NSW State Seasonal Update - October 2020

NSW overview

Prepared by NSW DPI

NSW overview

Recovery from drought continued across large areas of NSW in October 2020. The NSW DPI Combined Drought Indicator (CDI) shows 88% of NSW is in the Non-Drought or Recovery categories. Favourable Spring conditions have supported recovery from the 2017-2020 drought in many regions. Rainfall and storm activity has caused damage and harvest difficulty for some winter crop districts and horticultural areas. The official climate outlook indicates moderate to high probabilities of above median rainfall across NSW for the next three months.

Most of NSW received average to well above average rainfall in October. This has supported high levels of Spring productivity, especially pasture growth, and increased the confidence of longer-term drought recovery in most regions. Most of the northern irrigation region has low stored water availability, though there have been reports of increased stream flows in some areas.

Heavy rain, storm and isolated hail damage has impacted the 2020 winter crop harvest. Yield and grain quality loss has occurred in some areas, especially in the north and western areas of the cropping zone. Crop lodging is also becoming an increasing problem across large areas. The current Seasonal Outlook signals further risk of storm damage and wet harvest conditions as more of the NSW winter crop reaches maturity. There have also been reports of storm related damage occurring to emerging summer crops.

Drier areas of the state, particularly in parts of western and north-eastern NSW received rain in October. Despite this, the variability between districts and farms remains evident and consistent follow up rain is still needed to increase the confidence of drought recovery.

The current three-month Seasonal Outlook from the Bureau of Meteorology (BoM) indicates moderate to high probabilities of above median rainfall across NSW. This is largely driven by the La Niña event occurring in the tropical Pacific which is forecast to persist into February 2021. La Niña is associated with above to well-above median rainfall during spring and summer, including the possibility of flood events.

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 6-18 months 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.

Drought Support

Producers and members of rural communities are encouraged to maintain contact with their local professionals who can facilitate access to appropriate support. If you or someone you know needs support, please visit DroughtHub. Alternatively, you can contact the DPI Rural Resilience Team, Rural Financial Counsellors, or your Local Land Services representatives.

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). Higher than average October anomalies were recorded throughout western and parts of central and eastern NSW. Rainfall was lower than average in the north-east, parts of central NSW and some coastal areas.

The majority of NSW received totals above 25mm during October (Figure 2b). Higher totals (above 100mm) were received across large areas of eastern NSW, while totals above 200mm were received in the alpine region and isolated coastal areas. Lower rainfall totals (below 25mm) were received in parts of central NSW.

Rainfall accumulation for 2020 has been near or above average across NSW. Large areas across eastern NSW have accumulated totals of above 600mm (Figure 2c). Higher totals of more than 1,000mm have been received along parts of the eastern seaboard, with some above 1,400mm in the North Coast and South Coast LLS regions, Blue Mountains and alpine region. The far west has received 100mm or more for the year, though the rainfall has been variable.

Temperature

Maximum temperatures in October were generally 0-3°C higher than average across most of NSW (Figure 3a). The average maximum temperatures recorded in October (Figure 3b) were warmest across northern NSW (above 24°C). Elsewhere temperatures ranged between 18-30°C and the alpine regions experienced maximum average temperatures between 9-18°C.

Minimum temperature anomalies for October were generally 0-3°C warmer than average across most of NSW (Figure 3c). Most of western and coastal NSW experienced average minimum temperatures above 12°C during the month (Figure 3d). Elsewhere minimum temperatures ranged between 6-12°C and were lower in some southern regions (3-6°C).

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 large areas of NSW for the August to October period. Parts of the South East continue to slowly respond to rainfall received in late winter and during Spring, while plant greenness levels remain variable in the Western LLS region. Low plant greenness remains evident in much of the bushfire affected areas of the Central Tablelands, South East and Alpine areas of the state.

NSW Farm Dam Survey

The latest data from the NSW Farm Dam Survey (Figure 5) indicates that dam levels in most central regions of the state are above 40% of capacity. There has been a rapid improvement to dam levels in the far west due to rainfall over recent weeks. Deficiencies of less than 20% of dam capacity remain evident in parts of the Western, Murray, Riverina, North West, North Coast and Northern Tablelands Local Land Services (LLS) regions.

Individual drought indicators

Soil Water Index

The Soil Water Index (SWI, Figure 6) continues to improve and the majority of NSW is currently at average or above average levels. Parts of western, northern and southern NSW continue to be experiencing below average to extremely low soil water values.

Plant Growth Index

The Plant Growth Index (PGI, Figure 7) response generally mirrors the SWI with large areas of the NSW in the average category at the end of October. However, parts of the far west, south-east and north-east continue to be experiencing below average to extremely low plant growth values.

Rainfall Index

Rainfall accumulation during 2020 has improved the Rainfall Index (RI, Figure 8) across NSW. The majority of NSW is currently in the average or above average category.

Drought Direction Index

The Drought Direction Index (DDI, Figure 9) tracks the 150-day trend of daily rainfall totals. The DDI shows that most of the state is displaying a weak to strong wetting trend. In contrast some coastal areas show a weak to strong drying trend over the last 150 days.

