January Outlook 2025 SA
January outlook 2025 SA
*Forecast
prepared between Jan 1st-5th 2024
Review:
G’Day one and all and a very Happy New Year to you, I
hope 2025 brings far better fortune than 2024 did with regards to the weather
and cropping in general as that was not a pleasant year to say the least. I
trust and hope you have all had a great Christmas with family. Myself unfortunately not so, being extremely ill for
nearly 3 weeks from mid-December till now and spending all of Christmas Day
staring at the ceiling in bed with severe Bronchitis or Pneumonia – it
certainly does knock the stuffing out of you and as a result I was unable to
even get out of bed for a good week and do the mid-month update. But in any
case, we will take a look back now at how the month
went.
December 2024 was for the most part a relatively dry
month across the agricultural areas with general below average rainfall as per
Figure 1 shows below:
Figure 1: December 2024 rainfall
deciles – source BoM http://www.bom.gov.au/climate/
The Lower and Upper North regions exhibited very-much
below average rainfall embedded in that broader below average area. Large areas
of the state were average with small pockets of above average over the Lower SE
corner and parts of the Far West Coast, NW Corner and generally a good chunk of
the NE corner of the state.
Figure 2:
December 2024 rainfall percentages – source BoM http://www.bom.gov.au/climate/
Figure 3:
December 2024 rainfall anomalies – souce BoM http://www.bom.gov.au/climate/
Revealing a little more detail as
usual, both the percentage and anomaly charts show the major dry hole across
the Lower and Upper North, at least handy to allow harvest to finish but
contrasting that December 2023 was quite wet giving a boost to the sub-soil.
Not so this time round although November was indeed wet but given it came after
one of the drier years in history, a lot of that moisture soaked in very well.
Now looking back at the December
outlook: “Given the late outlook, no official December rain outlook but I
would have expected a wetter first half trending drier middle and possibly
moisture to increase late. It looks to me like the northern half of the
Pastorals will see above average rainfall and potentially the far west coast
however most agricultural areas are likely to be in the average to below
average category.”
Granted I wasn’t making it
official, we can see it still worked out fairly well
as the trends were easier to see by the time I made that forecast a few days later
than usual.
Overall, however in terms of
patterns, December was quite a mobile month with relatively frequent cold
fronts passing through the south of the state, not allowing significant heat or
moisture to build to the north and feed down. The SAM sat more on the negative
side as a result and despite a relatively strong MJO which drove an increase in
showers and storms over the tropics, we could not get a proper monsoon onset
into the Top End of the nation, with much of that staying north across
Indonesia.
Meteorological
Discussion:
January 2025 is here and for the
most part a time where many of you are wondering what the year ahead will
bring, and especially so after what 2024 dished up. On first glance I am
certainly expecting improvement but by no means a wet year, perhaps closer to
average for most areas.
Now currently we have a combined weak
surface trough and mid to upper trough approaching from the west with some
mid-level patchy rain and isolated thundery showers. This activity is moving in
behind a few days of hot conditions where temperatures reached the high 30’s to
low 40’s across the agricultural areas. Now there is a fair amount of mid-level
moisture and convergence ahead of this mid to upper level trough, especially
over the SE Districts so as the night of the 5th and early hours of
the 6th progress, I will expect general scattered showers and
isolated thunderstorms tending to patchy rain and embedded thunderstorms and
perhaps activity tending to areas of rain across the Lower and Upper SE as well
as general western VIC with some falls into double digits are likely (hopefully
dampening the fires in the Grampians as well). Overall due to this convergence
alone there may be some useful totals for areas east of the ranges in SA mainly
in the 3-5mm range but scattered totals to 10mm and some isolated 10-15mm falls
are definitely possible, with general 8-15mm and isolated 15-20mm falls likely
over Western VIC.
Beyond this system a strong ridge
will push in causing fresh S-SE winds and seabreezes with gully winds at night
about the ranges, especially on the 7th before the high moves
further east and weakens. This will be a trend over the coming week or two with
a semi-permanent surface trough parked over QLD/NSW and ridging below the Bight
keeping at least the coastal areas in a S-SE flow for the most part however
further inland closer to the trough, conditions will remain quite hot.
Two further weak surface troughs
are likely to move east from the west on the 9th and 11th
with isolated thundery showers possible but without upper support, rainfall
totals will be slim compared to the first system. A further weak trough is
possible around the 15th keeping with the theme of a relatively
mobile pattern. I do expect however the second half of the month to see greater
heat potential building inland so whilst we will see quite a lot of 30-35C
temperatures across the agricultural area, the 40-45C temperatures for now
should hold across the Far North but I am looking for that sort of temperature
to advect south for the second half of January, especially if the SAM gets
closer to a positive. Random fact – January 24th is by average the
hottest day of the year with some notable extremes, it will be interesting to
see if the day can live up to expectations. Jan 25th is also right
up there (2003 being one I remember well).
