Monday, 3 August 2009 - Monthly Climate Summary for ACT Monthly Summary - Product code IDCKGC25R0

ACT Monthly Summary in July 2009
Dry and sunny July for ACT

  • Below average rainfall
  • Warm days
  • Above average sunshine hours

An archive of previous monthly summaries for ACT Monthly Summary 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 29.8 mm during July, which is below the 41.2 mm average for the month. A total of 11 raindays were recorded during July, which is close to the historical average of 10.5 days. The average amount of rainfall on any day during the month was only 1.0 mm.

The majority of the month's rainfall fell in two main events. The first occured between the 1st and 3rd and the second between the 23rd and 27th. Both of these rain events were caused by the passage of a front and trough over southern NSW and the ACT.

Temperature

Canberra Airport recorded a mean maximum (daytime) temperature of 12.3°C, which is 1.0°C above the average for July. This is now the 11th consecutive July with above average maximum temperatures and ranks equal 12th highest out of 70 years of record. The lowest maximum temperature in the ACT was −1.8°C at Mount Ginini AWS on the 3rd.

Minimum temperatures were slightly above average across the ACT. The average minimum temperature at Canberra Airport was 1.3°C, which is 1.5°C above the historical July average. Frost was observed on 15 days during July, which is below the average of 21.2 days. Average minimum temperatures at Tidbinbilla, to the south west of Canberra, were only 0.2°C above the historical July average.

Temperature extremes in the ACT ranged from a high of 17.2°C at Canberra Airport on the 22nd, to an overnight low of −5.7°C at Mount Ginini on the 6th. This minimum temperature coincided with a high pressure system in The Bight which brought cool air north into the ACT.

Wind

North-westerly winds prevailed during 22% of mornings and 42% of afternoons in the Canberra area, however winds remained relatively calm throughout most of the month. The strongest wind gust of 74 km/h was recorded at Mount Ginini AWS (elev 1760 metres) on the 1st, associated with a cold front moving through central NSW.

Other phenomena

Canberra Airport recorded an average 6.6 hours of daily sunshine, above the long-term average of 5.8 hours, however slightly above average cloud cover was also recorded during July (4.1 oktas compared to the historical average of 3.9 oktas). This can be accounted for by mixed clear and cloudy conditions throughout the month, caused by the passage of a series of high pressure systems over the territory. Occurences of fog at Canberra Airport were below average, with only 4 fog occurences reported during July, compared to the historical average of 7.5 days. No thunderstorms were recorded during July in the ACT.

Further information

Claire Krause
Climate Officer
NSW Climate Services Centre
Bureau of Meteorology
Phone (02) 9296 1555
Email climate.nsw@bom.gov.au

Extremes

Hottest day
Highest temperature		 17.2°C at Canberra Airport on the 22nd
Warmest days on average
Highest mean daily maximum temperature		 12.6°C at Tuggeranong (Isabella Plains) AWS
Coolest days on average
Lowest mean daily maximum temperature		 1.4°C at Mount Ginini AWS
Coldest day
Lowest daily maximum temperature		 −1.8°C at Mount Ginini AWS on the 3rd
Coldest night
Lowest temperature		 −5.7°C at Mount Ginini AWS on the 6th
−4.0°C at Tuggeranong (Isabella Plains) AWS on the
Coolest nights on average
Lowest mean daily minimum temperature		 −2.6°C at Mount Ginini AWS
Warmest nights on average
Highest mean daily minimum temperature		 1.3°C at Canberra Airport
Warmest night
Highest daily minimum temperature		 7.5°C at Canberra Airport on the 1st
7.5°C at Tuggeranong (Isabella Plains) AWS on the 1st
Wettest overall
Highest total rainfall		 112.6 mm at Mount Ginini AWS
Driest overall
Lowest total rainfall		 29.8 mm at Canberra Airport
Wettest day
Highest daily rainfall		 29.0 mm at Mount Ginini AWS on the 2nd
Highest wind gust
 74 km/h at Mount Ginini AWS on the 1st

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Summaries

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

Summary statistics for July 2009
Maximum temperatures
for July
(°C)		 Minimum temperatures
for July
(°C)		 Rainfall
for July
(millimetres)
Mean for
July
2009		 Diff
from
average		 Highest for
July
2009		 Mean for
July
2009		 Diff
from
average		 Lowest for
July
2009		 Total for
July
2009		 Average
for
July		 Rank of
July
2009		 Fraction of
July
average
Canberra Airport 12.3 +1.0 17.2 22nd 1.3 +1.5 −3.4 18th 29.8 41.2 average 72%
Mount Ginini AWS 1.4   6.0 22nd −2.6   −5.7 6th 112.6
Tidbinbilla Nature Reserve 11.6 +0.8 16.5 22nd 0.4 +0.2 −3.0 24th 88.1 83.7 average 105%
Tuggeranong 12.6   17.0 22nd 1.1   −4.0 18th 33.4

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Notes

This statement has been prepared based on information available at 10 am on Monday 3 August 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

Claire Krause
Climate Officer
NSW Climate Services Centre
Bureau of Meteorology
Phone (02) 9296 1555
Email climate.nsw@bom.gov.au