Thursday 1 October 2015 — Monthly Summary for Australia — Product Code IDCKGC1A00
Australia in September 2015
September rainfall was below average for much of the country. It was the third-driest September on record for Australia and ranked in the bottom 10 of all years for three States. Significant above-average rainfall was largely confined to the coastal strip of New South Wales and southern Queensland. Below average rainfall extended from Tasmania, through much of Victoria into New South Wales west of the ranges, central and western Queensland, throughout much of Northern Territory and covering most of Western Australia. Nationally, rainfall was 63% below average.
Daytime temperatures were near average across large areas of Australia. Above-average daily maximum temperatures were experienced in a broad coastal strip along the nation's west and north as well as in Tasmania and the northern and central parts of Victoria. Below-average maximums were recorded in central Australia, small parts of New South Wales and the northern interior of Queensland. Nationally, maximum temperatures were 0.82 °C warmer than average.
Overnight temperatures were below average to very much below average in a broad strip across the country. The cooler overnight temperatures extended from the Kimberley region in the northwest to Victoria in the south, including the Alice Springs region of Northern Territory, much of the eastern half of South Australia, and most of New South Wales west of the Great Dividing Range. Minimum temperatures were above average along coastal areas of the Pilbara and down into the Gascoyne region. Nationally, minimum temperatures were 0.44 °C below average.
The national September mean temperature was 0.19 °C above the long-term mean. Maximum temperatures were 0.82 °C above average while minimum temperatures were 0.44 °C below average for the country as whole.
The first widespread warm spell of the season made its way across the country starting in Western Australia on September 8. Over the week that followed, daytime temperatures reached their highest since autumn for most of the country. On September 17, the first 40 °C of the season was recorded at both West Roebuck (40.5 °C) and Derby Aero (40.2 °C) in Western Australia. This was close to the median date for Australia to record its first 40 °C in the second half of the year. Generally cooler seas off Australia's northern coast mean that the first 40 °C typically occurs later during an El Niño than during ENSO neutral or La Niña years.
South Australia (−0.09 °C) and Northern Territory (−0.62 °C) were the only States and Territories to record below-average September mean temperatures.
September maximum temperatures were above average to very much above average around broad areas of coastal Australia. The western half of Western Australia was particularly warm, with large areas experiencing September daytime temperatures in the top 10% of all years (decile 10). For Western Australia as a whole, the mean maximum temperature was the eighth-highest since comparable records commenced in 1910 (1.73 °C above normal). Many sites near the west coast experienced their warmest September on record. In the Northern Territory, nearly all of the Top End and most of the Carpentaria district experienced above-average to very-much-above-average maximum temperatures. South of the Top End, a broad region extending down into northern South Australia recorded below-average daytime temperatures. The above-average maximum temperatures across the north of the country extended into areas of far northern Cape York Peninsula and parts of the Gulf Country. Most of New South Wales recorded close to average daytime temperatures, with the exception of the northeast and parts of central western districts, which recorded below-average maximum temperatures. Warm days in the second half of the month resulted in above-average maximum temperatures for central and northern parts of Victoria that extended into the neighbouring areas of New South Wales and South Australia. Daytime temperatures were above average to very much above average for all of Tasmania. Several Tasmanian sites experienced their warmest September on record.
A broad strip from Australia's northwest to the southeast experienced below-average overnight temperatures during September. Included in that were large areas that experienced September minimum temperatures in the lowest 10% of all years (decile 1), including parts of inland New South Wales, eastern South Australia and the Kimberley region of Western Australia. The below-average minimum temperatures covered the Top End of Northern Territory, the Kimberley in Western Australia, down through central Australia and Alice Springs, the eastern half of South Australia, most of inland New South Wales and adjacent areas of southeastern Queensland, and northern parts of Victoria. The cool nights in Northern Territory resulted in a mean minimum temperature that was 1.25 °C below normal. Below-average nights were also experienced in parts of southwest Western Australia and the southern Goldfields. Minimum temperatures for New South Wales and South Australia were the lowest in September since 1994. South Australia had no areas of above-average minimum temperatures and some central and eastern parts of South Australia had their lowest September mean daily minimum temperature on record or lowest in 20 years.
