The Fast Break Newsletter 29 November 2019 Seasonal climate risk information for Southern NSW Volume 1 | Issue 11 |29 November 2019 Welcome to the “Fast Break” newsletter for the Southern New South Wales grains industry. We have been constructing these summaries for the last 11 years in Victoria, and started last year in South Australia, New South Wales and Tasmania as part of the GRDC funded “Using Seasonal Forecasts Project” project. If you like it, please consider passing it on through your networks and subscribing. The positive Indian Ocean Dipole is showing slow signs of decay, but all factors that point to its existence are still in play. Cooler water off Sumatra at the surface and at depth, strong easterly winds, lack of cloud over Indonesia and stronger pressure in that region. Models are mixed as to whether the +IOD will die off in December or January, which would be historically a very late demise. There is very little of interest going on in the Pacific Ocean, though the Coral Sea is warmer and greater cloud has been evolving from it, all good if you could get a connection to it. Of greatest interest for the month was the strongly negative Southern Annular Mode that evolved from the Sudden Stratospheric Warming in September, finally connecting with lower altitudes in late October. A negative SAM means storm tracks and westerly winds are moved further north towards the mainland from the Southern Ocean. Traditionally a negative SAM over spring and summer has led to a drier eastern SNSW. Some models are predicting the current -SAM could persist into summer but predictability of this phenomena only goes out to a fortnight. Pressure patterns have shown some change this month, but overall the more northward position of high pressures is still resulting in greater stability and lack of access to troughs for SNSW. Pressure remains higher to the north of Australia which is not conducive to moisture transport from the north. The majority of models surveyed predict drier and warmer than average conditions are most likely for summer.
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The Fast Break Newsletter 29 November 2019Seasonal climate risk information for Southern NSW
Volume 1 | Issue 11 |29 November 2019
Welcome to the “Fast Break” newsletter for the Southern New South Wales grains industry. We have been constructing these summaries for the last 11 years in Victoria, and started last year in South Australia, New South Wales and Tasmania as part of the GRDC funded “Using Seasonal Forecasts Project” project. If you like it, please consider passing it on through your networks and subscribing.
The positive Indian Ocean Dipole is showing slow signs of decay, but all factors that point to its existence are still in play. Cooler water off Sumatra at the surface and at depth, strong easterly winds, lack of cloud over Indonesia and stronger pressure in that region. Models are mixed as to whether the +IOD will die off in December or January, which would be historically a very late demise.
There is very little of interest going on in the Pacific Ocean, though the Coral Sea is warmer and greater cloud has been evolving from it, all good if you could get a connection to it.
Of greatest interest for the month was the strongly negative Southern Annular Mode that evolved from the Sudden Stratospheric Warming in September, finally connecting with lower altitudes in late October. A negative SAM means storm tracks and westerly winds are moved further north towards the mainland from the Southern Ocean. Traditionally a negative SAM over spring and summer has led to a drier eastern SNSW. Some models are predicting the current -SAM could persist into summer but predictability of this phenomena only goes out to a fortnight.
Pressure patterns have shown some change this month, but overall the more northward position of high pressures is still resulting in greater stability and lack of access to troughs for SNSW. Pressure remains higher to the north of Australia which is not conducive to moisture transport from the north.
The majority of models surveyed predict drier and warmer than average conditions are most likely for summer.
We are describing SNSW as a line south of Dubbo. In the predictions, I divide this region into quarters, hence N, S, E, W, NW, NE, SW, SE, defines zones in this southern half. If the models are more precise, I might use terms such as coast, Riverina, central west, etc.
You can use the new Local Climate Tool to identify how historical +IOD events have affected rainfall in your area.
File - soil moisture SNSW.pngAlt text - map of Southern NSW showing plant available moisture (%).Caption – The BoM Australian Water Resources Assessment (AWRA) modelled soil moisture shows the cropping areas of NSW is dry. A small increase happened for the month north of Griffith. West of the Newell Highway this is classified as normal, east of the Newell is rated decile one to three. Lowest one percent is along the coastal ranges.
Model distribution summary for the next three months
File - 1-3 month SNSW.pngAlt text - Graphs showing the distribution of global model forecasts for December-February with models showing increased chances of drier rainfall and warmer temperatures.
Model distribution summary for the next four to six months
File - 4-6 month SNSW.pngAlt text- Graphs showing the distribution of March-May forecasts with models showing increased chances of average rainfall and warmer temperatures.
