NSW State Seasonal Update - September 2022

Prepared by NSW DPI

NSW overview

September rainfall was above average for most of NSW, with well above average rainfall in the north east. NSW is currently experiencing further wet weather and a high risk of flooding is present in parts of the state. In September severe flooding was reported in the North West and Central West LLS regions along the Namoi, Macquarie and Lachlan Rivers.

Across the state conditions remain wet with high soil moisture and many on farm and major water storages are full. The NSW DPI Combined Drought Indicator (CDI) reflects these conditions, with 100% of the state in the Non-Drought category at the end of September.

The drought indicators tracking soil water, plant growth, and rainfall remain high across the state.  However the drought indicators do not reflect the on-going challenges agricultural industries face with very wet conditions. In particular constraints to on-ground field management, disease and weed control, and maintaining animal health and welfare.

Water availability for production remains strong, with high on-farm dam levels across much of the state and irrigation schemes are at full capacity.

Climate forecasts indicate that cool and wet conditions are expected to continue across NSW this spring. The latest Bureau of Meteorology (BoM) Seasonal Outlook indicates a very high chance of above median rainfall across NSW for the three months between October and December. These conditions are driven by the current La Niña phase of the El Niño Southern Oscillation (ENSO), and this is expected to continue into the coming months.  In addition the Indian Ocean Dipole (IOD) is also negative, further increasing the likelihood of above average spring rainfall across Australia. A positive Southern Annular Mode (SAM) is also contributing to increased rainfall in eastern NSW.

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 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 (1961-1990; Figure 2a). Above average rainfall has been received across most of NSW in September. The highest positive rainfall anomalies were recorded in the North Coast, Northern Tablelands and North West LLS regions. The lowest negative rainfall anomalies occurred in the far north-west of NSW, to the north and west of White Cliffs, and to the east of Goulburn in the South East LLS region.

The highest rainfall totals were recorded in the North Coast LLS region around Coffs Harbour where rainfall of more than 300mm has been received (Figure 2b). The far north-west of the Western LLS region received less than 25mm of rainfall. For the calendar year to date coastal NSW has received between 600mm to above 2000mm of rainfall. Rainfall west of the Great Dividing Range has totalled between 100mm and 600mm (Figure 2c). Year to date rainfall has been average to above average for most of NSW and very much above average for coastal NSW.

Temperature

Below average maximum temperatures were experienced across most of NSW in September (Figure 3a). Average to slightly warmer than average maximum temperatures were recorded in south-eastern NSW south of Wagga Wagga and Bega. The average September maximum temperatures ranged from 3°C in the southern alps to more than 24°C in parts of northern NSW. Most of northern NSW experienced day time temperatures above 21°C, except for parts at higher altitudes. Central and southern NSW experienced average day time temperatures below 21°C (Figure 3b).

September minimum temperatures for NSW were above average for most of NSW. Parts of the far west and east of the Western LLS region experienced below average overnight temperatures (Figure 3c). The average September minimum temperatures (Figure 3d) ranged between -3°C to 3°C in the southern alps. The north coast of NSW recorded the highest average minimum temperature of above 12°C. Minimum temperatures in the Tablelands ranged from -3 to above 6°C. In September the extent of frost across NSW was significantly reduced from August, and predominantly occurred in south eastern NSW (Figure 3e).

Normalised Difference Vegetation Index (NDVI) Anomaly

The seasonal Normalised Difference Vegetation Index (NDVI, Figure 4) indicates that plant greenness levels are close to normal, to well above normal across most of NSW for the July to September period. Slightly lower than normal plant greenness remains evident across parts of the Central West and North West LLS regions, whilst levels of plant greenness continue to noticeably improve in western NSW. Some of the extremely negative NDVI areas (brown patches) are water bodies. White areas shown on the map in the North West, Riverina, and Murray LLS regions are due to cloud cover.

NSW Farm Dam Survey

The NSW Farm Dam Survey indicates dam levels are generally greater than 60% of capacity across central, eastern, and parts of western NSW (Figure 5). Parts of the Western, Riverina and Murray LLS regions of NSW maintain farm dam levels at less than 20% of capacity. Data is unavailable for significant areas of NSW due to cloud cover.

