NSW Seasonal Conditions Summary May 2017

Overview

During April, rainfall was slightly below average to near-average across 58 per cent of NSW, but was above average in areas of the south and far west. Rainfall was below average across areas of the north east, northern slopes and plains, upper Hunter valley, Sydney basin, central tablelands, central west and southern highlands. Daytime and overnight temperatures were generally near-average in the west of the state but slightly below average in the east.

Pastures generally responded well to the April rainfall, particularly in the central and southern areas of the state. Pasture growth improved across areas of southern, western and central western NSW and was maintained across areas of coastal NSW and the tablelands. Growth remained limited across some areas of NSW. Seed of some pasture species such as Phalaris and lucerne is in short supply, with an increased interest in pasture sowing in some areas.

Relative to historical records, pasture growth ranged from average to above average across areas of northern, eastern, southern and central NSW. Growth was below average growth across limited areas of the state.

Other pasture growth models indicated near-average growth across southern, coastal and areas of western NSW. Growth in the far west and in some areas of the north coast was below average. Above average growth was indicated for the tablelands, Monaro, slopes, upper Hunter valley and areas of the north west and central west being above average.

Pasture biomass was relatively unchanged, and generally remained quite low across the eastern half of NSW. Relative to historical records, biomass was generally average to above average across inland NSW and areas of the south east, but was below average across areas of the tablelands, northern slopes, upper Hunter valley and the coast.

Good winter growth and pasture establishment will be dependent on a continuation of mild conditions into early winter and on follow up rainfall.

Stock condition was average to good during the month, with an increase in pasture growth allowing supplementary feeding to be scaled back in many areas.

The April rainfall provided sufficient topsoil moisture to allow both preparation for and sowing of winter crops to commence. However, follow up rainfall will be necessary in many areas. The favourable price for canola has led to a high demand for seed, with hybrid seed in short supply. Chickpeas are also popular given current prices and the possibility of a drier season. Difficulties have been encountered in handling heavy stubbles from last year’s winter crops. An increased amount of stubble burning has been occurring to facilitate paddock preparation, crop sowing (particularly of canola) and to reduce disease and weed burdens.

Topsoil moisture declined across most of the coast as moisture moved into the subsoil. Levels improved in the south and across some areas of central and north western NSW. Subsoil moisture levels were relatively stable across most of NSW, but improved across coastal areas.

Run off during April was above average across most north eastern, southern and far western NSW, as well as areas of the central to north coast. Run off across the far north coast was well above average.

NSW Seasonal Conditions Report – May 2017

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Seasonal outlook

The Bureau of Meteorology’s rainfall outlook for May to July (see the Climatic Outlook Summary below) indicates drier than normal conditions are likely across NSW. Daytime temperatures are likely to be warmer than normal across most of NSW and there is a near-equal chance of cooler or warmer than normal overnight temperatures. Overnight temperatures are likely to be warmer than normal across areas of eastern, south eastern and far north western NSW.

During May, drier than normal conditions are likely for NSW. Daytime temperatures are likely to be warmer than normal across most of NSW. Overnight temperatures are likely to be cooler than normal across areas of south western, southern, central and north eastern NSW, with warmer than normal temperatures likely across areas of the south east and central coast.

The NOAA Climate Forecast System (CFS) rainfall outlook for May to July is near-neutral (that is, a near equal chance of drier or wetter than normal conditions) for most of NSW. For this outlook, below average rainfall is indicated for areas of the far south. The overall temperature outlook is near-neutral for most of NSW, with warmer than normal conditions possible for areas of the coast, far north east, central tablelands and Hunter valley.

For May, the CFS rainfall outlook is near-neutral for NSW. The overall temperature outlook is near-neutral for most of NSW, below average for areas of the south west and far west and above average for the far north east.

A survey of the major global circulation models in early May indicated that for the majority of NSW the outlook for May to July was equally split between drier than normal and near-neutral for most models (45 per cent of each). One model favoured a generally wetter outlook. For temperature, most models (64 per cent) favoured a warmer than normal outlook, with four (36 per cent) favouring a generally near-neutral outlook.

It should be noted that climate model accuracy currently remains low beyond a few months, but will improve as the year progresses.

Overall NSW outlook -

major climate models

Rainfall Outlook

(number of models)

Temperature Outlook

(number of models)

Period

Generally wetter

Generally
near-neutral

Generally
drier

Generally warmer

Generally
near-neutral

Generally
cooler

May – July

1

5

5

7

4

0

June – August

1

2

5

5

3

0

The AussieGRASS pasture growth outlook for May to July suggests that above average pasture growth is possible for areas of the central west, eastern Riverina, far south, Monaro and areas of the central to north coast. Below average growth is suggested for areas of the far north west, far west, southern and central tablelands, northern slopes, south west slopes and western Riverina, however in some cases this is likely to be due to the model assuming limited soil nitrogen in these areas.

