NSW Seasonal Conditions Summary April 2017

Overview

During March, rainfall was above average across more than half of NSW, particularly north eastern, northern, central and coastal NSW, but was well below average in the far west. Heavy rainfall resulted in flooding in the north east.

March was the second-warmest on record for NSW, following the record set in 2016. Overnight temperatures were the warmest on record, with daytime temperatures well above average in the west.

Pasture growth was low across much of western NSW, the western Riverina and western areas of the central west, north west and tablelands. Growth was also low in some areas of the upper Hunter valley and the north coast.

Relative to historical records, pasture growth was near-average across half of NSW, with below average growth in the far west, western Riverina and areas of the central west. Growth across the coast ranged from average to above average.

Other pasture growth models indicated near-average growth across most of NSW, with below average growth in the far west. They indicated above average growth across the tablelands, Monaro, upper Hunter valley and areas of the central west and north west.

Pasture biomass remained low, particularly across the eastern half of NSW. Relative to historical records biomass was generally average to above average across inland NSW, but was below average across areas of the tablelands and coast.

The March rainfall stimulated the germination of annual grasses and legumes and the growth of perennial pastures across much of NSW. Good winter growth for some areas of the state will be dependent on warmer conditions and follow up rainfall.

Stock condition was average to good. Supplementary feeding of breeding and younger stock occurred in some areas, and will be necessary until pasture quantity and quality is sufficient to maintain condition. In other areas, the timely rainfall and warm temperatures has allowed pasture growth to improve to levels where supplementary feeding of stock can be reduced.

Strong winds, heavy rainfall and flooding along the mid-north to north coast caused severe damage to pastures and crops including sugar cane and bananas, and increased the risk of root disease in soybeans. Some pastures in inundated areas have required resowing.

Elsewhere, the March rainfall has provided an early autumn break for farmers and graziers, although falls were lighter in the south and areas of the north west than across central and eastern NSW. Preparation for and sowing of dual purpose cereals and canola is underway. Earlier sown crops have responded well. However, follow up rainfall will be necessary, particularly in areas of southern and north western NSW. Paddock preparation is also underway for pasture sowing and main season sowings of winter crops, particularly weed control. Hybrid canola seed is in short supply, with the demand for seed high. In the south, rice harvesting is commencing. Yields from late sown summer crops in northern NSW have been affected by the high summer temperatures and limited rainfall.

Topsoil moisture improved across eastern NSW and areas of north western and central NSW during March. Subsoil moisture levels were relatively stable, but improved across coastal areas.

Run off during March was above average across most of eastern, central and northern NSW, particularly in the north east.

NSW Seasonal Conditions Report – April 2017

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Seasonal outlook

The Bureau of Meteorology’s rainfall outlook for April to June (see the Climatic Outlook Summary below) indicates drier than normal conditions are likely across most of NSW, with a near-equal chance of drier or wetter than normal conditions across areas of the coast, Hunter valley, northern tablelands and northern slopes. Daytime temperatures are likely to be warmer than normal across the western half of NSW, as well as areas of the far south east and far north east. Overnight temperatures are likely to be warmer than normal across western NSW, as well as areas of the coast and the south east.

During April, wetter than normal conditions are likely for much of eastern NSW and areas of the tablelands, central west and north west. Drier than normal conditions are likely across the far west, with a near-equal chance of drier or wetter than normal conditions for areas of the west, central west and south. Daytime temperatures are likely to be cooler than normal across most of the eastern half of NSW, and warmer than normal in areas of the far west. Overnight temperatures are likely to be warmer than normal in the west and far south east and cooler in areas of the north east, north west, Hunter valley and the northern and central tablelands.

The NOAA Climate Forecast System (CFS) rainfall outlook for April to June is near-neutral for most of NSW. Below average rainfall is possible for areas of the southern and central tablelands, Monaro and the south east. The overall temperature outlook is for warmer than normal conditions across areas of the north west and south east, with a near-neutral outlook for most of NSW.

For April, the CFS rainfall outlook is near-neutral for NSW. The overall temperature outlook is near-neutral for most of NSW, but below average for areas of the far north east and southern tablelands.