Model consensus forecast for the next six months
Current outlook (to 29 November) Current outlook (to 28 October)Dec-Feb Mar-May Nov-Jan Feb-Apr
Rainfall Slightly drier Average Slightly drier Average/slightly drier
Temperature Slightly warmer Slightly warmer Slightly warmer Slightly warmer
Sea Surface Temperature Anomalies
File - SSTa.pngAlt text - Equatorial Pacific Ocean Sea surface temperatures are at neutral levels but a +IOD continues in the Indian Ocean.Caption The +IOD is still in existence, (+1.36oC as of 27 November, threshold for +IOD is +0.4oC) but has backed off somewhat. The Arafura and Timor Seas off Darwin have returned to normal. Traditionally further westward propagation of this normal temperature water would wipe out the cold patch at Sumatra. Sea surface temperature (SST) anomalies along the Equatorial Pacific have remained stable during October at neutral temperatures. NINO3 is at +0.54oC and NINO3.4 is +0.61oC (as of 27 November). In the Coral Sea temperatures are warmer as a good moisture source.Equatorial Pacific Sub-Sea Temperature Anomalies
File - Deep sea a.pngAlt text - Equatorial undersea temperature anomalies in the Pacific show some warming in the centre.Caption - The Pacific Ocean Equatorial sub-surface temperatures anomalies have cooled somewhat and have turned to a confused state of a warmer surface overlying a cooler subsurface. At this stage of the year the Pacific undersea is of little use to be monitoring, as the window for serious El Niño and La Niña activity has passed.Southern Oscillation Index
File - SOI.pngAlt text - The SOI value is currently at -11.1 (as at 27 November).The SOI has fallen rapidly to significant negative values during November. The value is currently at -11.1 (as at 27 November). This indicates El Niño like pressure patterns around the Equator, flying alone compared to other El Niño indicators. Once we reach summer, the SOI is less reliable due to pressure changes at Darwin and Tahiti occurring because of tropical weather systems. In any case the impact of the El Niño Southern
Oscillation in southern Australia tends to end in November/December.Pacific Ocean Surface Wind Anomalies
File - trade winds.pngAlt text - The Equatorial trade wind anomalies are strongly reversed off Indonesia.Caption - The Equatorial Pacific Easterly Trade Winds have shown some westward reversal off Papua New Guinea, but it’s too late to kick off ENSO activity now. The strong Trade Wind reversals off Indonesia continue due to the +IOD. The +IOD won’t start to decay properly until these winds return to normal or reverse.World Cloudiness Anomalies
File - OLR.jpgAlt text - Cloud is lacking off Sumatra and over eastern Australia.Caption - Cloud at the International Dateline (180oW) junction with the Equator is slightly less (brown colour) which is weakly suggestive of La Niña, but no other indicator points towards this. The lack of cloud (brown colour) off Sumatra and over Indonesia has enlarged greatly this month and the cloud anomaly in a NW direction typical of +IOD pattern has increased. There has been greater cloud in the Coral Sea, in part due to
cyclone Rita.Southern Annular Mode
File- SAM.pngAlt text- the SAM had spent most of November in strong negativity.The Southern Annular Mode (SAM) or Antarctic Oscillation (AAO) was strongly negative in most of November. This was due to the Sudden Stratospheric Warming that occurred in September coupling with lower altitudes in October. Such behaviour by SAM is characteristic of this phenomenon. In spring and summer, a negative SAM would be expected to cause drying along eastern, particularly coastal SNSW. November’s rainfall pattern would appear to be consistent with this a -SAM pattern. Air Pressure
File - STR posn.pngAlt text - the STR of high pressure has been higher than its normal position of Adelaide.Caption - In the past 30 days, the Sub Tropical Ridge of High Pressure (STR) has been just above the Bight, much further north of a spring position of Adelaide. While this can have a variable effect in spring, this November it has been inhibiting NW cloud bands and blocking transport of moisture from the north-west. It’s not impossible that the negative SAM - keeping storm fronts further north - is in part responsible for the non-southward migration of the sub-tropical ridge.Air Pressure Anomalies
File - STR strength.pngAlt text - Pressure at Darwin is higher and Tahiti is lower, pressure over SNSW has been normal.Caption - The Sub Tropical Ridge of High Pressure has finally changed from stronger to normalish. Stronger pressure over the tropics is still a downer on moisture transport from the north. In conjunction with the lower pressure over Tahiti, this is why the SOI is currently negative. Higher pressure over Antarctica and a lower pressure belt in the mid-latitudes is a classic signal of a negative SAM.
Modelled Climate and Ocean Predictions for Southern NSW from November 2019 run models
Ocean-Atmosphere Coupled Models Multi Model Ensembles Statistical
System 5ECMWFEurope
ACCESS-SBoM
Australia
SINTEX-FJAMSTEC
Japan
CFSv2NCEPUSA
GEOS-S2SNASAUSA
EPSJMA
Japan
CSM1.1mBCCChina
GloSea5UKMO
UK
NMMEUSA
C3SEurope
MMEAPCCKorea
SOI phaseUSQ/QldAustralia
Month of Run Nov Nov Nov Nov Nov Nov Nov Nov Nov Nov Nov Nov
SummerRainfall Slightly drier Slightly drier Slightly drier Average N,
slightly drier SAverage W,
slightly drier E
Average W, slightly drier
EAverage Slightly drier Slightly drier Slightly drier Slightly drier Average
Summer Temperature
Average, slightly
warmer NE
Slightlywarmer W, warmer E
Slightlywarmer
Slightlywarmer
Slightlywarmer
Average W, slightly
warmer E
Slightlywarmer,
average SW
Slightlywarmer W, warmer E
Slightlywarmer
Slightly warmer,
warmer NESlightlywarmer -
Forecast months MAM MAM MAM MAM MAM - MAM FMA MAM FMA MAM -Autumn Pacific Ocean NINO3.4 Neutral Neutral Neutral Neutral Slightly cool - Neutral Slightly cool Neutral Neutral Neutral -
File- big table SNSW.jpgAlt text- 12 climate models show their predictions for the next six months for the Pacific Ocean, Indian Ocean, rainfall and temperature for SNSW
