Thursday, 2 October 2008 - Monthly Climate Summary for Canberra rainfall extremes - Product code IDCKGC2xx0

Dry, warm and sunny in Canberra during September

Summary

A sunny month with well above average daytime temperatures.

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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Details

  • Below average rainfall.
  • Above average maximum (daytime) temperatures, 4th highest on record
  • 11th consecutive year with above average maximum temperatures in September
  • Above average minimum (overnight) temperatures
  • 14th consecutive year with above average minimum temperatures in September
  • Plentiful sunshine, averaging 8.7 hours per day, ranking 7th sunniest September over past 30 years.

Rainfall

Canberra Airport recorded a total rainfall of 39.4 mm during the month, which is below the historical average1 of 52.1 mm and lies within the 4th decile (lowest 40% of all records). The rain fell on 7 rain days which is below the normal 10 rain days for September. Most of Canberra's rain came from two main systems; a cold front and cloud band on the 14th and an active cold front on the 22nd and 23rd which caused widespread rain and thunderstorms throughout the ACT. The wettest day in the ACT was on the 23rd when Mount Ginini AWS recorded 55 mm (the wettest day for any month at this station since records commenced in June 2004). However, much of the month was dominated by the stabilising effects of prevailing high pressure systems over the region.

Rainfall totals were highest in the north and west of the ACT and lowest in the south. Monthly totals for the ACT ranged from a high of 99.8 mm at Mount Ginini AWS and Corin Dam, in the highlands SW of Canberra. The highest in the Canberra metropolitan area was 56.8 mm at Nicholls. The lowest monthly total in the ACT was 26.6 mm at Farrer.

Temperatures

The mean maximum (daytime) temperature at Canberra Airport was 18.0°C, which is 1.9°C above the historical average1 of 16.1°C. This is the 4th warmest September for mean maximum temperatures since records commenced in 1939. It is also the 11th consecutive year with above average maximum temperatures in September. There were 5 days when the temperature exceeded 23°C, the highest since 1987 and the 2nd highest on record for September. Normally Canberra would experience only one day above 23°C in September. The persistent high pressure system in the Tasman Sea directed mild N-NW winds over the ACT for extended periods during the month. The prevailing winds and an abundance of clear, sunny days were mainly responsible for the mild to warm days during September.

Nights were generally cool across the ACT and close to the September average. The average minimum temperature at Canberra Airport was 3.9°C which was 0.7°C above the September historical average. It is also the 14th consecutive year with above average minimum temperatures in September. The average minimum at Tuggeranong was slightly below the historical average due to its more sheltered location. There were 10 days of frosts recorded at the airport site (average of 13 frost days for September).

Extreme temperatures in the ACT ranged from a high of 26.0°C at Tuggeranong AWS on the 27th to a low of −5.0°C at Mount Ginini AWS on the 16th (elevation 1760 metres). The lowest in the Canberra metropolitan area was −4.4°C at Tuggeranong AWS on the 11th. The coldest day (lowest maximum temperature) was 11.3°C at Canberra Airport on the 4th and zero degrees at Mount Ginini AWS on the 4th and 16th.

Some sites had their equal highest September temperature on record.

Wind

The prevailing wind direction over Canberra during the afternoons was N-NW for around 73% of the time, above the normal frequency of 59% expected from this direction during September. Canberra recorded 4 strong wind days which included one day of gale force winds on the 15th (both normal for September). The highest wind gusts recorded in the ACT were 98 km/h at Canberra Airport on the 15th, the strongest winds at the airport since December 2005. A gust of 98 km/h was also recorded at the high elevation station of Mount Ginini AWS on the 14th, associated with the passage of a cold front.

Other phenomena

The amount of sunshine averaged 8.7 hours per day which is well above the historical daily average for September of 7.6 hours. The frequency of fog was below average with only 2 fogs reported at Canberra Airport on the 8th and 18th, with visibility reduced to 300 metres on the 18th. The normal frequency is around 4 days of fogs. There were two thunderstorms recorded at Canberra Airport, on the 14th and 22nd. The normal for September is 2 storms.

Further information

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

Extremes for the ACT

Hottest day
Highest temperature		 26.0°C at Tuggeranong AWS on the 27th
Warmest days on average
Highest mean daily maximum temperature		 18.3°C at Tuggeranong AWS
Coolest days on average
Lowest mean daily maximum temperature

18.0°C at Canberra Airport
8.9°C at Mount Ginini AWS
Coldest day
Lowest daily maximum temperature		 11.3°C at Canberra Airport on the 4th
0.0°C at Mount Ginini AWS on the 4th and 16th
Coldest night
Lowest temperature

−4.4°C at Tuggeranong AWS on the 11th
−5.0°C at Mount Ginini AWS on the 16th
Coolest nights on average
Lowest mean daily minimum temperature

3.1°C at Tuggeranong AWS
0.1°C at Mount Ginini AWS
Warmest nights on average
Highest mean daily minimum temperature		 3.9°C at Canberra Airport
Warmest night
Highest daily minimum temperature		 14.4°C at Canberra Airport on the 28th
Wettest overall
Highest total rainfall		 99.8 mm at Mount Ginini AWS and at Corin Dam
56.8 mm at Nicholls (Gungahlin Lakes)
Driest overall
Lowest total rainfall		 26.6 mm at Farrer
Wettest day
Highest daily rainfall		 55.0 mm at Mount Ginini AWS on the 23rd
26.6 mm at Nicholls (Gungahlin Lakes) on the 23rd
Highest wind gust
 98 km/h at Canberra Airport on the 15th
98 km/h at Mount Ginini AWS on the 14th

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Records for the ACT

Record highest September temperature
Highest temperature
in September 2008 (°C) 		Previous highest
for September		 Years of
record		 Normal for
September
Tidbinbilla Nature Reserve 25.0 on the 13th = 25.0 on the 22nd in 2003 23 14.7


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Summaries for the ACT

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

Summary statistics for September 2008
Maximum temperatures
for September
(°C)		 Minimum temperatures
for September
(°C)		 Rainfall
for September
(millimetres)
Mean for
September
2008		 Diff
from
normal		 Highest for
September
2008		 Mean for
September
2008		 Diff
from
normal		 Lowest for
September
2008		 Total for
September
2008		 Normal
for
September		 Rank of
September
2008		 Fraction of
September
normal
Canberra Airport 18.0 +1.9 25.7 27th 3.9 +0.7 −3.7 9th 39.4 52.1 average 76%
Tuggeranong 18.3 +0.7 26.0 27th 3.1 −0.9 −4.4 11th 31.2 60.2 low 52%
Mount Ginini AWS* 8.9   16.0 27th 0.1   −5.0 16th 99.8

* new station, no historical averages available

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Notes

This statement has been prepared based on information available at 12 pm on Thursday 2 October 2008. Some checks have been made on the data, but it is possible that results will change as new information becomes available.

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 10 years of record, as they cannot then be calculated reliably.
The median is sometimes more representative than the mean of long-term average ("normal") 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, 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
NSW Regional Office
Bureau of Meteorology
Phone (02) 9296 1555
Email reqnsw@bom.gov.au