Looking ahead, I see more
opportunities for rainfall this Feb-May period that last year simply due to the
warmer waters off WA, I will expand more on that in the climate section but
historically that does have some impact. Having said that, I still don’t expect
a strong wet signal and there will be an Indian summer like period most likely
through April where we transition to that winter pattern. I’ve noticed most
years exhibit this; it’s just the degree of intensity that varies. An old
saying of a drier summer, wetter winter can ring true and this year whilst I
see a return to better rainfall at more traditional times, I still don’t see a
proper wet year at this stage. I will have a much better idea on autumn-spring
and the monthly breakdown by about March at this stage, right now there is no
clear signal either way that I see standing out. Neutral years for the IOD can
be frustrating in parts of SA but still better than what we saw in 2024. And
just further to that, I still intend on a special update dedicated on exactly
why 2024 was so dry with some explanations. It is a landmark year that will be
good for future reference and no doubt one to learn on, and what to look for
again in the future. Having said that, a year like 2024 is unlikely to repeat
itself again in a hurry.
The overall outlook for January
is for a very close to average month rainfall wise, but perhaps a slight bias
to below average over the Central to Western agricultural areas. The greatest
chance of above average will be over the far NE Pastoral District and
potentially into the Riverland. Overall, though, no strong signals either way.
Climate
Drivers:
The Pacific has shown a continued move towards
La Nina with a defiance on weakening back to neutral areas. Sustained trade
winds through December have pushed the thresholds right down the lower end of
cool neutral but when one looks at Figure 4 with the SST anomalies, they could
be forgiven to think that we are already in a La Nina – and yes, we are quite
close. It is going to be a lineball call if we actually make it official but it
has hung around a little longer than I would have expected at least which is a
good sign for later summer rain at least over the Northern and Eastern half of
the nation, a little more touch and go whether we have the penetration for SA
but factoring in the warm Indian which I will discuss shortly, it is making a
good fist of things, or setting up for that type of event.
Figure 4: Current SST anomalies –
source Tropical Tidbits https://www.tropicaltidbits.com/analysis/ocean/cdas-sflux_ssta_global_1.png
The Indian has now returned to neutral after scraping in
for a negative IOD in December (although not officially recognised, by the old
count of 7 consecutive weeks, it was). However, the main area of interest is
the very warm waters off the immediate NW shelf of WA. These would have to be
some of the warmest anomalies I can remember for this region and are similar to
a Ningaloo Nino albeit further north. Any Tropical Cyclone activity that moves
through here will have a lot more grunt than usual. Going forward this should
generally enhance moisture supply from the NW so we should see a greater
potential for NW infeeds through Feb-April this year as opposed to last year
however which was bone dry given it is only a localised area, I do not expect a
heavy wet signal by any stretch.
As for an official Indian Ocean Dipole outlook for 2025,
it certainly is not presenting hard either way, but I would lean 60-40 odds on
for it to be on the negative side at the current state of the ocean. I thought
the same this time last year albeit a heavier lean to negative and we all know
how the IODA behaved in 2024....positive then negative then positive then
finished on a more sustained negative – the stuff of nightmares and something I
do not expect a repeat of in 2025 unless we get multiple rounds of SSW (Sudden
Stratospheric Warming).
The MJO has been a focal point for the increased tropical
activity across northern and NE Australia, especially with strong impacts over
coastal QLD which until December has been incredibly dry and well below average
in rainfall. Unfortunately, a very mobile westerly belt did no favours for us
trying to get sustained infeeds of moisture into our state although those still
finishing harvest were no doubt thankful for that. Overall, the MJO was
moderate in strength but as it has moved into the Pacific now, the signal is
much weaker and is expected to remain weak to indiscernible for a number of
weeks. I cannot see a meaningful MJO pulse until at least very late January or
well into Feb.
The SAM has been negative to neutral for much of December
and as mentioned before, has been responsible for our mobile pattern and
changeable conditions seen. Right now, the index is neutral with no strong
tendency either way. I still see a struggle for a positive SAM through January
so neutral is the most likely which generally means very much average
conditions both temperature and rainfall wise. February may see a slight hint
towards more Positive levels.
