Prepared by NSW DPI Climate Branch
Widespread drought conditions continued to impact New South Wales (NSW) during August 2019. The majority of the state experienced below average rainfall throughout the month, providing no significant relief to drought conditions. The NSW DPI Combined Drought Indicator (CDI) shows that 95.1% of NSW remains in one of the three drought categories. The supporting indicators highlight that this is driven by poor agronomic conditions, principally low stored soil moisture and crop/pasture growth.
Winter rainfall, a key time for hydrological and soil water recharge, was below average for much of NSW. This creates a challenging forward scenario for water resource managers, irrigators and dryland farming operations over the next 6 months. Recovery from this setting will require very high rainfall over the coming spring.
Recent conditions were more favourable to the south and parts of eastern NSW. Late winter rainfall and warmer than average temperatures supported some crop and pasture growth in parts of these regions of NSW. Many farms have reasonable dam levels and water available for livestock. Despite this recent lift in seasonal conditions, these areas remain in the Drought Affected category of the NSW CDI because of continued below average soil moisture levels for much of the region.
The intensity of the drought event is currently high for much of Northern and Central West of NSW as well as parts of the far west. These areas remain in the Drought and Intense Drought categories. Field reports indicate very low ground cover, a low area of winter crop, and with no soil moisture or irrigation water the prospects of sowing summer crop is also poor at this stage. The small area of winter crop that was sown has very low yield potential.
The drought event has now reached an 18-24 month or more duration in many parts of NSW. The accumulation of failed cropping seasons, low water availability and stock feed deficits has known impacts on farming businesses. Available benchmarks highlight that once a drought event reaches this duration there are cumulative impacts, for example producers have been implementing their drought management plans for some time and are accumulating a negative farm cash flow.
The prospects of the drought breaking this coming spring are also not favourable. The Bureau of Meteorology (BoM) provided a dry spring forecast for NSW in the official climate outlook released on 29 August 2019. It states that the likelihood of above median rainfall this coming spring is at 30% or lower for much of the state. A positive Indian Ocean Dipole (IOD) remains the dominant feature in the forecast which is correlated with dry conditions for central and southern Australia. The BoM also provided an updated ENSO outlook on 3 September 2019, where the El Niño status remains neutral. This current ENSO forecast is expected to remain relatively unchanged for the remainder of 2019.
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.
Drought duration is widely recognised as an important component of drought impact on farm businesses. The drought duration map (Figure 2) shows the number of months since 2016 that an area in NSW has been in any one of three CDI drought categories; Drought Affected, Drought or Intense Drought. The drought duration map indicates that at 24 August 2019 large parts of NSW have experienced long-term drought conditions for greater than 18 months or more since 2016.
*Note: The accumulated months reported in time of drought are non-consecutive.
Well below average rainfall was the prominent feature across the majority of NSW during August. Extensive areas of the state received less than 40% of the August average. Some small isolated areas around the Sydney and Newcastle coastal regions were the only exceptions, where above average rainfall totals ranging between 100-200mm were received for the month.
August daytime temperatures ranged between 18-24°C across northern NSW including most of the coast, with higher elevations in the north ranging between 12-18°C. In southern NSW, temperatures ranged from 12-18°C, with higher elevations in the south ranging between 3-12°C. Daytime temperatures were generally 1-3°C warmer than average across the whole state with the exception of the far northwest and part of the Victorian border region where temperatures were -1 to 0°C below the August average.
Overnight temperatures ranged between 3-9°C across most the plains and coastal hinterland areas of NSW. The majority of the remaining coastal areas received temperatures between 6-9°C. Areas at higher elevations on the central and southern slopes and tablelands continued to experience frosts during August 2019. Overnight temperatures ranged from -3 to 3°C for August, with southern alpine areas ranging from -6 to -3°C. The majority of the northern tablelands experienced overnight temperature range between 0-3°C. Overnight temperatures were 0 to -3°C cooler than the August average, except for parts of the central and northern coastal areas where temperatures were 0-1°C above average.
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 August across most of NSW. The NDVI is an index that provides a measure of vegetation density and condition. The NDVI anomaly is the separation of the current NDVI from the long-term average for this time of year.
