NSW State Seasonal Update - December 2021

Prepared by NSW DPI

NSW overview

Average rainfall has been recorded across most of NSW during December and the state continues to experience a strong production outlook. Most of NSW is currently in non-drought with the NSW DPI Combined Drought Indicator (CDI) showing 93% of NSW in the Recovery or Non-Drought categories at the end of December. The official rainfall outlook indicates that there is a 45% to above 70% chance of rainfall being above the median values for the next three months.

The 2021 NSW winter crop harvest was mostly completed in December. Wet conditions in November and early December negatively impacted winter grain crops in some regions. The wet conditions also affected crop quality in some horticultural regions.

The irrigated crop forecast for the 2021-22 season remains high due to high soil moisture levels and water availability in the state’s reservoir and irrigation scheme. Water availability is expected to support a strong irrigated crop forecast for the 2021-22 season.

Pasture growth remains high across the state though in many districts the nutritional value of pasture for livestock is lower given the warmer temperatures. The seasonal conditions also create challenges for livestock producers, such as weed management. There have been opportunities in many parts of the state to conserve fodder for future droughts.

Despite the strong overall outlook, parts of Western NSW and western areas of the Riverina and Murray regions continue to experience a slow, variable or delayed drought recovery. The agronomic indictors of the CDI remain at low levels across parts of these regions and consistent follow-up rain is needed to improve current conditions.

The latest Bureau of Meteorology (BoM) Seasonal Outlook indicates moderate to high chances of above median rainfall across NSW for the three months between February and April. The ENSO Outlook status is currently at La Niña. The Indian Ocean Dipole (IOD) is neutral and models indicate that the IOD will remain neutral in the coming months. Sea surface temperatures in the central-to-eastern tropical Pacific Ocean remain cooler than average. Warmer than average sea surface temperatures persist across the far western Pacific.

The CDI and its individual rainfall, soil moisture and crop/pasture growth metrics are leading biophysical indices of drought. Factors affecting production and economic responses usually lag the CDI. Further information about the correct interpretation of the CDI at a region and industry level is provided in the regional breakdown section of this report.

It is important to recognise the CDI provides an aggregated view of the State, and that on-ground conditions can be different to those displayed in the maps. They provide an ‘on average’ view of a particular region only. To report local conditions, use DPI Farm Tracker.

Rainfall

The rainfall anomaly data shows the difference between total monthly rainfall and the long-term average (1961-1990; Figure 2a). Most of eastern NSW has received near average to above average rainfall in December. Western NSW has generally received average to below average rainfall. The highest rainfall totals have been across eastern NSW where falls above 100mm have been recorded (Figure 2b). Some regions have received rainfall totals above 300mm. Western NSW has generally received falls below 50mm.

Rainfall accumulation during the 2021 calendar year has been near or above average across NSW. Most of coastal NSW, alpine regions and parts of the central and northern tablelands have received more than 1000mm in the year (Figure 2c). Central NSW has received between 300 to 1000mm of rainfall during the year. The far west of NSW has generally received less that 300mm of rainfall.

Temperature

Most of NSW experienced near average maximum temperatures during December (Figure 3a). Warmer than average anomalies (1-2°C) were recorded in parts of western NSW and cooler than average anomalies were recorded in parts of central and south-eastern NSW. The average December maximum temperatures ranged between 21°C to 30°C in eastern NSW. Areas west of the Great Dividing Range had maximum temperatures above 27°C, and above 36°C in the far north-west of NSW (Figure 3b).

Minimum temperatures were near average across most of NSW in December (Figure 3c). The average December minimum temperatures were above 12°C across most of the state (Figure 3d). Tablelands and alpine regions at higher altitudes experienced cooler temperatures between 3 to 12°C.

Normalised Difference Vegetation Index (NDVI) Anomaly

The seasonal Normalised Difference Vegetation Index (NDVI, Figure 4) indicates that plant greenness levels are close to, or above normal across most of NSW for the October to December period. Slightly lower than normal plant greenness remains evident across parts of the Western LLS region.

NSW Farm Dam Survey

The NSW Farm Dam Survey indicates dam levels are generally greater than 40% of capacity across eastern areas of NSW and above 80% capacity in regions that have received higher rainfall totals (Figure 5). Areas of western, southern and some coastal regions of NSW have farm dam levels less than 20% of capacity.

Soil Water Index

The Soil Water Index (SWI, Figure 6) indicates the majority of NSW is currently in the average to above average categories. This is a result of the rainfall that has been received over the last few months. Parts of western and south-western NSW are in the below average category.

