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NSW State Seasonal Update - December 2018

Prepared by NSW DPI Climate Unit

Drought Status

As of 31 December 2018, large parts of western and central NSW remain in the Drought or Intense Drought categories of the NSW monitoring framework. While some isolated storms were recorded in these parts of the state over December 2018, they were ineffective for significant pasture and crop production. The climatic and agronomic indicators reflect local reports of on-ground conditions; where there has been minimal opportunity for dryland summer cropping, very low levels of ground cover and livestock feeding programs continue. The duration of the current drought event continues to build in the west of the state, where, since 2016, areas in the North West such as Walgett and Coonamble have experienced 18 months or more of extremely dry conditions given long term historical expectations.

The available hydrological data from the NSW farm dam survey re-enforces that surface water supplies are critically low for many areas in Western regions. In this part of NSW, the nature of the drought event has shifted such that farmers and communities are not just managing an agronomic event (low primary production), but the hydrological impact is evident with critically low water reserves.

The eastern seaboard and parts of the ranges and tablelands received moderate to high rainfall over December 2018, with intensive storms continuing to track across this part of NSW. This continues the weak to moderate recovery trajectory being experienced in these regions, building on rainfall received in late spring 2018. While there are continued positive signs of recovery, these regions remain in the Drought Affected category. This reflects that a moderate level of risk remains over the coming one to two months, due to below average soil moisture reserves and high summer evaporation rates. It is prudent to continue to monitor the strength of recovery over the summer of 2018-19 in these regions.

Official climate forecasts from the Bureau of Meteorology indicate that the next three months have a 50% or greater chance of drier than median conditions. The likelihood of exceeding average daytime temperatures over the next 3 months is greater than 75% across all of NSW, and the likelihood of exceeding average overnight temperatures is 80% in most of NSW and greater than 65% across the state. The major climate drivers remain in a near neutral state, and as we approach the southern Autumn Prediction Barrier (February-April each year), the skill level of seasonal climate forecasts typically decline. This suggests that current rainfall patterns, characterised by convective thunderstorm activity, are expected to continue into the coming season. Given that there is a high probability (greater than 80 percent) of temperatures in the coming summer to be above median, a likely forward scenario is for drought conditions across NSW to remain at current levels or intensity over the coming months

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

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.

Rainfall

Rainfall was below average across most of northern New South Wales, and above average in the southwest and southeast. Above average rainfall was recorded along much of the eastern coast, with very much above average rainfall in the northeast. Rainfall totals (Figure 2) ranged from 0-10mm across the northwest of the state, while the majority of the state received between 10 and 100mm of rain, with some regions along the eastern coast received up to 200mm. Parts of the North Coast LLS region received up to 400mm of rainfall.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

Temperature

All of NSW experienced above average daytime temperatures in December with anomalies of up to 4°C occurring in the west of the state and up to 2°C in the east. Average daytime temperatures ranged from 24-39°C across most of the state with alpine areas recording slightly cooler temperatures of 18- 24°C. Overnight temperatures during December were above average to very much above average across most of New South Wales and average in the northeast. Overnight temperature anomalies of up to 5°C occurred across the western part of the state. Average overnight temperatures ranged from 9 to 27°C across the majority of the state with the northwest recording the warmest temperatures and alpine areas recording slightly cooler temperatures between 6-9°C.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

Normalised Difference Vegetation Index (NDVI) Anomaly

The monthly NDVI anomaly data (Figure 5) indicates that most of NSW continues to be experiencing lower than normal levels of greenness. However there are some areas, in central and eastern NSW, that are showing signs of improvement and are exhibiting slightly above average levels of greenness for December. This includes areas around Grafton and Tenterfield, Tamworth through to Singleton, Wellington, Orange, Parkes, Lithgow, Wagga Wagga, Bega, south of Young and central parts in the Greater Sydney LLS region.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

Farm Dam Water Status

As of 8 December, stock water levels remain critically low across large parts of NSW with conditions remaining largely unchanged from the previous update on 22 November. Critically low areas can be identified in most LLS regions, but the most extensive areas of concern cover much of the Western, North West and Central West. There are also large areas of concern in the western Murray and Riverina, reflecting the continuing drought conditions during early December. Regions which experienced isolated thunderstorms during mid-to-late December may have experienced some increases in water levels in dams, however, these falls were not captured in the data provided here. Due to the highly localised nature of convective rainfall, farm dam recovery along thunderstorm tracks is highly isolated and variable across the state.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

Extreme events

A very large low pressure system impacted NSW from 13 to 17 December with rainfall totals in exceedance of 200 mm across parts of the North Coast. Rainfall up to 200mm were also recorded for parts of northeastern NSW.

The Orange area was declared an agricultural natural disaster area after a storm cell hit the central west in mid-December. Minor to severe damage to farm infrastructure was also reported in parts other parts of the Central Tablelands as well as the Central West.

Additional storms passed through Blue Mountains, Central Coast and the Sydney Basin on 19 December bringing hail and heavy rain. Severe thunderstorms also affected the NSW coast on 20 December.