Dry August conditions have not made any notable improvements to farm dam levels across the majority of NSW. Despite some data limitations, Figure 7 shows that surface water availability remains at critical levels across large areas of the state as temperatures begin to increase with the onset of spring. Extensive and consistent rainfall is needed to initiate adequate dam recharge.
* There are some physical limitations for the farm dam water status this month, due to the low angle of the sun influencing the quality of satellite imagery. The hashing added to the map (Figure 7) indicates areas where high data uncertainty may be expected.
Low pressure systems brought snow events to many elevated areas during August with moderate falls occurring in the highlands. A significant event brought snow to the Alps from about 7 August, and by 10 and 11 August many locations above about 600m received snow, including Orange, Guyra, Lithgow, Canberra, the Barrington Tops and the Blue Mountains.
The Soil Water Index (Figure 8, SWI) remains below average to extremely low across the majority of NSW. A small area to the east of Albury in the Murray Local Lands Services (LLS) region, and parts of central and northern areas of the Western LLS region are currently in the average classification. Despite this, rainfall received in August was not sufficient to improve the soil water status which remains at similar levels to those experienced over the past few months.
There were no major improvements to the Plant Growth Indicator (Figure 9, PGI) during August due to the extent of dryness being experience across NSW. The majority of NSW continues to experience below average to extremely low plant growth relative to the long term data.
There were no improvements to the Rainfall Index (Figure 10, RI) during August. This highlights the continued of dry conditions being experienced across NSW.
The majority of NSW experienced a drying trend during August as indicated by the Drought Direction Index (Figure 9, DDI). This provides another indication for the scale of the dry conditions experienced throughout the month capping a very dry winter rainfall period for 2019.
Changes in the individual drought indicators may have occurred since this update was released. For the most current information, please visit DroughtHub.
Figure 12 displays the CDI status for each individual Local Land Services region to 31 August 2019.
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 majority of this region is classified as being in the Drought or Drought Affected categories. Well below average August rainfall has intensified conditions and placed pressure on crop and feed potential. There continues to be signs of recovery on the alpine areas of the Murray LLS regions, driven by falls of rain and snow.
The monthly NDVI anomaly data (Figure 14) indicates that the region continues to be experiencing below normal levels of greenness. This has been driven by poor agronomic activity over the past few months and insufficient rain to sustain agronomic growth. Areas in the west of the region appear to be slightly better than the east relative to long term expectations.
The time series charts (Figure 15) shows the individual response of the drought indices for Hay, Finley and Temora. The charts reflect the periods where some beneficial rainfall has been received since May allowing prospects of some winter crop opportunity. Despite this, the charts also indicate that conditions have remained marginal for building longer term confidence of sustained drought recovery. Rainfall is now critical to prevent the increasing potential of yield decline and to maximise any spring feed potential that currently exists.
The status of drought conditions remains relatively unchanged since the July State Seasonal Update. The Combined Drought Indicator (CDI) shows that the majority of the region as being in one of the three drought categories of Drought Affected, Drought or Intense Drought (Figure 16). Although the Ivanhoe district continues to show signs of recovery, this relief remains heavily reliant on the continuation of follow up rainfall as temperatures begin to warm into spring.
The monthly NDVI anomaly data (Figure 17) indicates that most of the region continues to be experiencing below normal levels of greenness, when compared to the long term expectations. This has been driven by poor agronomic activity over the past few months and insufficient winter rain to encourage widespread agronomic growth as spring approaches. The NDVI suggests slightly better conditions relative to the long term comparisons in the areas that have received higher rainfall totals around Ivanhoe over the winter months.
The time series charts (Figure 16) showing the individual response of the drought indices for Bourke, Ivanhoe, and Wentworth reflect the variation between locations. Despite not being drought breaking, Bourke experienced a positive shift in the indices during April and May. This was short lived with the indices declining due to the lack of follow up rainfall. Ivanhoe experienced similar relief in April and May but with a slightly greater magnitude initiating a short-term period of recovery. Conditions have plateaued since and highlights the importance of follow up rainfall to instil longer term drought recovery as warmer spring conditions approach. Wentworth has experienced a longer period of time where the drought indices have struggled to surpass the lowest 10th percentile. There has been little if any relief to drought conditions for a long period of time.