Plant Growth Index

The Plant Growth Index (PGI, Figure 7) indicates that the majority of NSW is in the average to above average categories at the end of December. Parts of south-western and western NSW reflect a similar pattern with the SWI and are in the below average category.

Rainfall Index

The Rainfall Index (RI, Figure 8) indicates that the majority of NSW is currently in the average to extremely high category. This reflects the distribution of average or above rainfall accumulated over the last 12 months. Smaller areas in south-western and western NSW are in the below average RI category.

Drought Direction Index

The Drought Direction Index (DDI, Figure 9) tracks the 150-day trend of daily rainfall totals. The DDI indicates most of NSW is in a weak to strong wetting trend. This reflects the rainfall that has been received in the past few months.

Changes in the individual drought indicators may have occurred since this update was released. For the most current information, please visit DroughtHub.

CDI status for the regions

Figure 10 displays the CDI status for each individual Local Land Services (LLS) region to 31 December 2021. The following regional descriptions are based on data available until the end of December 2021.

Murray and Riverina regions

The Combined Drought Indicator (CDI, Figure 11) shows that conditions in the Riverina and Murray Local Land Services (LLS) regions have remained stable since the November Update. Most of both regions are in the Recovery or Non-Drought categories. Western areas of the Riverina and Murray LLS regions have remained in the Drought Affected category. Further rain is needed to support drought recovery.

The seasonal NDVI anomaly data (Figure 12) shows that most of the Murray and Riverina regions were experiencing near to or higher than normal plant greenness levels for the October to December period. Plant greenness levels remain lower than expected in some western areas of the Murray and Riverina LLS regions. The impact of the 2019/2020 bush fires is still evident south of Tumut.

The time series charts (Figure 13) show the individual response of the drought indices for Hay, Finley, Temora and Moulamein. Temora and Finley remain steady with average to high soil water, plant growth and rainfall indices. Continued rainfall has allowed Hay to remain in the Non-Drought category, but further rainfall is needed maintain conditions. Further rainfall is required at Moulamein to improve the drought indices.

The Combined Drought Indicator (CDI) is a tool that monitors drought conditions across NSW. The drought categories are based on assessing the response of three drought indicators: soil water, plant growth and rainfall. The indicators track the data over the past 12 months and show how the indices are tracking compared to long-term averages. The information provided in the map is aggregated to a Parish level and provides a regional assessment of conditions. Variability within and between farms is possible and this may not be reflected in the CDI map.

Western region

The Combined Drought Indicator (CDI, Figure 14) shows that drought conditions are variable across the region. Although most of the region is in the Non-Drought or Recovering CDI category, the area in the Drought Affected category expanded during December. The DPI continues to closely monitor conditions in Western LLS.

The seasonal NDVI anomaly data (Figure 15) shows variability across the Western LLS region. Much of the region is experiencing near normal or higher levels of plant greenness for the October to December period. Areas in the far west and south-west continue to have lower than normal plant greenness levels, along with parts of central Western LLS region near Bourke.

The time series charts (Figure 16) show the individual response of the drought indices for Bourke, Ivanhoe and Wentworth. Ivanhoe remains in the Non-Drought category with high soil water, plant growth and rainfall indices. Continued rainfall is required at Bourke and Broken Hill to maintain the Non-Drought status and improve the soil water and plant growth indices. Wentworth is currently in the Drought Affected category and rainfall is required to improve conditions. NSW continues to monitor the Western LLS region closely. To access a time series for your Parish, visit the Combined Drought Indicator website.

The Combined Drought Indicator (CDI) is a tool that monitors drought conditions across NSW. The drought categories are based on assessing the response of three drought indicators: soil water, plant growth and rainfall. The indicators track the data over the past 12 months. This shows how the indices are tracking compared to the long-term averages. The information provided in the map is aggregated to a Parish level and provides a regional assessment of conditions. Variability within and between farms is possible and this may not be reflected in the CDI map.

North West, Northern Tablelands and North Coast regions

The North West, Northern Tablelands and North Coast Local Land Service regions continue longer-term drought recovery. Productive conditions have generally been maintained due to rainfall received throughout the year. The Combined Drought Indicator (CDI, Figure 17) shows that the LLS regions are in the Non-Drought category.

The seasonal NDVI anomaly data (Figure 18) indicated near to above-normal greenness across most of the regions for the October to December period.

The time series charts (Figure 19) show the individual response of the drought indices for Moree, Walgett, Tenterfield and Lismore. The indicators remain high at all locations. To access a time series for your Parish, visit the Combined Drought Indicator website.

