NSW State Seasonal Update - April 2021

Prepared by NSW DPI

NSW overview

April 2021 rainfall was below average across much of NSW resulting in a drying of surface soil in pastoral and cropping regions. Despite the drying event, recovery from the 2017-2020 drought continued across most of the state. Stored sub-soil moisture levels are relatively high and limit the on-farm impact of dry April conditions, and much of the state continues to have a strong production outlook.

The NSW DPI Combined Drought Indicator (CDI) shows 83% of NSW is in the Recovery or Non-Drought categories. Despite a favourable production outlook in most regions, parts of western, south-west, south-east and north-eastern NSW continue to face variable, weak or delayed recovery from drought. The NSW CDI showed an increase in the Drought Affected category since March, particularly to the south of the state. Rain is still needed to build confidence of long-term recovery from drought in these areas.

The 2021 winter crop sowing program has commenced. Sub-soil moisture levels are generally high across most grain regions, however surface conditions dried in April. Rain will likely be needed for further sowing, as the main window approaches in May-June.

The first frost events of the season were recorded in April. Pasture production is expected to slow, especially in Slopes and Tableland regions as winter approaches. Early fodder crops have experienced good growing conditions despite lower rainfall totals in April.

Flood water continues to move through the western NSW Murray-Darling system following significant rainfall in March, while the clean-up from flooding in north-eastern NSW continues. Water storage levels in the northern valley reservoirs has increased over recent weeks and is now around 44% of capacity. The NSW Farm Dam Survey has shown localised improvement since March, though dam levels in parts of southern and south-western NSW remain low.

The latest Bureau of Meteorology (BoM) Seasonal Outlook indicates near equal to high chances of above median rainfall across NSW for the next three months. The La Niña event in the Pacific Ocean has concluded and global climate drivers remain in a neutral state. The neutral status is expected to remain throughout winter at this stage. Historically, forecast skill for the seasonal outlook is lower during autumn.

The CDI and its individual rainfall, soil moisture and crop/pasture growth metrics are leading biophysical indices of drought. While the CDI points to a strong recovery and transition out of biophysical drought for much of NSW, production and economic responses usually lag the CDI. Full drought recovery can occur over an extended time and depends on several factors including rainfall. Further information about the correct interpretation of the CDI at a region and industry level is provided in the regional breakdown section of this report.

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

Rainfall

The rainfall anomaly data shows the difference between total monthly rainfall and the long-term average (1961-1990; Figure 2a). Most of NSW received below average rainfall with deficiencies of greater than 25mm. The largest negative anomalies were along the south NSW coast. A small area in the northeast of the state received slightly above average rainfall. Large areas of the state received less than 25mm during April (Figure 2b). The highest rainfall totals were in the north-east of the state (up to 200mm along the North Coast).

Rainfall accumulation during the 2021 calendar year has been near or above average across most of NSW. Most of coastal NSW has received accumulated totals of 400-1200mm for the year (Figure 2c) while central areas west of the Great Dividing Range have received 200-400mm. Large parts of the of Western LLS region have received up to 200mm in the year. The far south-west area has accumulated totals between 25-50mm of rain.

Temperature

Average maximum temperature anomalies were slightly below average across much of the north of the state and slightly above average in the south of the state (Figure 3a). The average March maximum temperatures were generally above 21°C across NSW and cooler in NSW’s Tableland regions (Figure 3b).

Minimum temperatures were below average across most of NSW, with negative anomalies in excess of 3°C across some central regions (Figure 3c). Mean minimum temperatures ranged between 3-15°C, except for the high Tableland and Alpine regions that ranged between 0-3°C (Figure 3d).

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 February to April period. Lower than normal plant greenness remains evident in some areas of the Central Tablelands, South East and Alpine areas that were affected by the 2019/20 bushfires.

NSW Farm Dam Survey

Rainfall in late March has improved dam levels across northern, central and eastern NSW (Figure 5). There are still areas where farm dam levels are less than 20% of capacity, especially across western and southern NSW.

Soil Water Index

The Soil Water Index (SWI, Figure 6) indicates the majority of NSW is currently at below average to average levels. Large areas of southern, western and northern NSW have transitioned into the below average category since the March Update. This has been driven by dry April conditions. DPI continues to monitor conditions closely across NSW.

Plant Growth Index

The Plant Growth Index (PGI, Figure 7) indicates that the majority of NSW is currently at below average or average levels at the end of April. This reflects the changes that have been reported in the SWI.

Rainfall Index

The Rainfall Index (RI, Figure 8) indicates that NSW is currently in the below average or average category. This reflects the cumulative rainfall totals that have been received during 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 most of the state ranges from a neutral to strong drying trend. This is driven by the dry conditions during April.

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 30 April 2021. The following regional descriptions are based on data available until the end of April 2021.

Murray and Riverina regions

The Combined Drought Indicator (CDI; Figure 11) shows that large areas of the Riverina and Murray Local Land Services (LLS) regions transitioned into the Drought Affected category during April. The dry conditions over April have driven this response. As the region enters the winter crop sowing window, DPI continues to monitor conditions closely.

The seasonal NDVI anomaly data (Figure 12) shows that most of the region was experiencing near to or higher than normal plant greenness levels for the February to April period. Plant greenness levels are slightly lower than expected near the Victorian border in the Murray LLS region. 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 conditions steadily improved during 2020 and highlights the effectiveness of more consistent follow-up rainfall. At Moulamein and Finley, the improvement to conditions occurred later in 2020 due to lower rainfall, especially in the winter period. Rain in mid Spring improved the indices, however recently there has been a decline in the indicators. Continued rainfall is needed to support drought recovery in 2021.

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.

