NSW Seasonal Conditions Summary October 2015

Highlights

  • Rainfall during September was below average across most of the north western, central and southern areas of NSW.
  • The rainfall outlook for October to December indicates drier than normal conditions are likely across southern, south eastern and much of central and coastal NSW. There is a near-neutral outlook for the north and west. Warmer daytime and overnight temperatures are likely.
  • During October, drier and warmer than normal conditions are likely across NSW.
  • The El Niño has continued to intensify and its effects on rainfall in south eastern Australia are now being reinforced by a positive Indian Ocean dipole event.
  • Topsoil moisture levels were maintained in the south east but declined across most of NSW, putting pressure on pasture production, winter crop grain fill and holding back dryland summer crop sowings.
  • Pasture growth was maintained in the south during September, but declined across the north west and northern central west. It was maintained or improved over the tablelands and coast. Hot, dry conditions are accelerating pasture maturity.
  • Lack of rainfall during flowering and grain fill has reduced winter crop yield prospects, particularly for late sown crops on the western margins of the cropping belt. Early sown crops were less affected. Yield potential remains good in the east, particularly in the south. However, potential will continue to decline if follow up rainfall does not occur during October.
  • Dryland summer crop sowings in northern and central NSW have been delayed due to lack of topsoil moisture, and water allocations in central and southern areas will restrict irrigated sowings.

Overview

Rainfall during September was below average across 65 per cent of the state. Above average rainfall was restricted to areas of the north, mid-north and central coast. Below average rainfall occurred across much of the south, Riverina, central west, central and southern tablelands, north west, far north west, the upper Hunter valley and the west of the northern tablelands.

September pasture growth declined across north western NSW and the northern areas of the central west, as well as areas of the far south. Growth generally improved across the coastal areas and across the tablelands. Growth declined slightly in the south but was still maintained at moderate to high levels. Haymaking has commenced in these areas. Hot, dry weather in late September and early October caused growth to decline and has hastened pastures haying-off, particularly in western areas.

Bloat has been an issue in areas of the Riverina, south west slopes, tablelands and the coast, although the risk lessened in inland areas as pastures matured.

Relative to historical records, pasture growth was average in the south and across the slopes and tablelands, but average to above average along the coast. Areas of below average relative growth occurred in the north west, southern Hunter valley and in northern areas of the central west and central tablelands.

Biomass levels improved in the eastern and central Riverina, and across the tablelands and coast. Biomass remained low across areas of the far west, the south east and areas of the tablelands. Levels were generally good across the central west, Riverina and southern NSW with the exception some eastern areas.

Lack of rainfall during September and dry, hot conditions in early October affected winter crop yield prospects, particularly in the west. Early sown crops have tolerated the conditions best; particularly those in mid-late grain fill. Later sown crops in the western half of the cropping belt have been worst affected, particularly in the far north west and south west where crops were sown on marginal moisture. Some cereal crops in these areas are being grazed out or cut for hay. The dry conditions combined with hot, windy weather in early October caused many winter crops across the state to lose around 10-20% of potential yield, particularly in the west. Grain quality is also likely to be affected. Barley crops have been less affected than wheat.

The yield potential for cereals and canola remains good across the south west slopes and the eastern areas of the central west and north west. Average to somewhat above average yields are still possible. Pulse crops in central and southern areas have been under pressure due to the warm temperatures. Despite some frosts occurring across central and southern areas in late September there have been no reports of major crop damage. Aphids have proven a problem in some areas and have required control.

Follow up rainfall in October will benefit grain fill in many areas, particularly in the east, and is necessary to maintain current yield potential. However, further reductions in potential yield are likely given the October rainfall and temperature outlooks and remaining soil moisture reserves.

Dryland summer crop sowing in northern and central areas has been delayed due to lack of topsoil moisture, even where reasonable levels of moisture are present in the subsoil. Those crops that have been sown urgently require further rainfall for germination and emergence. Water costs and allocations in southern and central NSW will restrict irrigation to mostly high-value crops. The area sown to rice is likely to be low, and a proportion of water allocations have been used to maintain winter crop yields.

Topsoil moisture levels declined across most of NSW, but were maintained across areas of the south, south east, central tablelands and southern central west. Relative to historical records, they were below average in areas of the north west, central west, southern and central tablelands, south west slopes and upper Hunter valley. They were above average across areas of the south east and north coast. Subsoil moisture remained relatively stable across most of the cropping areas in September, but were low over areas of the north west, northern central west and far south west. Relative to historical records, they were below average across areas of the north west and far western Riverina. 

Run off remained limited in areas of the north west, northern and central tablelands, the central west, the south west and western Riverina. In these areas, stock water supplies remain variable.

