Prepared by NSW DPI Climate Unit
Drought conditions continued across the majority of New South Wales (NSW) during June 2019, with signs that the event is intensifying in northern half of NSW. Low June rainfall totals were insufficient to provide the widespread follow up falls needed to continue the momentum from the easing of conditions experienced in some regions during May. Producers and rural communities are expected to continue drought mitigation strategies for the remainder of winter and into spring.
The June rainfall pattern was variable, with only isolated areas of the state receiving average monthly totals. Parts of southern NSW benefited from larger totals, which have aided the establishment and prospects of recently sown winter crops. While this is welcome, winter crop yields in Southern NSW remain critically dependant on follow up rainfall over the next few months. Some isolated coastal regions also benefited from some larger rainfall totals which may provide some short term fodder potential. These totals were still below historical averages and the dependency on follow up rainfall also continues.
The remainder of the state experienced the continuation of dry conditions throughout June. Winter crop sowing conditions have been tough, especially in the north and west of the cropping region, where the sowing period is almost closed. The onset of cold conditions and frost is also limiting agronomic productivity in many areas, particularly at high elevations, where feed growth is now typically slow.
The NSW DPI Combined Drought Indicator (NSW CDI) provides a general regional assessment of the complex pattern of field conditions across NSW. Overall the CDI at the end of June shows little change from May in terms of the total area of the state affected by drought conditions. There has been an increase in the area categorised as Drought Affected (Intensifying), reflecting the lack of follow up or breaking rainfall that is required to provide longer term relief to agronomic and hydrological conditions. Overall the CDI shows that 97.6% of NSW remains in one of the three drought categories.
The official climate forecast released by the Bureau of Meteorology (BoM) on 27 June 2019 continues to indicate a higher chance of drier than average conditions across NSW for winter and into spring. The emerging influence of the Indian Ocean Dipole (IOD) reported last month remains the dominant feature of the forecast, with the IOD still predicted to move into a positive phase over coming months. A positive IOD is generally correlated with dry conditions for central and southern Australia. The BoM also provided an updated ENSO outlook on 25 June 2019, where the El Niño status was downgraded to Inactive, a small amount of positive news despite the IOD situation likely being the dominant influence for NSW rainfall moving into spring.
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.
The majority of NSW received below average rainfall throughout June. Large areas of central and northern NSW experienced rainfall totals that were very much below average. Despite being below average, larger totals of >50mm were received in some parts of southern NSW and isolated coastal areas. The northwest of the state remained very dry for the month with drought conditions intensifying.
Daytime temperatures ranged between 18-24°C across northern NSW including the coast, with higher elevations in the north ranging between 12-15°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 0-2°C warmer than average across the whole state.
Overnight temperatures ranged between 3-12°C across most of north west NSW and the coast. For the south west, southern slopes and areas at higher elevations, overnight temperatures ranged between -3 to 0°C. Overnight temperatures were generally -1 to 0 cooler than average in the far west and southern areas of NSW, while the remainder of the state experienced average to slightly warmer than average overnight temperatures.
Plant greenness levels continue to remain well below the long term expectations across NSW throughout June. Despite some technical issues with data availability for the month*, this is reflected in the Normalised Difference Vegetation Index (NDVI) Anomaly (Figure 5) below.
NDVI is an index that provides a measure of vegetation density and condition. The NDVI anomaly is the departure of the current NDVI from the long-term average for this time of year.
*Unfortunately there are some physical limitations for data capture of the NDVI details at this time of year. This is due to the sun elevation being too low at southern latitudes across Australia during the satellite observation time. Occasionally this results in missing data, as is the case for June.
Based on field reports and the limited data that is available*, farm dam levels generally remain low to critically low across NSW. The situation is more severe moving west and in the northern parts of the state. There is evidence that dams located in parts of the Warrego and Paroo river systems have benefited from recent stream flows, resulting from the significant rainfall events occurring earlier in the year in Queensland. This relief is expected to be isolated in these areas. Widespread and consistent rainfall is required to gain long term improvement to critical dam levels across the state.
*Unfortunately there are some physical limitations for the farm water status to be comprehensively assessed for this Update. This is the same physical issue impacting the quality of the NDVI data for June.
The Soil Water Index (Figure 6, SWI) remains below average and extremely low across the majority of the state. Rainfall received over June was not sufficient to improve the soil water status which remains at similar levels to the May State Seasonal Update.
With limited rainfall and similar soil water conditions, there was no major improvements to the Plant Growth Indicator (Figure 7, PGI) during June. The majority of NSW continues to experience below average to extremely low plant growth.
There was essentially no improvement to the Rainfall Index (Figure 8, RI) since May. This is reflective of the dry conditions experienced across the majority of the state in June. This also suggests that the totals received in the areas that did experience rain for June were not large enough to influence the long term rainfall deficits.
