Australia in September 2011

In Brief

Southern parts of the country recorded generally warmer than average daytime temperatures in September 2011, whilst minimum temperatures were generally on the cool side of normal across much of Australia. Rainfall across Australia was generally below average, with northern New South Wales and southern Queensland recording above average falls for this time of year.


Temperatures

Maximum temperatures averaged across Australia for September were 0.92 °C warmer than usual. Daytime temperatures averaged across southeastern Australia were particularly warm, ranking as the sixth warmest on record, with Victoria observing its fifth warmest September for daytime temperatures and Tasmania its warmest September maxima since 2001. South Australia also had its 8th warmest September daytime temperatures.

Maximum temperatures along the southern half of Australia were generally 1 to 3 °C above average, except for the southwest of WA. A small region experienced maxima up to 4 °C warmer than usual stretching from Port Augusta in South Australia to the central New South Wales border. A large area spanning eastern South Australia, the western half of both Victoria and New South Wales, and northern Tasmania, as well as southeast WA, recorded daytime temperatures in the highest 10% of records. The more notable below average temperatures were recorded in the Kimberley region of WA, with maximum temperatures 1 to 2 °C below normal. The warmest temperature for September often tends to occur in northwest Australia. This region experienced maximum temperatures on the cooler side of normal this month, and as a result, this was the first September since 1993 that it has failed to record any 40 °C days by the end of September.

Overnight temperatures were generally on the cool side of normal, with a nationally averaged anomaly of −0.57 °C, the lowest value since 1985 (26 years). The northwest tropics were particularly cool, with the Kimberley region of WA and the Victoria River region of the NT experiencing night-time temperatures up to 4 °C below normal. Above normal minima was mostly confined to the southern states, with Tasmania and SA recording above average temperatures, and Victoria and NSW near-normal for the month. Western Australia as a whole was particularly cool, with the September minima 0.67 °C below normal, its coolest since 1978 (33 years).


Areal average temperatures
  Maximum Temperature Minimum Temperature
Rank
(out of 62)
Anomaly*
(°C)
Comment Rank
(out of 62)
Anomaly*
(°C)
Comment
Australia 41 +0.92 15 −0.57 Lowest since 1985
Queensland 42 +0.68 14 −0.94 Lowest since 1994
New South Wales 53 +2.07 23 −0.09 Lowest since 1994
Victoria 58 +1.77 31.5 −0.09
Tasmania 53 +1.07 Highest since 2001 51 +0.50
South Australia 55 +2.15 33 +0.43
Western Australia 39 +0.44 15 −0.67 Lowest since 1978
Northern Territory 29 +0.35 13 −1.12

*Anomaly is the departure from the long-term (1961-1990) average.


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

Rainfall averaged over Australia was 26% below normal (46th driest in 112 years of record), with all states, except New South Wales, recording below average rainfall in September 2011, although no states fell in the driest 20 years of record.

Large areas of southeastern Australia were drier than usual this month, with southeast SA, western Victoria and northern Tasmania recording below average falls. Most of tropical and central Australia were seasonally dry, with no rain recorded this month at most locations in the Northern Territory, the northern half of WA, northern Queensland and northern SA. The most notable above average falls were in an area encompassing northern NSW and southern Queensland.

Much of the widespread rainfall across Tasmania, Victoria and New South Wales this month was associated with a deep frontal system passing the area on the 28th and 29th which extended as far north as the Queensland border.


Areal average rainfall
Rank
(out of 112)
Average
(mm)
Departure
from mean*
Comment
Australia 46 12.2 −26%
Queensland 54 9.2 −29%
New South Wales 78 38.3 +10%
Victoria 28 45.3 −31%
Tasmania 38 114.4 −17%
South Australia 30 8.6 −50%
Western Australia 40 7.6 −28%
Northern Territory 32 0.9 −87%
Murray-Darling Basin 71 35.7 +5%

*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 2011
Hottest day 39.7 °C at Bradshaw (NT) on the 30th
Coldest day −3.5 °C at Mount Hotham (VIC) on the 9th
Coldest night −11.0 °C at Charlotte Pass (NSW) on the 22nd
Warmest night 25.9 °C at Lockhart River (QLD) on the 23rd
Wettest day 175.0 mm at Wyong (NSW) on the 26th


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 2pm EST on Monday 3 October 2011. 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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