Drought conditions continue to impact the entire northern area of NSW with the Combined Drought Indicator (CDI) showing the region to be in one of the three drought categories of Drought Affected, Drought or Intense Drought (Figure 19). Conditions have remained relatively stable since the July State Seasonal Update, except for an area to the south of Walcha, where conditions have deteriorated. Widespread field reports continue to confirm the severity of enduring drought conditions across the region.
The monthly NDVI anomaly data (Figure 20) indicates that most of the region continues to be experiencing below normal levels of greenness compared to the long term expectations. This reflects the insufficiency of rainfall over recent months and corresponding 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 indices tracking in the bottom 5th percentile of the historic range. Despite a small positive rainfall shift at Tenterfield in early 2019, the rainfall effectiveness was poor as indicated by the lack of response in the soil moisture and plant growth indices. 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.
The vast majority of the Central Tablelands, Central West, Hunter and Greater Sydney Local Land Services regions (LLS) continue to experience drought conditions. The Combined Drought Indicator (CDI) shows that most of the area remains categorised in either the Drought Affected, Drought or Intense Drought categories (Figure 22). The current nature of drought conditions remain similar to July, however another month of poor conditions in addition to the already prolonged exposure to drought conditions has continued to create difficulty for feed management and crop prospects as spring arrives.
The monthly NDVI anomaly data (Figure 23) indicates that most of the region continues to be experiencing below normal levels of greenness, when compared to the long term expectations. This has been driven by poor agronomic activity over the past few months and insufficient rain to encourage agronomic growth.
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, however the charts show some variation in the nature of the drought between the locations. There have been periods of short term relief at Singleton since February, however this has been short lived as reflected in the declining indices, due to the lack of follow up rainfall. The importance of follow up rainfall can also be observed at Cowra, where the rainfall that has been received has largely been ineffective on soil moisture and plant growth. The duration and intensity of conditions at Condobolin have been far more severe, with the drought indices all tracking below the bottom 5th percentile for the last eight months.
The majority of the South East Local Land Services (LLS) region is classified as either Drought Affected (intensifying) or Drought as shown by the Combined Drought Indicator (CDI) (Figure 25). There has been little change since June with low winter rainfall totals extending the already prolonged duration of drought.
The monthly NDVI anomaly data (Figure 26) indicates that most of the region continues to be experiencing 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 growth.
The time series charts (Figure 27) show the individual response of the drought indices at Bega, Goulburn and Cooma. Of the three locations, Bega experienced the greatest amount of relief with a short term recovery occurring between March and June before rapidly falling below drought thresholds in July. This false recovery highlights the need for sustained follow up rainfall to create confidence of longer term drought recovery. Both Goulburn and Cooma received some meteorological relief with rainfall occurring from April, however this rainfall has been ineffective for driving soil water and plant growth indicators above the lowest 20th percentile. Conditions plateaued during the winter period and rainfall is still needed to provide spring growth opportunities.
The official National Climate Outlook for September to November was released by the Bureau of Meteorology (BoM) on 29 August 2019. The rainfall outlook for the next three months indicates a drier than average spring for most of Australian, except for parts of western Tasmania and south-west Western Australia that will likely have a wetter than average Spring.
Both daytime and overnight temperatures for the next three months are likely to be warmer than average for much of Australia, however parts of the south-east of Australia and the tropics are likely to have cooler than average overnight temperatures.
The main climate influence is the forecast for the Indian Ocean Dipole (IOD) to become positive over the coming months. A positive IOD is usually associated with below average rainfall and warmer than average daytime temperatures for large parts of southern and central Australia.
New South Wales is forecast to have a lower chance of exceeding median rainfall for the next three months. The historical rainfall outlook accuracy at this time of year is moderate to high for NSW.
The BoM temperature outlook for September to November (Figures 29 & 30) indicates an increased chance of warmer than average daytime temperatures across all of NSW. Overnight temperatures are also predicted to have a higher chance of being warmer than average for a large portion of NSW, however areas on the central and southern slopes and tablelands, as well western NSW have a near equal chance of experiencing warmer or cooler than average temperatures.
The Bureau of Meteorology’s (BoM) El Niño–Southern Oscillation (ENSO) assessment was released on 3 September 2019, with the forecast remaining neutral. Atmospheric and oceanic indicators of ENSO are generally close to average, reflecting neutral tropical Pacific cloud and rainfall patterns.
