NSW State Seasonal Update - December 2022

Prepared by NSW DPI

NSW overview

December rainfall was below average for most of NSW. However, parts of the state in the west continue to experience flooding as water moves across saturated landscapes and through river systems. The NSW DPI Combined Drought Indicator (CDI) shows 100% of NSW in the Non-Drought category at the end of December.

Soil water, plant growth, and rainfall indices have remained high across the state, despite the comparatively drier conditions in December.

Water availability for production remains strong, with high soil moisture, and many on-farm dam levels and irrigation schemes at full capacity. However, below average rainfall in December has seen dam levels fall in some areas particularly in the northwest of the state.

Seasonal climate forecasts indicate warmer than average days in the north, south and west of NSW, and average to cooler than average day time temperatures in parts of the east for the February to April period. Overnight temperatures are likely to be average to warmer than average during this period. Rainfall is likely to be average across most of NSW, above average along the coast, and below average in western NSW between February to April. The ENSO Outlook status is at La Niña. The Indian Ocean Dipole (IOD) is neutral, with a low likelihood of influencing Australian climate in the next few months.

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). Below average rainfall has been received across most of NSW in December. The highest negative rainfall anomalies were recorded in the North Coast, Northern and Central Tablelands, Hunter, Greater Sydney and South East LLS regions. Positive rainfall anomalies were observed in the Western and South East LLS regions.

The highest monthly rainfall totals in December were recorded in the southern alpine regions and parts of the North Coast where rainfall of more than 100mm was received (Figure 2b). Most of NSW received rainfall of more than 25mm in December with parts of the northeast and southeast NSW receiving at least 50mm. For the calendar year from 1 January to 31 December 2022 most of coastal NSW received between 1000mm to above 2400mm of rainfall. Rainfall west of the Great Dividing Range totalled between 300mm and 1400mm (Figure 2c). Year to date rainfall from 1 January to 31 December 2022 was 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 December (Figure 3a). Maximum temperatures were 2 to 3 degrees below average in central NSW. In December the average maximum temperatures ranged from 12°C in the southern alps to more than 33°C in parts of north western NSW. Most of central NSW experienced day time temperatures above 24°C, except for parts at higher altitudes. The Tablelands and southeast NSW experienced average day time temperatures below 24°C (Figure 3b).

Minimum overnight temperatures were below average across all of NSW, particularly in the Central West and North West LLS regions, in December (Figure 3c). The average December minimum temperatures (Figure 3d) ranged between 0°C to 9°C in the southern alps. The far northwest of NSW recorded the highest average minimum temperatures of above 18°C. Minimum temperatures in the Tablelands ranged from 3 to above 6°C.

In December the extent of frost was limited to the southern alpine regions of NSW (Figure 3e).

Normalised Difference Vegetation Index (NDVI) Anomaly

The seasonal Normalised Difference Vegetation Index (NDVI, Figure 4) indicates that plant greenness levels are normal to well above normal across most of NSW for the October to December 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 greater than 40% of capacity across central and eastern NSW (Figure 5). Large areas of the Western LLS region, particularly along the Darling River, have dam levels at greater than 80% capacity. 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 that most of NSW is currently in the extremely high category due to the high rainfall received over the past several months prior to the drier conditions in December.

Plant Growth Index

The Plant Growth Index (PGI, Figure 7) shows that most of NSW is in the extremely high category at the end of December due to the high Spring rainfall. Some areas of coastal, northeast and southern NSW show an average to above average Plant Growth Index due to the lower December rainfall and warming Summer temperatures.

Rainfall Index

The Rainfall Index (RI, Figure 8) for 2022 shows that at the end of December most of NSW continues to be in the extremely high category due to the above average rainfall received over the past several months. Drier December conditions have resulted in some areas showing pockets of average to above average Rainfall Index 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 drying trend throughout most of central and eastern NSW. Both weak wetting and drying trends can be seen in parts of the Western and the South East LLS regions. The drying trends are a result of extremely high rainfall recorded earlier in 2022 and the comparatively drier conditions in the few last months. 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 previous very wet conditions in these central and coastal regions.

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 2022. The following regional descriptions are based on data available until the end of December 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 December. Rainfall received throughout the region in December, combined with rainfall received over past months has led to minor to moderate flood alerts for the Murray and Murrumbidgee Rivers.

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 October to December period. Some of the extremely negative NDVI areas (brown patches) represent water.

The Drought History charts (Figure 13) show the individual response of the drought indices for Hay, Temora, Finley, and Moulamein. The indicators are high at all locations due to continued rainfall in December and below average daytime and overnight temperatures. 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 14) shows that all of the Western LLS region is in the Non-Drought category. Rainfall throughout the region in December and the flow of water through the river systems has meant that minor to major flood alerts are currently in place for the Lachlan, Darling, and Murray rivers as flood waters accumulated in upstream catchments flow downriver resulting in flooding and isolation of downstream communities.

