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Volume 1 | Issue 4 | South Australia | 03 Aug 2018 4:32pm

Northern cropping areas are doing it tough, but some of the southern areas are hanging in there. Many farmers have commented that there isn’t a lot of moisture under the crop, as a buffer for a dry spring.

There are still no concrete signs of an actual El Niño in surface temperature, cloud, wind or pressure patterns, only the warm slug of water under the eastern Pacific, which this month cooled off a bit.

All eyes are on the Indian Ocean, which is kind of playing up. A sort of “+IOD” exists in the cool water anomaly off Java and the cloud patterns off Sumatra. Measurements of the IOD are neutral though, due to the Kenyan and Sumatran ocean regions being both warm and cool. This month there has been a rapid change, with most models jumping on the +IOD band wagon. Models are predicting the cool area off Java to progress further westwards to the Sumatran region. Whether the African region can rewarm is the key question.

In the last 12 years when Indian Ocean patterns around Indonesia have been like this, the spring rainfall has usually been lower than normal. Our only saving grace is that this is a very abnormal “+IOD” at the moment. With a weak connection between ocean and atmosphere and the Indian Ocean Equatorial wind patterns are normal. Ocean temperatures to depth off Sumatra are normal to warmer, and are not cooler, as you would expect to see for a classical +IOD. Time is going to tell whether any of these differences matter or not. Historically the IOD has had a significant effect on SA winter and spring rainfall and a +IOD often suppresses North West cloud band activity.

Through May and June, pressure patterns were very high and in an unfavourable position. This has partially improved during July. Each month the pressure ridge has been moving further eastwards, so any benefits should happen for SA earlier than for Victoria. Hope to see those pressure patterns keep moving through, rather than hanging around like unwanted house guests.

A majority of models still suggest a late forming El Niño (BoM ENSO Outlook still at El Niño WATCH) and now, most are gunning for a +IOD. This month a few more models changed to drier forecasts, but the majority are still suggesting anything is possible. Spring temperature predictions are mixed between average and warmer.

Model skill is about as good as it gets this month.

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 building moisture in the high rainfall districts and modest improvements to the lower EP. The northern EP and Mid-North could be better. The scatter of moisture probes (courtesy of NR-SAMDB, EPARF, SARDI and Agbyte) shows most subsoils have barely moved this month (30-100cm). The exceptions are the North Shields and Parndana probes that have in fact wet up
Graphs showing the distribution of August-October modelled rainfall as average/drier, and temperature as warmer to average
graphs showing the distribution of November-January modelled rainfall is for average and temperature warmer to average

Model consensus forecast for the next six months

Model consensus forecast for the next six months

Current outlook (27 July)

Previous outlook (28 June)

Aug-Oct outlook

Nov-Jan outlook

Jul-Sep outlook

Sept-Nov outlook

Pacific Ocean

El Niño

El Niño

Neutral (possible El Niño)