A survey of the major global circulation models in early April indicated that for the majority of NSW most models (60 per cent) favoured a generally drier rainfall outlook for April to June. One model favoured a generally wetter outlook and three a near-neutral outlook (that is, a near-equal chance of drier or wetter than normal conditions). 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 is low in late summer to autumn, particularly for outlooks spanning the winter.

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

April – June

1

3

6

7

4

0

May – July

1

1

6

5

3

0

The AussieGRASS pasture growth outlook for April to June suggests that below average pasture growth is possible across areas of western NSW and the western Riverina. Above average growth is suggested for areas of the coast, the east of the tablelands, the south west slopes and the south of the central west. Low growth is suggested for areas of the tablelands, although 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 NSW between April and June, with drier conditions possible in areas of the far west and the far north east. This was based on a rapidly rising SOI phase during February and March. In comparison, the Bureau of Meteorology’s April to June rainfall outlook suggests drier than normal conditions across most of NSW, with a near-equal chance of drier or wetter than normal conditions in areas of the east.

The current growth outlook has a low to very low past accuracy across most of NSW.

El Niño Southern Oscillation (ENSO)

The Pacific Ocean remains in an ENSO-neutral state. Most models suggest neutral conditions continuing throughout autumn, although with gradual warming of sea surface temperatures in the central equatorial Pacific. A number of models suggest warming to El Niño levels during winter or spring. This is based on the current sea surface temperatures in the far western and far eastern equatorial Pacific and the current rate of warming. However, model skill tends to be low until early winter and a number of other indicators still remain neutral or La Niña-like.

Sea surface temperatures during March were near-average to slightly below average across the central and eastern-central equatorial Pacific. Temperatures have been warming and were above average across the eastern equatorial Pacific, and the warmer temperatures expanded westwards during January and February. Temperatures were also near-average to above average in the western equatorial Pacific. Temperatures in the equatorial Indian Ocean were near-average, with some indications of warming in the west and cooling in the east. Temperatures to the north east of Australia were slightly above average, above average along the east coast and below average in areas of the bight and the west coast.

During March, cloud levels remained low near the junction of the equator and the International Date Line in a continued La Niña-like pattern. Cloud levels were high over South East Asia and Papua-New Guinea as well as north western, western and most of eastern Australia.

A cool subsurface temperature anomaly remains in the central and eastern equatorial Pacific. Weak warm anomalies are present in areas of the west, and both at depth and near the surface in the east.

The easterly Pacific trade winds were near average over the month over areas of the central Pacific, with a reversal in the eastern Pacific and strengthening in the central to western Pacific.

The SOI remained neutral during the month.

The Bureau of Meteorology’s ENSO outlook status remains at El Niño watch. This indicates an increased chance (50 per cent, about double the normal probability) of El Niño conditions developing, although ENSO neutral conditions are currently still present.  The CPC/IRI also currently indicate that ENSO neutral conditions are present and are likely to continue into winter. However, they suggest there is an increasing chance for El Niño development into spring. Note that the Bureau and CPC/IRI use different ENSO thresholds.

The Southern Annular Mode (SAM) was strongly negative in early March but near-neutral to weakly positive into early April. The current outlook is for it to be weakly-moderately positive through to mid-late mid-April.

Climatic outlook summary

NSW Seasonal Outlook (BoM)

Current outlook

Previous outlook

Quarterly Rainfall

Drier

(most of NSW)

Near neutral

(areas of the coast and eastern NSW)

Drier

(most of NSW)

Near neutral

(areas of the coast)

Quarterly Maximum Temperature

Warmer

(western NSW)

Near neutral

(most of the eastern half of NSW)

Warmer

Quarterly Minimum Temperature

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)

Warmer

El Niño Southern Oscillation (ENSO)

ENSO (overall)

Neutral

Neutral

BoM ENSO Outlook Status

El Niño watch

El Niño watch

SOI

Neutral

(slowly falling)

Neutral

(slowly falling)

Pacific Ocean (NINO3.4)

Neutral

(slowly warming)

Neutral

(slowly warming)

Indian Ocean (IOD)

Neutral

Neutral

Southern Annular Mode (SAM/AAO)

Weakly positive

(tending to remain weakly to moderately positive)

Near-neutral

(tending to remain near-neutral to weakly positive)

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

Rainfall and temperature

Rainfall was less than 40-60 per cent of average across much of the far west during March. The majority of the state had rainfall of more than 200 per cent of average, with areas of the north east and central west receiving rainfall of more than 300 per cent of average. Rainfall in the Riverina and the south was generally between 80-150 per cent of average.