However, rainfall has not been uniform 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 October to December period. Some of the extremely negative NDVI areas (brown patches) represent water.

The Drought History charts (Figure 16) show the individual response of the drought indices for Bourke, Ivanhoe, Wentworth, and Broken Hill. The indicators are high at all locations. 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 17) shows that the North West, Northern Tablelands and North Coast Local Land Service regions are in the Non-Drought category.

The seasonal NDVI anomaly data (Figure 18) indicates normal to above-normal levels of greenness across most of the regions for the October to December period. Parts of the North West LLS region has 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 Drought History charts (Figure 19) show the individual response of the drought indices for Tenterfield, Moree, Walgett,and Lismore. The indicators remain high at all locations. 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 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 December.

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. 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 Drought History charts (Figure 22) show the individual response of the drought indices for Cowra, Condobolin and Singleton. The CDI indicators remain 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 23) shows that the South East Local Land Services region remains in the Non-Drought CDI category.

The seasonal NDVI anomaly data (Figure 24) showed near normal to high levels of plant greenness have increased across the region in the October to December 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 Drought History charts (Figure 25) show the individual response of the drought indices at Bega, Cooma and Goulburn. The three regions are in the Non-Drought category with high soil water, plant growth and rainfall indices. 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.

Official national outlook

The official national outlook was released by The Bureau of Meteorology on 5 January 2023. The rainfall outlook for February to April shows that much of Australia has a near equal chance of above or below median rainfall.

Maximum temperatures are likely to be cooler than average for New South Wales central coast and far eastern Victoria, and likely to very likely to be above median for the rest of Australia. Above median minimum temperatures are expected for most of Australia for the 3-month period between February to April. Except northeastern NSW and the Great Australian Bight where there is an equal chance of above or below median minimum temperatures.

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

NSW outlook

The east coast of NSW has a greater than 55% chance of receiving above median rainfall between February and April. The far west and parts of central NSW have a less than 45% chance of receiving above median rainfall. In general, the rest of NSW has a near equal chance of above or below median rainfall over the 3-month period (Figure 26).

The maximum temperature outlook indicates a less than 20% to 50% chance of warmer than median daytime temperatures in for most of eastern NSW. The chance of warmer than median daytime temperatures increases in parts of the north, south and towards the west; there is up to a 75% chance of above median maximum temperatures in the Western and South East LLS regions (Figure 27).

There is a 45% to above 80% chance of warmer than median overnight temperatures across NSW during the February to April period (Figure 28). The highest chance of above median overnight temperatures is in south eastern NSW.

Global climate drivers

El Niño–Southern Oscillation (ENSO)

The Bureau of Meteorology’s El Niño-Southern Oscillation (ENSO) Outlook was released on 4 January 2023. The ENSO Outlook status is currently at La Niña. La Niña typically increases the chance of above average rainfall in eastern Australia in summer. Climate models suggest a possible return to neutral ENSO conditions in early 2023.

Southern Oscillation Index

The 30-day Southern Oscillation Index (SOI; Figure 29) for the 30 days ending 2 January was +20.0. The 90-day SOI value was +14.3. 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 central and eastern tropical Pacific Ocean. Cool anomalies have developed off the east coast of Australia, south of the Gold Coast. Warm anomalies continue around the Maritime Continent, northern Australia, and in the Coral Sea to the north-east of Australia (Figure 30).

The latest values of the three NINO indices in the tropical Pacific for the week ending 1 January were: NINO3 -0.5 °C, NINO3.4 -0.6 °C, NINO4 -0.5 °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 1 January 2023) shows cool anomalies to 150m depth in the eastern equatorial Pacific Ocean (Figure 31). Warm anomalies between 100m and 250m depth persist west of 160^oW.

Indian Ocean (IOD)

The Indian Ocean Dipole (IOD) is currently neutral. All of the five international climate models surveyed by the Bureau of Meteorology indicate that a neutral IOD will continue through January and February and into autumn. Whilst the monsoon trough is in the southern hemisphere from December to April, the IOD has little influence on Australia’s climate. The latest weekly value of the Indian Ocean Dipole (IOD) index to 1 January 2023 was +0.07 °C.

Southern Ocean (Southern Annular Mode – SAM)

The Southern Annular Mode (SAM) index is positive (as of 06 January) and is expected to be remain positive through to mid-January (Figure 32). In summer a positive SAM increases the chance of above average 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 their 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 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 (2023), Panorama Avenue, Bathurst 2795 and data which is © Commonwealth of Australia 2023, 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.