NSW State Seasonal Update - April 2023

Prepared by NSW DPI

NSW overview

The NSW DPI Combined Drought Indicator (CDI) shows greater than 99% of NSW in the Non-Drought category at the end of April. Despite variable rainfall in April, the production outlook for May remains strong for most areas of NSW.

Current conditions

• April rainfall was variable, concentrated largely in central and southern NSW
• Dry conditions have impacted parts of the state leading to a decline in the soil water, plant growth, and rainfall indicators in the north, north-east, and south-east.
• Subsoil moisture levels for NSW are mostly average, generally drier in the north-east and coastal areas.
• Water availability for production remains positive, with many irrigation schemes at near full capacity.

Seasonal Climate Outlook

• Seasonal climate forecasts indicate warmer than average days for most of NSW for the May to July period.
• Overnight temperatures are likely to be warmer than average for southern NSW during this period.
• Rainfall is likely to be below average for all of NSW from May to July.
• The ENSO Outlook status is at El Niño WATCH, indicating a 50% chance of El Niño forming in winter. It is important to note that ENSO forecast accuracy in autumn is lower than for forecasts made later in the year.
• The Indian Ocean Dipole (IOD) is currently neutral; models suggest a positive IOD event may occur in late autumn or winter. However, as for ENSO predictions, the accuracy of IOD forecasts made at this time of year is low.

The CDI and its individual rainfall, soil moisture and crop/pasture growth metrics are leading biophysical indices of seasonal conditions and drought status. Other 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 NSW, 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.

Rainfall

The rainfall anomaly data shows the difference between total monthly rainfall and the long-term average monthly rainfall (1981 – 2010; Figure 2a). Variable rainfall was received across NSW in April. Above average rainfall has been received in central and southern parts of NSW. Average to below average rainfall has been received in the North Coast, Northern Tablelands, North West, and parts of the Western, Central West, Hunter, Sydney and South East LLS regions. The highest negative rainfall anomalies were recorded in the North Coast LLS region. The highest positive rainfall anomalies were recorded around Tumut in the Riverina, between Orange and Crookwell across the Central Tablelands and South East LLS regions, and also around Ulladulla in the South East.

The highest monthly rainfall totals in April were recorded in eastern NSW where rainfall of more than 100mm was received (Figure 2b). Western NSW received less than 25mm and the North West LLS region, west of Moree received less than 5mm of rainfall in April.

For the calendar year to date most of coastal NSW has received between 200mm to above 400mm of rainfall. Areas east of Coffs Harbour and north of Taree have received more than 600mm for this calendar year to date. Rainfall west of the Great Dividing Range has totalled between 10mm and 300mm (Figure 2c). Year to date rainfall has been below average for most of NSW, particularly in eastern and northern regions.

Temperature

Below average maximum temperatures were experienced across western, southern, and Tableland areas of NSW in April. Maximum temperatures were more than 2 degrees below average between Wagga Wagga and Cowra, and south of Glen Innes (Figure 3a). In April the average maximum temperatures ranged from 6°C in the southern alps to above 27°C in north-western NSW. Most of NSW experienced day time temperatures above 18°C. Temperatures were generally cooler in the east: parts of the Tablelands and southeast NSW experienced average day time temperatures below 18°C (Figure 3b).

Minimum overnight temperatures were near to below average across NSW in April. Temperatures were more than 2 degrees below average in central NSW, west and north-west of Condobolin (Figure 3c). The average April minimum temperatures (Figure 3d) ranged between 0°C to more than 6°C in the alps and Tablelands. The far northwest and east coast of NSW recorded the highest average minimum temperatures of above 12°C. There were more than 4 frost days recorded in the alpine region in April (Figure 3e).

Normalised Difference Vegetation Index (NDVI) Anomaly

The seasonal Normalised Difference Vegetation Index (NDVI, Figure 4) indicates that plant greenness levels are near normal to slightly below normal for central, southern, and eastern areas of NSW, including areas of the Northern Tablelands, North West and Hunter Local Land Services regions. Normal to well above normal plant greenness levels are shown for western areas of NSW for the February to March period. Some of the extremely negative NDVI areas (brown patches) are water bodies.

NSW Farm Dam Survey

The NSW Farm Dam Survey indicates dam levels are generally less than 60% of capacity across most of NSW (Figure 5). Areas west of the Great Dividing Range and parts of northern and coastal NSW maintain farm dam levels at less than 40% of capacity. Data is unavailable for some areas of NSW due to cloud cover.

Soil Water Index

The Soil Water Index (SWI, Figure 6) shows more variability across NSW than seen in March. Areas in northern and eastern NSW have moved from the extremely high category to the above average category. The areas in the average category have expanded in the North Coast and South East LLS regions. Parts of the North West and Hunter LLS regions are now also in the average category. This is due to the low and variable rainfall received in February, March, and April.

Plant Growth Index

The Plant Growth Index (PGI, Figure 7) shows areas in eastern NSW, particularly around the Tablelands, continue to transition from the above average to the average PGI category during April. Most of central and western NSW is in the extremely high PGI category.

