NSW State Seasonal Update - July 2021

Prepared by NSW DPI

NSW overview

Average to above average winter rainfall has supported a strong seasonal production outlook for most of NSW. The rainfall has raised concerns of waterlogging in some districts, particularly the central and tableland areas of the state. The NSW DPI Combined Drought Indicator (CDI) shows 96% of NSW in the Recovery or Non-Drought categories at the end of July. The seasonal rainfall outlook indicates moderate to high chances of above median rainfall across inland NSW for the next three months.

While winter rain has improved conditions across most of NSW, slow, variable and delayed patterns of drought recovery continue in parts of Western NSW and western areas of the Riverina and Murray regions. The NSW DPI continues to monitor the agronomic conditions in these areas with drought indicators remaining at low levels. The lead up to Spring is an important time and consistent follow-up rain remains the key focus to build confidence of longer-term recovery.

The 2021 winter crop potential remains high; however many areas have begun to manage wet conditions after high rainfall accumulation in June and July. Soil water conditions currently support a high yield potential across most regions, though high rainfall in August could cause longer-term waterlogging and crop health issues in some areas.

Rainfall accumulation has improved the state’s large reservoir and irrigation scheme levels over the last six months, especially in the northern basins. Water availability has increased and is expected to increase irrigated crop potential for the 2021-22 season.

Winter rainfall has supported pasture growth potential and livestock productivity across most of NSW. Soil moisture levels should support accelerated pasture growth in the lead up and throughout spring as temperatures begin to increase.

The latest Bureau of Meteorology (BoM) Seasonal Outlook indicates moderate to high chances of above median rainfall across inland NSW for the next three months. A negative Indian Ocean Dipole (IOD) event has developed and is forecast to persist into Spring. A negative IOD event is typically associated with increased chances of above median winter and spring rainfall across south-eastern Australia. Pacific Ocean sea-surface indicators remain in a neutral state; however a small subset of global models indicates possible La Nina conditions could develop in Spring. La Nina typically increases the chance of above average rainfall.

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). Average to well-above average July rainfall was received across large areas of central NSW west of the Great Dividing Range. The highest anomalies (above 50mm) occurred across the Northern Tablelands, Central Tablelands and eastern areas of the Murray and Riverina LLS regions. Coastal regions generally received below average rainfall with deficits of 25-50mm. North-western NSW recorded deficits of 10-25mm.

Most of NSW received more than 25mm of rain in July (Figure 2b). The highest totals (above 200mm) were received in the Alpine areas, while parts of the Northern Tablelands, Central Tablelands, South East and eastern areas of the Riverina, Murray and North West LLS regions received more than 100mm. The South Coast and North-western NSW were comparatively dry and received less than 25mm in July.

Rainfall accumulation during the 2021 calendar year has been near or above average across most of NSW. The main exception is the far west and south-west of NSW where 2021 rainfall has been much lower than average at the end of July. Most of coastal NSW has received a total above 600mm for the year (Figure 2c). Central areas west of the Great Dividing Range have generally received between 400-600mm. Eastern areas of the Western LLS region have recorded 200-300mm, while the far west has received less than 100mm for the year.

Temperature

Maximum temperature anomalies were near average across most of NSW during July, though were 1-3°C warmer in the north-west (Figure 3a). The average July maximum temperatures were generally above 12°C across NSW, though were cooler in the Tableland and Alpine regions (Figure 3b).

Minimum temperatures were near average across most of NSW in July (Figure 3c). Mean minimum temperatures ranged between 3-6°C, except for the higher elevation areas of the Tablelands and Alpine regions that ranged between -3 to 3°C (Figure 3d).

The frost days map (Figure 3e), shows the number of days that overnight temperatures fell below 0°C across NSW in July. There was an increase in the frequency of frost across larger areas of NSW compared to June.

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 May to July period. Lower than normal plant greenness remains evident across large areas of the Western LLS and western areas of the Riverina and Murray LLS regions. Some areas affected by the 2019/20 bushfires also remain evident in the Central Tablelands, Northern NSW and South East.

NSW Farm Dam Survey

There are large areas of southern and western NSW where farm dam levels are less than 20% of capacity (Figure 5). Further east and in areas of north-western NSW, dam levels are generally greater than 40% of capacity. Large areas in central and central northern areas with dam capacities greater than 80%.