Districts:
Eyre Peninsula:
Weak surface trough combining with mid to upper-level
trough to generate increasing patchy rain and isolated thunderstorms from late
afternoon/early evening on 5th. Activity clearing by early 6th
as new firm ridge moves in from Bight with fresh to strong S/SE winds, chiefly
about exposed coasts. Becoming hot to very hot once again ahead of a series of
weak troughs on 9th and 11th with isolated thundery
showers but minimal rainfall. A further stronger follow up trough is likely
around the 15th or so with some thundery conditions. Also, there is the
possibility of more significant heat towards the second part of January,
especially in the west. Rainfall for the period generally 4-8mm decreasing down
to 2-4mm over the Northern part of the Peninsula. Local totals to 10-12mm
possible about Lower Eyre Peninsula, mostly with the first system.
Upper North
Weak surface trough combining with mid to upper-level
trough to generate a little patchy rain and isolated thunderstorms from mid-evening
on 5th. Activity clearing by early 6th as new firm ridge
moves in from Bight with fresh to strong S/SE winds, chiefly about exposed
coasts with fresh gully winds about the western slopes of the ranges early on
the 7th. Becoming hot to very hot once again ahead of a series of
weak troughs on 9th and 11th with isolated thundery
showers but minimal rainfall. A further stronger follow up trough is likely
around the 15th or so with potential thundery conditions, chiefly
with northern and eastern extent. Also, there is the possibility of more
significant heat towards the second part of January. Rainfall for the period a
general 3-5mm, with isolated 5-10mm falls in the far N/NE of the district with
thunderstorm activity.
Lower North
Weak surface trough combining with mid to upper-level
trough to generate a little patchy rain and isolated thunderstorms from mid-evening
on 5th. Activity clearing by early 6th as new firm ridge
moves in from Bight with fresh to strong S/SE winds, chiefly about exposed
coasts with fresh gully winds about the western slopes of the ranges early on
the 7th. Becoming warm to hot once again ahead of a series of weak
troughs on 9th and 11th with isolated thundery showers
but minimal rainfall. A further stronger follow up trough is likely around the
15th or so with potential thundery conditions, chiefly with northern
and eastern extent beyond the ranges towards the Eastern parts of the Upper
North. Also, there is the possibility of more significant heat towards the
second part of January. Rainfall for the period a general 3-5mm, with isolated 4-8mm
falls in the far N/NE of the district with thunderstorm activity.
Yorke Peninsula
Weak surface trough combining with mid to upper-level
trough to generate patchy rain and isolated thunderstorms from early evening on
5th, chiefly about the foot. Activity clearing by early 6th
as new firm ridge moves in from Bight with fresh to strong S/SE winds, chiefly
about exposed coasts during the afternoon. Becoming warm to hot once again
ahead of a series of weak troughs on 9th and 11th with
isolated thundery showers but minimal rainfall. A further stronger follow up
trough is likely around the 15th or so with potential thundery
conditions. Also, there is the possibility of more significant heat towards the
second part of January. Rainfall for the period a general 4-6mm, with scattered
6-10mm falls and isolated 10-12mm falls about the foot.
Kangaroo Island
Weak surface trough combining with mid to upper-level
trough to generate patchy rain and isolated thunderstorms from early evening on
the 5th. Activity clearing by early 6th as new firm ridge moves in
from Bight with fresh to strong S/SE winds, chiefly about exposed coasts during
the afternoon. Becoming warm once again ahead of a series of weak troughs on 9th
and 11th with isolated thundery showers but minimal rainfall. A
further stronger follow up trough is likely around the 15th or so
with potential thundery conditions before cooler onshore showers follow. Also,
there is the possibility of more significant heat towards the second part of
January. Rainfall for the period a general 3-5mm, with scattered 5-8mm falls
and isolated 8-12mm about the central to eastern parts of the island.
Adelaide Plains
Weak surface trough combining with mid to upper-level
trough to generate patchy rain and isolated thunderstorms from late evening on
5th, chiefly about the southern suburbs. Activity clearing by early
6th as new firm ridge moves in from Bight with fresh to strong S/SE
winds. Fresh gully winds likely about western slopes early 7th.
Becoming warm to hot once again ahead of a series of weak troughs on 9th
and 11th with isolated thundery showers but minimal rainfall. A
further stronger follow up trough is likely around the 15th or so
with potential thundery conditions. Also, there is the possibility of more
significant heat towards the second part of January. Rainfall for the period a
general 4-6mm, with isolated totals to 10mm possible in the south. Totals
decreasing to 2-4mm about the outer plains.