The Combined Drought Indicator (CDI) is a tool that monitors drought conditions across NSW. The drought categories are based on assessing the response of three drought indicators: soil water, plant growth and rainfall. The indicators track the data over the past 12 months and shows how the indices are tracking compared to the long-term averages. The information provided in the map is aggregated to a Parish level and provides a regional assessment of conditions. Variability within and between farms is possible and this may not be reflected in the CDI map.

Central Tablelands, Central West, Hunter and Greater Sydney regions

The majority of the Central West, Central Tablelands, Hunter and Greater Sydney Local Land Services (LLS) regions remain in the Non-Drought Combined Drought Indicator (CDI) category at the end of December (Figure 20). There has been an area transition into the Drought Affected category since the November Update (south-east of Singleton), and this region is being closely monitored by DPI. Generally, the LLS regions remain in a strong position, with average to above average soil water levels across the region.

The seasonal NDVI anomaly data (Figure 21) shows near normal to high levels of plant greenness across most of the LLS regions for the October to December period. The 2019/20 bushfire impact is still evident in parts of the Central Tablelands, lower Hunter and west of Greater Sydney.

The time series charts (Figure 22) show the individual response of the drought indices for Cowra, Condobolin and Singleton. Follow-up rainfall has supported the CDI indicators at all locations and there is evidence of a strong drought recovery. These regions currently remain well placed for productive conditions in the coming months.

The CDI is a tool that monitors drought conditions across NSW. The drought categories are based on assessing the response of three drought indicators: soil water, plant growth and rainfall. The indicators track the data over the past 12 months and show how the indices are tracking compared to the long-term averages. The information provided in the map is aggregated to a Parish level and provides a regional assessment of conditions. Variability within and between farms is possible and this may not be reflected in the CDI map.

South East region

The Combined Drought Indicator (CDI, Figure 23) shows that most of the South East Local Land Services region is in the Non-Drought CDI category. The CDI shows that an area around Nowra continues to remain in the Recovery category. Further rainfall is needed to improve conditions in this region.

The seasonal NDVI anomaly data (Figure 24) showed near normal to high levels of plant greenness across most of the region for the October to December period. Some areas impacted by the 2019/20 bushfires continue to have lower than average plant greenness levels.

The time series charts (Figure 25) show the individual response of the drought indices at Bega, Goulburn and Cooma. The three regions remain in the Non-Drought category with high soil water, plant growth and rainfall indices. These regions currently remain well placed for productive conditions in the coming months.

The Combined Drought Indicator (CDI) is a tool that monitors drought conditions across NSW. The drought categories are based on assessing the response of three drought indicators: soil water, plant growth and rainfall. The indicators track the data over the past 12 months and shows how the indices are tracking compared to the long-term averages. The information provided in the map is aggregated to a Parish level and provides a regional assessment of conditions. Variability within and between farms is possible and this may not be reflected in the CDI map.

Official national outlook

The official national outlook was released by the Bureau of Meteorology (BoM) on 06 January 2022. Rainfall during February to April is likely to be above median for most of eastern Australia and northern parts of the Northern Territory. Western Tasmania are likely to have below median rainfall. Elsewhere there is near equal chance of above or below median rainfall.

Maximum temperatures are likely to be above median for most of Australia. Below median maximum temperatures are likely for eastern New South Wales, and eastern Victoria. Minimum temperatures for February to April are likely to be above median across most of Australia

The Bureau issues a new 3-month seasonal update weekly, each Thursday afternoon.

NSW outlook

Most of NSW has a 50% to above 70% chance of receiving above median rainfall between February and April (Figure 26). The maximum temperature outlook (Figure 27) indicates a 20% to above 40% chance of warmer than median temperatures at higher altitudes in eastern NSW. There is a 60% to above 80% chance of above median maximum temperatures in western NSW and some coastal regions. There is a 70% to above 80% chance of warmer than median overnight temperatures across most of the state (Figure 28).

Global climate drivers

El Niño–Southern Oscillation (ENSO)

The Bureau of Meteorology’s (BoM) El Niño-Southern Oscillation (ENSO) Outlook was released on 05 January 2022. The La Niña continues in the tropical Pacific Ocean. Climate models suggest that this La Niña will persist until early autumn 2022. La Niña typically increases the chance of above median rainfall in NSW during spring and summer.

Southern Oscillation Index

The 30-day Southern Oscillation Index (SOI) for the 30 days ending 3 January was +12.7 (Figure 29). The 90-day SOI value was +10.7. Sustained negative values of the SOI below −7 typically indicate El Niño while sustained positive values above +7 typically indicate La Niña.

Sea surface temperatures (SST)

Sea surface temperatures (SST) in the central-to-eastern tropical Pacific remain cooler than average. Warmer than average SSTs persist across the far western Pacific, including parts of the Maritime Continent and waters around northern Australia (Figure 30).