During December, NSW experienced extremely hot daytime temperatures (19-21 December and 26-31 December) and overnight temperatures (7-22 December, 26-31 December).

Rainfall Index

The Rainfall Index (RI, Figure 7) show that the majority of NSW continues to exhibit below average to extremely low values in the RI. Parts of the northern Hunter and central North Coast are experiencing average RI values.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

Soil Water Index

The Soil Water Index (SWI, Figure 8) is currently extremely low for the majority of NSW with regions along the eastern seaboard experiencing below average to average values.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

Plant Growth Index

The Plant Growth Index (PGI, Figure 9) displays a similar pattern to the SWI, with the majority of the state experiencing extremely low values. PGI values along the coast and in alpine regions are below average to average.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

Drought Direction Index

The Drought Direction Index (DDI, Figure 10) indicates an expansion of regions experiencing a negative trend in the Rainfall Index, particularly in the northwest Western LLS, and the northern North West and North Coast LLS regions. The majority of the state retains a weakly positive DDI, indicating a wetter trend.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

Changes in the individual drought indicators may have occurred since this update was released. For the most current information, please visit Drought Hub.

CDI status for the regions

Figure 11 displays the CDI status for each individual Local Land Services region to 31 December 2018.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

Murray and Riverina regions

Drought conditions have continued to expand in the Murray and Riverina Local Land Services (LLS) regions during December (Figure 12). A large area, centered on West Wyalong, has transitioned into the Intense Drought category, and areas between Deniliquin, Hay and Coleambally are also currently in the Intense Drought category. The extent of the LLS regions in the Drought category has also expanded. There is an area to the east of Holbrook and Albury that has transitioned into the Drought Affected (Intensifying) category and should be monitored closely in the coming weeks.

The monthly NDVI anomaly data (Figure 13) indicates that there has been improvement in conditions in the eastern half of the region since the November SSU, with areas around Lockhart, Wagga Wagga, and Cootamundra experiencing average to above average levels of greenness for December. The western half of the LLS regions have experienced a decline in the level of greenness since the last update, with areas including Hay, Moulamein, Deniliquin, Finley, and West Wyalong showing the greatest decrease in levels of greenness.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

Western region

The Western Local Land Services (LLS) region continues to experience drought conditions with the entire region being in one of the three drought categories of Drought Affected, Drought or Intense Drought (Figure 15). Scattered storms have brought some relief to farms in the south of the region, although the meteorological network is not dense enough to accurately capture storm rainfall on a farm by farm basis. Available field reports indicate that many livestock producers in this region are still feeding livestock.

The monthly NDVI anomaly data (Figure 16) indicates although there has been a slight improvement in the levels of greenness for some parts of the LLS region, conditions are still well below expected levels of greenness for December. Minimal grass cover across large parts of the region continue to be of concern, with risks like dust storms and erosion losses remaining at extremely high levels.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

North West, Northern Tablelands and North Coast regions

Conditions across the North West, Northern Tablelands and North Coast Local Land Services (LLS) regions are varied, with parts seeing improvements since the November State Seasonal Update (Figure 18), whilst other areas deteriorated. Information from the Combined Drought Indicator (CDI) shows that since the last SSU, conditions have deteriorated into the Intense Drought category around Warialda, Inverell, Tenterfield, while areas around Narrabri, Gunnedah and Quirindi have transitioned out of the Intense Drought category.

The North Coast LLS region continues to show signs of recovery, with areas around Ballina, Grafton and Coffs Harbour in the Recovering and Non-Drought categories. However, without continued rainfall over the next few weeks, these areas will transition back into one of the three drought categories. At the time of writing this update, these areas, along with parts of the north-east corner of the Northern Tablelands LLS region, show signs of deteriorating conditions.

Some high rainfall was recorded south of Tamworth around Nundle during December 2018, and satellite data indicates that there has been a flush of growth over the last 3-4 weeks. While this is positive it did little to shift the drought indicators, which provided an aggregated assessment of conditions over the past twelve months. As a result the region remains in the Drought or Intense Drought category.

The monthly NDVI anomaly data (Figure 19) indicates that there has been improvement in conditions since the November State Seasonal Update. Areas experiencing average to above average levels of greenness for December include parts surrounding Quirindi, Tamworth, Grafton and Barraba.  These areas are responding to falls of rain that have been experienced in these parts over the past three months.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

Central Tablelands, Central West, Hunter and Greater Sydney regions

Conditions across the Central Tablelands, Central West, Hunter and Greater Sydney Local Land Services (LLS) regions have generally improved since the November State Seasonal Update. The Hunter LLS region has seen significant reductions in the extent of the area in the Intense Drought category. Intense Drought has now retracted, and is currently being experienced primarily in the north-west of the LLS region. The Central Tablelands and Greater Sydney LLS regions currently do not have any parish in the Intense Drought category, however ongoing falls of rain will be needed to ensure that parts of the regions do not transition back into the Intense Drought category. A large part of the southern Central West is still considered to be in the Intense Drought category, including areas around Condobolin, east of Lake Cargelligo, Forbes, Parkes and Grenfell. Areas in the north of the region, including to the west of Coonamble and around Coonabarabran are also currently in the Intense Drought category.