Rainfall Index

The Rainfall Index (RI, Figure 8) for 2023 shows that at the end of April the majority of NSW is in the extremely high category, with parts of northern, central and eastern NSW in the above average and average RI categories. In the North Coast region between Grafton and Lismore some areas are in the below average category. Drier conditions and variable rainfall have led to parts of northern and eastern NSW moving back into above average, average, and below average RI values.

Drought Direction Index

The Drought Direction Index (DDI, Figure 9) tracks the 150-day trend of daily rainfall totals. The DDI shows a strong wetting trend throughout eastern NSW due to April rainfall following a previous dry start to the year. Parts of Western NSW and the North Coast are in the no trend category reflecting stable conditions over the past 5 months. Areas in the weak drying trend category have experienced a slightly drier April compared to previous months. A strong drying trend in the south-east is due to higher rainfall recorded in November and December 2022, and the comparatively drier conditions in the last few months.

Importantly the weak to strong drying trend on its own does not indicate the emergence of a drought in the regions, rather it indicates a degree of drying following on from the previous very wet conditions.

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

NSW outlook - April to June

(issued 4 May 2023)

Below average rainfall for all of NSW

• There is a 60% to greater than 80% chance of below median rainfall west of the Great Dividing Range between May and July.
• Areas east of the ranges, and in far-north NSW have a 60 to 70% chance of receiving below median rainfall over the 3-month period (Figure 10).

High chance of warmer days for NSW

• The maximum temperature outlook indicates a more than 70% chance of exceeding median daytime temperatures across most of NSW.
• The chance of warmer than median daytime temperatures increases in the west, north, and south-east where there is a greater than 80% chance of above median maximum temperatures (Figure 11).

Warmer nights in south, cooler in the north

• There is a 50% to above 80% chance of warmer than median overnight temperatures in southern NSW during the May to July period (Figure 12).
• Across central and northern NSW there is a near equal to less than 35% chance of above median overnight temperatures.

Official national outlook

The official national outlook was released by The Bureau of Meteorology on 4 May 2023. The rainfall outlook for May to July shows that most of Australia has a likely to very likely (60 to more than 80%) chance of below median rainfall. There is an equal chance of above or below median rainfall for southern Victoria, north-west Western Australia, and Cape York. Parts of the south-west and south-east have a 70 to 80% chance of below average rainfall. Forecast accuracy at this time of year has generally been high to very high for most of Australia.

Maximum temperatures from May to July have a likely to very likely (60 to more than 80%) chance of being warmer than average for most of Australia. Parts of the Northern Territory and north-west Queensland have an equal chance of above or below average maximum temperatures.

Above median minimum temperatures are likely to very likely (60 to more than 80% chance) for most of Australia for the 3-month period between May to July. Central, north-east, and parts of eastern Australia have a 50% to 70% chance of below median minimum temperatures.

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

Global climate drivers

El Niño–Southern Oscillation (ENSO)

The Bureau of Meteorology’s El Niño-Southern Oscillation (ENSO) Outlook was released on 26 April 2023. The ENSO Outlook status is currently at El Niño WATCH and sea surface temperatures (SSTs) and atmospheric ENSO indicators in the tropical Pacific Ocean are at ENSO-neutral conditions.

Long range forecasts suggest that El Niño may form later this winter however long range ENSO predictions made in autumn have lower accuracy than ENSO predictions made in winter or spring. The Bureau of Meteorology’s El Niño WATCH indicates a 50% chance of El Niño occurring in 2023.

Southern Oscillation Index

The 30-day Southern Oscillation Index (SOI; Figure 13) for the 30 days ending 24 April was -3.6. The 90-day SOI value was +3.6. 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) were close to average along the equator in the central tropical Pacific Ocean. Weak warm anomalies were observed around the Maritime Continent to the north of Australia. Warm anomalies persist off the south-west Western Australian coastline, and south-east Australia across to New Zealand, and southern Tasmania (Figure 14).

The latest values of the three NINO indices in the tropical Pacific for the week ending 23 April were: NINO3 +0.8 °C, NINO3.4 +0.4 °C, NINO4 0.4 °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 20 April 2023) shows warm anomalies across the Pacific basin down to 350m depth in the west, 100m to 200m depth in the central Pacific, and from 0m to 100m depth in the eastern Pacific Ocean (Figure 15). These warm anomalies are more than 2^oC above average for most of the region.

Indian Ocean (IOD)

The Indian Ocean Dipole (IOD) is currently neutral. The latest weekly value of the Indian Ocean Dipole (IOD) index to 23 April 2023 was +0.04 °C.

Most of the international climate models surveyed by the Bureau of Meteorology suggest a positive IOD may emerge in late autumn or winter. However, IOD forecasts made through autumn historically have very low accuracy. A positive IOD occurs at values greater than +0.4 °C and can suppress winter and spring rainfall over much of Australia, including NSW.

Southern Ocean (Southern Annular Mode – SAM)

The Southern Annular Mode (SAM) index is neutral (as of 26 April) and is expected to be positive in early May before returning to neutral conditions (Figure 16).