Soil Water Index

The Soil Water Index (SWI, Figure 6) indicates the majority of NSW is currently in the above average category. Due to the high rainfall in September large areas of central and eastern NSW have moved into the extremely high category. Areas of the Western, North West, Riverina and Murray LLS regions previously in the average category have also moved into the above average soil water category as landscapes become more saturated.

Plant Growth Index

The Plant Growth Index (PGI, Figure 7) indicates that the majority of NSW is in the above average category at the end of September. Areas of central, north eastern and south eastern NSW have moved into the extremely high category due to high rainfall and milder spring temperatures. Some areas of central and south-eastern NSW in the extremely high category also reflect the SWI.

Rainfall Index

The Rainfall Index (RI, Figure 8) indicates that at the end of September most of NSW is in the above average category or extremely high categories. This is due to the above average rainfall received in September and also reflects the distribution of above average rainfall 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 a strong wetting trend throughout eastern and parts of southern NSW. Both weak and strong drying trends can be seen in western, northern, and parts of coastal NSW. The drying trends are a result of extremely high rainfall recorded in late summer and early Autumn of 2022 and the comparatively drier conditions in the last month, despite the above average rainfall received across NSW in September. Importantly the weak to strong drying trend does not indicate the emergence of a drought in the regions, rather it indicates a degree of drying following on from the very wet summer and 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 (LLS) region to 30 September 2022. The following regional descriptions are based on data available until the end of September 2022.

Murray and Riverina regions

The Combined Drought Indicator (CDI, Figure 11) shows that all of the Riverina and Murray Local Land Services (LLS) regions remain in the Non-Drought category at the end of September.

The seasonal NDVI anomaly data (Figure 12) shows that most of the Murray and Riverina regions were experiencing higher than normal plant greenness levels for the July to September period. Some of the extremely negative NDVI areas (brown patches) represent water. White areas are missing data due to cloud cover.

The time series charts (Figure 13) show the individual response of the drought indices for Hay, Temora, Finley, and Moulamein. Temora continues to have high soil water, plant growth and rainfall indices. Above average September rainfall and below average temperatures have contributed to improved conditions in Hay, Finley, and Moulamein and they remain in the Non-Drought category. 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 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 all of the region is in the Non-Drought category. Rainfall throughout the region in September has meant that minor to major flood alerts are in place. However, this rainfall has not been uniform throughout the region and some parts currently have low farm dam levels. The DPI continues to closely monitor conditions in Western LLS.

The seasonal NDVI anomaly data (Figure 15) shows normal to very high levels of plant greenness across the Western LLS region for the July to September period. Flood affected areas may be represented by lower levels of greenness. Some of the extremely negative NDVI areas (brown patches) may represent water.

The time series charts (Figure 16) show the individual response of the drought indices for Bourke, Ivanhoe, Wentworth, and Broken Hill. Average to high soil water, plant growth, and rainfall indices are evident at all locations, and recent rainfall has resulted in an increase in the indices. Parts of the region with saturated soils and high dam levels continue to face production challenges due to flooding and continued wet and cool conditions during winter. 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 Combined Drought Indicator (CDI, Figure 17) shows that the North West, Northern Tablelands and North Coast Local Land Service regions are in the Non-Drought category. Heavy rainfall experienced in September has resulted in flooding to some parts of these regions.

The seasonal NDVI anomaly data (Figure 18) indicates near to above-normal greenness across most of the regions for the July to September period. Parts of the Northern Tablelands have average to well below average levels of greenness. Flood affected areas may be represented by lower 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 white area between Gunnedah and Quirindi in the North West is missing data due to cloud cover.

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 Combined Drought Indicator (CDI; Figure 20) 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 September. Heavy rainfall experienced in September resulted in flooding to some regions.

The seasonal NDVI anomaly data (Figure 21) shows near normal to high levels of plant greenness across most of the LLS regions for the July to September period. Parts of each region have average to well below average levels of greenness. Flood affected areas may be represented by lower 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 time series charts (Figure 22) show the individual response of the drought indices for Cowra, Condobolin and Singleton. The CDI indicators remain high at all locations. On-going wet conditions over an already saturated landscape and cooler temperatures continue to provide productivity challenges with respect to infield management, lower pasture growth rates and maintaining animal welfare. To access a time series for your Parish, visit the Combined Drought Indicator website.

