the southern Mallee. Cold front on
5th with a band of showers, becoming isolated over the Riverland.
Another weaker front clipping the coast on the 6th with isolated
light showers in the far southern Mallee followed by a repeat third weak front
on the 7th however no rainfall is expected. Weak trough around 10th
though generally remaining dry apart from a possible mid-level shower.
Increasing instability likely through the mid-month period from 13th-19th
or so with a couple of potential stronger systems with showers and
thunderstorms extending from the NW. Rainfall for the period 3-5mm generally,
increasing to 5-8mm about the SW/S Mallee. Totals decreasing towards the
Riverland with 1-3mm expected there.
Upper SE
Trough and cold front will combine to generate
areas of patchy light rain during the evening of the 3rd and into
early 4th with isolated showers and thunderstorms to follow, chiefly
towards the north. Weak upper trough on 4th with isolated showers.
Cold front on 5th with a band of showers. Another weaker front
clipping the coast on the 6th with isolated showers followed by a
repeat third weak front on the 7th with further isolated shower
activity. Weak trough around 10th though generally remaining dry
apart from a possible mid-level shower. Increasing instability likely through
the mid-month period from 13th-19th or so with a couple
of potential stronger systems with showers and thunderstorms extending from the
NW. Rainfall for the period 8-12mm generally, increasing to 12-15mm in the far
south. Totals decreasing towards the Mallee with 5-8mm expected there.
Lower SE
Trough and cold front will combine to generate
areas of patchy rain during the evening of the 3rd and into early 4th
with isolated showers and possible thunderstorms to follow, chiefly towards the
north. Weak upper trough on 4th with isolated showers. Cold front on
5th with a band of showers, potentially heavy at times. Another
weaker front clipping the coast on the 6th with another band of
slightly lighter showers followed by a repeat third weak front on the 7th
with further showery periods within the frontal zone. Weak trough around 10th
though generally remaining dry apart from a possible mid-level shower.
Increasing instability likely through the mid-month period from 13th-19th
or so with a couple of potential stronger systems with showers and
thunderstorms extending from the NW. Rainfall for the period 15-25mm generally,
increasing to 25-30mm towards the southern coastline. Totals decreasing towards
the Upper SE with 12-15mm expected there.
Western VIC
Trough and cold front will combine to generate
areas of patchy rain during the late evening of the 3rd and into
early 4th with isolated showers and possible thunderstorms to
follow, chiefly towards the Mallee. Weak upper trough on 4th with
isolated showers, with possible thunderstorms in the east of the SW District.
Cold front on 5th with a band of showers, potentially heavy at times
in the afternoon over the SW District and southern Wimmera. Another weaker
front clipping the coast on the 6th with another band of showers
followed by a repeat third weak front on the 7th with further
showery periods within the frontal zone. All activity struggling to reach past
the Wimmera District. Weak trough around 10th though generally
remaining dry apart from a possible mid-level shower. Increasing instability
likely through the mid-month period from 13th-19th or so
with a couple of potential stronger systems with showers and thunderstorms
extending from the NW. Rainfall for the period 15-25mm generally about the SW
District increasing to 25-35mm towards the southern coastline of the SW
District. Totals decreasing towards the Wimmera with 5-12mm and then less again
for the Mallee with 3-5mm expected there.
Final Notes
·
A few weak fronts and troughs to keep some totals ticking over, but more
is needed
·
October will be what I call a lead in month with improvements to heat
and troughing, but moisture won’t properly come down till November and December
with increased shower and thunderstorm activity, but with a mid-level flavour
·
Brief negative IOD attempt for November, otherwise on the negative side
of neutral
·
Weak La Nina attempt but otherwise on the cool side of neutral
·
Above average wet season likely for ther tropics and adjacent inland
·
Summer rainfall and temperatures in SA looking very close to the mean at
this stage
Link to temporary blog website: https://farmweathersa.blogspot.com/
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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