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

Monthly regional breakdown

CDI status for the regions

Figure 10 displays the CDI status for each individual Local Land Services regions to 31 October 2020. The following regional descriptions are based on data available until the end of October 2020.

Murray and Riverina regions

The Combined Drought Indicator (CDI) shows large areas of the Riverina and Murray Local Land Services (LLS) regions continue to transition through a recovery from drought conditions. October rainfall maintained good spring conditions with most of the region currently in the Non-Drought CDI category (Figure 11). Some areas in the south-west and around Tumut remain in the Drought Affected category. Further rain is needed to provide longer-term confidence for drought recovery in these areas. Heavy rain and storm damage has been reported in some winter cropping and horticultural areas.

The seasonal NDVI anomaly data (Figure 12) shows that the region is predominately experiencing near normal to higher than normal plant greenness levels for the August to October period. The impact of the recent 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 Hay, Finley and Temora charts show that conditions continue to improve and highlights the effectiveness of more consistent follow-up rainfall over recent months. The Moulamein chart shows that conditions plateaued during May to June due to less follow up rain. Rain in late October has recently improved the indices.

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

A number of high rainfall events have improved conditions across large areas of the Western Local Land Services (LLS) region over the last three months. Some areas are experiencing a productive Spring and are well placed for longer-term drought recovery. However there is considerable variation in on-ground conditions across the region, a result of rainfall patterns and land management. The Combined Drought Indicator (CDI) shows that most of the region is now in the Recovery or Non-Drought categories (Figure 14). This improvement highlights the importance of consistent follow-up rain for a longer-term transition towards drought recovery.

The NSW DPI advises that conditions remain variable in the Western LLS region. Recent rainfall has begun recovery, however further rainfall is needed, particularly in areas that have only recently received rainfall in the last few weeks. Drought management continues and further follow-up rain remains a key focus in these areas, as well as for much of the western region as hot summer temperatures come into effect.

The seasonal NDVI anomaly data (Figure 15) shows high variability in plant greenness levels across the region compared to long-term expectations for the August to October period. There has been a general improvement in plant greenness levels since the September update, with some districts experiencing well above normal levels of greenness. Other parts of the region continue to experience below normal levels of greenness (brown areas on the map). Rainfall has been lower, later or less effective in these areas.

The time series charts (Figure 16) show the individual response of the drought indices for Bourke, Ivanhoe and Wentworth. All three locations show variable rainfall patterns and responses in the soil water and plant growth indices. All locations have only recently moved towards the Non-Drought category and continue to rely on follow-up rain to maintain longer-term drought recovery. 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

A transition towards longer-term drought recovery continues across much of the North West, Northern Tablelands and North Coast Local Land Services (LLS) regions. October rainfall caused an expansion in the area of the Non-Drought category (Figure 17). Despite this, some regions continue to be in one of the three drought categories and further rainfall is needed. Heavy rainfall and storm damage was reported during harvest in some winter cropping districts.

The seasonal NDVI anomaly data (Figure 18) indicates near-normal to positive anomalies across much of the region for the August to October period. The data indicates that improvements gained from rainfall received earlier in the year has been maintained in most areas at the end of October.

The time series charts (Figure 19) show the individual response of the drought indices for Moree, Walgett, Tenterfield and Lismore. There have been variable responses to rainfall in recent months. The drought indices have improved at Walgett and Moree where rain during the month maintained the recovery from drought. Lismore highlights the importance of adequate follow-up rain. After a relatively dry seven months, follow-up rainfall remains crucial for sustaining any improvements gained in autumn. Tenterfield has experienced slight improvements to the rainfall index over the last six months and continues to lag in drought recovery.

Central Tablelands, Central West, Hunter and Greater Sydney regions

The Central West, Central Tablelands, Hunter and Greater Sydney Local Land Services (LLS) region continued a strong transition through drought recovery during October. Winter and Spring rainfall has aided recovery in all four LLS regions, especially in Central West and Greater Sydney where recovery has been occurring longer (Figure 20). Rainfall during the month further strengthened recovery in the Central Tablelands and Hunter LLS regions.

The seasonal NDVI anomaly data (Figure 21) continues to show above average levels of plant greenness across large areas of these LLS regions. The bushfire impact remains 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 in recent months has improved the indicators, especially at Condobolin, and shows that strong drought recovery has been occurring throughout winter and spring.

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

Conditions continued to improve in the South East Local Land Services region during October. The Combined Drought Indicator (CDI) (Figure 23) shows an expansion in the area of the Recovering and Non-Drought categories across southern parts of the region during the month. October rainfall also continued the strong transition towards recovery that has been ongoing since winter in the northern parts of the region.

The seasonal NDVI anomaly data (Figure 24) shows higher than expected levels of plant greenness across much of the region for the August to October period. Plant greenness remains below expected levels in parts of the south, including the Monaro high plain. The areas impacted by bushfires continue to have well below average plant greenness.

