NSW Seasonal Conditions Summary April 2015

Highlights

  • Rainfall during March was below average across 72 per cent of NSW. This included western, south eastern and central NSW and areas of the north west.
  • Wetter than normal conditions are likely across most of NSW between May and July. Daytime temperatures are likely to be cooler in the west and areas of central and north western NSW. There is a near-equal chance of warmer or cooler than normal temperatures over the remainder of NSW. Overnight temperatures are likely to be warmer.
  • During the remainder of April, wetter than normal conditions are likely across coastal, northern and north eastern NSW. Drier conditions are likely in the south and south west. Daytime and overnight temperatures are likely to be cooler than normal.
  • During May, there is a near-equal chance of drier or wetter than normal conditions across NSW, with warmer daytime temperatures in the north west and some central areas, and a near-equal chance of warmer or cooler than normal temperatures for the rest of NSW. Overnight temperatures are likely to be warmer in the north.
  • ENSO is neutral, although warming has continued in the equatorial Pacific. NINO3.4 temperatures are now close to the El Niño threshold and may exceed it in April-May. NOAA indicates that a weak El Niño commenced in February. However, model skill is low until early winter.
  • Topsoil moisture levels were low over western and central NSW. Subsoil moisture levels were generally stable, but low in areas of the west and north. Farm water supplies are limited in many areas.
  • Pasture growth declined over most of NSW except the north coast. Pastures will respond to April rainfall in the eastern and central areas if temperatures remain mild.
  • Forage crops have responded to the March and April rainfall. Further sowing occurred in late March/early April. Winter crop prospects have improved and sowings are underway. Some supplementary feeding of stock is occurring. Rain has delayed cotton harvesting.
  • Resources to assist in management for areas suffering poor rainfall and growth are available at Managing drought.

Overview

Rainfall during March was below average across 72 per cent of NSW and average across 22 per cent. Rainfall was below average over much of western, southern, central and south eastern NSW and in areas of the north west.

Areas of the northern slopes and plains, northern tablelands, the Hunter valley and the north of the central tablelands received average rainfall during March. Over most of the State, rainfall was less than 20-40 per cent of normal.

During March, pasture growth declined across most of NSW. Growth slowed across southern areas of the northern tablelands and the south and central coast, but remained reasonable across areas of the north and mid-north coast.

Relative to historical records, growth was below average across western, central and south eastern NSW but near average across much of the tablelands, northern slopes and mid-north to north coast.

Biomass levels were low over most of NSW, particularly across north western and central NSW and areas of the west. Relative to historical records, biomass was well below average in these areas but average in the west, and average or above in the east, tablelands and areas of the far west.
Supplementary feeding of stock increased in March due to lack of pasture growth, but pastures in many areas have responded to the early-mid April rainfall. The extent of early winter growth will be dependent on temperature.

March rainfall in the east and early-mid April rainfall across eastern, central and southern NSW benefited winter forage crops and stimulated additional sowings.

The rainfall has improved the prospects for winter crops over much of central and southern NSW and areas of the north west, with early sowings commencing. Some rainfall has occurred in drought-affected regions of the north west (west of the Newell Highway), but has been insufficient for winter crop sowing.
Cotton harvesting has been delayed by the rainfall, particularly in the south. Flooding has affected pastures and forage crops in areas of the Hunter valley and mid-north coast.

Topsoil moisture levels declined during the month and were low across most of NSW except the mid-north to north coast. Subsoil moisture levels remained relatively stable, but are low in areas of the north and west.

Streamflow analysis indicated an increase in areas with below average run off, extending across most of northern and central NSW, the tablelands, Hunter Valley, Sydney basin and Riverina.  Many areas are showing well below average or extremely low run off over three years. Farm water supplies are low and becoming critical many areas. The Bureau of Meteorology's streamflow forecast indicates low streamflow is likely at most locations during April to June.

NSW Seasonal Conditions Report – April 2015

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Seasonal outlook

Note: The Seasonal Conditions Summary has been updated to reflect the latest seasonal outlook (May to July) released by the Bureau of Meteorology on 23 April, due to delays in publishing the reports. The Seasonal Conditions Report and Climate Summary show the previous outlook information.

Wetter than normal conditions are likely across most of NSW between May and July, with the probabilities increasing towards the west. There is a near equal chance of drier or wetter than normal conditions in the far south east.