With the exception of some parts of southern NSW, the majority of NSW experienced a drier trend for June as indicated by the Drought Direction Index (Figure 9, DDI). This provides another indication of the scale of the dry conditions experienced throughout June.
Changes in the individual drought indicators may have occurred since this update was released. For the most current information, please visit Drought Hub.
Figure 10 displays the CDI status for each individual Local Land Services region to 30 June 2019.
The Murray and Riverina Local Land Services (LLS) regions continue to experience drought conditions. The Combined Drought Indicator (CDI) shows the majority of these regions classified as being in the Drought or Drought Affected categories (Figure 11). There has been an increase in the intensification of drought conditions in parts of the western area since May, highlighting a lack of follow up rainfall in June.
Despite some technical issues with data availability at this time of year, the monthly NDVI anomaly data (Figure 12) indicates that most of the region continues to be experiencing below normal levels of greenness. Despite rainfall improving isolated areas of the region in May, the resulting agronomic activity throughout June has not surpassed the long term expectations for this time of year.
The time series charts (Figure 13) showing the individual response of the drought indices for Hay, Griffith and Wagga Wagga reflect the period of beneficial rainfall occurring in May. This resulted in a positive soil water and agronomic response and some opportunity for winter crop potential. More recently it also highlights that follow up rainfall is required to maintain this potential.
Dry conditions throughout June have resulted in the intensification of drought conditions for the Western Local Land (LLS) services region. The Combined Drought Indicator (CDI) continues to show the majority of the area as being in one of the three drought categories of Drought Affected, Drought or Intense Drought (Figure 14). There was a widespread increase in the Drought Affected (Intensifying) category since May, highlighting the June rainfall deficiency across the region.
Field reports indicate that on-ground conditions remain generally poor and the NDVI (Figure 15) shows the continuation of poor agronomic conditions compared to long term expectations.
The time series charts (Figure 16) showing the individual response of the drought indices for Bourke, Broken Hill, and Wentworth reflect the variation between locations. Despite not being drought breaking, Bourke and Broken Hill experienced a positive shift in the indices during April and May. This has been short lived with the indices declining due to the lack of follow up rainfall, highlighting the importance of follow up to instil long term drought relief. Wentworth has experienced a longer period of time where the drought indices have failed to surpass the lowest 10th percentile, indicating that there has been little if any relief to drought conditions over recent months.
Drought conditions continue to intensify across the entire northern area of NSW. The Combined Drought Indicator (CDI; Figure 17) shows that the entire region continues to experience drought conditions with more than half of the region now classified as being in the Intense Drought category. There has also been an increase in the area categorised as Drought Affected (Intensifying) since May and is a direct consequence of the ongoing extremely dry conditions experienced during June.
On-ground conditions remain poor and this is reflected in the NDVI anomaly data (Figure 18) which remains below long term expectations.
The time series charts (Figure 19) showing the individual response of the drought indices for Moree, Walgett and Tenterfield reflect the long term trend of the indices declining and 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 highlight the ongoing intensity and duration of drought conditions occurring in northern NSW.
The majority of the Central Tablelands, Central West, Hunter and Greater Sydney Local Land Services regions (LLS) continue to experience drought conditions with the Combined Drought Indicator (CDI) showing that most of the area is classified in either the Drought Affected, Drought or Intense Drought categories (Figure 20). Conditions in the western and northern areas of the Central West LLS region intensified during June, while the Hunter LLS region has not experienced any improvement in conditions. The small areas in the Central Tablelands and Greater Sydney regions showing Non-drought conditions persist in June and are unchanged since the May State Seasonal Update (SSU), while conditions outside of these areas intensify.
Despite some technical issues and missing data availability for June, the monthly NDVI anomaly data (Figure 21) indicates that the majority of the region continues to experience lower than normal levels of greenness. The agronomic response to rainfall received in isolated areas over recent months has not surpassed the long term expectations in these regions for June.
The time series charts (Figure 22) show the individual response of the drought indices for Cowra, Condobolin and Singleton. Drought conditions have impacted all locations for a long period time, however does show some variation in the nature of the drought between the locations. There was a period of short term relief at Singleton, however any relief 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 six 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 23). The small area classified as Non-drought and Recovering indicated around the Bega district during May, has retracted with the intensification of drought conditions re-occurring in June.
The monthly NDVI anomaly data (Figure 24) experienced some technical issues with data availability that is often common at this time of year. The data that is available continues to indicate that the region is experiencing below normal levels of greenness for June, and given current conditions, this is likely across the entire South East LLS region.
The time series charts (Figure 25) showing the individual response of the drought indices at Bega, Goulburn and Cooma reflects the period of beneficial rainfall occurring in May. This resulted in a positive soil water and agronomic response. Despite this, it also indicates that conditions have recently plateaued and highlights the importance of follow up rainfall for maintaining this potential.
The Bureau of Meteorology (BoM) released the official National Climate Outlook for July to September on 27 June 2019. The rainfall outlook for the next three months suggests drier than average conditions is likely for the majority of Australia.