The seasonal rainfall prediction that the growth outlook is based upon is for a near-equal chance of drier or wetter than normal conditions for most of eastern NSW between May and July. The outlook suggests drier conditions are possible across much of the far west and south as well as the southern and central tablelands and areas of the central west. This was based on a rapidly falling SOI phase during March and April. In comparison, the Bureau of Meteorology’s May to July rainfall outlook suggests drier than normal conditions across NSW. If these eventuate, potential growth may be very different from the outlook.

The current growth outlook has a low to very low past accuracy across much of NSW, but a high past accuracy across areas of southern and south eastern NSW, areas of the far north west and areas of the coast.

El Niño Southern Oscillation (ENSO)

The Pacific Ocean remains in an ENSO-neutral state, with the outlook from most models suggesting neutral conditions continuing into winter, but with increasing chances of warming to El Niño levels in late winter and spring. Recently, many models have reduced the extent of this warming over that from earlier outlooks. Model outlooks are still affected by the ‘autumn predictability barrier’ (due to the Pacific Ocean ‘resetting’ itself and often weaker coupling between the ocean and atmosphere) and their prediction skill still remains low.

The current signals from the Pacific Ocean also remain mixed (see below), increasing the uncertainty. It is also quite unusual for an El Niño event to follow immediately after an El Niño then La Niña-like sequence.

Despite the combination of low model skill and mixed signals from the Pacific, the consensus is that there is an increased risk of an El Niño event developing over the next six months. This is why the Bureau of Meteorology’s ENSO outlook status is currently at ‘El Niño watch’, which indicates an increased chance (50 per cent, about double the normal probability) of El Niño conditions developing.  The CPC/IRI also currently indicate that ENSO neutral conditions are present and are likely to continue into winter but that there is an increasing chance for El Niño development into spring. Note that the Bureau and CPC/IRI use different ENSO thresholds.

Much of the outlook has been based on the warm temperatures in the eastern equatorial Pacific since early this year (an ‘eastern El Niño’). Some forecasters are suggesting the possibility of a central Pacific El Niño (an El Niño Modoki) event developing. Such events are characterised by warm sea surface temperatures in the central equatorial Pacific, with cooler temperatures in the east and west (rather than a normal event, where warm temperatures extend from the eastern to the central Pacific). The strength of a central Pacific El Niño event is more strongly linked to the degree of rainfall suppression across eastern Australia than in a normal event.

It is likely that a positive Indian Ocean Dipole event will develop during winter and that this will extend into spring. Such events tend to suppress rainfall across Australia during winter and spring and can exacerbate the effects of an El Niño event. The Dipole Mode Index has been rising (although still currently within the neutral range) as sea surface temperatures warm in the western Indian Ocean.

Sea-surface temperatures have continued to warm in the central equatorial Pacific but still remain within the neutral (neither El Niño nor La Niña) range. Sea surface temperatures in the western and eastern Pacific are above normal, but have weakened slightly in the east. Sub-surface temperatures show a cool anomaly, which has now weakened to an area of the western Pacific. Weak warm anomalies in the west now extend into the central Pacific. Warm anomalies in the east have weakened. Cloud and convection levels across South East Asia and the central equatorial Pacific continued to be La Niña-like during April but have recently declined to neutral. The easterly trade winds were normal throughout April, but are showing some signs of reversal. The SOI has declined to below neutral, due to near-normal pressure at Tahiti and higher pressure at Darwin. A sustained SOI of levels below -7.0 is an indicator of El Niño conditions.

The Southern Annular Mode (SAM) is currently strongly positive, with the outlook suggesting it will decline towards moderately positive and then to near-neutral later in the month.

Climatic outlook summary

NSW Seasonal Outlook (BoM)

Current outlook

Previous outlook

Quarterly Rainfall

Drier

Drier
(most of NSW)

Near neutral
(areas of the coast and eastern NSW)

Quarterly Maximum Temperature

Warmer

Warmer
(western NSW)

Near neutral
(most of the eastern half of NSW)

Quarterly Minimum Temperature

Near neutral
(most of NSW)

Warmer
(areas of eastern, south eastern and far north western NSW)

Warmer
(western and areas of coastal and far south eastern NSW)

Near neutral
(most of the north west, tablelands, central west, Riverina and areas of the south)

El Niño Southern Oscillation (ENSO)

ENSO (overall)

Neutral

Neutral

BoM ENSO Outlook Status

El Niño watch

El Niño watch

SOI

Falling, currently below El Niño threshold

Neutral
(slowly falling)

Pacific Ocean (NINO3.4)

Neutral
(slowly warming)

Neutral
(slowly warming)

Indian Ocean (IOD)

Neutral
(western Indian Ocean slowly warming)

Neutral

Southern Annular Mode (SAM/AAO)

Strongly positive
(trending to moderately positive then to near-neutral)

Weakly positive
(tending to remain weakly to moderately positive)

Note: Climate model outlooks are updated regularly. To check whether updates are available, use the hyperlinks provided.

Rainfall and temperature

Rainfall was 40-60 per cent of average or less across much of NSW during April. Some areas of the central west, north west, south east and north coast had rainfall of less than 40 per cent of average. Areas of the far west and south had rainfall of 80-300 per cent of average.

