Prepared by NSW DPI Climate Unit
The drought event has eased across some part of New South Wales (NSW) during May 2019. Despite this relief, drought management is still ongoing in most regions, and will remain a feature of farming across NSW for the 2019 winter period. For some regions this may involve preparing for recovery, while in others, full scale drought mitigation continues.
Significant rainfall in early May continued an easing of conditions for some areas of the state. Parts of western NSW extending south into the Riverina received high May rainfall totals. This has provided short term feed relief and the opportunity to sow winter crops. This rainfall does not represent a full break from drought conditions, and there has been little follow up rainfall for the remainder of the month.
The distribution of May rainfall was variable with significant areas of the state remaining dry. Large areas in the far west and north east regions of NSW will continue to experience feed shortages and lack of soil moisture over the remainder of the winter crop sowing window. Extensive areas across the state continue to wait for a significant break in conditions, with a particular concern being the cereal growing regions in the north-west of the state.
The NSW DPI Combined Drought Indicator (NSW CDI) provides a general regional assessment of the complex pattern of field conditions across NSW. The CDI at the end of May reflects an easing of the drought, with parts of the state changing from the Intense Drought to the Drought category. This shift reflects a meteorological recovery given the rainfall received in early May, however agronomic and hydrological conditions remain challenging for most of the state. Overall the CDI is relatively unchanged since the April State Seasonal Update (SSU) with 97.4% of NSW in one of the three drought categories.
Official climate forecasts released on 30 May 2019 from the Bureau of Meteorology (BOM) indicate a higher chance of drier than average conditions across NSW for the next three months. This is largely driven by the Indian Ocean Dipole (IOD), which is forecast to become positive during winter 2019. The IOD becomes an increasingly dominant influence on rainfall patterns in central and southern Australia at this time of year. The outlook also indicates that temperatures have a higher chance of being warmer than average across NSW between June to August. The latest ENSO Outlook issued by the BOM on 28 May 2019 indicates an El Niño Watch status, with approximately a 50% chance of an El Niño developing in 2019.
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.
Variable rainfall patterns were again observed in May (Figure 2). Significant rainfall was received in a centralised band in the Western Local Land Services (LLS) region where totals between 25-100mm were received. This reflected positive anomalies of 25-50mm in isolated areas of this region. This rainfall also extended south into parts of the Riverina and Murray LLS regions. The far north coast also received isolated higher totals, however, like the majority of the entire NSW coast, this rainfall was well below median for May. Elsewhere across NSW, rainfall totals were smaller and generally below median for this time of year.
Daytime temperatures ranged between 21-27°C across northern NSW including the coast, with higher elevations in the north ranging between 15-21°C. In the south temperatures ranged from 12-21°C, while the southern areas at higher elevations ranged between 12-18°C .
Overnight temperatures ranged between 8-12°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 0-9°C.
The Normalised Difference Vegetation Index (NDVI) summary for May showed the general continuation of poor plant conditions across the state (Figure 5). The general agronomic conditions across NSW remain well below long term expectations. As indicated, any improvements have been isolated, highlighting the patchy distribution and effectiveness of the rainfall received over recent months.
While farm dam water volumes have improved in some areas of the state during May, the general situation across NSW is that farm dam levels remain relatively low (Figure 6). The situation is generally more severe moving west, however there has been some relief in areas that experienced higher rainfall totals in May. Conversely, the variable rainfall patterns experienced throughout May means that there are still large areas of NSW with critically low farm dam water levels. Tablelands and coastal areas have shown some improvements over recent months, however there is still a large degree of variability for farm dam status in these areas.
The Soil Water Index (Figure 7, SWI) remains below average and extremely low across the majority of the state. Rainfall in May contributed to an improvement in the southern and other isolated areas of the Western Local Land Services (LLS) region. The remainder of the state continues to show an extremely low SWI with little change since April.
The Plant Growth Indicator (Figure 8, PGI) shows the majority of NSW having below average to extremely low plant activity. Despite this, areas receiving higher rainfall totals in the west during May have improved since April, but remained similar in the east.
Rainfall during the March to May period has contributed to an improved Rainfall Index (Figure 9, RI) in parts of the Western LLS region. Elsewhere the RI remained below average to extremely low, especially in the north east of the state and a large area in the Western LLS region. This highlights the variable distribution of rainfall over recent months and limited follow up rainfall.
