NSW State Seasonal Update - November 2019

Prepared by NSW DPI

NSW overview

Widespread drought conditions continued to impact NSW during November 2019. The main impacts include livestock feed deficits, water shortages and low crop yields. Below average rainfall and warm temperatures intensified the drought across most of the state during the month. Rainfall received in some districts was insufficient for drought recovery. The official climate outlook indicates a low chance of the drought breaking this summer; the latest forecast is for an increased chance of low rainfall and high temperatures. Farmers and communities are expected to stay in a drought response setting well into 2020.

The NSW DPI Combined Drought Indicator (CDI) has 99.9% of the state in one of the three drought categories. The CDI shows that intense drought conditions continued in far western and north eastern NSW during November. Drought conditions intensified in the Central West and in parts of the Hunter, Central Tablelands and South East. The states agronomic drought indicators that track soil water, pasture and crop growth are particularly low. The conditions monitored by the CDI are consistent with independent estimates from the NSW farm dams survey and remote sensing of vegetation.

Widespread storms bought rainfall to parts of the state in the first week of November. Larger rainfall totals were received in the central and northern regions of Western NSW. Valuable surface water runoff was captured in these areas, however there has been minimal pasture growth response. Parts of north eastern NSW also received isolated storm rainfall late in the month. This rainfall was ineffective and did little to improve on-ground conditions. In some instances the storms caused wind and water damage.

The drought event is prolonged with most of NSW experiencing drought conditions for longer than two years. Producers have passed a key decision period with the arrival of summer. Dryland production opportunities are now limited by heat and high evaporation, particularly in central and southern NSW. Summer crop potential in the north is poor, limited by severe soil moisture deficits. Water resource and livestock feed supply management remains a priority across NSW. The next significant decision period is in February 2020 when producers start preparing for the autumn break.

The Bureau of Meteorology (BoM) Climate Outlook released on 5 December 2019 indicates that NSW has a low to near equal chance of receiving median rainfall for the next three months. The outlook continues to be driven by a strong positive Indian Ocean Dipole (IOD) and negative Southern Annular Mode (SAM). Both events are known drivers of dry conditions for central and southeast Australia. The persistence of this positive IOD event is unusual and is due to the late arrival of the monsoon trough in northern Australia. The El Niño forecast remains neutral into the early part of 2020, leaving the positive IOD and negative SAM events as the dominant influence on the climate.

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.

Drought Duration

Drought duration is an important factor in determining the impact of an event on farm businesses and communities. The drought duration map (Figure 2) shows the number of months since June 2017 that an area in NSW has been in any one of the three CDI drought categories. The drought duration map indicates that as of 30 November 2019 large parts of NSW continue to experience long-term drought conditions. There are large areas of NSW showing drought duration greater than 24 months.

*Note: The accumulated months reported are non-consecutive.

Rainfall

The majority of New South Wales (NSW) received well below average rainfall throughout November. There was an exception early in the month when parts of the central and northern region of Western NSW received totals of 50-100mm (Figure 3). This represented higher than average falls for November. Elsewhere rainfall totals were between 0-50mm with large areas receiving less than 25mm during November.

Temperature

November daytime temperatures (Figure 4) ranged between 27-33°C across much of northern and central NSW. Temperatures were higher in the far north ranging up to 36°C. Daytime temperatures were cooler at the higher altitudes in the Northern and Central Tablelands, as well as the South East region of the state where temperatures ranged between 21-27°C. The daytime temperatures ranged between 27-33°C for the majority of southern NSW east of the Great Dividing Range, as well as the coastal region north of Sydney including the Hunter.

Overnight temperatures (Figure 5) in large parts of the north western and northern coastal regions of NSW ranged between 15-21°C. The majority of the northern slopes, south west and Hunter regions of the state experienced overnight temperatures between 12-15°C. The remainder of the state including the tablelands, southern slopes, Murray and south east of regions of NSW received average overnight temperatures between 6-12°C, with Alpine regions being cooler with temperatures between 3-6°C.

