NSW State Seasonal Update - February 2021



Prepared by NSW DPI

NSW overview

Drought recovery continued across most of NSW in February 2021. February rainfall strengthened recovery across much of central and eastern NSW. Many of these areas remain well placed for 2021 and conditions favourable for agricultural production are highly likely to continue. The NSW DPI Combined Drought Indicator (CDI) shows 94% of NSW is in the Recovery or Non-Drought categories. The official climate outlook indicates near equal to moderate chances of above median rainfall across NSW in the next three months.

Despite improvements, the strength of recovery remains inconsistent. Weak recovery and the risk of ‘false recovery’ continues to affect some isolated areas of NSW. Far western NSW experienced dry conditions in February and a low confidence of drought recovery continues. Similar scenarios remain in place for parts of the North West, Northern Tablelands, North Coast, and South East Local Land Services (LLS), where weak drought recovery continues.

The NSW Farm Dam Survey indicates that surface water deficits have intensified across many farms in these western and north-eastern areas. There has been no substantial improvement to large reservoirs or irrigation water availability in northern NSW during February. This is largely due to normal seasonal patterns with high evaporative demand at the end of summer, but in some areas, it is also driven by rainfall deficits. Full recovery from drought can take 6-18 months of favourable seasonal conditions and depends on the consistency of rainfall. Follow-up rainfall is required throughout 2021 in these regions to build the chances of longer-term drought recovery.

The latest official global climate drivers update provided by the Bureau of Meteorology (BoM) indicates the La Niña event in the tropical Pacific Ocean has peaked, however is expected to remain a key influence on NSW weather in the short-term. It is important to remember that the historical skill of the seasonal forecasts begins to decline at this time of year. Local synoptic patterns are expected to have a large bearing on rainfall variability in the coming months. The official BoM Seasonal Outlook released on 25 February 2021 indicates near equal to moderate probabilities of above median rainfall across NSW for the next three months.

The CDI and its individual rainfall, soil moisture and crop/pasture growth metrics are leading biophysical indices of drought. While the CDI currently points to a strengthening recovery and transition out of biophysical drought for large areas of NSW, production and economic responses lag behind the CDI. Full drought recovery can take an extended period of time depending on a number of influences 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.

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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 central and eastern NSW received near or above average rainfall for February. The largest anomalies of 100-200mm above average were received in parts of the mid-north coast region. Rainfall was below average in parts of western NSW, the far north-east and the South Coast.

Most of central and eastern NSW received more than 50mm of rainfall in February (Figure 2b). The highest totals occurred over parts of the north coast (200-400mm).  Western NSW received low totals (0-25mm) during the month.

Rainfall accumulation during the 2021 calendar year has been near or above average across most of the central interior of NSW and in isolated parts of the north-coast. Elsewhere rainfall during 2021 has been below average. Most of NSW has received accumulated totals above 50mm for the year. Parts of the North Coast have received greater than 300mm for the year.

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Temperature

Maximum temperatures in February were below average across most of the NSW (Figure 3a). Some areas in north-eastern NSW received temperatures that were 0-1°C higher than average. The average maximum temperatures recorded in February (Figure 3b) were warmest across northern-western NSW (above 33°C). Elsewhere temperatures ranged between 27-33°C, while the tablelands, the south-east and alpine regions experienced lower maximum average temperatures between 18-24°C.

Minimum temperature anomalies were below average across most of the state, however the coast and parts of northern NSW received temperatures that were 0-1°C higher than average (Figure 3c). Most of NSW experienced average minimum temperatures above 15°C during the month (Figure 3d). Temperatures were cooler in the state’s Tablelands areas extending to the southern areas of the Murray LLS regions. The higher altitudes in the Central Tablelands and Alpine areas received minimum temperatures of 6-12°C.

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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 December to February period. The data shows the high level of variability within and between regions. 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.

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NSW Farm Dam Survey

The data from the NSW Farm Dam survey (Figure 5) indicates large areas where farm dam levels are less than 20% of capacity, especially across the western, southern and northern NSW. The data indicates the need for further rain to adequately account for evaporation and usage across large areas of the state. Farm dam levels tend to be at higher capacities in central and parts of eastern NSW.

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Soil Water Index

The Soil Water Index (SWI, Figure 6) indicates the majority of NSW is currently at average or above average levels. Isolated parts of western and southern NSW continue to experience below average SWI values. The area in the below average category in Northern NSW has expanded. DPI continues to monitor conditions closely across NSW.

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Plant Growth Index

The Plant Growth Index (PGI, Figure 7) indicates that the majority of NSW is currently at average or above average levels at the end of February. Some isolated parts of the south-east and-north east continue to experience below average to extremely low plant growth values.

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Rainfall Index

The Rainfall Index (RI, Figure 8) indicates that NSW is currently in the average or above average range. This reflects the cumulative rainfall totals that have been received during the last 12 months. Parts of northern NSW have transitioned into the below average category during February.