The Drought Direction Index (Figure 10, DDI) indicates a wetter trend for large areas of NSW during May and reflects the areas receiving higher rainfall totals for the month. The remainder of the state continues to exhibit a drier trend.
Changes in the individual drought indicators may have occurred since this update was released. For the most current information, please visit DroughtHub.
Figure 11 displays the CDI status for each individual Local Land Services region to 31 May 2019.
The majority of the Murray and Riverina Local Land Services (LLS) regions continue to experience drought conditions, with the Combined Drought Indicator (CDI) showing widespread areas of the regions classified as Drought and Drought Affected (Figure 12). There has been an easing in conditions since the April State Seasonal Update (SSU), however improvements are still variable in distribution and follow up rainfall is required to improve the chance of longer term recovery. The southeastern area of the Murray LLS region continues to show longer term signs of recovery.
The monthly NDVI anomaly data (Figure 13) indicates that the entire region continues to be experiencing below normal levels of greenness. Despite rainfall impacting some of the region in May, agronomic activity is still below long term expectations for this time of year, particularly in the south east of the region where there has been a history of higher rainfall totals over recent months.
Some areas in the Western Local Land Services (LLS) region experienced a shift in the nature of drought conditions during May. Some parts through the central area of the region received significant May rainfall leading to an easing of conditions, with some isolated positive agronomic responses being reported. Some improvements can be observed in the monthly NDVI anomaly data (Figure 16). Despite this, the Combined Drought Indicator (CDI) still shows the majority of the area as being in one of the three drought categories of Drought Affected, Drought or Intense Drought (Figure 15). Follow up rainfall for the areas experiencing some short term relief is required to increase the confidence of longer term recovery.
Despite some areas of the region showing improvement, there are still large areas that received little rainfall and therefore continue to experience very poor on ground conditions. Feed and water conditions remain severe in these districts. The NDVI (Figure 16) shows the continuation of extremely poor agronomic conditions relative to long term expectations across most of the region.
The Combined Drought Indicator (CDI; Figure 18) shows that the entire region continues to experience drought conditions and is classified in either the Drought Affected, Drought or Intense Drought categories. Lower rainfall totals in May have done little to alleviate conditions. Areas showing signs of improvement are generally confined to isolated parts on the coastal plain and a small area around Gunnedah. As suggested by the Soil Water Index (SWI), a consistent rainfall pattern is still required over coming months to replenish long-term soil moisture deficits.
The monthly NDVI anomaly data (Figure 19) indicates that the entire region continues to experience below normal levels of greenness, highlighting the agronomic challenge that continues to exist.
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 21). The small areas in the Central Tablelands and Greater Sydney regions showing Non-drought conditions persist in May and are unchanged since the April State Seasonal Update (SSU).
A consistent rainfall pattern is still required over coming months to correct long term moisture deficits and provide any dramatic agronomic recovery. The monthly NDVI anomaly data (Figure 22) indicates that the majority of the region continues to be experiencing below normal levels of greenness and that the response to rainfall has been slow.
Conditions remain mixed across the South East Local Land Services (LLS) region at the end of May. The majority of the region is still classified as being in either the Drought Affected, Drought or Intense Drought categories as shown in the Combined Drought Indicator (CDI) (Figure 24). Small areas classified as Non-drought and Recovering persist around the Bega district during May, with no significant changes to the extent of this area. Relatively dry May conditions have placed increasing significance on the requirement for follow up rainfall to initiate any widespread or long term agronomic recovery.
The monthly NDVI anomaly data (Figure 25) indicates that the entire region continues to be experiencing below normal levels of greenness for May and that there has yet to be significant response to late April or May rainfall.
The Bureau of Meteorology (BoM) released the official national climate outlook for June to August on 30 May 2019. The rainfall outlook for the next three months suggests a drier than average winter is likely for much of eastern and parts of southern Australia. Large areas of Western Australia (WA) have a neutral forecast with no strong indication towards wetter or drier than average conditions, however the mid west region of WA has a higher chance of above average rainfall.