NSW Seasonal Conditions Report – October 2015

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Seasonal outlook

The Bureau of Meteorology's rainfall outlook for October to December indicates that drier than normal conditions are likely for the south eastern, southern and central areas of NSW. Drier than normal conditions are also likely along the south to mid-north coast, and across the Hunter Valley and the southern areas of the northern tablelands and northern slopes. There is a near-neutral outlook for most of northern and western NSW for the period. This means there is a near-equal chance of drier or wetter than normal conditions for this area. There is a high probability of warmer than normal daytime and overnight temperatures across NSW during the period.

During October, there is a high probability of drier than normal conditions and warmer than normal daytime and overnight temperatures across all of NSW.

Of the global climate models surveyed in late September and early October, about 70 per cent suggest drier than normal conditions are likely across most areas of NSW between October and December. About 30 per cent suggest near-neutral conditions. Nearly 90 per cent of models suggest conditions will be warmer than normal.

The pasture growth outlook for October to December suggests generally below average growth is likely across most of NSW. Average to above average growth is suggested for some areas of the mid-north and north coast. Average growth is suggested for some areas of the far west. Skill levels for the outlook are moderate to high across eastern and central NSW, but low across most of the west. The rainfall outlook that this outlook is based upon is reasonably consistent with that of the Bureau of Meteorology. The growth outlook is based upon a consistently negative SOI during July/August. This is linked to the possibility of below average rainfall across much of southern and central NSW and the south to mid-north coast, but near-average rainfall across much of northern NSW.

El Niño Southern Oscillation (ENSO)

The Pacific Ocean is in a strong El Niño event, which continues to intensify with sea surface temperatures in the central equatorial Pacific being around two degrees above average. The El Niño event is being reinforced by a positive Indian Ocean Dipole (IOD) event, which when associated with an El Niño reduces the likelihood of spring rainfall in NSW. Fortunately, the positive IOD event is likely to be short-lived; such events normally decay with the onset of the monsoon. Most modelling suggests the positive IOD will only persist into November and that the El Niño event will reach its peak soon and is likely to end in autumn 2016.

The SOI and equatorial Pacific sea temperatures, trade wind and cloud conditions remain consistent with an El Niño event. Warm sea surface temperature anomalies extend across the central and eastern equatorial Pacific. The greatest anomalies are in the east and sea surface temperatures are below average in the west. Sub-surface warm temperature anomalies remain across most of the central to eastern equatorial Pacific to a depth of 100-200m. A cool anomaly exists at depth in the west and western-central areas. This pattern of warm and cool anomalies is consistent with an El Niño event.

Sea surface temperatures to the north, north east and north west of Australia have now cooled. This has reduced sources of convection and moisture, causing reduced rainfall across Indonesia, the Philippines and Papua New Guinea during September. Of particular concern has been the cooling of sea surface temperatures near Sumatra, resulting in reduced cloud and rainfall in this region. This is consistent with a positive IOD event. The effect of this may be below-average rainfall in south eastern Australia during spring. However, sea surface temperatures remain warm to the west and south west of Western Australia and may partly moderate this effect.

An El Niño event is generally associated with below-average rainfall across NSW (particularly inland NSW) during spring, above average daytime temperatures, lower than average streamflow and an increased risk of frost. A positive IOD event in association with this reinforces the likely reduction in spring rainfall across NSW, particularly in the south.

Historically, El Niño events have had a limited effect on summer rainfall across NSW.

Climatic outlook summary

NSW Seasonal Outlook Current outlook Previous outlook
Quarterly Rainfall Drier
(south eastern, southern and central NSW, south to mid-north coast, Hunter valley and southern areas of the northern tablelands and northern slopes)

Near neutral – neutral
(northern and western NSW)
Near neutral – neutral
(most of NSW)

 Wetter
(western NSW)
Quarterly Maximum Temperature Warmer Near neutral – neutral
(most of NSW)

 Warmer
(central - north coast, lower Hunter valley)

 Cooler
(areas of the far south)
Quarterly Minimum Temperature Warmer Warmer
(northern, north eastern and coastal NSW)

 Near neutral – neutral
(most of NSW)
El Niño Southern Oscillation (ENSO)
ENSO (overall) El Niño El Niño
BoM ENSO Tracker Status El Niño El Niño
SOI Strongly negative Strongly negative
Pacific Ocean (NINO3.4) Very warm
(Above El Niño thresholds)
Warm
(Above El Niño thresholds)
Indian Ocean (IOD) Positive
(trending to neutral during November)
Trending towards a positive IOD event
Southern Annular Mode (SAM/AAO) Near neutral Near neutral – slightly positive

Rainfall and temperature

During September, rainfall across the state ranged from 0-262 mm. Above average rainfall was restricted to coastal and adjacent areas along the central to far north coast.

Falls over most of the state ranged from 5-25 mm. Falls of less than 10 mm occurred across north western and the northern half of western NSW, as well as most of the central west. Areas of the coast, the south east, the eastern half of the northern tablelands and some areas of the southern slopes received 25-50 mm. Areas of the Illawarra and central to north coast received 50-100 mm, with some areas of the central coast receiving up to 100-200 mm.