Western region

The Combined Drought Indicator (CDI; Figure 14) shows that large parts of the Western Local Land Services region transitioned into the Drought Affected category during April. The dry conditions over April have driven this response. This transition into the Drought Affected category highlights the need for further follow up rainfall to support long term drought recovery. Other areas in the LLS region remain in the Non-Drought category. Further rainfall will continue to support drought recovery in these regions.

The seasonal NDVI anomaly data (Figure 15) shows most of the region experiencing near to or higher than normal plant greenness levels for the February to April period. Plant greenness levels are slightly lower than expected in 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 generally improved at all locations during 2020, however have dried during the first four months of 2021. The DPI continues to monitor conditions 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 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

Conditions are variable across the North West, Northern Tablelands and North Coast Local Land Services regions, as indicated by the Combined Drought Indicator (CDI; Figure 17). Despite rain during the month, there are still areas in the Drought Affected category. The Soil Water Index remains below average in many northern areas of these regions. The risk of a “false recovery” remains in some areas. Continued follow-up rain is needed for a full transition to longer-term drought recovery. The NSWDPI continues to monitor conditions closely across the region.

The seasonal NDVI anomaly data (Figure 18) indicated near-normal to above expected greenness anomalies across most of the region for the February to April period. The plant greenness anomaly remains below normal levels in parts of central and northern areas of the Northwest LLS region.

The time series charts (Figure 19) show the individual response of the drought indices for Moree, Walgett, Tenterfield and Lismore. Tenterfield has seen recent improvement in the indicators, driven by rainfall since February. The other three locations’ Non-Drought status continue to be driven by the Rainfall Index. 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 continued drought recovery during April and most of the region remains in the Non-Drought CDI category (Figure 20). Given the strength of recovery over the last 12-months, these regions are well positioned for full production in the coming seasons.

The seasonal NDVI anomaly data (Figure 21) continues to show above average levels of plant greenness across most of the LLS regions for the February to April 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 has improved the indicators at all locations and shows that drought recovery remains strong. These regions currently remain well placed for a productive 2021.

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) indicates that the majority of the South East Local Land Services region is in the Non-Drought CDI category (Figure 6). Some southern parts of the region continue to be in the Drought Affected category in April. These areas didn’t experience relief to drought until later in 2020. These areas didn’t experience relief to drought until later in 2020. The strong drought recovery across northern parts of the region that commenced in winter 2020 has continued during autumn.

The seasonal NDVI anomaly data (Figure 24) showed higher than expected levels of plant greenness across most of the region for the February to April period. The areas impacted by the 2019/20 bushfires continued 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 the gradual improvement in conditions, however the agronomic recovery at Cooma and Bega has lagged in comparison to Goulburn. Considering the long duration of Intense Drought conditions during 2020, the NSW DPI continues to monitor the South East region closely.

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 latest official national outlook was released by the Bureau of Meteorology (BoM) on 29 April 2021. Rainfall during May to July is likely to be close to or above average across the southern half of mainland Australia. Western Tasmania and the northern tropics of Australia are likely to be drier than average during the May to July period. May marks the start of the northern Australian dry season and this means that northern Australia typically receives very low rainfall totals.

Maximum temperatures for May to July are likely to exceed median across most of Australia. Central and south-eastern Western Australia have equal chances of warmer or cooler than median maximum temperatures. Minimum temperatures are also likely to exceed median across southern Western Australia, western and south-east South Australia, eastern NSW, southern Victoria and Tasmania. Most other regions have equal chances of warmer or cooler than median minimum temperatures.

NSW outlook

NSW has a near equal to high chance of receiving above median rainfall in the May to July period (Figure 26). The daytime temperature outlook indicates a moderate to high chance of temperatures being above median (Figure 27). There is a moderate to high probability of warmer than median overnight temperatures across NSW during the next three months. (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 April 2021. The ENSO Outlook status is currently in the Inactive phase. Currently, models indicate ENSO will remain neutral until the end of the winter.

The Madden–Julian Oscillation (MJO) has moved out of the Australian region and is currently over tropical America. It is expected to more eastwards towards Africa over the coming weeks.

Southern Oscillation Index

The 30-day Southern Oscillation Index (SOI) for the 30 days ending 25 April was +0.5. The 90-day SOI value was +6.0. Both the 30 and 90-day values are in the ENSO-neutral range.

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.

Sea surface temperatures (SST)

The monthly sea surface temperatures (SST) were normal to slightly cooler than average across parts of the central and eastern tropical Pacific Ocean during April (Figure 30). Warm anomalies remain around the Maritime Continent and in the waters around northern and western and parts of southern Australia.

The latest values of the three NINO indices in the tropical Pacific for the week ending 25 April were: NINO3 −0.2 °C, NINO3.4 −0.3 °C, NINO4 −0.0 °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 22 April) shows weak cool anomalies across the top 50 to 100m of the central and eastern equatorial Pacific. The strength and extent of cooler than average water has decreased compared to March and is typical of the break-down of La Niña. Warm anomalies remain across the column depth west of the International Date Line, though have decreased in strength and extent since March.

Indian Ocean (IOD)

The Indian Ocean Dipole (IOD) is neutral. The latest weekly value of the IOD index to 25 April was +0.32 °C. The IOD typically has little influence on Australian climate from December to April. When the monsoon trough shifts southwards into the southern hemisphere at this time of year, it changes the broadscale wind patterns. This means that the IOD pattern is unable to form.

Southern Ocean (Southern Annular Mode – SAM)

The Southern Annular Mode (SAM) is currently neutral and expected to remain neutral for the coming fortnight. A neutral SAM has little influence on Australian rainfall. The SAM typically has less influence on rainfall in autumn than other times of the year.

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.