Tuesday, 2 September 2008 - Monthly Climate Summary for ACT - Product code IDCKGC15R0

A cool and dry August 2008 for the ACT

Summary

  • Below average rainfall.
  • Coolest average maximum temperature since 1992 at the Airport site.
  • Cooler than average minimum temperatures.

Rainfall

Canberra Airport recorded a total rainfall of 16.8 mm during the month, which is well below the historic average1 of 46.6 mm and lies within the 2nd decile (lowest 20% of all records). The below average rainfall was generally associated with a blocking high pressure in the Southern Ocean south of Western Australia, bringing persistent southerly to south-westerly flow over the eastern states. These cool air masses typically lose moisture after crossing the south coast, bringing little rain to the ACT.

A frontal system which passed through the ACT on the the last weekend of August, contributed towards most of the month's rainfall, with 35.4 mm being recorded at Mt Ginini AWS. A cold front on the 1st of the month also brought some rainfall to the region, with 20.0 mm recorded at Tidbinbilla for the 24 hours to 9am on the 2nd.

Monthly totals for the ACT ranged from a high of 91.8 mm at Mount Ginini AWS in the highlands SW of Canberra while the lowest in the ACT was 16.8 mm at Canberra Airport.

See a map of total rainfall. See a map of rainfall deciles.

Temperature

The mean maximum (daytime) temperature at Canberra Airport was 12.8°C, which is 0.2°C below the historical average1 of 13.0°C. This is the coolest August for mean maximum temperatures since 1992. The lowest mean maximum temperature in the ACT was 1.6°C at Mount Ginini AWS. This location also recorded the coldest day of the month of −3.5°C on the 10th.

Nights were generally cool to cold, with 20 days of frosts recorded at the airport site (average of 19 days). The mean minimum (overnight) temperature at Canberra Airport was 0.3°C, which is below the August average of 1.0°C.

The blocking high pressure systems mentioned above in "Rainfall" were also responsible for the cooler than average temperatures through the ACT. The resulting air masses from the southwest are typically cold and dry, therefore keeping temperatures down.

Extreme low temperatures in the ACT ranged from −7.0°C at Mount Ginini AWS (elev 1760 metres) on the 18th and −5.3°C at both Tuggeranong AWS and Canberra Airport on the 19th. The mildest night was 6.1°C at Canberra Airport on the 31st.

See a map of mean maximum temperatures. See a map of maximum temperature anomalies.

See a map of mean minimum temperatures. See a map of minimum temperature anomalies.

Wind

The prevailing wind direction over Canberra during the afternoons was W-NW for around 61% of the time, about the normal frequency expected from this direction during August. During the mornings prevailing N-NW winds had a frequency of 47% compared to the usual 32% from this direction. The highest wind gust recorded was 65 km/hr at Canberra Airport on the 1st associated with the passage of a cold front.

Other phenomena

The amount of sunshine averaged 7.2 hours per day which is slightly above the historic average for August of 7.0 hours. The frequency of fog was well below average with only 1 fog reported at Canberra Airport on the 19th, compared to the normal frequency of around 5 days of fogs. No thunderstorm or hail activity occurred in the Canberra region during the month. No snow was officially reported at the Airport site, however, there were reports of snow around the northwest suburbs on the 10th.

Further information

NSW Climate Services Centre
Bureau of Meteorology
Phone (02) 9296 1555
Email reqnsw@bom.gov.au

Extremes

Hottest day
Highest temperature
17.3°C at Canberra Airport on the 26th
Warmest days on average
Highest mean daily maximum temperature
13.0°C at Tuggeranong (Isabella Plains) AWS
Coolest days on average
Lowest mean daily maximum temperature
1.6°C at Mount Ginini AWS
12.0°C at Tidbinbilla Nature Reserve
Coldest day
Lowest daily maximum temperature
−3.5°C at Mount Ginini AWS on the 10th
Coldest night
Lowest temperature
−7.0°C at Mount Ginini AWS on the 18th
−5.3°C at Canberra Airport on the 19th
−5.3°C at Tuggeranong (Isabella Plains) AWS on the 19th
Coolest nights on average
Lowest mean daily minimum temperature
−3.7°C at Mount Ginini AWS
−1.0°C at Tuggeranong (Isabella Plains) AWS
Warmest nights on average
Highest mean daily minimum temperature
0.3°C at Canberra Airport
Warmest night
Highest daily minimum temperature
6.1°C at Canberra Airport on the 31st
Wettest overall
Highest total rainfall
91.8 mm at Mount Ginini AWS
45.1 mm at Tidbinbilla Nature Reserve
Wettest day
Highest daily rainfall
35.4 mm at Mount Ginini AWS on the 31st
Highest wind gust
65 km/h at Canberra Airport on the 1st

Summaries

Summary statistics for August 2008
Maximum temperatures
for August
(°C)
Minimum temperatures
for August
(°C)
Rainfall
for August
(millimetres)
Mean for
August
2008
Diff
from
normal
Highest for
August
2008
Mean for
August
2008
Diff
from
normal
Lowest for
August
2008
Total for
August
2008
Normal
for
August
Rank of
August
2008
Fraction of
August
normal
Canberra Airport 12.8 −0.2 17.3 26th 0.3 −0.6 −5.3 19th 16.8 46.1 low 36%
Mount Ginini AWS 1.6 7.0 24th −3.7 −7.0 18th 91.8
Tidbinbilla Nature Reserve 12.0 −0.7 15.5 26th −0.1 −1.2 −4.0 17th 45.1 92.9 low 49%
Tuggeranong 13.0 17.2 31st −1.0 −5.3 19th 20.8

Notes

This statement has been prepared based on information available at 10 am on Tuesday, 2 September 2008. Some checks have been made on the data, but it is possible that results will change as new information becomes available.

1Averages: historic rainfall and temperature averages are based on all available data.

Normals 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 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, normal in decile 4 to 7, high in decile 8 or 9 and very high is in decile 10).
The Fraction of normal shows how much rain has fallen this time as a percentage of the long-term mean.

Further information

NSW Climate Services Centre
Bureau of Meteorology
Phone (02) 9296 1555
Email reqnsw@bom.gov.au