Daytime temperatures were near normal across most of the state, with areas of the far south being slightly above normal and areas of the coast from the Illawarra north, Hunter Valley and northern tablelands being cooler than normal. Overnight temperatures were cooler than normal across the state, particularly in central and southern areas during the first and last week of September. Overnight temperatures were near-normal along the south to mid-north coast.

Relative rainfall

Relative to historical records, rainfall during September was below average across much of the northern, central and southern areas of the state. Relative rainfall was extremely low across the central and southern tablelands, south west slopes, the upper Hunter Valley, the eastern half of the central west and areas of the north west.

The coastal areas, the east of the northern tablelands and areas of the far south west had generally average rainfall. Above average rainfall occurred across the coastal strip from the central to north coast.

Quarterly relative rainfall was below average across areas of the north west, central tablelands, northern and eastern central west, southern areas of the northern tablelands, upper Hunter valley, far eastern Riverina and the far south. It was above average across areas of the south east, central Riverina and south east areas of the central west. Most of the state had near-average rainfall for the period.

Soil moisture

Modelled topsoil moisture levels declined across most of NSW, but were maintained across the south, south east, most of the central tablelands and the southern central west. Relative to historical records, topsoil moisture was below average in areas of the north west, northern central west, southern and central tablelands and areas of the south west slopes and upper Hunter valley. It was above average across areas of the south east, the north coast and some central areas of western NSW.

Modelled subsoil moisture levels were relatively stable, but declined slightly in areas of the south west slopes, northern slopes and central west. Relative to historical records, subsoil moisture remained below average across areas of the north west and far western Riverina.

Streamflow

Yearly run off estimates were similar for the period to August, but remained variable in many areas. Run off was low in the north of the central tablelands and the central west, as well as the western areas of the central west, north west, Riverina and the far south. Areas of low run off also occurred in the upper Hunter valley, areas of the south west slopes and central areas of the northern tablelands. Run off was high over areas of far western NSW, the south east and areas of the central coast and lower Hunter valley.

The Bureau of Meteorology's streamflow forecast indicates generally low streamflows are likely across most inland southern NSW monitoring stations during October to December, with some tending towards near-median. A mix of low and near-median flows are likely at northern NSW monitoring stations. Near-median flows are likely in the far north east and in southern coastal locations.

Relative pasture growth and biomass

Relative to historical records, AussieGRASS modelled pasture growth for September was average in the south and across the slopes and tablelands. It was average to above average along the coast. Areas of the north west, northern central west and the north of the central tablelands had below average relative growth.

Other pasture growth models indicated below average relative growth across the north, north west, tablelands, central west and areas of the far south. For these models, relative growth was average to above average along the coast and generally average in the south and south west.

Over the quarter, AussieGRASS relative growth was generally average to above average across the state. Above average growth occurred across areas of the west, north and south east. 

During September, relative biomass levels declined slightly, with most of the state being average. Levels improved along the south and central coast. They declined but still remained above average across areas of the central west, the northern tablelands, northern slopes and areas of the far south and far west .

Figure 1: Relative monthly topsoil moisture

Soil moisture map 

Figure 2: Relative quarterly pasture growth

Pasture growth map

More information

For more information, contact the NSW Department of Primary Industries on 02 6391 3100 or Local Land Services on 1300 795 299.

Acknowledgements

Information used in this report was sourced from the Australian Bureau of Meteorology, CSIRO, the Queensland Department of Science, Information Technology and Innovation, the Australian Export Grains Innovation Centre, the Queensland Alliance for Agriculture and Food Innovation, the U.S. Department of Agriculture, U.S. Department of Commerce, the U.S. National Oceanic and Atmospheric Administration, the International Research Institute for Climate and Society (Columbia University), the UK Meteorological Office, the APEC Climate Centre, NSW Local Land Services and NSW Department of Primary Industries.

External links

Disclaimer

The seasonal outlooks presented in this report are obtained from the Australian Bureau of Meteorology and other sources. These outlooks are general statements about the likelihood (chance) of (for example) exceeding the median rainfall or minimum or maximum temperatures. Such probability outlooks should not be used as categorical or definitive forecasts, but should be regarded as tools to assist in risk management and decision making. Changes in seasonal outlooks may have occurred since this report was released. Outlook information was up to date as at 13 October 2015.

Recognising that some of the information in this document is provided by third parties, the State of New South Wales, the author and the publisher take no responsibility for the accuracy, currency, reliability and correctness of any information included in the document provided by third parties.

The information contained in this publication is based on knowledge and understanding at the time of writing (13 October 2015). However, because of advances in knowledge, users are reminded of the need to ensure that information upon which they rely is up to date and to check currency of the information with the appropriate officer of the Department of Primary Industries, Local Land Services or the user's independent adviser.