Australia in September 2012

In Brief

A warm month for Australia, with maximum temperatures nationally the third highest in 63 years of record. Minimum temperatures were generally closer to normal, with parts of the west and far south above normal, and parts of the north and east below normal.

Rainfall was generally below average across most of the southern mainland, although not exceptionally so, with Tasmania and southwest Western Australia average to above average. Most of northern Australia had a dry month, as is typical during their dry season, with a few showers over the last two days of September.


Temperatures

September maximum temperatures averaged across Australia were very warm, with a national anomaly of +1.94 °C, ranking as the third warmest September of 63 years. All of the States were well above average for the month, with WA fourth warmest (1.96 °C above average), SA sixth warmest, both NSW and Queensland ninth, and the NT tenth in 63 years of records.

Generally, most areas of the country recorded an above average month for maximum temperatures, with most of the Australian mainland more than 1 °C above the historical average (1961-1990). An area encompassing central WA, stretching across SA and parts of the NT, to southwest Queensland and NSW, recorded temperatures more than 2 °C above normal. An area near Broome in WA, and the central Top End of the NT experienced their warmest September on record.

Overnight temperatures were generally closer to normal, with some regional variation. For Australia as a whole, temperatures were 0.42 °C above normal, which ranks as the midpoint of records (32nd coolest of 63 years). While none of the States ranked in the top or bottom ten of historical records, NSW and the Murray Darling Basin experienced their coolest September minimum temperatures since 1994 (18 years).

An area extending from the Pilbara coastline in WA across to the southwest NT, as well as small areas near Geraldton and Eucla in WA were all more than 1 °C above normal for the month. The majority of these areas were in decile 10 (i.e., warmest 10% of records). Areas cooler than 1 °C below normal included the northern Kimberley in WA, the western Top End of the NT, the Flinders Ranges in SA, and parts of Queensland and NSW. Small parts of these areas were in decile 1.

September temperatures towards the end of the month were particularly warm. A number of sites broke their warmest daily maximum temperatures (the greatest occurrence of record highs was on the 27th), in parts of the NT, WA and SA. While no daily records were broken in Victoria, Mildura Airport recorded the State's second warmest September daily temperature, with 36.4 °C on the 27th (Victorian record is 37.4 °C, recorded at Mildura Airport in 2003). Likewise, on the 28th, a large area of western NSW, and neighbouring areas over the NSW border experienced their warmest September daily overnight temperature. Ivanhoe Airport in NSW recorded the State's second warmest September daily overnight temperature, with 25.6 °C on the 28th (NSW record is 25.8 °C, recorded at Bourke Airport in 2003).


Areal average temperatures
  Maximum Temperature Minimum Temperature
Rank
(out of 63)
Anomaly*
(°C)
Comment Rank
(out of 63)
Anomaly*
(°C)
Comment
Australia 61 +1.94 3rd highest; record is +2.49 (1980) 32 +0.42
Queensland 55 +1.44 33 +0.14
New South Wales 55 +2.18 17 −0.54 Lowest since 1994
Victoria 49.5 +1.28 35 +0.02
Tasmania 49 +0.81 44 +0.26
South Australia 58 +2.62 38 +0.85
Western Australia 60 +1.96 4th highest; record is +2.25 (1980) 54 +1.05
Northern Territory 54 +2.08 30 +0.11

*Anomaly is the departure from the long-term (1961–1990) average.
A fractional rank indicates that the value is tied for that rank.


Temperature maps
MeanAnomalyDeciles
Mean
daily
maximum
temperatures
Map of mean daily maximum temperature Map of mean daily maximum temperature anomalies Map of mean daily maximum temperature deciles
Mean
daily
minimum
temperatures
Map of mean daily minimum temperature Map of mean daily minimum temperature anomalies Map of mean daily minimum temperature deciles

Rainfall

September rainfall was generally below average for large parts of the country. While neutral (neither El Niņo nor La Niņa) conditions were in place over the tropical Pacific, a positive Indian Ocean Dipole formed during late July to early August in the Indian Ocean. A positive Indian Ocean Dipole is typically associated with decreased winter and spring rainfall over much of southern, central and northern Australia, and this is largely reflected in the rainfall pattern for September.

Area averaged rainfall for Australia was 10.0 mm (40% below normal), ranking as the 27th driest September of 113 years. Most of the States recorded below average rainfall for the month, except Tasmania and the NT. SA recorded its tenth driest September, with an area average of 4.1 mm (76% below normal).

Below average rainfall was recorded over southeast WA, most of SA, southeast Queensland, most of NSW and Victoria. Areas of decile 1 (lowest 10% of records) were generally confined to areas of southeast WA, northern Victoria, and southern parts of both SA and NSW. Above average rainfall was recorded in Tasmania, and small parts of western WA.

As is usual during the northern dry season, parts of northern and central Australia recorded no rainfall for the month. Most of the far north experienced a dry September, with some rain over the last two days of the month. While central Australia typically receives very little rainfall from the May to September dry season period, this year they experienced a particularly long dry spell, with Alice Springs Airport not recording rain for 157 days straight, with the dry spell broken by light rain on the 29th of September (3 mm). This is the longest dry spell at Alice Springs Airport since records began there in 1940.


Area-average rainfall
Rank
(out of 113)
Average
(mm)
Departure
from mean*
Comment
Australia 27 10.0 −40%
Queensland 43 6.8 −47%
New South Wales 20 16.7 −52%
Victoria 15 39.3 −40%
Tasmania 86 167.1 +21%
South Australia 10 4.1 −76%
Western Australia 36.5 7.0 −34%
Northern Territory 90 7.4 +5%
Murray-Darling Basin 20 15.9 −53%

*The mean is calculated for the 1961–1990 reference period.


Rainfall maps
TotalsPercentagesDeciles
Total
rainfall
Map of total rainfall Map of percentage of normal rain Map of rainfall deciles


Australian weather extremes in September 2012
Hottest day 41.9 °C at Curtin Aero (WA) on the 23rd and Fitzroy Crossing (WA) on the 25th
Coldest day −4.5 °C at Thredbo Top Station (NSW) on the 29th
Coldest night −9.0 °C at Cooma Aiport (NSW) on the 2nd
Warmest night 27.1 °C at Argyle Aerodrome (WA) on the 28th
Wettest day 97.0 mm at Thredbo Village (NSW) on the 29th


Notes

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.

This statement has been prepared based on information available at 12 noon EST on Monday 1 October 2012. 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.

In the tables, fractional ranks denote tied values.

A new area-averaging method was adopted for rainfall in May 2009. Current and historical totals for Tasmania are substantially higher than under the old scheme, but differences for other states, and nationally, are negligible. The rankings and departures from mean shown here use the new method.


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