Conditions continue to improve along the coast, with areas around Forster and Gosford currently in the Recovering or Non-Drought categories.

The monthly NDVI anomaly data (Figure 22) shows continued improvement in plant condition since the November State Seasonal Update. There are currently parts of the LLS regions experiencing average to above average levels of greenness for December including isolated areas surrounding Merriwa, Singleton, Oberon, Bathurst, Forbes and Wellington. This improvement is in response to falls of rain that have been experienced in these parts over the past three months.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

South East region

Conditions across the South East Local Land Services (LLS) region have improved since the November State Seasonal Update. The area in the Intense Drought category has retracted significantly and is currently being experienced primarily in the regions south of Cooma and to the west of Nowra. The extent of the region in the Drought and Drought Affected categories remains stable, as does the area in the Recovering and Non-Drought categories.

The monthly NDVI anomaly data (Figure 25) shows continued improvement in plant condition since the November State Seasonal Update. There are currently parts of the LLS region experiencing average to above average levels of greenness for December including parts surrounding Bega, Nowra and Braidwood.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

Official national outlook

The official national climate outlook for January to March was issued by the Bureau of Meteorology on 20 December 2018. The outlook shows that Western Australia, parts of the Northern Territory and eastern mainland Australia are likely to be drier than average over the next three months. Elsewhere there is a near equal chance of drier or wetter than average conditions.

The outlook shows January to March daytime and overnight temperatures have an increased chance of being warmer than average across all of Australia, except for parts of the western Western Australia coastline that are likely to have cooler than average overnight temperatures.

NSW outlook

For New South Wales, the rainfall outlook (Figure 27) for January to March indicates that there is an increased chance of drier than normal conditions (between 65-75%) across large parts of NSW over the next three months. Areas that have a near equal chance of wetter or drier average conditions include the central and north coast regions, parts of the central west and tablelands, southern and western NSW.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

The temperature outlook (Figures 28 & 29) indicates that there is an increased chance of warmer than average daytime (above 75% chance) and overnight temperatures (above 60% chance) across all of NSW.

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

Climate drivers

ENSO

As of 8 January 2018, the Bureau of Meteorology’s ENSO assessment remains at El Niño Alert.  Pacific Ocean sea surface temperatures (SSTs) have cooled slightly and are currently just below El Niño thresholds in the ENSO-neutral range. While SSTs remain above average across the tropical Pacific, atmospheric indicators of an El Niño, such as cloudiness and trade winds, have remained neutral. Five of the eight international climate models suggest that tropical Pacific SST will remain above El Niño thresholds through March, however, an atmospheric response is required for an El Niño event to occur.

Southern Oscillation Index and other indicators

The 30-day SOI value as of 6 January is positive (30 day value = +6.2, 90 day value = +4.0), but remains in the neutral ENSO range.

Cloud levels at the junction of the equator and the International Date Line has fluctuated around average over the last two months. Cloudiness would typically be well above average during an El Niño.

Trade winds were stronger than average across the western to central tropical Pacific during December but have weakened slightly in the first week of January. A sustained weakening of trade winds is sometimes indicative of El Niño.

For an accessible explanation of this grph contact the author kim.broadfoot@dpi.nsw.gov.au

Sea surface temperatures

Monthly sea surface temperatures anomalies (SST) for December (Figure 31*) were warmer than average across the equatorial Pacific Ocean. The December values were +0.8°C for NINO3, +0.8°C for NINO3.4, and +0.9°C for NINO4. These values have decreased slightly in the first week of January.

* Note this is a different source of data than usually provided because of delays in the provision of SST analysis from NOAA.

For an accessible explanation of this grph contact the author kim.broadfoot@dpi.nsw.gov.au

Sea Sub-surface Temperatures

Sub-surface temperatures as of 31 December (Figure 32) show warmer than average waters in the top 150m of the subsurface across the equatorial Pacific. Weak cool anomalies have appeared below the warm anomalies in recent weeks. The warm anomalies have weakened compared to previous months, but remain well above average in the western Pacific.

For an accessible explanation of this grph contact the author kim.broadfoot@dpi.nsw.gov.au

Indian Ocean

The Indian Ocean Dipole (IOD) is currently neutral. The IOD has little influence on Australian climate between December and April.

Southern Ocean

The Southern Annular Mode (SAM) is currently positive and is predicted to remain positive over the coming two weeks. Positive SAM in summer tends to promote synoptic rainfall across southern Australia.

How does it work?

For an accessible explanation of this map contact the author kim.broadfoot@dpi.nsw.gov.au

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 Drought Hub.

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 2 below.

Table 2: Description of the Combined Drought Indicator framework

CDI Phase

Technical definition

Description - typical field conditions

Intense Drought

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.

Drought

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.

Recovering

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.

Non-drought

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 (2018), Panorama Avenue, Bathurst 2795 and data which is © Commonwealth of Australia 2018, 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, 2018. 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 (December 2018). 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 6 Issue 10.