Adelaide Metro & Hills in September 2012: Dry with warm days across the Adelaide region

  • Rainfall was very much below average across the Adelaide region with many locations receiving less than half of the long term September average.
  • Adelaide observed its driest September in 4 years, with several locations observing record lowest September Rainfall
  • Daytime temperatures in excess of 1C above average while nights were near average.

Rainfall

The September 2012 rainfall total at Adelaide (Kent Town) was 21.8mm received on 12 rain days. This is very much below the long term average of 60.3 mm on 13 or more rain days, and results in the driest September in Adelaide since 2008 when only 16.0 mm was observed. The long term median September rainfall for Adelaide (Kent Town) is 56.4 mm, last time exceeded in September 2010 when 60.6 mm was observed. By comparison, 46.8 mm was observed in September 2011.

Most rainfall during September for the Adelaide and Hills regions was observed through the first and last week of the month. On the 5th, a vigorous cold front associated with a deep low pressure system to the south of the State brought strong winds, squally showers and isolated thunderstorms for the Adelaide and Hills region. Showers continued through to the 7th when Bridgewater reported the wettest day of the month with 25mm in the 24 hours to 9am. Apart from the passage of cold front on the 13th which saw several locations across the Adelaide Hills and Plains observe 2 to 4mm, most of the month remained relatively dry up until 28th when another vigorous cold frontal system brought showers and thunderstorms across southern parts of the State. 2-day rainfall totals of between 5 to10mm were observed across the Adelaide Plains owing to this event, while higher values greater than 20mm were observed about the Hills.

Most locations received less than half of the long term September average with monthly rainfall totals typically ranging between 10 to 30mm on the Adelaide Plains, with higher totals in the 40 to 60mm range throughout the Adelaide Hills. Tea Tree Gully Council reported a record lowest September rainfall total in 127 years of observations, with just 4.9 mm against an average of 68 mm, the previous lowest at this site was 14.7 mm observed in September 1951. The wettest location across the region was at Bridgewater where 73.6 mm was recorded for the month, much of that occurring between the 5th and 7th. The long term September average rainfall for Bridgewater is 112 mm.

Note that the Adelaide official climate rainfall record is taken from the manually observed 203mm rain gauge at the Kent Town site in Adelaide. These figures may differ from totals on some Bureau of Meteorology web pages as these may be from automatic tipping bucket rain gauge readings.

Some sites had their lowest total September rainfall on record.
Some sites had their lowest total September rainfall for at least 25 years.

Temperature

The average maximum temperature recorded at Adelaide (Kent Town) for September 2012 was 19.9°C, 0.9°C above the long term average September maximum temperature. In comparison, September 2011 saw average maximum temperatures of 20.8°C at Adelaide (Kent Town). The record warmest September average maximum in Adelaide is 21.5°C, observed in 1944 at the West Terrace site.

The warmest period of the month occurred between the 26th and 27th as northerly winds were directed across the State ahead of a low pressure trough approaching from the west. The hottest day for any location across the Adelaide and Hills region was reported at Edinburgh RAAF where the maximum reached 29.0°C on the 26th. Edinburgh RAAF also reported the warmest days on average, with a monthly average of 20.4 °C, which is 1.5 °C above the long term average for this site.

Daytime temperatures in the Adelaide regions were coolest on the 7th and 14th following the passage of cold frontal systems. The coldest day of the month for any location in the Adelaide and Hills region was reported at Mount Lofty on the 7th when the maximum reached 8.3 °C. The coolest days on average were at Mount Lofty where the September maximum temperature averaged 13.9 °C.
Mean minimum temperatures were generally slightly above average across the Adelaide Plains and Hills this September, with the minimum temperature at Adelaide (Kent Town) being 9.8°C, 0.1 °C above the long term September average. During September 2011, the minimum temperatures averaged 10.2 °C.

The coldest nights for most locations occurred through the third week of September as a high pressure system centred well south of South Australia directed mainly light to moderate south to southeasterly winds across southern parts of the State.