Rainfall across the state ranged from 0-1170 mm, with the eastern half of NSW generally receiving more than 50-100 mm for the month. Extremely heavy falls occurred across areas of the coast. These were as a result of severe thunderstorms and the effects of ex-tropical cyclone Debbie and resulted in severe flooding, particularly across the mid-north to north coast. Areas of the far west received little to no rainfall.

March was the second-warmest on record for NSW, following the record set in 2016. Overnight temperatures were the warmest on record, with daytime temperatures well above average in the west.

Relative rainfall

Rainfall across NSW during March was above average across 52 per cent of the state and near-average across most of the remainder of NSW.

Most of the coast, tablelands, Monaro, Hunter valley, north west and central west received above average rainfall for the period. The Riverina, south and most of the far west received near-average rainfall for the month. Below average rainfall was limited to areas of the far west.

Quarterly relative rainfall was average across 53 per cent of the state, below average across 30 per cent and above average across 17 per cent. Below average rainfall occurred across areas of the far west, north west, Riverina and far south east. The north east received above average rainfall, including most of the northern tablelands, north and mid-north coast. Above average rainfall also occurred across the Sydney basin and Illawarra, and limited areas of the central west. The remainder of the state had near-average rainfall.

Soil moisture

Topsoil moisture improved across eastern NSW and areas of north western and central NSW during March. Across most of the coast, average monthly topsoil moisture was between 60-80 per cent of a saturated profile and 30-50 per cent across areas of the central and northern tablelands and areas of the slopes. Areas in the west and south had less than 20 per cent of a saturated profile. By the end of the month, levels were more then 60-70 per cent across most of the east, with areas of the north coast having fully saturated topsoil.

Relative to historical records, March topsoil moisture levels were well above average to extremely high across most of eastern, northern, north eastern and central NSW. Levels were generally near-average elsewhere, but below average in the far west.

Subsoil moisture levels were relatively stable, but improved across coastal areas. Relative to historical records, levels remained extremely high across much of inland NSW. Levels were average across areas of the north west, the eastern areas of the tablelands, the south west slopes and areas of the south coast. Subsoil moisture was below average for areas of the Hunter valley and the lower north coast, but improved by the end of the month.

Streamflow

Run off during March was above average across most of eastern, central and northern NSW, particularly in the north east. It was generally average in the south, but below average in the far west.

Yearly run off to March was above average to extremely high across much of NSW, with the exception of areas of the north west and Liverpool Plains. In these areas, run off was below average.

The Bureau of Meteorology's streamflow forecast indicates near-median to high streamflows are likely in most NSW locations during April to June, with low streamflows likely across some southern inland monitoring stations.

Relative pasture growth and biomass

Relative to historical records, AussieGRASS modelled pasture growth during March was near-average across much of inland NSW, but below average across areas of the far west, central west and western Riverina. Most of the coast and the eastern areas of the tablelands had average to above average growth.

Other pasture growth models indicated well below average growth in the west, but well above average growth across the tablelands, Monaro, upper Hunter valley and areas of the central west and north west.

Over the quarter, AussieGRASS relative growth was below average across large areas of inland NSW, but generally average across the coast and areas of the south.

During March, relative biomass levels generally remained above average across much of inland NSW. Much of the tablelands, areas of the slopes and the central to north coast had below average biomass.

Figure 1: Relative monthly topsoil moisture

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

Figure 2: Relative quarterly pasture growth

Small version map of pasture growth relative to historical records from 1957 (January 2017 to March 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 April 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 April 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.