Normalised Difference Vegetation Index (NDVI) Anomaly

The Normalised Difference Vegetation Index (NDVI) anomaly (Figure 6) shows that plant greenness levels continue to remain well below the long term levels expected during November across most of NSW. The NDVI is an index that provides a measure of vegetation density and condition. The anomaly map shows the deviation of the current NDVI from the long-term average for this time of year.

Note, The Bureau of Meteorology (BoM) issued a Service Caution Notice this month as follows: From March 2019, and possibly earlier, NDVI data have shown lower values in southern Australia due to a drift in the source NOAA satellite. The issue is being investigated and we expect corrections to be made in the coming two months. In the interim, please note the data may have a low (brown) bias and should be used with caution.

Farm Dam Water Status

The available satellite data indicates that farm dam levels remain low across the majority of NSW (Figure 7). The low levels of dam recharge across much of the state are a result of low rainfall and high evaporative rates over recent months. The exception during November was for the central and northern parts of the Western Local Land Services (LLS) region. Larger rainfall totals in these areas resulted in surface runoff. Water availability and management remains a priority across the state as summer commences.

DPI and Geoscience Australia monitor 67,000 farm dams each month by the Landsat satellite and report average information for each parish.

Significant Events

Heightened Dust Activity

Dust activity has been increasing in recent months as outlined in the NSW Environment Energy and Science (EES) DustWatch reports. On-ground reporting indicates the prevalence of dust activity occurring throughout the month. Large areas of low ground cover due to the extended periods of dryness are likely to continue the risk of increased dust activity for at least the short-term.

As the risk of dust activity increases, it is important to remain vigilant to possible health risks associated with dust exposure. The NSW Department of Health has provided a brief overview of health effects and precautions relating to dust exposure.

Further information and subscription services relating to the NSW EES Dustwatch report. The November edition the DustWatch report is scheduled to be available in the second half of December.

Soil Water Index

The Soil Water Index (Figure 8, SWI) remains below average to extremely low across the majority of NSW. Continued widespread dryness throughout November contributed to the drying of soil moisture since September. A large area to the north of Bega in the South East LLS region has seen a decline in the soil water index since the October report. This has been confirmed by on-ground reports in this region.

Plant Growth Index

There was little improvement to the Plant Growth Indicator (Figure 9, PGI) during November, highlighting the continuation of dry conditions. The majority of NSW is experiencing below average to extremely low plant growth relative to the long term data.

Rainfall Index

Dry conditions during November caused no notable improvements to the Rainfall Index (Figure 10, RI). The majority of the state remains below average to extremely low following very dry conditions during spring.

Drought Direction Index

The majority of NSW experienced a drying trend during November as indicated by the Drought Direction Index (Figure 11, DDI). This confirms the continuation of widespread dryness during Spring in addition to the dry winter period. The blue areas on the map represent areas receiving higher rainfall totals during the month. Despite this there has been no initiation of drought recovery in these areas.

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 12 displays the CDI status for each individual Local Land Services region to 30 November 2019.

Murray and Riverina regions

The Murray and Riverina Local Land Services (LLS) regions continue to experience widespread drought conditions. The Combined Drought Indicator (CDI, Figure 13) shows that the region is in one of the three drought categories. The intensification of conditions is occurring across the region despite isolated rainfall received early in the month.

The monthly NDVI anomaly data (Figure 14) shows that the LLS regions continue to experience below normal levels of greenness. Extended periods of below average and ineffective rainfall has caused poor agronomic activity in the region.

The time series charts (Figure 15) shows the individual response of the drought indices for Hay, Finley and Temora. The charts show that there were some beneficial periods of rainfall since May, however this has not improved conditions. The drought indices at the end of November reflect the poor spring resulting in diminishing crop yields and pasture growth in much of the region.

Western region

The Western Local Land Services (LLS) region continues to experience widespread drought conditions. The Combined Drought Indicator (CDI, Figure 16) shows that the whole region is in one of the three drought categories. Central and northern areas received higher rainfall totals early in November with reports of improved surface water availability occuring for some. This was supported by the Farm Dam Indicator (Figure 7) for the month.

Despite the rain there was very little change to other on-ground conditions in these areas. The DPI undertook a verification of the pasture response to the rainfall event near Bourke using National Map. Visit a high resolution sample analysis.