The coldest minimum temperature during September 2012 in the Adelaide and Hills area was 1.8 °C observed at both Parafield Airport on the 18th and at Mount Lofty on the 29th. The coolest nights on average were recorded at Mount Lofty with 6.4 °C. Mount Barker observed an average September minimum of 6.8°C, 1.0°C above the long term average for that site. The warmest night was observed at Noarlunga with 15.0°C on the 26th. Noarlunga also recorded the warmest nights overall, with a monthly average of 10.1 °C

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Extremes in September 2012
Hottest day 29.0 °C at Edinburgh RAAF on the 26th
Warmest days on average 20.4 °C at Edinburgh RAAF
Coolest days on average 13.9 °C at Mount Lofty
Coldest day 8.3 °C at Mount Lofty on the 7th
Coldest night 1.8 °C at Parafield Airport on the 18th
1.8 °C at Mount Lofty on the 29th
Coolest nights on average 6.4 °C at Mount Lofty
Warmest nights on average 10.1 °C at Noarlunga
Warmest night 15.0 °C at Noarlunga on the 26th
Warmest on average overall 14.9 °C at Adelaide (Kent Town)
Coolest on average overall 10.2 °C at Mount Lofty
Wettest overall 73.6 mm at Bridgewater
Driest overall 4.9 mm at Adelaide (Tea Tree Gully Council)
Wettest day 25.0 mm at Bridgewater on the 7th
Highest wind gust 100 km/h at Mount Crawford (Mt Crawford AWS) on the 5th

Record lowest total September rainfall
Total rainfall
for September 2012 (mm)
Previous driest
for September
Years of
record
Average for
September
Adelaide (Tea Tree Gully Council) 4.9 14.7 in 1951 127 68.0
Heathfield Works Depot 41.4 42.4 in 2008 28 111.0

Lowest total September rainfall for at least 25 years
Total rainfall
for September 2012 (mm)
Most recent September
at least this dry
Years since
drier
Average for
September
Adelaide (Hope Valley Reservoir) 24.2 23.2 in 1987 25 63.7
Adelaide (Pooraka) 12.8 12.4 in 1987 25 48.1
Blackwood (Wittunga) 29.6 27.6 in 1987 25 74.1



Summary statistics for September 2012
Maximum temperatures
for September
(°C)
Minimum temperatures
for September
(°C)
Rainfall
for September
(millimetres)
Mean for
September
2012
Diff
from
average
Highest for
September
2012
Mean for
September
2012
Diff
from
average
Lowest for
September
2012
Total for
September
2012
Average
for
September
Rank of
September
2012
Fraction of
September
average
Adelaide (Kent Town) 19.9 +0.9 28.2 27th 9.8 +0.1 5.3 1st 21.8 60.3 v low 36%
Adelaide Airport 19.2 +1.1 27.9 26th 9.0 +0.1 3.8 25th 18.2 45.6 low 40%
Edinburgh RAAF 20.4 +1.5 29.0 26th 8.3 +0.2 1.9 18th 21.8 47.8 low 46%
Mount Barker 17.5 +1.0 25.7 27th 6.8 +1.0 2.2 25th 66.4 85.5 average 78%
Mount Crawford (Mt Crawford AWS) 15.7   24.5 27th 7.3   3.0 29th 43.2
Mount Lofty 13.9   22.9 27th 6.4   1.8 29th 49.4
Noarlunga 18.9   26.7 27th 10.1   6.0 18th 36.4
Parafield Airport 20.2 +1.3 28.7 26th 8.2 0.0 1.8 18th 28.6 44.1 low 65%

Notes

A Monthly Climate Summary is prepared to list the main features of the weather in Adelaide Metro & Hills 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.

This statement has been prepared based on information available at 5 pm on Sunday 30 September 2012. Some checks have been made on the data, but it is possible that results will change as new information becomes available.

Averages are long-term means based on observations from all available years of record, which vary widely from site to site. They are not shown for sites with less than 20 years of record, as they cannot then be calculated reliably.
The median is sometimes more representative than the mean of long-term average rain.

The Rank indicates how rainfall this time compares with the climate record for the site, based on the decile ranking (very low rainfall is in decile 1, low in decile 2 or 3, average in decile 4 to 7, high in decile 8 or 9 and very high is in decile 10).
The Fraction of average shows how much rain has fallen this time as a percentage of the long-term mean.

Further information

Media
(03) 9669 4057
Enquiries