Friday, 2 October 2009 - Monthly Climate Summary for Canberra rainfall extremes - Product code IDCKGC15x0

Canberra has warm September with above average rainfall

  • Slightly above average rainfall
  • Above average maximum temperatures
  • Above average minimum temperatures
  • High frequency of NW winds.
  • Sunny month, averaging 8.4 hours of sunshine per day

An archive of previous monthly summaries for Canberra rainfall extremes is also available, as are summaries for other states and many other climate summaries and diagnostics.

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Rainfall

Canberra Airport recorded a total rainfall of 56.2 mm during the month, which is slightly above the historical average of 52.1 mm. It is the first time in 5 months that Canberra has recorded above average monthly rainfall. However, this is well below the wettest September of 151 mm set in 1978. The number of rain days was also slightly above average at 12 days (September average 10 days) but several of these rain days were less than 1 mm.

Several cold fronts passed over the ACT producing light showers. However, a strong cut-off low pressure system over southern NSW on the 22nd caused thunderstorms and moderate showers in the ACT, accounting for more than half of the total monthly rainfall at Canberra Airport. The storms were heaviest in northern suburbs where 51.4 mm was recorded at Nicholls for the 24 hours to 9am on 23rd, the wettest day in the ACT during the month.

Monthly totals for September in Canberra suburbs ranged from a high of 89.4 mm at Nicholls in the northern suburbs to a low of 48.6 mm at Kingston in the inner south. Higher falls occurred on the ACT ranges where Corin Dam recorded a monthly total of 165.6 mm.

Temperatures

The mean maximum (daytime) temperature at Canberra Airport was 17.4°C, which is 1.2°C above the historical September average of 16.2°C. This ranks as the 14th warmest September in the 71 year record at Canberra. It is now the 12th consecutive September with above average maximum temperatures, the last 'cool' September occurring back in 1997. The highest daily maximum temperature was 25.2°C on the 13th. Although temperatures exceeding 25°C in Canberra normally occur only once in every 5 years on average, they have now occurred 4 times in the last 4 years.

Nights were generally mild, with the mean minimum temperatures at Canberra Airport of 4.3°C, 1.1°C above the September historical average of 3.2°C. This is the 13th warmest September for average minimum temperatures since records commenced in 1939. It is also the 15th consecutive September with above average monthly minimum temperatures; the last September with below average minimums was back in 1994. Canberra Airport recorded only 8 frosts during the month (minimum temperature below 2°C) well below the normal 13 frosts for September, and the lowest since September 1998. The lowest temperature in Canberra suburbs was −2.5°C at Tuggeranong AWS on the 6th.

Prevailing NW winds and the lack of any significant cool changes contributed towards the mild temperatures during September. An El Niño) event is currently maturing in the equatorial Pacific Ocean. These events are usually (but not always) associated with above average temperatures in eastern Australia. Very high temperatures experienced throughout August and September are likely due to the current influence of El Niño) combined with the background, long-term warming that has been observed across Australia since the start of last century.

Wind

The prevailing wind direction over Canberra during the afternoons was between N and W for a significant 94% of the time, compared to the normal frequency of 77% from this direction. Two days of strong winds were recorded at Canberra Airport, on the 13th and 23rd. The highest wind gust at Canberra Airport was 70 km/hr on the 25th, although much higher gusts (113 km/hr) were recorded on the ACT ranges on the same day.

Other phenomena

Only one thunderstorm occurred in the Canberra region during the month, on the 22nd, which produced heavy showers in some northern suburbs. This was preceded by widespread raised dust which reduced visibility to 3 km over the city. Only one fog was reported at Canberra Airport compared to the normal frequency of around 4 fogs in September. The amount of sunshine averaged 8.4 hours per day, which is above the historical September average of 7.7 hours.

Further information

Mike De Salis
Climate Monitoring Officer
NSW Climate Services Centre
NSW Regional Office
Bureau of Meteorology
Phone (02) 9296 1555
Email climate.nsw@bom.gov.au

Extremes for the ACT

Hottest day
Highest temperature		 25.2°C at Canberra Airport on the 13th
Warmest days on average
Highest mean daily maximum temperature		 17.6°C at Tuggeranong AWS
Coolest days on average
Lowest mean daily maximum temperature		 17.4°C at Canberra Airport
8.7°C at Mount Ginini AWS
Coldest day
Lowest daily maximum temperature		 9.0°C at Canberra Airport on the 27th
−2.5°C at Mount Ginini AWS on the 26th
Coldest night
Lowest temperature		 −2.5°C at Tuggeranong AWS on the 6th
−6.1°C at Mount Ginini AWS on the 27th
Coolest nights on average
Lowest mean daily minimum temperature		 3.8°C at Tuggeranong AWS
0.5°C at Mount Ginini AWS
Warmest nights on average
Highest mean daily minimum temperature		 4.3°C at Canberra Airport
Warmest night
Highest daily minimum temperature		 11.7°C at Tuggeranong AWS on the 22nd
Wettest overall
Highest total rainfall		 92.6 mm at Nicholls (Gungahlin Lakes)
165.6 mm at Corin Dam
Driest overall
Lowest total rainfall		 48.8 mm at Kingston
Wettest day
Highest daily rainfall		 51.4 mm at Nicholls (Gungahlin Lakes) on the 23rd
Highest wind gust
 70 km/hr at Canberra Airport on the 25th
113 km/hr at Mount Ginini AWS on the 25th

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Records

Nil recorded

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Summaries for the ACT

This table is very wide and may not fit if printed.

Summary statistics for September 2009
Maximum temperatures
for September
(°C)		 Minimum temperatures
for September
(°C)		 Rainfall
for September
(millimetres)
Mean for
September
2009		 Diff
from
average		 Highest for
September
2009		 Mean for
September
2009		 Diff
from
average		 Lowest for
September
2009		 Total for
September
2009		 Average
for
September		 Rank of
September
2009		 Fraction of
September
average
Canberra Airport 17.4 +1.2 25.2 13th 4.3 +1.1 −2.3 6th 56.2 52.2 average 108%
Tuggeranong 17.6 0.0 24.9 13th 3.8 −0.2 −2.5 6th 65.6 60.6 average 108%
Mount Ginini AWS 8.7   16.2 13th 0.5   −6.1 27th 142.0

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Notes

This statement has been prepared based on information available at 10 am on Friday 2 October 2009. 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

Mike De Salis
Climate Monitoring Officer
NSW Climate Services Centre
NSW Regional Office
Bureau of Meteorology
Phone (02) 9296 1555
Email climate.nsw@bom.gov.au