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Drought Direction Index

The Drought Direction Index (DDI, Figure 9) tracks the 150-day trend of daily rainfall totals. The DDI indicates that the majority of the state ranges from a neutral to strong wetting trend. Areas in western NSW, the south-east and northern Hunter are showing a neutral to strong drying trend.

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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 regions to 28 February 2021. The following regional descriptions are based on data available until the end of February 2021.

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Murray and Riverina regions

The Combined Drought Indicator (CDI; Figure 11) shows that the Riverina and Murray Local Land Services (LLS) regions continue to transition through a recovery from the 2017-20 drought event. Most of the regions are currently in the Non-Drought or Recovery CDI categories. Western parts of the Murray LLS region have transitioned into the Drought Affected category during February, primarily driven by a decrease in soil moisture reserves as indicated by the Soil Water Index (Figure 6). This region is being closely monitored as the winter crop sowing window approaches.

The seasonal NDVI anomaly data (Figure 12) shows that the region was experiencing near normal to higher than normal plant greenness levels for the December to February period. 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 over recent months. At Moulamein, the improvement to conditions occurred later in 2020 due to lower rainfall, especially in the winter period. Rain in mid Spring improved the indices. Follow-up rainfall is now needed at both Moulamein and Finley following a declining trend in the rainfall index during February.

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.

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For an accessible explanation of this map contact the author seasonal.conditions@dpi.nsw.gov.auMap

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Western region

The Combined Drought Indicator (CDI; Figure 14) shows that the Western Local Land Services region continues to show variability in conditions. Rainfall in the eastern parts of the region during February will continue to provide relief to drought conditions across the region. Further west, there was no widespread effective rainfall received in February. On-ground reports continue to describe the highly variable conditions and the need for continued rainfall.

The NSW DPI advises that conditions remain variable in the Western LLS region. Rainfall over recent months has begun recovery, however further rainfall is needed, particularly in areas where improvements have been more recent. The NSW Farm Dam survey (Figure 5) indicates that farm dam levels remain well below capacity across much of the region. Drought management continues amid hot conditions and further follow-up rain remains a key focus to secure a longer-term transition to drought recovery.

The seasonal NDVI anomaly data (Figure 15) shows variability in plant greenness levels across the region compared to long-term expectations for the December to February period. Some districts continue to experience well above normal levels of greenness while other districts experience below normal levels of greenness (brown areas on the map). Rainfall has been lower, later or less effective in these areas. In comparison to the January report, greenness levels have declined closer to expected values across the far western areas of the region.

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. A declining trend in the rainfall index during February indicates the need for follow-up rain to maintain any confidence of a longer-term recovery to drought. 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.

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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 beneficial rain received during recent months, the area in the Drought Affected category has increased. There is concern that parts of the region have experienced a “false recovery” from drought, particularly the region centred on Tenterfield. Conditions are deteriorating and there is a chance that some areas are now re-entering a severe drought. This highlights the importance of follow up rain for a full transition to longer-term drought recovery.

Elsewhere large areas continue to build recovery from the 2017-20 drought event, however relatively dry conditions in January and February have caused conditions to plateau in some areas.

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

The time series charts (Figure 19) show the individual response of the drought indices for Moree, Walgett, Tenterfield and Lismore. The most recent trends observed in the charts at the end of February highlight the risks of a potential false drought recovery when consistent follow-up rainfall is not received. While conditions have been slightly better at Walgett in recent months, the charts indicate the need for effective follow-up rainfall to drive a long-term recovery to drought.  The NSW DPI continues to monitor these 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.

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Central Tablelands, Central West, Hunter and Greater Sydney regions

The Central West, Central Tablelands, Hunter and Greater Sydney Local Land Services (LLS) regions continued a strong transition through drought recovery during February. Consistent follow-up rainfall since Autumn 2020 has aided a strong recovery in all four LLS regions (Figure 20).

The seasonal NDVI anomaly data (Figure 21) continues to show above average levels of plant greenness across large areas of the regions. The data indicates that improvements gained from rainfall received in 2020 continue to be maintained in most areas at the end of February. The 2019/20 bushfire impact is still evident in parts of the tablelands.

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 remained strong throughout Spring and Summer. 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.

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For an accessible explanation of this map contact the author seasonal.conditions@dpi.nsw.gov.auMap

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South East region

The Combined Drought Indicator (CDI; Figure 23) indicates that the majority of the South East Local Land Services region continues to maintain the recent improvement in conditions. Southern parts of the region transitioned back into the Drought Affected category during February. This was driven by a decrease in soil moisture reserves, as indicated by the Soil Water Index (Figure 6). The strong drought recovery across northern parts of the region that commenced in winter 2020 has continued during February.

The seasonal NDVI anomaly data (Figure 24) showed higher than expected levels of plant greenness across most of the region for the December to February period. The areas impacted by the 2019/20 bushfires continued to have lower than expected 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. Despite improvements, the areas in the south-east of the region would benefit from further follow-up rainfall; a longer duration of Intense Drought conditions persisted in this area later 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.

