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 13 October 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 - October 2015Summary Seasonal outlook Current

Outlook Previous Outlook

Rainfall (quarter) Drier (south east, south & central NSW, south to mid-north coast) Near neutral (northern & western NSW)

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

Max Temperature (quarter)

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

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

ENSO

ENSO (overall) El Niño El Niño

BoM ENSO Tracker Status

El Niño El Niño

SOI Strongly negative Negative

Pacific Ocean (NINO3.4)

Very warm (Above El Niño thresholds)

Warm (Above El Niño thresholds)

Indian Ocean (IOD) Positive (trending neutral in Nov)

Trending positive

Southern Annular Mode (SAM/AAO)

Near neutral Near neutral – weakly positive

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 October and December, drier than normal conditions are likely for the south eastern, southern and central areas of NSW. Drier conditions are also likely across the south to mid-north coast, Hunter Valley and the southern edge of the northern tablelands and northern slopes. There is a near-equal chance of drier or wetter than normal conditions across most of northern and western NSW.

During the period, warmer than normal daytime and overnight temperatures are likely across NSW.

NSW Climate Summary - October 2015

2 NSW Department of Primary Industries, November 2015

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

The Pacific Ocean remains in a strong El Niño event. Sea surface temperatures in the central Pacific have continued to rise. The event is likely to peak late in the year and to persist through to autumn 2016. There is a possibility that a La Niña event may follow. The SOI, equatorial Pacific sea temperatures, trade wind and cloud conditions remain consistent with an El Niño event. The Bureau of Meteorology’s ENSO tracker status remains at ‘El Niño’. The effects of the El Niño over NSW were moderated during winter by warm sea surface temperatures in the eastern Indian Ocean. However, the development of a positive IOD during August/September has reinforced the effects of the El Niño event on spring rainfall.

The CPC/IRI consensus ENSO forecast probabilities indicate that more than 95% of global climate models consider El Niño conditions are likely to continue through summer, gradually weakening in 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 27 September) 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, declining during autumn.

All eight climate models surveyed by the Bureau (as at 16 September) also indicate sea surface temperatures are likely to remain well above the Bureau’s El Niño threshold during October to February.

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 September in eastern areas.

Temperatures are well above the Bureau’s El Niño thresholds. Temperatures are average to below average in the west. The most recent monthly temperature anomaly value in the key NINO3.4 region is +2.28°C, an increase from +2.07°C for August. The weekly value to 11 October is +2.22°C.

Monthly Sub-surface Temperatures (Source: Bureau of Meteorology) The sub-surface sea temperatures continue to show the strong warm anomaly present to depth across the central and eastern equatorial Pacific. A cool anomaly remains in the west and has weakened slightly.

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

The Southern Oscillation Index (SOI) was more strongly negative over the month, consistent with enhanced convection in the central-eastern equatorial Pacific and suppressed convection over Indonesia. On 12 October, the 30-day SOI value was -21.7. It has remained strongly negative since late June, indicating atmospheric coupling with the Pacific Ocean in an El Niño event.

NSW Climate Summary - October 2015

3 NSW Department of Primary Industries, November 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 positive, with values being above +0.4 for two months. The current value is +1.18 for the week to 11 October, a jump from +0.70 on 6 September. The Bureau of Meteorology’s POAMA model outlook suggests the IOD will remain positive till November/December. Four climate models surveyed by the Bureau (as at 16 September) favour a positive IOD in October and one favours a neutral IOD. One model favours a positive IOD into December. 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 6 October was at close to the normal latitude and at a higher pressure for the time of year. Atmospheric pressure over NSW during September was substantially higher than normal, as indicated on NOAA and Bureau of Meteorology mean sea level pressure charts and acted to block low pressure systems 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 were high but were low across Indonesia and Papua New Guinea, consistent with an El Niño event. Low cloud also occurred west of Sumatra, consistent with a positive IOD event. Cloud was low over southern NSW. Trade winds were reversed (westerly) during September across the western to the east-central equatorial Pacific, 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 7-11 October. The outlooks from POAMA and NOAA suggest the SAM index will move range from weakly negative to near neutral during mid-late October.

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 - October 2015

4 NSW Department of Primary Industries, November 2015

Conditions during September Rainfall (Source: Queensland DSITI)

Rainfall across NSW ranged between ranged from 0-262 mm during September, with most of the state receiving 5-25 mm. Less than 10 mm was received across areas of the north and central west. Relative to historical records, rainfall was below average across much of the northern, central and southern areas of the state. It was extremely low across the central and southern tablelands, south west slopes, the upper Hunter Valley, the eastern half of the central west and areas of the north west.

Soil moisture (Source: CSIRO)

Modelled topsoil moisture levels declined across most of NSW, but were maintained across areas of the south, south east, and central tablelands. Relative to historical records, topsoil moisture was below average in areas of the north west, central west, southern and central tablelands, south west slopes and upper Hunter valley. It was above average across areas of the south east and north coast. Modelled subsoil moisture levels were relatively stable. Relative to historical records, subsoil moisture was below average across areas of the north west and far western Riverina.

Pasture growth (Source: Queensland DSITI)

During September relative pasture growth was average in the south and across the slopes and tablelands. It was average to above average along the coast. Areas of the north west, northern central west and the north of the central tablelands had below average relative growth. Other models indicated below average relative growth across the north, north west, tablelands, central west and areas of the far south. For these models, relative growth was average to above along the coast and average in the south and south west.

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 (October 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) PUB15/442 Volume 2/Number 9