Isolated areas of above-average minimum temperatures were dotted around the country. In Western Australia, mean minimum temperatures were above average to very much above average in much of the Pilbara, Gascoyne and Eucla. The far southwest of Queensland was above average, as was the southern half of Tasmania.
|Areal average temperatures|
|Maximum Temperature||Minimum Temperature||Mean Temperature|
|Australia||75||+0.82||= 36||−0.44||= 64||+0.19|
|New South Wales||= 67||+0.75||= 30||−0.54||= 48||+0.10|
|Tasmania||90||+0.83||= 61||+0.15||= 83||+0.49|
|South Australia||= 48||+0.35||31||−0.55||= 40||−0.09|
|Western Australia||99||+1.73||8th highest||= 41||−0.28||86||+0.73|
|Northern Territory||50||−0.01||= 24||−1.25||39||−0.62|
Rank ranges from 1 (lowest) to 106 (highest). A rank marked with ’=‘ indicates the value is tied for that rank. Anomaly is the departure from the long-term (1961–1990) average.
Nationally-averaged rainfall during September was 63% below the long-term mean, making it the third-driest September average on record. Rainfall in all States and Territories was well below the September monthly average.
September began with a cold front that moved across the southern part of the continent, bringing widespread rain to Western Australia, South Australia, Victoria and New South Wales. On September 18, a low pressure trough brought heavy rain, thunderstorms and hail to the Mid North Coast of New South Wales. For much of the month, high pressure systems tended to dominate Australia's weather, resulting in mostly dry conditions.
Tasmanian average rainfall was the fifth-driest September on record and the lowest since 1977. Much of Victoria recorded below-average rainfall with very-much-below average rainfall on and inland from the ranges, including patches of lowest-on-record. In New South Wales, above-average rainfall was only recorded along the northern half of the coastal fringe. Little or no rain was recorded in the western half of Queensland, northern half of Western Australia and almost all of Northern Territory except around Darwin, where localised heavy falls were recorded on the 16th and 25th. Western Australian rainfall was 67% below normal, its fourth driest September on record.
|Australia||3||6.2||−63%||3rd lowest (record 5.6 mm in 1957)|
|New South Wales||17||15.5||−55%|
|Tasmania||5||58.2||−58%||5th lowest; lowest since 1977|
|Western Australia||4||3.5||−67%||4th lowest (record 1.6 mm in 1939)|
|Northern Territory||= 16||0.4||−94%|
|Murray-Darling Basin||9||11.7||−66%||9th lowest|
Rank ranges from 1 (lowest) to 116 (highest). A rank marked with ’=‘ indicates the value is tied for that rank. Departure from mean is relative to the long-term (1961–1990) average.
|Australian weather extremes during September 2015|
|Hottest day||41.4 °C at West Roebuck (WA) on 18 September|
|Coldest day||−3.6 °C at Thredbo AWS (NSW) on 23 September|
|Coldest night||−8.3 °C at Thredbo AWS (NSW) on 24 September|
|Warmest night||26.9 °C at Argyle Aerodrome (WA) on 1 September|
|Wettest day||89.0 mm at Smoky Cape Lighthouse (NSW) on 26 September|
The Monthly Climate Summary is prepared to list the main features of the weather in Australia using the most timely and accurate information available on the date of publication; it will generally not be updated. Later information, including data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review, usually published in the fourth week of the month.
Climate Summaries are usually published on the first working day of each month.
This statement has been prepared based on information available at 10 am EST on Thursday 1 October 2015. Some checks have been made on the data, but it is possible that results will change as new information becomes available, especially for rainfall where much more data becomes available as returns are received from volunteers.
Long-term averages in this statement and associated tables are for the period 1961 to 1990 unless otherwise specified.
The system used for calculating areal averages of rainfall was changed in August 2009; the main effect was that current and historical values for Tasmania were increased. Since August 2012, ACORN-SAT has been used for calculating areal averages of temperature; the major change from earlier datasets is that the ACORN-SAT dataset commences in 1910, and hence rankings are calculated using a larger set of years.