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Official national outlook

The latest official national outlook was released by the Bureau of Meteorology (BoM) on 25 February 2021. Autumn rainfall is likely to be above median for large parts of eastern Australia. Most of Western Australia, the Northern Territory, Victoria, South Australia, Tasmania and western parts of Queensland are likely to be close to average over the next three months.

Maximum temperatures for autumn are likely to be warmer than average for parts of northern Australia, western WA and the far south-east of Australia. Minimum temperatures are likely to be warmer than average for most of Australia, except for parts of the south and west.

NSW outlook

Most of NSW has a near equal to moderate chance of exceeding median rainfall in the autumn period (Figure 26). The chances of above median rainfall are slightly higher in the north-east of NSW. The daytime temperature outlook indicates a near equal to moderate chance of being below median across most of the state (Figure 27). There is a moderate to high probability of warmer than median overnight temperatures across NSW. (Figure 28).

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Global climate drivers

El Niño–Southern Oscillation (ENSO)

The Bureau of Meteorology’s (BoM) El Niño-Southern Oscillation (ENSO) Outlook was released on 2 March 2021. The 2020–21 La Niña has peaked and is now weakening. Climate model outlooks indicate the El Niño–Southern Oscillation (ENSO) are likely to return to neutral (neither La Niña nor El Niño) during autumn.

As the Pacific Ocean water temperatures return towards neutral values, the atmospheric indicators generally remain at La Niña levels. Trade winds continue to remain stronger than average. Generally, a sustained strengthening of these trade winds occurs during the development and throughout a La Niña event. Equatorial cloudiness near the Date Line has been below average since mid-March. Equatorial cloudiness near the Date Line typically decreases during La Niña. The Southern Oscillation Index was still above La Niña thresholds at the end of February.

While the influence of a La Niña event on Australian rainfall typically decreases during autumn, it can still bring above average rainfall to parts of northern and eastern Australia during the final months of the northern wet season.

Southern Oscillation Index

The 30-day Southern Oscillation Index (SOI) for the 30 days ending 28 February was +11.0. The 90-day SOI value was +15.3. Recent 30-day values have continued their gradual decline from a peak of around +20 maintained for much of early to mid-January, but continue to remain within La Niña thresholds.

Sustained positive values of the SOI greater than +7 are typical of a La Niña event.

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Sea surface temperatures (SST)

The monthly sea surface temperatures (SST) were cooler than average across most of the eastern tropical Pacific Ocean, and south of the equator during February (Figure 30). Warm anomalies remain around the Maritime Continent and in the waters close to parts of Australia, particularly the northern Coral Sea and east and south of Tasmania.

The latest values of the three NINO indices in the tropical Pacific for the week ending 28 February were: NINO3 −0.4 °C, NINO3.4 −0.8 °C, NINO4 −0.7 °C. All three NINO indices have warmed compared to two weeks ago.

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.

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Sea sub-surface temperatures

The four-month sequence of equatorial Pacific sub-surface temperature anomalies (to 25 February) shows cooler than average water extending across the top 200m of the sub-surface of the equatorial Pacific east of around 160°E. The strength of cooler than average water has remained consistent since September.

Warm anomalies persist across large parts of the column depth west of the International Date Line. These warm anomalies have strengthened month-on-month since October.

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Indian Ocean (IOD)

The Indian Ocean Dipole (IOD) is neutral. The latest weekly value of the IOD index to 28 February was −0.15 °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 Annual Mode (SAM) is currently positive but is expected to be neutral throughout March. The SAM typically has less influence on rainfall in autumn than during 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.

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How does it work?

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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

CDI Phase

Technical definition

Description - typical field conditions

Intense Drought

All three indicators (rainfall, soil water, plant growth) are below the 5th percentile

Ground cover is very low, soil moisture stores are exhausted and rainfall has been minimal over the past 6-12 months.

Drought

At least one indicator is below the 5th percentile

Conditions may be very dry, or agronomic production is tight (low soil moisture or plant growth). It is possible to be in Drought when there has been some modest growth, or a few falls of rain.

Drought Affected (intensifying)

At least one indicator is below the 30th percentile and the rainfall trend is negative over the past 90 days.

Conditions are deteriorating; production is beginning to get tighter. Ground cover may be modest, but growth is moderate to low for the time of year. When indicators are close to the Drought threshold drought conditions are severe.

Drought Affected (weakening)

At least one indicator is below the 30th percentile and the rainfall trend is positive over the past 90 days.

Production conditions are getting tighter, but there have been some falls of rain over the past month. It is rare to enter the Recovering phase from the Non-Drought category; Usually there is a quick (1-2 week) transition into Drought Affected or Drought. When indicators are close to the Drought threshold drought conditions are severe.

Recovering

All indicators are below the 50th percentile but above the 30th percentile

Production is occurring but would be considered ‘below average’. Full production recovery may not have occurred if this area has experienced drought conditions over the past six months.

Non-drought

At least one indicator is above the 50th percentile.

Production is not limited by climatic conditions.

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 (2020), Panorama Avenue, Bathurst 2795 and data which is © Commonwealth of Australia 2020, 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.