The latest values of the three NINO indices in the tropical Pacific for the week ending 2 January were: NINO3 -1.0°C, NINO3.4 -0.7°C, NINO4 -0.3°C.

Persistent NINO3 or NINO3.4 values warmer than +0.8 °C are typical of El Niño, while persistent values cooler than −0.8 °C typically indicate La Niña.

Sea sub-surface temperatures

The four-month sequence of equatorial Pacific sub-surface temperature anomalies (to December 2021) shows strong cold anomalies have persisted and strengthen in the central to eastern equatorial Pacific Ocean during December (Figure 31). Sub-surface anomalies were 3-4ºC cooler than average in the eastern equatorial Pacific. Warm anomalies are present across parts of the water column in the western Pacific.

Indian Ocean (IOD)

The Indian Ocean Dipole (IOD) remains neutral. All five international climate models surveyed by the Bureau of Meteorology indicate that the IOD will remain neutral in the coming months. This is consistent with the typical life cycle of an IOD event. IOD events are typically unable to form between December and April when the monsoon trough shifts south over the tropical Indian Ocean. The latest weekly value of the Indian Ocean Dipole (IOD) index to 29 November 2021 was −0.16 °C.

Southern Ocean (Southern Annular Mode – SAM)

The Southern Annular Mode (SAM) index is currently neutral (as of 3 January), though is expected to approach positive thresholds during January (Figure 32). A positive SAM typically increases the chance of above average rainfall for much of New South Wales during spring and summer.

The Southern Annular Mode (SAM) refers to the north-south shift of rain-bearing westerly winds and weather systems in the Southern Ocean compared to the usual position. This indicator can be quite volatile and generally influences weather conditions on 1-3 week timescales. SAM forecasts are highly uncertain beyond 2-3 weeks.

How does it work?

Much of the information in the Seasonal Conditions Report is sourced from the NSW DPI Enhanced Drought Information System (EDIS) ™. The EDIS system is currently available in prototype form and is subject to an intensive ground truthing process. For more information, visit the interactive website via DroughtHub.

EDIS is an ongoing project aimed at improving the quality and timeliness of efforts to monitor conditions across the state. Key features of the system are:

• It tracks drought by using four indicators; rainfall, soil water, plant growth, as well as tracing rainfall trends. Agronomic conditions have equal value to rainfall recorded at meteorological stations.
• The Combined Drought Indicator (CDI) brings this information together and has been designed to characterise developing drought conditions. The key purpose for building the CDI was as a drought early warning system.
• The rainfall, soil moisture and plant growth indicators in EDIS account for conditions over a 12-month window. This provides a compromise between a highly sensitive indicator (e.g. six months) and a less sensitive indicator (e.g. 24 months).
• Climate and remote sensing data drive the information system at a high resolution, but the CDI is reported at a Parish level.
• Because of its configuration and purpose, there will be differences to the indicator used in the National Drought Monitoring Framework (the Australian Rainfall Deficiency Analyser) which relies on rainfall alone.
• The CDI has three drought categories that characterise NSW according to drought intensity as well as the main drivers of a drought event (meteorological, hydrological and agronomic). DPI considers areas Drought Affected to be experiencing a drought event.
• The Drought Affected category encompasses a wide range of conditions from the very early stages of drought entry through to a drought event becoming intense. This enables the drought monitoring system to detect a drought event early. It is also possible to stay in the Drought Affected category for some period of time.

The way in which the indicators are combined to form the CDI is described in Table 1 below.

Table 1: Description of the Combined Drought Indicator framework

The NSW State Seasonal Update is provided each month by the NSW DPI Climate Branch.

Information used in this report was primarily sourced from the Australian Bureau of Meteorology, the US National Oceanic and Atmospheric Administration, the International Research Institute for Climate and Society (Columbia University), Geoscience Australia’s Digital Earth Australia Program, and NSW Department of Primary Industries.

Maps in this document contain data which is © Spatial Services – NSW Department of Finance, Services and Innovation (2022), Panorama Avenue, Bathurst 2795 and data which is © Commonwealth of Australia 2022, Australian Bureau of Meteorology, Melbourne. All rights reserved.

The seasonal outlooks presented in this report are obtained from the Australian Bureau of Meteorology and other sources (including World Meteorological Organisation Global Producing Centres). 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.

All climate and remote sensing input data is supplied to the Enhanced Drought Information System ™ under the Australian Creative Commons Licence (CCY 4.0) and is made available by the Terrestrial Ecosystem Research Network.