NSW State Seasonal Update - January 2020

Prepared by NSW DPI

NSW overview

Drought continued across most of NSW in January 2020. Much of western NSW remained dry, while parts of north east and central NSW received higher rainfall totals. Field and on-ground responses were mixed, and the need for consistent follow-up rainfall for drought recovery remains. The official climate outlook is neutral and indicates a near equal chance of receiving above or below median rainfall for the next three months. The continued management of livestock feed deficits, water shortages and the potential of reduced crop output is expected well into 2020..

The NSW DPI Combined Drought Indicator (CDI) shows 100% of NSW in one of the three drought categories. The majority of eastern NSW remained in the Intense Drought category despite higher rainfall. Rainfall totals were lower across western NSW. Conditions intensified and much of the far west remains in the Intense Drought category. The CDI continues to show that soil moisture and plant growth remains low across the state.

Some areas in north eastern and central NSW received high rainfall during January. This caused a short-term pasture response and some areas now have potential to grow fodder crops. These opportunities are short-term unless follow-up rainfall occurs. Some of the rainfall received was intense. There were instances of improved farm dam water levels and domestic supplies, however ground cover loss, soil erosion and damage to infrastructure were also reported. Parts of the northern cropping belt have improved soil moisture levels; though further rainfall is needed to reduce risk in the upcoming 2020 winter crop.

Western, southern and central areas of the state remained comparatively dry in January. Drought conditions continued with only isolated areas receiving some storm rainfall. There is currently little expectation of a pasture growth response, and there has been minimal improvement to soil moisture levels in much of the southern and central cropping belt. The enduring dryness contributed to large dust storm events occurring in January. The risk of further large dust storms occurring remains high.

The Bureau of Meteorology (BoM) Climate Outlook released on 6 February 2020 indicates that the majority of NSW has a near equal chance of receiving above or below median rainfall for the period to May 2020. All climate drivers are currently neutral meaning that the chance of rainfall is likely to be driven by the volatile short-term synoptic weather patterns.

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 component of drought impact 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 one of the three CDI drought categories. The map indicates that as of 31 January 2020, NSW continues to experience long-term drought conditions. The majority of NSW has experienced drought conditions for longer than 24 months.

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

Rainfall

The highest rainfall totals were received in eastern New South Wales (NSW) during January. Much of the rain came as convective summer storms and there was significant variability between regions and also farm-to-farm. The North Coast received the largest totals ranging between 200-400mm for the month. Parts of the North West and Northern Tablelands Local Land Services (LLS) regions also received higher totals of 100-200mm for the month, Elsewhere, higher rainfall totals were more isolated, while large areas in central and western NSW received totals of less than 25mm for the month.

Temperature

The average January daytime temperatures (Figure 4) were above 30°C across most of NSW, with temperatures up to 42°C in the Western, Central West and North West Local Land Services region. Coastal areas experienced temperatures between 18-33°C. Overnight temperatures (Figure 5) were above 12°C across NSW.

Bureau of Meteorology data indicates that daytime temperatures were average to highest on record and overnight temperatures were above average to very much above average for the majority of NSW.

Normalised Difference Vegetation Index (NDVI) Anomaly

The Normalised Difference Vegetation Index (NDVI) anomaly (Figure 6) shows that plant greenness levels for January 2020 remain below the expected long-term levels across 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 late in 2019 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.

Significant Events

Heightened Dust Activity

The high level of dust activity continued during January. Large areas of low ground cover are likely to continue the risk of increased dust activity for at least the short-term.

The NSW Environment Energy and Science (EES) DustWatch provides a dust monitoring service. The January edition of the DustWatch report is scheduled to be available in the second half of February.

As the risk of dust activity increases, it is recommended 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.

Bushfires

A number of bushfires impacted eastern NSW during January 2020.  Drought and other climatic variables such as humidity are one of many factors that affect bushfire risk and occurrence.  Further information about bushfires is available from emergency management authorities such as the Rural Fire Service.

Soil Water Index

The Soil Water Index (Figure 7, SWI) remains below average to extremely low across the majority of NSW. Despite higher rainfall totals received in eastern NSW in January, there has yet to be wide scale improvements in the Soil Water Index. While the index suggests slightly better soil moisture conditions in parts of western NSW, the Plant Growth Indicator, on-ground reports and available satellite imagery continues to indicate that low soil moisture is still an important factor influencing drought conditions.

Plant Growth Index

The Plant Growth Indicator (Figure 8, PGI) continues to indicate below average to extremely low plant growth. Despite some areas receiving higher rainfall totals during the month, the Plant Growth Indicator suggests a slow plant growth response and the need for further follow-up rainfall. Parts of western NSW had a slightly higher Plant Growth Index compared to other areas of the state. However, the absolute value of the PGI remains low, indicating that growth conditions remain poor in this region. The available satellite imagery supports this by showing low levels of plant health compared seasonal expectations.