The time series charts (Figure 25) show the individual response of the drought indices at Bega, Goulburn and Cooma. The plant growth index has begun to respond in all examples now that further rainfall and spring temperatures have increased potential growth rates. Despite improvements it is likely that areas like the Monaro and Bega will need further follow rainfall due to a longer duration of Intense Drought conditions persisting later throughout 2020.

Seasonal climate outlook

Official national outlook

The latest official national outlook was released by the Bureau of Meteorology (BoM) on 29 October 2020. The outlook indicates that November to January rainfall is likely to be above average for most of Australia. The west coast of Tasmania is likely to be below average.

Daytime temperatures for November to January are likely to be warmer than average across parts of south-east, central, and western Australia, as well as along Australia’s northern coastline. Overnight temperatures very likely to be warmer than average across Australia.

An updated seasonal outlook is released weekly by the BoM each Thursday afternoon.

NSW outlook

NSW currently has a moderate to high chance of exceeding median rainfall in the November to January period (Figure 26). The BoM temperature outlook for November to January indicates that the probability of exceeding median daytime temperatures (Figure 27) are higher in the west and some coastal regions, lower in the east and a near equal chance of temperature being above or below median in central NSW. There is a high probability of warmer than median overnight temperatures across the state (Figure 28). The BoM temperature outlook for November to January (Figure 27 & 28) indicates that the probability of exceeding median daytime temperatures are higher in the west and some coastal regions, lower in the east and a near equal chance of temperature being above or below median in central NSW. There is a high probability of warmer than median overnight temperatures across the state.

Global climate drivers

El Niño–Southern Oscillation (ENSO)

The Bureau of Meteorology’s (BoM) El Niño-Southern Oscillation (ENSO) Outlook was released on 27 October 2020. A La Niña event in the tropical Pacific Ocean continues. The Australian and international climate models indicate that La Niña could persist into February 2021. A La Niña event typically increases the likelihood of above average rainfall across much of Australia during spring, and across much of eastern Australia during summer.

Sea surface temperatures in the central and eastern Pacific, as well as most atmospheric indicators including trade winds and equatorial cloudiness remain at La Nina thresholds. The Southern Oscillation Index (SOI) has recently moved back into neutral values, however the SOI is expected to return to La Niña levels in the coming weeks.

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.

Southern Oscillation Index

The 30-day Southern Oscillation Index (SOI) for the 30 days ending 25 October was +5.4, falling into the neutral range (Figure 29). This was likely associated with the passage of the Madden-Julian Oscillation (MJO) and it is expected that this will be only temporary. The 90-day SOI value was +7.4.

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

Sea surface temperatures (SST)

Monthly sea surface temperatures (SST) were cooler than average in the central and eastern Pacific during October (Figure 30). Warm anomalies were present in the western Pacific, extending into the Maritime Continent and in the Tasman Sea.

The latest values of the three NINO indices in the tropical Pacific for the week ending 25 October were: NINO3 −0.8 °C, NINO3.4 −1.0 °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 22 October) shows the top 200 m of the equatorial Pacific near and to the east of the Date Line is cooler than average (Figure 31). The strength and extent of cooler than average water has increased since July.

Indian Ocean (IOD)

The Indian Ocean Dipole (IOD) is currently neutral, however parts of the Indian Ocean are generally warmer than average. The latest weekly value of the IOD index to 25 October was +0.09 °C. Most models suggest it will remain neutral for during summer. Only two of the six surveyed climate models indicate negative threshold values will be met in November. The IOD index needs to remain at or cooler than −0.4 °C for eight weeks for it to be classed as an official negative IOD event.

The IOD has decreasing influence on Australian weather patterns as the southern hemisphere wet season becomes more prominent from Spring and throughout Summer.

Southern Ocean (Southern Annular Mode – SAM)

The Southern Annual Mode (SAM) is expected to remain positive over November (Figure 32). A positive SAM during spring is typically associated with wetter and cooler than average conditions in parts of eastern Australia. La Niña tends to favour positive SAM during spring and summer. This typically enhances the wet signal in eastern Australia.

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.

Combined Drought Indicator (CDI) explained

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

CDI Phase	Technical definition	Description - typical field conditions
Intense Drought	All three indicators (rainfall, soil water, plant growth) are below the 5^thpercentile	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 5^th 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 30^th 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 30^th 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 50^th percentile but above the 30^th 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 50^th percentile.	Production is not limited by climatic conditions.

Acknowledgments

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.

© State of New South Wales through the Department of Regional NSW, 2020. You may copy, distribute and otherwise freely deal with this publication for any purpose, provided that you attribute the NSW Department of Primary Industries as the owner.

Disclaimer: The information contained in this publication is based on knowledge and understanding at the time of writing (November 2020). However, because of advances in knowledge, users are reminded of the need to ensure that information upon which they rely is up to date and to check currency of the information with the appropriate officer of the Department of Primary Industries or the user’s independent adviser.

Published by the NSW Department of Primary Industries. ISSN 2202-1795 (Online). Volume 8 Issue 11.