Neutral

Indian Ocean

Weak +IOD

Neutral

Mixed

Slightly warmer/neutral

Rainfall

Average/slightly drier

Average

Average

Average

Temperature

Slightly warmer/average

Slightly warmer

Average

Average

Equatorial Pacific and Indian Ocean Sea surface temperature anomalies are normal. A +IOD like cool patch is off Java
Caption- Sea surface temperatures (SST) along the Equatorial Pacific have stalled during July. NINO3 is at +0.44oC and NINO3.4 is +0.42oC (as of 30 July), both at neutral ENSO conditions. The Coral Sea is still a bit warmer, a good sign. In the Indian Ocean the cool patch off Java has grown larger and cooler and like a +IOD. The monitoring regions highlighted are both partly cooler and warmer off both Africa and Indonesia. Not a classic +IOD in any way shape or form. Warmer tropical ocean anomalies nearer to Australia can provide more evaporation as a moisture source, whereas cooler ocean anomalies can kill the moisture source.
Undersea warm temperatures have decreased in the eastern Pacific
The Pacific Ocean Equatorial sub surface temperatures went off the boil in July, with the extent of warm anomalies decreasing. This is probably why a few models got off the El Niño band wagon this month. This warmth at depth is still the only indicator of an El Niño across the globe, all other indicators are normal. For an El Niño to occur we would need to see trade winds reverse and the SOI to go strongly negative
The SOI value is currently at +0.1 and rising
The SOI is currently at +0.1 and rising (as of 27 July), as close to neutral as you get. Pressure patterns around the Equator as measured at Darwin and Tahiti are completely normal. Sustained values of the SOI greater or less than 8 are meaningful and can indicate El Niño (when negative) and La Niña (when positive)
The Equatorial Pacific trade winds have been normal throughout July, but a recent reversed burst near PNG is worth watching
The Equatorial Pacific easterly Trade Winds have been normal through July (shown by the small arrows). In the last week there has been a strong reversal close to PNG, which will be worth watching to see if it propagates further East. Whilst the short-term reversal in February kicked off the chance of an El Niño, sustained reversal is needed to make one happen. Central Pacific trade wind reversals can calm the ocean and cause the sun to warm the surface further
Cloud has finally returned to more normal levels 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 has finally returned to normal (white colour) in the last 30 days. Greater cloud above PNG is more like La Niña. In the Indian Ocean there is a classic +IOD lack of cloud off Sumatra but no corresponding greater cloud off Africa
SAM has spent July weakly positive and negative
The Southern Annular Mode (SAM) has bobbed up and down during July and has been no great influence on winter climate so far. The BoM and NOAA models suggest a moderately strong negative phase of the SAM in coming weeks. This might mean more frequent frontal rain for Tasmania. SAM has a major influence on frontal system positioning over Tasmania regions during winter. Positive SAM pulls fronts away from Tasmania and negative SAM pushes them towards us
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 is still sitting higher than normal (top of the Bight) allowing frequent fronts across Tasmania
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 is still sitting higher than normal (top of the Bight) allowing frequent fronts across Tasmania
12 climate models show their predictions for the next six months for the Pacific Ocean, Indian Ocean, rainfall and Temperature for South Australia
Download this table in word format here

Modelled Climate and Ocean Predictions for South Australia from July 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

July

July

July

July

July

July

July

July

July

July

July

July

Forecast months

ASO

ASO

SON

ASO

ASO

ASO

ASO

ASO

ASO

ASO

ASO

ASO

Rainfall Skill

Moderate

Low

NA

Moderate

Moderate

Moderate

NA

Low/Moderate EP

Low EP/ Moderate

NA

NA

NA

Spring Pacific Ocean NINO3.4

Warm

(weak El Niño)

Neutral

Warm

(El Niño Modoki)

Slightly warm

Slightly warm

Warm (weak El Niño)

Warm

(El Niño)

Warm

(El Niño)

Warm (El Niño)

Slightly warm

Warm (weak El Niño)

-

Spring Eastern

Indian Ocean

Cool (+IOD)

Slightly cool

(weak +IOD)

Cool (+IOD)

Cool

(weak +IOD)

Neutral,

(weak +IOD)

Slightly cool

(weak +IOD)

Slightly cool

Slightly cool

(weak +IOD)

Cool (+IOD)

Slightly cool

(weak +IOD)

Slightly cool

(weak +IOD)

-

Spring Rainfall

Slightly drier

Slightly drier

slightly drier

Average

Average

Average

Average

Average

Average, slightly drier SE

Average

Slightly drier, average EP

Average

Spring Temperature

Average, slightly

warmer EP

Slightly warmer

Slightly

warmer

Average

Slightly

warmer

Average

Average, slightly

warmer EP

Average

Average, slightly

warmer EP

Slightly

warmer

Average

-

Forecast months

NDJ

NDJ

DJF

NDJ

NDJ

-

NDJ

OND

NDJ

NDJ

OND

-

Summer Pacific Ocean NINO3.4

Warm

(El Niño)

Neutral

Warm

(El Niño Modoki)

Slightly warm

Warm

(weak El Niño)

-

Warm

(El Niño)

Warm

(El Niño)

Warm

(El Niño)

Warm

(El Niño)

Warm

(El Niño)

-

Summer Eastern

Indian Ocean

Neutral

Neutral

Neutral

Slightly warm

Slightly warm

-

Slightly cool

Neutral

Neutral

Neutral

Neutral

-

Summer Rainfall

Average W, slightly drier E

Average

Slightly drier

Average

Average

-

Average

Average

Average

Average

Average

-

Summer Temperature

Average, slightly

warmer EP

Average E, slightly

warmer W

Slightly

warmer

Average

Slightly

warmer

-

Average

Average

Slightly warmer

Slightly

warmer

Average

-

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