Rainfall across the state ranged from 2-255 mm, with the eastern and southern areas of NSW generally receiving more than 25-50 mm for the month. Some areas of the coast and the south west received more than 50-100 mm. Most of the remainder of NSW received 10-25 mm, although some areas of the far north west and central west received less than 10 mm. Over the state as a whole, rainfall was 41 per cent below average.

Temperatures were close to average, with the end of the month being cool. Both daytime and overnight temperatures were generally slightly cooler than normal in the east but near-normal in the west.

Relative rainfall

Rainfall across NSW during April was average across 58 per cent of the state and below average across 13 per cent of the state. Rainfall was above average across 18 per cent of the state, with a large area of missing data in the far north west.

Most of the far west and areas of the south received above average rainfall for the period. The far north east, including areas of the mid-north to far north coast and the northern tablelands received below average rainfall for the period. Much of the far north coast received well below average to extremely low rainfall. Other areas of below average rainfall extended across the central west, Liverpool plains, northern slopes, upper Hunter valley, Illawarra, Sydney basin, southern highlands and areas of the central tablelands.

Quarterly relative rainfall was average across 62 per cent of the state, below average across 18 per cent and above average across 20 per cent. Below average rainfall occurred across large areas of the far west, as well as areas of the north west and northern Riverina. Above average rainfall occurred across the north east, including the mid-north to north coast, northern tablelands, lower Hunter valley, Sydney basin and the Illawarra. Areas of the central tablelands, central west and far south also experienced above average rainfall for the period. The remainder of the state had near-average rainfall.

Soil moisture

Topsoil moisture declined across most of the coast as moisture moved into the subsoil. Levels improved in the south and across some areas of central and north western NSW. Across most of the coast, average monthly topsoil moisture was between 40-70 per cent of a saturated profile and 30-50 per cent across most areas of the tablelands and slopes. Most winter cropping areas had less than 30 per cent of a saturated profile, with levels lower in the west. By the end of the month, levels in southern NSW had improved to 30-50 per cent of a saturated profile.

Relative to historical records, April topsoil moisture levels remained above average to well above average across areas of the tablelands and slopes, as well as southern, south western, central western and coastal NSW. Levels were generally near-average elsewhere, but below average in areas of the far west and the western and central Riverina.

Subsoil moisture levels were relatively stable across most of NSW but improved across coastal areas.

Relative to historical records, subsoil levels remained extremely high across much of inland NSW. Levels were near average across areas of the north west, the eastern areas of the tablelands, the south west slopes and areas of the coast.

Streamflow

Run off during April was above average across most north eastern, southern and far western NSW, as well as areas of the central to north coast. Run off across the far north coast was well above average.

Yearly run off to April was above average to extremely high across much of NSW, and average for areas of the far south west, north west and lower Hunter valley. Areas of the north west and Liverpool Plains had below average run off for the period.

The Bureau of Meteorology's streamflow forecast indicates near-median to high streamflows are likely at most NSW monitoring stations during May to July.

Relative pasture growth and biomass

Relative to historical records, AussieGRASS modelled pasture growth during April was near-average across much of inland NSW, but above average across areas of the coast, central west, northern and central tablelands, far south, Monaro and the far south east. It was below average across some areas of the north west and central west.

Other pasture growth models indicated above average growth across the far west, areas of the south, the south to the central coast, Hunter valley and the northern tablelands. Growth across the remainder of NSW was generally near-average.

Over the quarter, AussieGRASS relative growth remained below average across large areas of inland NSW, but average across areas of the far west, south and the coast. Growth was above average in areas of the south east and far south west.

During April, relative biomass levels were above average across areas of central and western NSW, the far south and the south east. Levels were generally average across areas of the north west and the Riverina but were below average across areas of the coast, upper Hunter valley, tablelands and northern slopes.


Figure 1: Relative monthly topsoil moisture

Small version map of relative soil moisture (upper level) average value for April 2017

Figure 2: Relative quarterly pasture growth

Small version map of pasture growth relative to historical records from 1957 (February 2017 to April 2017)

More information

For more information, contact the NSW Department of Primary Industries on 02 6391 3100 or Local Land Services on 1300 795 299.

Acknowledgements

Information used in this report was sourced from the Australian Bureau of Meteorology, CSIRO, the Queensland Department of Science, Information Technology and Innovation, the Queensland Alliance for Agriculture and Food Innovation, the U.S. Department of Agriculture, U.S. Department of Commerce, the U.S. National Oceanic and Atmospheric Administration, the International Research Institute for Climate and Society (Columbia University), the UK Meteorological Office, the APEC Climate Centre, NSW Local Land Services and NSW Department of Primary Industries.

External links

Disclaimer

The seasonal outlooks presented in this report are obtained from the Australian Bureau of Meteorology and other sources. 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. Outlook information was up to date as at 10 May 2017.

Recognising that some of the information in this document is provided by third parties, the State of New South Wales, the author and the publisher take no responsibility for the accuracy, currency, reliability and correctness of any information included in the document provided by third parties.

The information contained in this publication is based on knowledge and understanding at the time of writing (10 May 2017). 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, Local Land Services or the user’s independent adviser.