South Australia - Fast Break

Welcome to your Fast Break newsletter

You are reading the 6th Fast Break for South Australia

Read the Tas issue of Fast Break

Volume 1 | Issue 6 | South Australia | Published: 02 Oct 2018

Welcome to our fifth “Fast Break” newsletter for the South Australian grains industry. Our team has been preparing this monthly newsletter for 12 years in Victoria and with GRDC support we are now able to present it for SA. If you like it, please consider passing it on through your networks and subscribing.

Still no sign of an El Niño and yet most models predict one will occur in late spring/summer. The Pacific Ocean surface is still neutral, the SOI is vaguely interested, the cloud patterns aren’t remotely keen, the deep sea is warm to depth, but only in the western and central Pacific. The major change this month is the easterly trade winds have shown some El Niño like behaviour, with at least two, one-week long reversals of significant strength from PNG to half way across. This is likely to force the warmer water to depth further to the east, and warm the surface in the middle of the Pacific. All this is likely to take months which will just about see out the growing season before it occurs. Historically, summer El Niño’s have been hit and miss for South Australia.

The Coral Sea is still warmer which is most unlike a “classic” El Niño.

All action has been in the Indian Ocean for some months. In the last weeks the Dipole Mode Index (DMI) measurement of the IOD has gone positive. Despite predictions from models for its occurrence all season, it has only just happened. We have had +IOD like cooling in the Timor Sea for many months but the current +IOD condition is being caused by the rapid warming off the African coast. Trade wind patterns are not consistent with a proper +IOD, but the lack of cloud off Sumatra is. Certainly, the lack of NW moisture feed for much of the season had something to do with the Indian Ocean not playing ball. If the +IOD hangs around for two months it will be called an event, but it would normally die in late October early November when the tropical wet season fires up. Historically around 50-60 per cent of springs in +IOD years have been in the driest third of records.

Pressure patterns, which were favourable in August, have deteriorated in September by increasing in pressure and position over SA and chasing rainfall triggers away. Such behaviour is classic +IOD induced.

The SAM which had been behaving itself in winter (particularly for the southern districts) will cease to be a major driver in spring. Connections to tropical moisture will be more important than weak fronts.

The models surveyed are predicting average/drier conditions for spring with warmer temperatures. The major warm signal is for December.

While the season is pretty much finished in lower rainfall regions, in mid to higher rainfall areas it would be prudent to be planning for a shorter, rather than longer spring.

map of SA showing dry soil to depth but moisture probes showing variable values
The BoM AWRA modelled plant available soil moisture (10-100cm) shows that the Adealide Hills , KI and the SE have some moisture but other areas are not ideal. The monitored moisture probes (courtesy of NR-SAMDB, EPARF, SARDI and Agbyte) shows soil moisture (30-100cm) has dramatically decreased in some paddocks and in some dry paddocks barely moved. Mallee paddocks are running on empty
Graphs showing the distribution of October-December modelled rainfall as average/drier and temperature as warmer
graphs showing the distribution of January-March modelled rainfall is for average and temperature warmer-average

Model consensus forecast for the next six months

Model consensus forecast for the next six months

Current outlook (28 September)

Previous outlook (27 August)

Oct-Dec outlook

Jan-Mar outlook

Sep-Nov outlook

Dec-Feb outlook

Pacific Ocean

El Niño (Modoki)

El Niño (Modoki)

El Niño

El Niño

Indian Ocean

Neutral

Neutral

Neutral (+IOD?)