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 the South East Local Land Services region remains in the Non-Drought CDI category. Generally these are productive conditions however, above average rainfall experienced in September has resulted in saturated landscapes and very wet conditions.

The seasonal NDVI anomaly data (Figure 24) showed near normal to high levels of plant greenness have increased across the region in the July to September period. Flood affected areas may be represented by lower 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 time series charts (Figure 25) show the individual response of the drought indices at Bega, Goulburn and Cooma. The three regions are in the Non-Drought category with high soil water, plant growth and rainfall indices. The on-going cool and wet conditions continue to provide production challenges with respect to saturated soils, lower pasture growth rates and maintaining animal welfare. 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.

Official national outlook

The official national outlook was released by the Bureau of Meteorology (BoM) on 27 September 2022. Rainfall during October to December is likely to be above median for the eastern half of Australia. The risk of flooding remains high for eastern Australia due to high soil moisture, high stream flows, and predicted above median rainfall.

Maximum temperatures are likely to be cooler than average for eastern Australia during the October to December period. Day time temperatures for Tasmania, northern and south west Australia are likely to be warmer than median. Overnight minimum temperatures for October to December are likely to be warmer than median across south eastern and northern Australia, and along the west coast. Cooler overnight minimum temperatures are forecast for south eastern Queensland and north eastern NSW.

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

NSW outlook

Most of NSW has an above 70% chance of receiving above median rainfall between November and January. South eastern NSW has an above 80% chance of receiving above median rainfall, whilst parts of northern, western and central coast of NSW have a slightly lower forecast of 65 to 70% chance of above average rainfall between November and January (Figure 26).

The maximum temperature outlook indicates a less than 20% chance of warmer than median temperatures across the eastern half of NSW. There is a 30% chance of above median maximum temperatures in central NSW increasing to a 50% chance in southern and western NSW (Figure 27).

There is a 70% to above 80% chance of warmer than median overnight temperatures across southern and western NSW. Most of north eastern NSW has a 50% chance of warmer overnight temperatures (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 27 September 2022. The ENSO status is currently at La Niña. Atmospheric and oceanic indicators such as the SOI, tropical Pacific sea surface temperatures and cloudiness near the Date Line are all representative of an established La Niña. Climate models suggest that this La Niña event may peak in Spring and return to a neutral ENSO in early 2023.

Southern Oscillation Index

The 30-day Southern Oscillation Index (SOI; Figure 29) for the 30 days ending 25 September was +19.2. The 90-day SOI value was +11.5. 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 cooler than average along the equator in the tropical Pacific Ocean and along most of the South American coastline. Warmer than average SSTs continue to strengthen around the Maritime Continent and northern Australia (Figure 30).

The latest values of the three NINO indices in the tropical Pacific for the week ending 25 September were: NINO3 -0.6 °C, NINO3.4 -0.7 °C, NINO4 -0.6 °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 22 September 2022) shows cool anomalies to 150m depth in the central and eastern equatorial Pacific Ocean (Figure 31). Warm anomalies between 100m and 250m depth persist west of the International Date Line. Cool anomalies observed in the central to eastern Pacific sub-surface in August, remained throughout September.

Indian Ocean (IOD)

The Indian Ocean Dipole (IOD) is negative. All five international climate models surveyed by the Bureau of Meteorology indicate that the negative IOD will continue through Spring. A negative IOD increases the likelihood of above average winter-spring rainfall and cooler days for eastern Australia. The latest weekly value of the Indian Ocean Dipole (IOD) index to 25 September 2022 was -0.78 °C.

Southern Ocean (Southern Annular Mode – SAM)

The Southern Annular Mode (SAM) index is positive (as of 30 September) and is expected to remain generally positive throughout spring (Figure 32). A positive SAM has a drying influence on parts of south-east Australia but increases the chance of rainfall in eastern NSW.

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.

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 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.