Daytime temperatures are forecast to be warmer than average for most of Australia. The majority of Australia is also predicted to have warmer than average overnight temperatures with the exception of western South Australia, north west New South Wales and southern Queensland.
For New South Wales, the rainfall outlook for May to July indicates a widespread low chance of exceeding median rainfall for the next three months (Figure 27). The forecast is currently being influenced by the emerging dominance that the Indian Ocean Dipole (IOD) is expected to have over the winter months and into spring for central and southern Australia.
The May forecast accuracy is still low for large parts of NSW, particularly in the south west and central west areas of the state, and should still be used with caution than at other times of the year. While the probability of rainfall is low, there are still possible synoptic scenarios that may develop and lead to relief being experienced in some areas of the state. These unique scenarios tend to develop quickly and are difficult to predict beyond a short term period.
The BoM temperature outlook for June to August (Figures 28 & 29) indicates an increased chance of warmer than average daytime and overnight temperatures across NSW. Despite the prediction of warmer nights overall, dry soils and more cloud free nights with the prediction of drier conditions may increase frost risk in susceptible areas. Overnight temperatures in the north west of NSW are predicted to have a near equal chance of being warmer or cooler than average, while coastal areas are forecast to experience warmer overnight temperatures.
The Bureau of Meteorology’s ENSO assessment was released on 28 May 2019. The ENSO outlook is currently at El Niño Watch. Models indicate the tropical Pacific Ocean will ease away from El Niño levels, becoming neutral during winter. An El Niño event typically brings drier than average conditions to eastern Australia in winter and spring. Note that model accuracy when forecasting through the autumn months is lower than at other times of the year. Forecast accuracy improves for outlooks issued in June.
The Indian Ocean is expected to become the dominant influence on Australian climate while the ENSO forecast currently remains relatively neutral. Models are predicting that a positive phase of the Indian Ocean Dipole (IOD) is likely to develop in the coming months, where a positive IOD increases the probability of below average winter–spring rainfall over southern and central Australia.
The 30-day Southern Oscillation Index (SOI) remains neutral (Figure 30). The SOI value for the 30 days to 26 May was −7.4, while the 90-day average has risen to −5.3. 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. The SOI typically becomes more stable and a better indicator of climatic conditions as the Australian monsoon season ends.
Cloudiness near the Date Line has generally been above average since early December, however values have fluctuated closer to average since late April. Equatorial cloudiness near the Date Line typically increases during El Niño.
Trade winds for the 5 days ending 26 May are weaker than average across most of the western half of the tropical Pacific. This is likely associated with the recent stalling of Madden-Julian Oscillation activity over the western hemisphere and Africa, potentially causing a small rise in sea surface temperatures (SSTs) in the central and western tropical Pacific Ocean and a drop in the Southern Oscillation Index (SOI). Persistent weaker trade winds could lead to further warming of parts of the tropical Pacific Ocean, and raise the odds of El Niño once again, however the majority of surveyed models suggest the tropical Pacific will cool to neutral levels during winter.
Monthly sea surface temperature (SST) anomalies for May (Figure 31) were warmer than average across the tropical Pacific Ocean. The latest values for the three key NINO indices in the Tropical Pacific (for the week ending 27 May 2019) are: NINO3 +0.7°C, NINO3.4 +0.8°C and NINO4 +0.7°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 23 May) shows a similar pattern of sub-surface anomalies for May to those for April. Despite this anomalies are generally weaker this month than last.
Very weak positive anomalies persist across most of the top 100 m of the sub-surface. Below 100 m depth, weak cool anomalies also persist, with some parts of the sub-surface up to two degrees cooler than average.
Warming off the horn of Africa in the Indian Ocean has meant that the IOD index exceeded the positive threshold value last week. Five of the six models show a tendency towards a positive IOD being maintained throughout winter. To be considered an event, these positive values would need to be maintained for at least 8 weeks. A positive IOD typically means below average winter–spring rainfall for much of southern and central Australia. The IOD is expected to become the dominant influencer of medium term rainfall probability over coming months.
The Southern Annular Mode is currently neutral and expected to trend towards positive values in the next two weeks. Positive SAM during winter pushes high pressure systems further south, forcing westerly fronts off the coast and decreasing the likelihood of southern Australian synoptic rainfall.
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.nsw.gov.au.
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 (May 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 5.