Mt.Lofty Ranges
Weak surface trough combining with mid to upper-level
trough to generate patchy rain and isolated thunderstorms from late evening on
5th, chiefly about the southern coasts and ranges where locally
heavier falls may occur. Activity clearing by early 6th as new firm
ridge moves in from Bight with fresh to strong S/SE winds, especially strong
about the southern coasts. Fresh gully
winds likely about western slopes early 7th. Becoming warm to hot
once again ahead of a series of weak troughs on 9th and 11th
with isolated thundery showers but minimal rainfall. A further stronger follow
up trough is likely around the 15th or so with potential thundery
conditions as well as onshore southern coastal showers behind the system. Also,
there is the possibility of more significant heat towards the second part of
January. Rainfall for the period a general 6-8mm, with isolated totals to 12-15mm
possible in the south. Totals decreasing to 2-6mm further north.
Riverland/Mallee
Weak surface trough combining with mid to upper-level
trough to generate patchy rain and isolated thunderstorms from late evening on
5th. Activity clearing by early to mid-morning on the 6th
as new firm ridge moves in from Bight with fresh to strong S/SE winds, chiefly
about the SW parts of the Mallee. Becoming hot to very hot once again ahead of
a series of weak troughs on 9th and 11th with isolated
thundery showers but minimal rainfall. A further stronger follow up trough is
likely around the 15th or so with potential thundery conditions,
chiefly with northern and eastern extent over the Riverland and north of. Also,
there is the possibility of more significant heat towards the second part of
January. Rainfall for the period a general 4-6mm, with scattered isolated 6-10mm
falls. Isolated 10-15mm totals about the southern Mallee area.
Upper SE
Weak surface trough combining with mid to upper-level
trough to generate areas of rain and isolated thunderstorms from late evening
on 5th. Activity clearing by early to mid-morning on the 6th
as new firm ridge moves in from Bight with fresh to strong S/SE winds,
especially about the Coorong coast where stiff seabreezes will occur. Becoming warm
to hot once again ahead of a series of weak troughs on 9th and 11th
with isolated thundery showers but minimal rainfall. A further stronger follow
up trough is likely around the 15th or so with potential thundery
conditions, chiefly with northern and eastern extent. Also, there is the
possibility of more significant heat towards the second part of January.
Rainfall for the period a general 5-8mm, with scattered isolated 8-12mm falls.
Isolated 12-16mm totals possible about the eastern border districts.
Lower SE
Weak surface trough combining with mid to upper-level
trough to generate areas of rain and isolated thunderstorms from late evening
on 5th. Activity clearing by late morning on the 6th as
new firm ridge moves in from Bight with fresh to strong S/SE winds, especially
about the southern and western coastline where stiff seabreezes will occur.
Becoming warm to hot once again ahead of a series of weak troughs on 9th
and 11th with isolated thundery showers but minimal rainfall. A
further stronger follow up trough is likely around the 15th or so
with potential thundery conditions, chiefly with northern and eastern extent.
Also, there is the possibility of more significant heat towards the second part
of January. Rainfall for the period a general 6-10mm, with scattered isolated 10-15mm
falls. Isolated 15-18mm totals possible about the eastern border districts.
Western VIC
Weak surface trough combining with mid to upper-level
trough to generate areas of rain and isolated thunderstorms from the early
hours of the 6th. Activity clearing by midday on the 6th
as new firm ridge moves in from Bight with fresh to strong S/SE winds,
especially about the southern coastline of the SW District where stiff
seabreezes will occur. Becoming warm to hot once again ahead of a series of
weak troughs on 9th and 11-12th with isolated thundery
showers but minimal rainfall. A further stronger follow up trough is likely
around the 15th or so with potential thundery conditions, chiefly
with northern extent where more humid conditions may prevail ahead of moisture
feeding in from NSW. Also, there is the possibility of more significant heat
towards the second part of January. Rainfall for the period a general 8-15mm,
with scattered isolated 15-18mm falls. Isolated 18-23mm totals possible closer
to the east of the Mallee/Wimmera and SW District.
Final Notes
·
Very warm SST’s off WA likely to assist
moisture coming into mainland in coming months however no significant wet
signals are showing
·
Cool neutral to borderline weak La Nina in Pacific will gradually weaken
in coming months for a neutral 2025
·
Weak Negative IOD likely for winter and moreso spring 2025 but still
very early days
·
Late monsoon impact across N Australia, potentially late Jan or early
February
·
Heat building for second half of January and into February once frontal
systems slow and SAM tends neutral to positive
·
Overall, at first glance near average rainfall likely for 2025 however
better detail will present from about March
Link to
temporary blog website: https://farmweathersa.blogspot.com/
Happy Farming and Cheers from The
Weatherman
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