Cooler than normal daytime temperatures are likely between May and July over the northern and central areas of the far west, and areas of the central west and north west of NSW. There is a near equal chance of cooler or warmer than daytime temperatures for most of eastern and southern NSW. Warmer than normal daytime temperatures are likely in the far south east.

Warmer than normal overnight temperatures are likely across NSW during the May to July period.

For the remainder of April, wetter than normal conditions are likely across coastal, northern and north eastern NSW. Drier than normal conditions are likely in the south and south west. For the rest of NSW, there is a near-equal chance of drier or wetter than normal conditions. Cooler than normal daytime and overnight temperatures are likely across most NSW.

During May, there is a near-equal chance of drier or wetter than normal conditions across NSW. Daytime temperatures are likely to be warmer than normal in the north west and areas of central NSW and the far north east. For most of eastern, central and southern NSW there is a near-equal chance of cooler or warmer than normal temperatures. Overnight temperatures are likely to be warmer than normal in the north and west of NSW. There is a near-equal chance of cooler or warmer than normal overnight temperatures in the south and areas of the mid-north coast and the south of the northern tablelands.

The pasture growth outlook for April to June suggests above average growth over the period for the tablelands and upper slopes, with moderate to high skill levels, but average to slightly below growth for the Riverina, with low-moderate skill levels. Average to above average growth is likely in some areas of the far west. The outlook for the remainder of the State has low skill. Due to its linkage to the SOI, pasture growth outlook skill is generally low during autumn.

El Niño Southern Oscillation (ENSO)

ENSO is currently neutral, although sea surface temperatures are warm across most of the equatorial Pacific. The Bureau of Meteorology's ENSO tracker status has moved from 'El Niño Watch' to 'El Niño Alert'. This indicates that the Bureau considers the chances of an El Niño event have shifted from 50 per cent to 70 per cent. Climate models surveyed by the Bureau suggest central Pacific (NINO3.4 region) sea surface temperatures warming to at or above the Bureau's El Niño threshold in April-May and continuing to exceed it in July-September.

The NOAA Climate Prediction Centre and International Research Institute for Climate and Society in the USA have indicated that (based on their thresholds and indicators) a weak El Niño event commenced in February, and has about a 70 per cent chance of continuing through winter.

However, model accuracy is currently low (the 'autumn predictability gap') and does not improve till May. If an El Niño event does develop, it will have most effect on rainfall across NSW during winter and spring.

Sea surface temperatures warmed in the eastern equatorial Pacific during March from below to above average and have continued to warm in the central area. Warm anomalies now extend across most of the equatorial Pacific.

Sub-surface warm temperature anomalies increased in the western-central Pacific over recent months and moved eastwards, displacing cool anomalies in the east and warming the sea surface. Warm sub-surface anomalies now extend across the central and eastern equatorial Pacific. A cool anomaly has appeared at depth in the west.

The SOI fell to be strongly negative in mid-late March but has now moved within the neutral range and was -5.7 as at 17 April. Fluctuations in the SOI are common at this time of year.

Trade winds showed a continued and very strong reversal during March over the western equatorial Pacific, while remaining near normal in the east. A similar event occurred in February. Trade winds have also been consistently weaker than average this year, all of which has facilitated the warming of the Pacific Ocean sub-surface. Cloud at the junction of the equator and the International Date Line is consistent with an El Niño pattern.

Climatic outlook summary

NSW Seasonal Outlook Current outlook Previous outlook
Quarterly Rainfall

Wetter

Wetter

Near neutral – neutral
(central to north coast)

Quarterly Maximum Temperature

Cooler
(western and areas of central NSW)

Near neutral
(southern, eastern, most of central NSW)

Warmer
(far south east)

Warmer
(eastern and eastern-central NSW)

Near neutral
(western, northern and central NSW)

Quarterly Minimum Temperature

Warmer

Warmer

El Niño Southern Oscillation (ENSO)
ENSO (overall) Neutral – probable El Niño developing in winter (NOAA - weak El Niño)Neutral – possible El Niño developing in winter (NOAA - weak El Niño)
BoM ENSO Tracker Status El Niño Alert El Niño Watch
SOI Neutral (negative) Neutral
Pacific Ocean (NINO3.4) Warm
(currently neutral, but near El Niño thresholds and warming)

Warm
(currently neutral, but warming)

Indian Ocean (IOD) Neutral Neutral
(currently negative)
Southern Annular Mode (SAM/AAO) Near neutral – weakly positive Near neutral - weakly positive

Rainfall and temperature

During March, rainfall across the State ranged from 0-300 mm, with most of the rainfall concentrated in the east of the State. Much of western and central NSW received only 0-10 mm. Areas of the north west between Brewarrina, Coonamble, Walgett and Lightning Ridge received little or no rainfall.