Most climate models indicate the tropical Pacific is likely to remain ENSO-neutral for the rest of 2019 and into early 2020. This means that other climate drivers, such as the IOD, are likely to remain as the primary influence on Australian and global weather towards the end of the calendar year.
The 30-day Southern Oscillation Index (SOI) is neutral, with the value for the 30 days ending 1 September at −3.8. The 90-day value was −6.1. Values between +7 and −7 generally indicate neutral conditions.
The overall pattern for sea surface temperatures (SSTs) are consistent with a neutral ENSO state, however temperatures for the week ending 1 September remained warmer than average across the western equatorial Pacific Ocean. The northern half and southwestern quarter of the Pacific Ocean is warmer than average, while most of the tropical Pacific has cooled over the past fortnight.
Some areas along the eastern half of the equator are cooler than average, with cool anomalies occurring close to South America in the east of the south Pacific. Negative anomalies are also visible along the southern coastline of the Indonesian archipelago. Cooler waters in this area typically occur during a positive IOD.
SSTs are warmer than average in some areas to the east and around the southwestern tip of Australia, however remain broadly close to average around the rest of Australia.
The latest values of the three key NINO indices in the tropical Pacific for the week ending 1 September are: NINO3 -0.1°C, NINO3.4 -0.1°C and NINO4 +0.6°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.
The four-month sequence of equatorial sub-surface temperature anomalies (to August) shows a pattern of weak cool anomalies extending across the equatorial Pacific, at a depth of around 100 to 200 m in the west of the Basin, rising to 0 to 100 m depth in the east. Weak warm anomalies extend across most of the column depth in the central to western equatorial Pacific above and below this band of cool anomalies. This general pattern has been in place since May.
Anomalies, both warm and cool, are mostly within 2 degrees of average, though some areas of cool anomalies more than 2 degrees cooler than average exist in the east of the Pacific sub-surface.
For the five days ending 1 September water temperatures were close to average across most of the sub-surface of the equatorial Pacific. This pattern is consistent with ENSO-neutral conditions.
The Indian Ocean Dipole (IOD) remains positive, with the latest weekly index value to 1 September at +0.98 °C. The IOD index has generally been above the positive IOD threshold since mid-July. Typically, to be considered a positive IOD event, index values need to remain above the positive threshold (+0.4 °C) for at least eight weeks. The index value has been above the threshold in six of the last seven weeks, and was also above the threshold from late May to mid-June.
The broader Indian Ocean patterns including sea surface temperature, cloud, and wind have been positive IOD-like since late May. This has contributed to the dry conditions affecting most of Australia. Specifically, the overall pattern of sea surface temperatures has generally remained consistent with a positive IOD pattern during this time. Warmer than average sea surface temperatures have occurred in the central and western tropical Indian Ocean, while the eastern tropical Indian Ocean, to the northwest of Australia and south of Indonesia has experienced average to cooler than average waters.
All climate models surveyed by the Bureau indicate that a positive IOD is likely to continue throughout spring for the southern hemisphere. It is predicted that the positive values will decline significantly in strength by December when values for two of the six international models drop below the threshold. IOD events typically dissipate by early summer as the monsoon trough moves into the southern hemisphere. This changes the broad scale wind patterns over the IOD region and means the IOD pattern is unable to be sustained. At this point the IOD typically begins to have less influence on Australian rainfall patterns throughout summer, autumn and early winter.
The current two week outlook for the Southern Annular Mode (SAM) is unstable, with values fluctuating around neutral. SAM can only be predicted accurately a few weeks in advance, however, longer term forecasts of stratospheric conditions being monitored by the Bureau of Meteorology suggest a weakening of the polar vortex that may lead to a strongly negative SAM in the upcoming spring months. A negative SAM in mid-to-late spring contributes to warmer temperatures, lower rainfall, and higher wildfire risk.
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:
The way in which the indicators are combined to form the CDI is described in Table 1 below.
Table 1: The way in which the indicators are combined to form the CDI
Description - typical field conditions
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.
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.
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.
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 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.
© State of New South Wales through the Department of Industry, Skills and Regional Development, 2019. 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 (September 2019). 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 7 Issue 8.