The satellite imagery highlights the minimal response or improvement to pasture conditions between 21 September 2019 and 27 November 2019. This highlights that the rainfall received in early November 2019 was largely ineffective and that there has been no initiation of drought recovery.  This is an interim assessment and the region will need to be monitored over the coming weeks.

The monthly NDVI anomaly data (Figure 17) shows below normal levels of greenness compared to the long term expectations. This has been driven by poor agronomic activity due to insufficient and ineffective rainfall during winter and spring. It is important to recognise that producers in the west and far west are managing total grazing pressure along with the dry meteorological conditions.

The time series charts (Figure 18) show the individual response of the drought indices for Bourke, Ivanhoe, and Wentworth. All locations show the continuation of poor conditions and a false recovery occurring at Ivanhoe from rainfall received in April and May. The rainfall received at Bourke and Wentworth was ineffective. This is highlighted by the soil moisture and plant growth indices failing to show any substantial response. There has been little if any relief to drought conditions for a long period of time.

North West, Northern Tablelands and North Coast regions

Drought continues to impact the entire North West, Northern Tablelands and North Coast Local Land Services (LLS) regions. The area categorised as Intense Drought has expanded and covers the majority of the entire region (Figure 19). Field reports continue to confirm the severity of drought conditions being experienced across the region.

The monthly NDVI anomaly data (Figure 20) shows that the region is experiencing below normal levels of greenness compared to long term expectations. This reflects the insufficient rainfall over several months resulting in poor agronomic activity.

The time series charts (Figure 21) showing the individual response of the drought indices for Moree, Walgett and Tenterfield reflect the long term trend of the drought indices tracking in the bottom 5th percentile of the historic range. All three locations show extremely low rainfall indices for the majority of 2019 and highlights the ongoing intensity and duration of drought conditions occurring in northern NSW. There was a small positive rainfall shift at Tenterfield in early 2019, however this rainfall was ineffective as shown by the lack of response in the soil moisture and plant growth indices.

Central Tablelands, Central West, Hunter and Greater Sydney regions

The Central Tablelands, Central West, Hunter and Greater Sydney Local Land Services regions (LLS) continue to experience drought conditions. The entire region experienced the intensification of conditions during November with the Combined Drought Indicator (CDI) showing a large transition from the Drought to Intense Drought categories (Figure 22).

The monthly NDVI anomaly data (Figure 23) shows the continuation of below normal levels of greenness compared to long term expectations. This has been driven by insufficient rainfall and poor agronomic activity over a long period of time.

The time series charts (Figure 24) show the individual response of the drought indices for Cowra, Condobolin and Singleton. Drought conditions have impacted all locations for an extended period of time. The soil moisture and plant growth indices have struggled to surpass the lowest 10th percentile of the long-term data. The charts show variations in the rainfall index between locations. Despite this, all sites show that rainfall deficits have been large and that the rainfall received has been ineffective.

South East region

The South East Local Land Services (LLS) regions continue to experience widespread drought conditions. The Combined Drought Indicator (CDI, Figure 25) shows that the whole region is in one of the three drought categories. Conditions have intensified since the October State Seasonal Update and on-ground reports indicate that the region continues to manage very difficult circumstances as summer commences.

The monthly NDVI anomaly data (Figure 26) indicates widespread below normal levels of greenness compared to the long term expectations. This has been driven by poor agronomic activity over the past few months and insufficient rain to encourage sustained agronomic activity.

The time series charts (Figure 27) show the individual response of the drought indices at Bega, Goulburn and Cooma. Bega shows an example of a false recovery where there was a short period of recovery between March and June. This rapidly fell below drought thresholds in July. This highlights the need for sustained follow up rainfall to initiate long-term drought recovery.

Official national outlook

The official National Climate Outlook was released by the Bureau of Meteorology (BoM) on 5 December 2019. The remainder of December is likely to be drier than average for most locations other than south-west Tasmania and north-west Western Australia. The rainfall outlook for January to March 2020 indicates drier conditions are likely in the east, while wetter than average conditions are possible in parts of WA.

NSW outlook

The majority of New South Wales (NSW) is forecast to have a low chance of receiving median rainfall during January to March (Figure 16). Some parts of western NSW have slightly better outlook with a near equal chance of receiving drier or wetter than average conditions.

