The seasonal outlooks presented in this report are obtained from the Australian Bureau of Meteorology & 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 & decision making. Changes in seasonal outlooks may have occurred since this report was released. Outlook information was up to date as at 10 September 2015. Changes in seasonal outlooks may have occurred since this report was released. Outlook information was up to date as at 3rd December 2013.

NSW Climate Summary - September 2015Summary Seasonal outlook Current

Outlook Previous Outlook

Rainfall (quarter) Near neutral – neutral (most of NSW) Wetter (western NSW)

Near neutral – neutral (most of NSW) Drier (far south east, north east)

Max Temperature (quarter)

Near neutral – neutral (most of NSW) Warmer (central - north coast, lower Hunter valley) Cooler (far south)

Near neutral – neutral (most of NSW) Warmer (coast, northern NSW)

Min Temperature (qtr) Warmer (northern, north eastern and coastal NSW) Near neutral – neutral (most of NSW)

Warmer

ENSO

ENSO (overall) El Niño El Niño

BoM ENSO Tracker Status

El Niño El Niño

SOI Negative Negative

Pacific Ocean (NINO3.4)

Warm (Above El Niño thresholds)

Warm (Above El Niño thresholds)

Indian Ocean (IOD) Trending towards a positive IOD

Neutral – positive

Southern Annular Mode (SAM/AAO)

Near neutral – weakly positive

Weakly positive –near neutral

Source: Derived from information provided by the Australian Bureau of Meteorology and the US National Oceanic & Atmospheric Administration.

Seasonal outlook (Source: Bureau of Meteorology)

Between September and November, there is a near-equal chance of drier or wetter than normal conditions and for cooler or warmer than normal temperatures across most of NSW.

Wetter than normal conditions are likely in western NSW. Warmer than normal daytime temperatures are likely across the central to north coast and lower Hunter Valley. Cooler than normal daytime temperatures are likely in the far south. Warmer than normal overnight

temperatures are likely across northern, north eastern and coastal NSW.

NSW Climate Summary - September 2015

2 NSW Department of Primary Industries, September 2015

ENSO (Source: Bureau of Meteorology & International Research Institute for Climate and Society)

The Pacific Ocean remains in an El Niño event, which has continued to intensify with sea surface temperatures in the central Pacific continuing to rise. It is likely to persist through spring and summer. There is a possibility that a La Niña event may follow in 2016, particularly if a positive Indian Ocean Dipole event occurs this spring The SOI, equatorial Pacific sea temperatures, trade wind and cloud conditions are consistent with an El Niño event. The Bureau of Meteorology’s ENSO tracker status remains at ‘El Niño’. NOAA CPC/IRI indicated that (based on their thresholds) the El Niño event is moderate, with models suggesting a strong event through spring and early summer. The effects of the El Niño’ on NSW have been moderated by warm sea surface temperatures in the eastern Indian Ocean.

The CPC/IRI consensus ENSO forecast probabilities indicate that more than 95% of global climate models consider El Niño conditions are likely to continue into spring, and about 75% through to early autumn. Note that the CPC/IRI uses a NINO3.4 anomaly of +0.5°C as an El Niño threshold, while the Bureau of Meteorology uses +0.8°C. The Bureau of Meteorology’s latest POAMA outlook (as at 30 August) indicates that the sea surface temperatures in the NINO3.4 Pacific Ocean region are likely to remain above the El Niño threshold during spring and summer.

All eight climate models surveyed by the Bureau (as at 30 August) also indicate sea surface temperatures are likely to remain well above the Bureau’s El Niño threshold during September to January.

Monthly Sea Surface Temperatures (Source: NOAA & Bureau of Meteorology)

Warm sea surface temperatures anomalies extend across the central and eastern equatorial Pacific, and

strengthened during August in central areas. Temperatures are well above the Bureau’s El Niño thresholds. Cooling has occurred in the west. The most recent monthly temperature anomaly value in the key NINO3.4 region is +2.06°C, an increase from +1.60°C for July. The weekly value to 6 September is +1.87°C.

Monthly Sub-surface Temperatures (Source: Bureau of Meteorology) The sub-surface sea temperatures show the strong warm anomaly present to depth across the central and eastern equatorial Pacific. Some cooling has occurred in the far east. A cool anomaly at depth in the west has strengthened and moved eastwards, and has cooled the subsurface in the western-central Pacific below 150m and surface temperatures between 155-170°E.

Southern Oscillation Index (SOI) (Source: Bureau of Meteorology & Queensland DSITI)

The Southern Oscillation Index (SOI) has remained strongly negative since late June. On 7 September, the 30-day value was -15.4.

NSW Climate Summary - September 2015

3 NSW Department of Primary Industries, September 2015

Values between -8 and +8 indicate neutral conditions, sustained values above +8 may indicate a La Niña event, and sustained values below -8 may indicate an El Niño event.