Daytime temperatures are likely to be warmer than average, except for parts of the Top End and northern Queensland, while overnight temperatures are also likely to be warmer than average, with the highest likelihood forecast for north western Australia and east of the Great Dividing Range. There is an increased frost risk in susceptible areas due to the expectation of dry soils and more cloud-free days and nights.
Climate influences include a positive Indian Ocean Dipole (IOD) and a continued weakening of El Niño-like patterns in the tropical Pacific Ocean. The state of these climate drivers mean that higher pressure systems are more likely over southern and eastern Australia, reducing cloud formation and keeping cold fronts further south than typically experienced.
Rainfall is forecasted to have a lower chance of exceeding median levels for the next three months across the majority of NSW (Figure 26). The latest outlook is an improvement from the May outlook, particularly in the far northwest of the state, where the outlook is currently showing a near equal chance of being wetter or drier than average. The remainder of the state is more likely to experience drier than average conditions.
The historical rainfall outlook accuracy at this time of year is moderate to high for most of NSW. The exception is the far southeast corner of the state where the current forecast accuracy tends to be lower for the next three months.
The BoM temperature outlook for July to September (Figures 27 & 28) indicates an increased chance of warmer than average daytime temperatures across all of NSW. The north west and coastal regions of the state are currently forecast to have a stronger chance of experiencing above average daytime temperatures. Overnight temperatures are also predicted to have a higher chance of being warmer than average in the northeast and coastal areas of the state. Elsewhere, the western half and southern areas of NSW are indicated to have a near equal chance of warmer or cooler than average overnight temperatures. The increased risk of frost has also been noted again this month due to the likely chance of more cloud free days and nights.
The Bureau of Meteorology’s ENSO assessment was released on 25 June 2019. While an El Niño event can’t be completely ruled out for 2019, the ENSO outlook was downgraded to an Inactive El Niño status. Most climate models are currently indicating that conditions in the tropical Pacific will continue to shift further away from El Niño thresholds through the winter. Oceanic and atmospheric indicators are now largely at ENSO-neutral levels, while tropical Pacific sea surface temperatures have cooled over the past fortnight but remain slightly warmer than average. Cloudiness near the Date Line and trade winds have been close to neutral over recent weeks, while the Southern Oscillation Index (SOI) has hovered around El Niño threshold values over the past month.
The 30-day Southern Oscillation Index (SOI) has remained near El Niño threshold levels over the past two weeks, while 90-day values have remained neutral. The SOI for the 30 days ending 23 June was −8.7, with the 90-day value −5.6.
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 (SSTs) for the week ending 23 June were warmer than average across much of the equatorial Pacific Ocean, however parts of the eastern equatorial Pacific have returned to near average temperatures.
Waters are also warmer than average across much of the southwest Pacific, including around the east and southeast of Australia. Sea surface temperatures around the remainder of Australia are broadly close to average, with weak negative anomalies along parts of the western and southern coastline.
The latest values of the three key NINO indices in the tropical Pacific for the week ending 23 June are: NINO3 +0.4 °C, NINO3.4 +0.6 °C and NINO4 +0.7 °C. All three have cooled 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.
The four-month sequence of equatorial sub-surface temperature anomalies (to 20 June) shows a pattern of very weak shallow warm anomalies, and very weak cool anomalies at greater depth. This pattern has been evident, although progressively weakening, since April.
Weak positive anomalies persist across most of the top 100 m of the sub-surface, with most of this region within one and a half degrees of average. For large areas below the 100m depth, weak cool anomalies persist, with anomalies up to one degree cooler than average in the east and mostly less than two degrees cooler than average in the west.
Despite dipping into neutral values during the last week, the overall pattern of the Indian Ocean Dipole is likely to remain positive over the coming months. A positive IOD often results in below average winter–spring rainfall over southern and central Australia. The latest weekly index value to 23 June is +0.26 °C.
Five of the six international models surveyed by the Bureau indicate positive IOD values are likely to continue through winter and spring, suggesting a positive IOD event may be underway. To be considered a positive IOD event, values above the positive threshold (+0.4 °C) would need to be sustained for at least eight weeks.
Surface waters in the central to western Indian Ocean are warmer than average, while in the east, cool anomalies are present south of the Indonesian island of Java, extending eastward to the island of Sumba. The latest fall in the IOD values is simply the result of average to cooler than average waters right on the African coastline, most likely generated in association with severe tropical cyclone Vayu. This means the strongest anomalies are just outside the data collection boundaries used to calculate the IOD index.
As of July 8, the Southern Annular Mode (SAM) is trending toward negative values and is expected to become increasingly negative through mid-July. In winter, a negative SAM means that the westerly wind belt is expanded further north, potentially allowing more rain-producing cold fronts to pass over southern parts of Australia.
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 2 below.
Table 2: 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 (July 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 8 Issue 1.