Rainfall Index

Despite rainfall occurring in parts of the state throughout January, the Rainfall Index (Figure 9, RI) shows most of the state remaining below average to extremely low. While there have been significant individual falls this month, up to 100mm or more in parts of the Northern NSW, it will take a few months of consistent rainfall for the RI to move into the average range.

The Rainfall Index shows slightly improved conditions in parts of western NSW. However the Plant Growth Index and satellite imagery continues to suggest that the rainfall has been ineffective for improving on-ground conditions.

Drought Direction Index

The Drought Direction Index (Figure 10, DDI) indicates the areas receiving higher rainfall totals during the month. The trend to wetter conditions occurred primarily in the north east, as well as isolated parts in the central area of the state. Elsewhere, the continuation of the widespread drier trend continued.

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 11 displays the CDI status for each individual Local Land Services region to 31 January 2020.

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 12) shows that the region is in one of the three drought categories. Isolated rainfall during January provided meteorological relief to some areas, however there has been little change to on-ground conditions. Conditions in the north of the region continued to intensify, reflecting lower rainfall totals received in those areas during the month.

The monthly NDVI anomaly data (Figure 13) shows that the LLS regions continue to experience below normal levels of greenness. Extended periods of below average and ineffective rainfall have caused poor agronomic activity in the region. This has been compounded by hot summer conditions.

The time series charts (Figure 14) shows the individual response of the drought indices for Hay, Finley and Temora. The charts show the long duration of dry conditions and that most of the rainfall received has had little benefit to soil moisture and plant growth. The drought indices at the end of January reflect the dry and hot conditions that have been experience this summer.

Western region

The Western Local Land Services (LLS) region continues to experience widespread drought conditions. Despite some isolated rain received during January, the Combined Drought Indicator (CDI, Figure 15) shows that the whole region is in one of the three drought categories. A consistent follow-up rainfall pattern is critical to provide a sustained improvement to conditions.

The monthly NDVI anomaly data (Figure 16) shows below normal levels of greenness compared to the long-term expectations. This has been driven by poor agronomic activity due to the extended period of insufficient and ineffective rainfall. In addition to enduring dryness, producers in the west and far west are also managing the effect of total grazing pressure and hot summer conditions.

The time series charts (Figure 17) 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 2019. The rainfall received at Bourke and Wentworth was ineffective, as 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

Despite parts of the region receiving higher rainfall totals for the month, drought continues to impact the entire North West, Northern Tablelands and North Coast Local Land Services (LLS) regions (Figure 18). Field reports continue to confirm the severity of drought conditions being experienced across the region.

The monthly NDVI anomaly data (Figure 19) 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 long-term agronomic activity.

The time series charts (Figure 20) 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.

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 region experienced variable rainfall patterns throughout January. Much of the area remained comparatively dry, however some areas did receive higher rainfall totals. The response to rainfall has been minimal and further rain is required to initiate drought recovery.

The monthly NDVI anomaly data (Figure 22) 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 an extended period. Hot summer conditions have also impacted the agronomic capacity of plants and increased evaporation rates.

The time series charts (Figure 23) show the individual response of the drought indices for Cowra, Condobolin and Singleton. Drought conditions have impacted the region for an extended period. 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 large rainfall deficits and that the rainfall received has been ineffective.

South East region

The South East Local Land Services (LLS) region continues to experience widespread drought conditions. The Combined Drought Indicator (CDI, Figure 24) shows that the whole region is in one of the three drought categories and that the intensification of conditions continues. On-ground reports indicate that the region continues to manage very difficult circumstances during the summer. In many areas this has been compounded by bushfire impact.

The monthly NDVI anomaly data (Figure 25) 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 26) 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 2019. This rapidly fell below drought thresholds in July 2019. 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 6 February 2020. March to May has roughly equal chances of being wetter or drier than average for most of Australia. A pocket of southeast and central Queensland, central-north NSW and parts of Western Australia are slightly more likely to be drier than average, while parts of the far north are more likely to be slightly wetter than average. Most of Australia's climate influences are now neutral. While outlooks for drier than average conditions have eased compared to those issued in late 2019, several months of above average rainfall are needed to see a recovery from current long-term rainfall deficiencies.

Daytime temperatures for March to May are likely to be warmer than average over Australia. Warmer nights are also likely for most of Australia during March to May.

NSW outlook

Large parts of NSW are forecast to have a near equal chance of receiving wetter or drier than average conditions during March to May (Figure 27). The region around Bourke, Cobar and Tamworth have a slightly lower chance of receiving median rainfall during the period.

The historical rainfall outlook accuracy for the forecast period is moderate for most of NSW.

The BoM temperature outlook for March to May (Figures 28 & 29) indicates higher chances of warmer than average daytime and overnight temperatures for the majority of NSW, particularly in the north eastern and coastal areas of the state.