Indian Ocean Dipole (IOD) (Source: Bureau of Meteorology)

The Indian Ocean Dipole (IOD) is currently regarded as being neutral, as the IOD index value needs to be at or above +0.4 for two months to be considered ‘positive’. The current value is +0.70 for the week to 6 September, a jump from +0.19 from 9 August. The Bureau of Meteorology’s POAMA model outlook indicates IOD index values at positive levels till November/December. Three models surveyed by the Bureau (as at 17 August) favour a positive IOD in September and two models favour a neutral IOD. Two models favour a positive IOD in November. A positive IOD increases the chances of below normal rainfall and may exacerbate the effect of an El Niño event over south eastern Australia. A negative IOD increases the chances of above normal winter and spring rainfall across southern and much of western and central NSW.

Sub-Tropical Ridge (STR) (Source: NOAA & Bureau of Meteorology) The sub-tropical ridge over the 30 days to 8 September was at close to the normal latitude and pressure for the time of year. Atmospheric pressure over NSW during August was higher than normal, particularly in the far west and south west as indicated on NOAA and Bureau of Meteorology mean sea level pressure charts. High pressure in the west of NSW may block rainfall from moving across the state. The sub-tropical ridge is a zone of high pressure which between January and March is normally located south of Australia at about 38° to 39°S, and can tend to suppress cold front activity. During June to September, it generally moves northwards to around

30° to 32°S allowing cold fronts to extend further into southern Australia. It has most effect on winter rainfall.

Cloudiness and trade winds (Source: Bureau of Meteorology & NOAA)

Levels of cloud at the junction of the International Date Line and equator are consistent with an El Niño event, as are cloud conditions across Indonesia. Trade winds were reversed (westerly) during August across the western to the east-central equatorial Pacific and are also consistent with an El Niño event.

Southern Annular Mode (SAM) (Source: Bureau of Meteorology [experimental] & NOAA)

The experimental Southern Annular Mode or Antarctic Oscillation (AAO) index is currently weakly negative as at 6-8 September. The outlooks from POAMA and NOAA suggest the SAM index will range from neutral to weakly positive during mid-late September.

A negative SAM indicates expansion of the belt of strong westerly winds towards the equator, resulting in more or stronger low pressure systems across southern Australia and potentially increased rainfall. A positive SAM indicates the contraction of the belt of westerly winds towards Antarctica and higher pressures over southern Australia, and can result in stable, drier conditions.

NSW Climate Summary - September 2015

4 NSW Department of Primary Industries, September 2015

Conditions during August Rainfall (Source: Queensland DSITI)

Rainfall across NSW ranged between ranged from 3-489 mm during August, with most of the state receiving 10-50 mm. Areas in the northern central west, the mid-north coast and the far south west received below average relative rainfall. Areas of the far west, Riverina, south and south east received above average rainfall. Rainfall was near average over most of the state. Relative rainfall was average or better across 91% of NSW.

Soil moisture (Source: CSIRO)

Modelled topsoil moisture levels were maintained across the south, south east, most of the central tablelands and the southern central west, but declined elsewhere. Relative to historical records, topsoil moisture was generally average but below average in areas of the north east. It was above average across areas of the south east, Riverina and the central areas of the far west. Modelled subsoil moisture levels improved across the south east and were maintained in the central and eastern areas of the state. Relative to historical records, subsoil moisture remained below average across areas of the north west and far western Riverina.

Pasture growth (Source: Queensland DSITI)

During August relative pasture growth was average to above average across most of the state. Areas of below average growth occurred in the north west, mid-north coast and far south west. Other models indicated well above average growth for temperate pastures across areas of the far west and central areas of the state. Growth for the coast was generally average. Below average growth occurred across the slopes, tablelands, Monaro and areas of the south east.

More information For more information, contact the NSW Department of Primary Industries on 02 6391 3100 or Local Land Services on 1300 795 299. Additional and more detailed information on seasonal conditions can be found in the NSW Seasonal Conditions Summary and Report, available at http://www.dpi.nsw.gov.au/agriculture/emergency/seasonal-conditions/regional-seasonal-conditions-reports, and the LLS On-ground Seasonal Conditions Reports available at http://www.lls.nsw.gov.au/agriculture/seasonal-conditions.

Acknowledgements Information used in this report was sourced from the Australian Bureau of Meteorology, CSIRO, Queensland Department of Science, Information Technology and Innovation, the US National Oceanic and Atmospheric Administration, the International Research Institute for Climate and Society (Columbia University) and NSW Department of Primary Industries.

Warning 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.

© State of New South Wales through the Department of Industry, Skills and Regional Development, 2015. 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 (September 2015). 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 Department of Primary Industries. ISSN 2203-5060 (Online) PUB15/397 Volume 2/Number 8