Soil Water Index

The Soil Water Index (SWI, Figure 6) indicates the majority of NSW is currently in the average to above average categories. Parts of south-western NSW continue to remain in the below average category at the end of July.

Plant Growth Index

The Plant Growth Index (PGI, Figure 7) indicates that the majority of NSW is currently in the average to above average categories at the end of July. Parts of south-western NSW remain 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 average rainfall that has been accumulated over the last 12 months.

Drought Direction Index

The Drought Direction Index (DDI, Figure 9) tracks the 150-day trend of daily rainfall totals. The DDI indicates that the south-west of NSW currently has a wetting trend, largely due to improved rainfall in June and July. Elsewhere large areas of NSW show a strong drying trend. This likely reflects the extent of rain deficits that occurred in late autumn.

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 region to 31 July 2021. The following regional descriptions are based on data available until the end of July 2021.

Murray and Riverina regions

The Combined Drought Indicator (CDI; Figure 11) shows a large area in the west of the Riverina and Murray Local Land Services (LLS) remains in the Drought Affected category at the end of July. Isolated rainfall during winter has begun to improve conditions in these districts, however follow-up rain is still needed to lift longer-term confidence of any drought recovery. Further rainfall in August would continue to improve the agronomic indicators in the lead up to spring. Elsewhere rainfall and agronomic conditions support confidence of a strong seasonal outlook.

The seasonal NDVI anomaly data (Figure 12) shows that eastern areas of the region were experiencing near to or higher than normal plant greenness levels for the May to July period. Plant greenness levels remain lower than expected in 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. The charts show that winter rainfall has improved the indicators following a declining period in autumn 2021. Follow-up rainfall remains a focus to build these indicators prior to spring, especially at Moulamein and further west. Variable, weak or delayed drought recovery has occurred in these areas compared to other locations due to lower rainfall during 2020/21.

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 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

Recent rainfall has continued the recovery from drought across the majority of the Western LLS region. The Combined Drought Indicator (CDI; Figure 14) shows that the majority of the Western LLS region is in the Non-Drought category. However, parts of the south-west remain in the Drought Affected category. Drought recovery has remained variable, weak or delayed across these districts. Follow-up rainfall in August is needed increase confidence in the lead up to spring.

The seasonal NDVI anomaly data (Figure 15) shows most of the region is experiencing near to or higher than normal plant greenness levels for the May to July period. Plant greenness levels remain lower than expected in parts of the far west and south-west.

The time series charts (Figure 16) show the individual response of the drought indices for Bourke, Ivanhoe and Wentworth. Conditions have generally improved or remained stable in recent months after declining earlier in 2021. June and July rainfall has improved the indicators at many locations, though follow-up rain in the last month of winter will be important to maintain these improvements. The DPI continues to monitor conditions closely across the Western LLS. 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 is then ranked against all other 12-month periods. 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

Winter rainfall has continued to support drought recovery across the North West and Northern Tablelands Local Land Service regions. The North Coast LLS region was comparatively dry in June and July, however, productive conditions have generally been maintained after the large rain totals received in March. The Combined Drought Indicator (CDI; Figure 17) shows most of these regions are now in the Recovery or Non-drought categories. The winter rainfall has replenished soil water levels to field capacity in some areas, especially where overland flooding occurred in March. The risk of waterlogging remains high in some areas.

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

The time series charts (Figure 19) show the individual response of the drought indices for Moree, Walgett, Tenterfield and Lismore. The soil water and plant growth indices plateaued or declined at the end of autumn, however rainfall during winter has improved the indices. Lismore is an exception and reflects the current trends across much of the North Coast where conditions have been variable and comparatively dry during winter. The NSW DPI continues to monitor the northern regions 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 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 Central West, Central Tablelands, Hunter and Greater Sydney Local Land Services (LLS) regions remained in the Non-Drought CDI category during July (Figure 20) and are in a strong position for remainder of the 2021 Winter. Soil water levels are high in many areas. There is an increased risk of waterlogging and for the remaining winter. NSW DPI continues to monitor the region closely.