A positive SAM in late autumn and winter can increase rain over eastern Australia, as more moisture than normal is drawn southward from the tropics and inland from off the east coast (East Coast Lows). A negative SAM has little influence on Australia’s rainfall and temperature.

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 their usual position. This indicator can be quite volatile and generally influences weather conditions on 1 to 3 week timescales.

CDI status for the regions

Figure 17 displays the CDI status for each individual Local Land Services (LLS) region to 30 April 2023. The following regional descriptions are based on data available until the end of April 2023.

Murray and Riverina regions

The Combined Drought Indicator (CDI, Figure 18) shows that all of the Riverina and Murray Local Land Services (LLS) regions remain in the Non-Drought category at the end of March.

The seasonal NDVI anomaly data (Figure 19) shows that parts of the Murray and Riverina regions, particularly in the west, were experiencing higher than normal plant greenness levels for the February to April period. Average levels of greenness are more predominant in parts of the northern and eastern Riverina and central Murray regions. Below average levels of greenness can be seen south of Griffith, Coleambally, and Jerilderie. Some of the extremely negative NDVI areas (brown patches) represent water.

The Drought History charts (Figure 20) show the individual response of the drought indicators for Hay, Temora, Finley, and Moulamein. The indicators are high at all locations and suggest a strong production outlook. To access a Drought History chart for your Parish, visit the Seasonal Conditions Information Portal.

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 21) shows that the Western LLS region is currently in the Non-Drought category.

April rainfall was variable for the Western region and some parts have low farm dam levels. Other areas are experiencing high to very high farm dam levels due to flooding in 2022. The DPI continues to closely monitor conditions in Western LLS.

The seasonal NDVI anomaly data (Figure 22) shows normal to very high levels of plant greenness across most of the Western LLS region for the February to April period. Lower levels of greenness are apparent in the far north-west and northern areas. Some of the extremely negative NDVI areas (brown patches) represent water.

The Drought History charts (Figure 23) show the individual response of the drought indicators for Bourke, Ivanhoe, Wentworth, and Broken Hill. Although still high, the rainfall indicator has declined at Bourke and Broken Hill, with smaller declines also visible in the soil water and plant growth indicators. Indicators remain high at Ivanhoe and Wentworth.  To access a Drought History chart for your Parish, visit the Seasonal Conditions Information Portal.

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 Combined Drought Indicator (CDI, Figure 24) shows that the North West and Northern Tablelands Local Land Services regions are in the Non-Drought category. Most of the North Coast LLS region is in the Non-Drought category however, an area west of Grafton and to the west of Tweed Heads have moved into the Drought Affected category.

The seasonal NDVI anomaly data (Figure 25) indicates near normal levels of greenness across the North Coast LLS region for the February to April period. Parts of the Northern Tablelands and North West LLS regions, around Glen Innes, Armidale, Lightning Ridge and north of Moree have average to below average levels of greenness. Some of the extremely negative NDVI areas (brown patches) represent water. The NSW DPI continues to closely monitor conditions in these regions.

The Drought History charts (Figure 26) show the individual response of the drought indicators for Tenterfield, Moree, Walgett, and Lismore. All indicators remain high at Moree. Indicators have declined at Tenterfield, Lismore, and Walgett. These declines are likely due to below average rainfall received for the calendar year to date. Further rainfall is required to maintain productive conditions. These regions should continue monitor conditions closely. To access a Drought History chart for your Parish, visit the Seasonal Conditions Information Portal.

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 Combined Drought Indicator (CDI; Figure 27) shows that the Central West, Central Tablelands, Hunter and Greater Sydney Local Land Services (LLS) regions continue to experience Non-Drought conditions at the end of April.

The seasonal NDVI anomaly data (Figure 25) indicates near normal levels of greenness across parts of the regions for the February to April period. Parts of the Central West around Coonamble, and the north-west of the Hunter LLS region have below average levels of greenness. Some of the extremely negative NDVI areas (brown patches) represent water. The NSW DPI continues to closely monitor conditions in these regions.

It is reported that due to low feed availability in parts of the northern Hunter region stock are being sold or put on agistment elsewhere to manage the drier conditions.

The Drought History charts (Figure 29) show the individual response of the drought indicators for Cowra, Condobolin and Singleton. There has been a decline in the CDI indicators at Singleton however, the CDI indicators are currently high at all locations. To access a Drought History chart for your Parish, visit the Seasonal Conditions Information Portal.

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 30) shows that the South East Local Land Services region is in the Non-Drought CDI category.

The seasonal NDVI anomaly data (Figure 31) shows near normal to above average levels of plant greenness. Some of the extremely negative NDVI areas (brown patches) represent water.

The Drought History charts (Figure 32) show the individual response of the drought indicators at Bega, Cooma and Goulburn. Indicators have stabilised at Comma and Goulburn due to April rainfall. There has been a large decline in all indicators at Bega since the last Update. Further rainfall is required to maintain productive conditions. The NSW DPI continues to closely monitor conditions in these regions. To access a Drought History chart for your Parish, visit the Seasonal Conditions Information Portal.

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.

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.nsw.gov.au.

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 National University, 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, and © Australian National University. 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.