Climate drivers

El Niño–Southern Oscillation (ENSO)

The Bureau of Meteorology’s (BoM) El Niño–Southern Oscillation (ENSO) Outlook was released on 4 February 2020. Atmospheric and oceanic indicators of ENSO remain neutral, however surface waters in the tropics near to and west of the International Date Line are warmer than average. This could potentially draw some moisture away from Australia.

International climate models surveyed by the Bureau indicate ENSO is likely to remain neutral until at least the end of the southern hemisphere autumn. This means it will have limited influence on Australian and global climate in the coming months.

Southern Oscillation Index

The average Southern Oscillation Index (SOI) for the 30 days ending 2 February 2020 was +0.8. The 90-day value was -4.1. 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 remained warmer than average across much of the western equatorial Pacific Ocean during January. (Figure 31). Sea surface temperatures were also warmer around most of Australia during January.

The December values of the three key NINO indices in the tropical Pacific were:  NINO3 +0.3°C, NINO3.4 +0.5°C and NINO4 +0.8°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 January) shows the top 150 m of the equatorial Pacific is warmer than average between about 160°E and 160°W, reaching more than two degrees warmer than average. Slightly cooler than average waters are present at a depth of around 50 to 150 m across most of the remainder of the equatorial Pacific.

The pattern has remained somewhat similar since November, with mostly weak to moderate temperature anomalies.

Indian Ocean

The Indian Ocean Dipole (IOD) is neutral. The IOD typically has little influence on Australian climate from December to April. When the monsoon trough shifts southwards into the southern hemisphere at this time of year, it changes the broadscale wind patterns. This means that the IOD pattern is unable to form. The latest weekly value to 2 February was −0.06 °C.

Southern Ocean

The Southern Annular Mode (SAM) is currently neutral. A negative phase of the SAM can bring a drying influence to parts of Australia, such as the negative event that occurred from October until late December 2019.

How does it work?

Much of the information in the Seasonal Conditions Report is sourced from the NSW DPI Enhanced Drought Information System (EDIS) ™. The EDIS system is currently available in prototype form and is subject to an intensive ground truthing process. For more information, visit the interactive website via DroughtHub.

EDIS is an ongoing project aimed at improving the quality and timeliness of efforts to monitor conditions across the state. Key features of the system are:

• It tracks drought by using four indicators; rainfall, soil water, plant growth, as well as tracing rainfall trends. Agronomic conditions have equal value to rainfall recorded at meteorological stations.
• The Combined Drought Indicator (CDI) brings this information together, and has been designed to characterise developing drought conditions. The key purpose for building the CDI was as a drought early warning system.
• The rainfall, soil moisture and plant growth indicators in EDIS account for conditions over a 12 month window. This provides a compromise between a highly sensitive indicator (e.g. six months) and a less sensitive indicator (e.g. 24 months).
• Climate and remote sensing data drive the information system at a high resolution, but the CDI is reported at a Parish level.
• Because of its configuration and purpose, there will be differences to the indicator used in the National Drought Monitoring Framework (the Australian Rainfall Deficiency Analyser) which relies on rainfall alone.
• The CDI has three drought categories that characterise NSW according to drought intensity as well as the main drivers of a drought event (meteorological, hydrological and agronomic). DPI considers areas Drought Affected to be experiencing a drought event.
• The Drought Affected category encompasses a wide range of conditions from the very early stages of drought entry through to a drought event becoming intense. This enables the drought monitoring system to detect a drought event early. It is also possible to stay in the Drought Affected category for some period of time.

The way in which the indicators are combined to form the CDI is described in Table 1 below.

Table 1: The way in which the indicators are combined to form the CDI.

The NSW State Seasonal Update is provided each month by the NSW DPI Climate Branch.

Information used in this report was primarily sourced from the Australian Bureau of Meteorology, the US National Oceanic and Atmospheric Administration, the International Research Institute for Climate and Society (Columbia University), Geoscience Australia’s Digital Earth Australia Program, and NSW Department of Primary Industries.

Maps in this document contain data which is © Spatial Services – NSW Department of Finance, Services and Innovation (2020), Panorama Avenue, Bathurst 2795 and data which is © Commonwealth of Australia 2020, Australian Bureau of Meteorology, Melbourne. All rights reserved.

The seasonal outlooks presented in this report are obtained from the Australian Bureau of Meteorology and other sources (including World Meteorological Organisation Global Producing Centres). These outlooks are general statements about the likelihood (chance) of (for example) exceeding the median rainfall or minimum or maximum temperatures. Such probability outlooks should not be used as categorical or definitive forecasts, but should be regarded as tools to assist in risk management and decision making. Changes in seasonal outlooks may have occurred since this report was released.

All climate and remote sensing input data is supplied to the Enhanced Drought Information System ™ under the Australian Creative Commons Licence (CCY 4.0) and is made available by the Terrestrial Ecosystem Research Network