The seasonal NDVI anomaly data (Figure 21) continues to show above average levels of plant greenness across most of the LLS regions for the May to July 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. Rainfall since Autumn 2020 improved the indicators at all locations and shows evidence of a strong drought recovery. These regions currently remain well placed for productive conditions in 2021.The winter rain improving the agronomic indices after they plateaued or declined in autumn.

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.

South East region

The Combined Drought Indicator (CDI; Figure 23) shows that the South East Local Land Services region is in the Non-Drought CDI category. Most of the South East LLS region remains well positioned for a productive 2021, noting that rainfall in July was comparatively low in south-eastern parts of the region. Rainfall in August would support confidence in a productive Spring period.

The seasonal NDVI anomaly data (Figure 24) showed near normal to higher than expected levels of plant greenness across most of the region for the May to July period. The 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 charts show more recent improvements in the indices at Bega and Cooma where higher rainfall was recorded in May and June. The indices at Goulburn reflect a dry period in April and May, however winter rainfall has maintained the indicators since this period.

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 5 August 2021. Spring rainfall is likely to be above median for the eastern two-thirds of Australia. Below median rainfall is likely for north-west WA and western Tasmania.

Daytime temperatures are likely to be above median for the northern tropics and Tasmania. Below median daytime temperatures are more likely across much of the southern mainland. Above median overnight temperatures are likely across Australia except southern WA.

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

NSW outlook

Most of NSW has moderate to high chances of receiving above median rainfall in the September to November period (Figure 26). The daytime temperature outlook indicates a moderate to high chance of cooler than median temperatures across most of NSW (Figure 27), though south-eastern NSW has near equal to high chances of warmer than median daytime temperatures. There is a high probability of warmer than median overnight temperatures across 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 3 July 2021. The ENSO Outlook status remains neutral with most Pacific oceanic and atmospheric indicators within neutral ranges. Most climate model outlooks indicate the central tropical Pacific is likely to cool over the coming months. Three of the seven models surveyed by the Bureau currently indicate this cooling could reach La Niña thresholds in spring.

These models, combined with the negative Indian Ocean Dipole (IOD) event currently occurring in the Indian Ocean, is likely contributing to the wetter than median seasonal climate outlooks in Australia.

Southern Oscillation Index

The 30-day Southern Oscillation Index (SOI) for the 30 days ending 1 August 2021 was +15.1. The 90-day SOI value was +8.5.

Sustained negative values of the SOI below −7 typically indicate El Niño while sustained positive values above +7 typically indicate La Niña. Values between +7 and −7 generally indicate neutral conditions.

Despite most of the ENSO indicators currently within neutral ranges, the current SOI value is one of the atmospheric indicators that is showing some La Niña like characteristics. It is likely that some of the shift in global pressure patterns is being caused by the warm conditions in the eastern Indian Ocean.

Sea surface temperatures (SST)

The monthly sea surface temperatures (SST) were close to average across most of the equatorial Pacific Ocean, however the warmer than average SSTs continued in the eastern Pacific Ocean near South America in July. SSTs were also warmer than average in waters around the north and south-east of Australia.

The latest values of the three NINO indices in the tropical Pacific for the week ending 1 August were: NINO3 0°C, NINO3.4 -0.1°C, NINO4 0.1°C. All three NINO indices are within the ENSO-neutral range.

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 July) shows a pattern consistent with a neutral ENSO state. Weak warm anomalies were present across much of the column depth west of the Date Line, while weak cool anomalies were present across the central and eastern equatorial Pacific between 175m depth and 75m depth. These cool anomalies developed during July.

Indian Ocean (IOD)

A negative Indian Ocean Dipole (IOD) event is underway. The latest weekly value of the Indian Ocean Dipole (IOD) index to 1 August 2021 was −0.76 °C. The IOD index has generally been below the negative IOD threshold (−0.4 °C) since mid-May.

Most climate models surveyed by the Bureau indicate negative IOD conditions are likely to persist throughout spring.

A negative IOD event increases the chances of above average winter and spring rainfall for parts of southern Australia.

Southern Ocean (Southern Annular Mode – SAM)

The Southern Annular Mode (SAM) index is currently positive, however is expected to return to neutral values over coming days and remain neutral for the remaining fortnight. A neutral SAM has little influence on Australian climate.

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 (2021), Panorama Avenue, Bathurst 2795 and data which is © Commonwealth of Australia 2021, 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.