Neutral

Rainfall

Average/slightly drier

Average

Slightly drier/average

Average

Temperature

Slightly warmer

Slightly Warmer/average

Average

Slightly warmer

Equatorial Pacific Ocean Sea surface temperature anomalies are normal. But a +IOD has formed in the Indian Ocean
Sea surface temperatures (SST) along the Equatorial Pacific hardly changed in September. NINO3 is at +0.17oC and NINO3.4 is +0.24oC (as of 26 Sept), both at neutral values. The Indian Ocean has changed dramatically. The Dipole Mode Index, (DMI) has screamed up to +0.87oC where the threshold for +IOD is +0.5 oC. The cold pool of water near Sumatra has moved a little further north into the east IOD region, but the critical change is that the water of Kenya has significantly warmed up the western region.
Undersea warm temperatures in the eastern Pacific have cooled, nothing like El Niño.
The Pacific Ocean Equatorial sub surface temperatures haven’t done much this last month. The undersea warmth made limited progress to the east, so an El Niño at the surface is at the earliest, many months away.
The SOI value is currently at -6.7
The SOI is currently at -6.7 and falling, in the neutral range. Sustained values of the SOI greater or less than 7 are meaningful and can indicate El Niño (when negative) and La Niña (when positive).
The Equatorial Pacific trade winds have been mostly normal throughout September, but mid-month a short lived strong reversal happened near PNG
The Equatorial Pacific Easterly Trade Winds have recently reversed (shown by the circled arrows). Early in the month the trade winds experienced another similar reversal for a week. The first real evidence the El Niño is attempting to fire up. The surface of the ocean should start to warm further as a result. Reversed trade winds are needed to kick off an El Niño and to maintain it. In the Indian Ocean trade wind patterns haven’t dramatically changed from normal, despite the +IOD ocean patterns
Cloud is slightly less than normal at the junction of the Equator with the Dateline, but less cloud exists off Sumatra.
Cloud at the International Dateline (180oW) junction with the Equator is slightly less (brown colour) in the last 30 days but has varied greatly from more, normal and less. The cloud building off PNG is unlike an El Niño. The lack of cloud off Sumatra remains +IOD like and the whole Indian Ocean basin is lacking in cloud.
the SAM has spent August moderately negative
The Southern Annular Mode (SAM) has spent the start of spring in a positive phase. Probably weakening the fronts for eastern Tasmania. SAM will cease to be the dominant force now that winter is over. Both BoM and NOAA predict the SAM to go moderately negative in the coming fortnight.
the STR of high pressure has been in a higher than normal winter position at the top of the Bight
In the past 30 days, the Sub Tropical Ridge of High Pressure has moved a bit southward, but at a normal winter position rather than spring. The middle of spring should see the ridge level with Adelaide. A ridge further north of normal may start to inhibit moisture troughing during spring. A high started to dominate over Victoria weakening the fronts, such that nothing much was left for eastern Tasmania.
pressure at Darwin and Tahiti are both normal, while pressure over SE Australia has been lower
The Sub Tropical Ridge of High Pressure was higher in pressure over SE Australia helping to keep push frontal strength south of the mainland and weakening it in the east the island. Pressure at Darwin and at Tahiti is normal which is why the SOI is neutral. The higher pressure over the whole of the eastern Indian Ocean is not helpful for getting moisture down to us.
Download this table in word format here

Modelled Climate and Ocean Predictions for South Australia from August 2018 run models

Modelled Climate and Ocean Predictions for South Australia from August 2018 run models

Ocean-Atmosphere Coupled Models

Multi Model Ensembles

Statistical

System 5

ECMWF

Europe

POAMA2

BoM

Australia

SINTEX-F

JAMSTEC

Japan

CFSv2

NCEP

USA

GEOS-S2S

NASA

USA

ENS

JMA

Japan

CSM1.1

BCC

China

UKMO

GloSea5

UK

NMME

USA

APCC

Korea

EUROSIP

Europe

SOI phase

USQ/Qld

Australia

Month of Run

August

August

August

August

August

August

August

August

August

August

August

August

Forecast months

SON

SON

SON

SON

SON

SON

SON

SON

SON

SON

SON

SON

Rainfall Skill

Low

Low

NA

Moderate

Low/Moderate

Low

NA

Moderate

Low

NA

NA

NA

Spring Pacific Ocean NINO3.4

Warm

(weak El Niño)

Neutral

Warm

(El Niño Modoki)

Warm

(El Niño)

Slightly warm

Warm (weak El Niño Modoki)

Warm

(El Niño

Modoki)

Warm

(El Niño Modoki)

Warm (El Niño Modoki)

Slightly warm

Warm (El Niño Modoki)

-

Spring Eastern

Indian Ocean

Cool (+IOD like)

Neutral

Cool (+IOD)

Neutral

Neutral

Neutral

Slightly cool

Slightly cool

(+IOD like)

Cool (+IOD)

Neutral

Neutral

-

Spring Rainfall

Slightly drier, average EP

Slightly drier

Slightly drier

Average, slightly drier WEP, SE

Average

Average

Slightly drier

Average, slightly drier, SE

Slightly drier

Slightly drier

Average

Average

Spring Temperature

Average

Slightly

warmer

Average

Average

Slightly

warmer

Average

Average

Average

Slightly

warmer

Slightly warmer, average EP

Average

 

Forecast months

DJF

DJF

DJF

DJF

DJF

-

DJF

NDJ

DJF

DJF

NDJ

-

Summer Pacific Ocean NINO3.4

Warm

(El Niño)

Neutral

Warm

(El Niño Modoki)

Slightly warm

Warm

(weak El Niño)

-

Warm

(El Niño

Modoki)

Warm

(El Niño)

Warm

(El Niño)

Warm

(El Niño Modoki)

Warm (El Niño Modoki)

-

Summer Eastern

Indian Ocean

Neutral

Neutral

Neutral

Slightly warm

Slightly warm

-

Slightly cool

Neutral

Neutral

Neutral

Neutral

-

Summer Rainfall

Average

Slightly drier

Slightly drier

Average

Average

-

Slightly drier

Average

Average

Average

Average

 

Summer Temperature

Slightly

warmer

Slightly

warmer

Average

Average

Slightly

warmer

-

Slightly

warmer

Average

Slightly

warmer

Slightly warmer, average EP

Slightly

warmer

 

Notes

Operational

Operational

Experimental

Operational

Experimental

Experimental

Operational

Operational

Experimental

Summary of 4 dynamic models

Experimental

Summary of 8 dynamic models

Experimental

Summary of 5 dynamic models

5 phase system based on previous 2 months SOI