On average, daytime temperatures were 1.4°C warmer than normal across NSW during March. Daytime temperatures were generally warmer in the north and near normal to cooler in the south. Overnight temperatures were 0.2°C above normal across NSW. Overnight temperatures were generally cooler in the south and near normal in the north.

Relative rainfall

Relative to historical records, rainfall during March was below average across most of western, central, southern and south eastern NSW (72 per cent of the State). Most of these areas received well below average to extremely low relative rainfall.

Areas of the far north west, northern tablelands and slopes, the Hunter valley and the north of the central tablelands received average rainfall.

Quarterly relative rainfall was average over 69 per cent of the State, but was below average across an area between Coonabarabran, Coonamble, Narrabri, Walgett, Lightning Ridge and Bourke. Above average rainfall for the period occurred primarily across the far west. Other areas of below average rainfall during the period occurred across the Liverpool Plains, the northern tablelands and the central west.

Half yearly relative rainfall was average across the west, south and east of NSW. It was above average over the far south east and areas of the north coast and far west. Below average relative rainfall for the period occurred in areas of the north west, the Liverpool Plains, areas of the Hunter valley and central west and an area of the far south west near Balranald.

Soil moisture

Modelled topsoil moisture levels declined across most of NSW during March except for areas of the north east and along the coastal strip north from Moruya.

Relative to historical records, topsoil moisture was generally below average across central, south western and southern NSW. Areas of extremely low relative topsoil moisture occurred across areas of the north west, central west and south west. Areas of the north east and far north west had average topsoil moisture.

Modelled subsoil moisture levels were generally stable during March, but were low in areas of the north and west.

Relative to historical records, subsoil moisture remained below average across much of the north west and areas of the northern tablelands, Liverpool plains, central tablelands and areas of the Riverina. Subsoil moisture was extremely low across areas of the north west. Subsoil moisture was above average across areas of the far west, north coast and far south east and high across areas of the south east, far west and north coast.

Streamflow

Streamflow analysis indicated areas of below average run off have increased substantially over one, two and three year time periods. In the last year, streamflow over much of northern and central NSW, the tablelands, Hunter valley, Sydney basin and the Riverina has been well below average.

Farm water supplies are low in many areas, with some areas critically low in March. Storm rainfall and rainfall in early-mid April has resulted in some run off, particularly in areas of central and eastern NSW.

The Bureau of Meteorology's streamflow forecast indicates low streamflows were recorded in March, and are likely at most locations during April to June.

Relative pasture growth and biomass

Relative to historical records, AussieGRASS modelled pasture growth declined across most of western central, southern and south eastern NSW during March. Growth remained above average in the north of the northern tablelands and areas of the northern slopes, far west and central tablelands. Across most of the mid-north to north coast, southern areas of the northern tablelands and areas of the central tablelands, growth remained near average. Relative growth was well below average across most of the west, north west, Riverina and the central areas of the State.

Relative growth for March was below average over 54 per cent of NSW, average over 18 per cent and above average over just 6 per cent. However, there were large areas of missing data, particularly in the west.

Other pasture growth models indicated well below average growth for temperate pastures across most of NSW, with the exception of the mid-north to north coast, northern slopes and the north of the central and northern tablelands. For tropical pasture species, the best growth occurred along the mid-north to north coast.

Over the three months to March, relative growth showed the influence of the January rainfall. Relative growth for the period was above average across most of tablelands and far west of NSW and areas of the south. It was below average across areas of the north west, Liverpool plains, the north of the central west and the western Riverina. Most of central and coastal NSW had average growth.

Relative biomass levels declined between February and March, remaining average to above average across the tablelands, coast and across areas of the far west, but low across the north west and much of central NSW and the Riverina. About 35 per cent of NSW had below average relative biomass levels, and 43 per cent average relative biomass levels.

Figure 1: Relative monthly topsoil moisture

Figure 2: Relative quarterly pasture growth

More information

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

Acknowledgments

Information used in this report was sourced from the Bureau of Meteorology, CSIRO, Queensland Department of Science, Information Technology, Innovation and the Arts, NSW Local Land Services, the US National Oceanic and Atmospheric Administration, the International Research Institute for Climate and Society (Columbia University) 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 23 April 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 (17 April 2015 for most information and 23 April for seasonal outlooks). 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.