The historical rainfall outlook accuracy at this time of year is variable across NSW. The forecast accuracy is low for parts of the Central West, the Hunter, Central Tablelands and Southern Tablelands. A moderate accuracy exists for most of South East NSW and parts of northern NSW. Forecast accuracy is higher for the majority of western NSW and North Coast areas of NSW.

The BoM temperature outlook for January to March (Figures 29 & 30) indicates a strong chance of warmer than average daytime and overnight temperatures occurring across all of NSW.

Climate drivers

El Niño–Southern Oscillation (ENSO)

The Bureau of Meteorology’s (BoM) El Niño–Southern Oscillation (ENSO) Outlook was released on 26 November 2019. The outlook remains neutral, meaning that the influence of the positive Indian Ocean Dipole (IOD) is likely to continue its dominance on the Australian climate in the short term.

The tropical Pacific Ocean sea surface temperatures are slightly warmer than average, atmospheric indicators are generally neutral. Trade winds have recently weakened temporarily in the western Pacific region in line with severe tropical cyclone Rita. This may mean there is some warming of surface waters in the coming few weeks. However, most climate models forecast ENSO-neutral conditions for the rest of 2019 and into the first quarter of 2020. When ENSO is neutral, it has little effect on Australian and global climate, meaning other influences are more likely to dominate.

Southern Oscillation Index

The 30-day Southern Oscillation Index (SOI) for the 30 days ending 24 November 2019 was -10.5 (Figure 31). The 90 day value was -9.7. The 30-day SOI values have remained fairly similar over the past week, and are more strongly negative than they were two weeks ago.

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

Monthly sea surface temperatures for November (Figure 32) were about average in the central Pacific, warmer than average in the western Pacific, and cooler than average in the eastern Pacific.  Ocean temperatures off the north coast of Australia were cooler than average. Cooler waters in the eastern Indian Ocean commonly occur during a positive Indian Ocean dipole.The latest values of the three key NINO indices in the tropical Pacific for the week ending 24 November are: NINO3 +0.5°C, NINO3.4 +0.6°C and NINO4 +0.9°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 sub-surface temperature anomalies (to 21 November) shows cool anomalies in the western to central equatorial Pacific, at a depth of around 100 to 200 m. Weak warm anomalies extend across most of the top 100 m of the equatorial Pacific. Warm anomalies in the central Pacific intensified in October, compared to September and August, but have decreased for November to date. Cool anomalies have extended further east since October.

Indian Ocean

The Indian Ocean Dipole (IOD) remains strongly positive, however IOD index values have decreased compared to values in October. The latest weekly value to 24 November was +1.36 °C.

The strong temperature gradient persists across the Indian Ocean. Sea Surface Temperatures to the south of the Indonesian islands of Sumatra are up to 2 degrees cooler than average for the week ending 24 November, while warm anomalies in the west of the Indian Ocean near the Horn of Africa are up to 2 degrees warmer than average. The sea surface temperatures have remained generally consistent with a positive IOD pattern since late May.

All six international climate models surveyed by the Bureau indicate the IOD will remain positive into December, with five of the six models indicating persistence into January.

While the IOD continues to show signs it will persisted later than usual this year, it remains unlikely that it will persist into the second half of summer. IOD events dissipate as the monsoon trough moves into the southern hemisphere. This changes the broad scale wind patterns over the IOD region and returns sea surface temperatures to near average.

Southern Ocean

The current index for the Southern Annular Mode (SAM) is currently strongly negative and is expected to remain negative over the next two weeks. The strong negative conditions at present are the result of September’s Sudden Stratospheric Warming finally reaching the lower atmosphere in late October.  A negative SAM in summer contributes to warmer daytime temperature, lower rainfall, and higher wildfire risk. The negative SAM has less influence on overnight temperatures.

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 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: how the indicators are combined to form the CDI

The NSW State Seasonal Update is provided each month by the NSW DPI Climate Unit, which is part of the Livestock Systems Branch in DPI Agriculture.

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 (2019), Panorama Avenue, Bathurst 2795 and data which is © Commonwealth of Australia 2019, 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.