Tuesday 2 October 2007 - Monthly Climate Summary for Sydney  - Product code IDCKGC1xx0

Warm, dry end to September in Sydney

Summary

Rainfall

The total September rainfall of 41.2 mm at Sydney Observatory Hill was below the historic September average1 of 69.4 mm but falls within the normal variability of all totals for September.  The majority of the rainfall occurred within the first week of the month caused by a moist on-shore air flow. There were 9 rain days during the month which is close to average.  Rainfall was below average over the entire Sydney area.  Monthly totals were highest in the eastern and southern suburbs and lowest in the western suburbs, particularly the north-west; totals ranged from 83.6 mm at Cronulla to 11.4 mm at Richmond.

The Warragamba Dam catchment received only light rainfall during September, with storage levels remaining almost stationary.  Monthly totals over the catchment were generally in the 15-30mm range.  Recent rainfall in Sydney's drinking water catchments can be found on the Sydney Catchment Authority web site http://www.sca.nsw.gov.au/dams/rainfall.html.

Temperature

The average maximum (daytime) temperature at Observatory Hill was 20.9C, which is slightly above the historic average1 temperature of 20.4C.  The elevated locations of Springwood (362 metres) and Terrey Hills (199 metres) recorded slightly cooler daytime temperatures: 20.0C and 19.7C respectively.  With Sydney experiencing both warm and cool spells during September, average maximum temperatures were close to normal throughout the metropolitan area.  During the unusually warm week at the end of the month, the temperature exceeded 26C on 4 days at Observatory Hill.

This is now the 10th consecutive September with above average maximum temperatures.  Since 1988, fifteen out of 20 Septembers have recorded above average maximum temperatures.

Night-time temperatures were mild throughout the Sydney metropolitan area. The average minimum temperature of 12.6C was 1.1C above the historic September average1. Minimum temperatures were about 5C cooler in far western suburbs, averaging 7.2C at Camden, however, they were still slightly above the historic September average.

The highest temperature at Sydney (Observatory Hill) during September was  28.6C on the 28th while the lowest temperature was 8.8C on the 23rd. Corresponding extremes in the Sydney area ranged from  29.6C at Sydney Airport on the 28th to 2.0C at Campbelltown (Mount Annan) on the 23rd.

Wind

There were 8 windy days as measured at Sydney Airport, compared to an average of 5.  The highest wind gust recorded was 93 km/h at Sydney Olympic Park on the 30th.  Except for brief spells of warm westerly winds, the prevailing direction was NE to SE.

Other phenomena

A thunderstorm on the 14th caused strong winds in the Sutherland area, blowing trees over roads and causing minor damage to houses.  On the last few days of the month, strong winds, high temperatures and low humidity created a very high bushfire danger. The humidity fell to a 13 year low for September with a 3pm reading of 12% on the 29th.

Further information

Mike De Salis
Climate Information Officer
NSW Climate Services Centre
Bureau of Meteorology
Phone (02) 9296 1555
Email mikede@bom.gov.au


Extremes for the Sydney area

Hottest day
Highest temperature
29.6 C at Sydney Airport on the 28th
Warmest days on average
Highest mean daily maximum temperature
22.4 C at Penrith Lakes
Coolest days on average
Lowest mean daily maximum temperature
19.7 C at Terrey Hills
Coldest day
Lowest daily maximum temperature
13.1 C at Springwood on the 4th and 6th
Coldest night
Lowest temperature
2.0 C at Campbelltown (Mount Annan) on the 23rd
Coolest nights on average
Lowest mean daily minimum temperature
7.2 C at Camden Airport and Campbelltown (Mount Annan)
Warmest nights on average
Highest mean daily minimum temperature
12.6 C at Sydney (Observatory Hill)
Warmest night
Highest daily minimum temperature
17.4 C at Sydney Olympic Park on the 28th
Wettest overall
Highest total rainfall
83.6 mm at Cronulla South
Driest overall
Lowest total rainfall
11.4 mm at Richmond
Wettest day
Highest daily rainfall
49.0 mm at Cronulla South
Highest wind gust
93 km/h at Sydney Olympic Park on the 30th

Summaries for the Sydney area

Summary statistics for September 2007
Maximum temperatures
for September
(C)
Minimum temperatures
for September
(C)
Rainfall
for September
(millimetres)
Mean for
September
2007
Diff
from
normal
Highest for
September
2007
Mean for
September
2007
Diff
from
normal
Lowest for
September
2007
Total for
September
2007
Normal
for
September
Rank of
September
2007
Fraction of
September
normal
Sydney (Observatory Hill)

20.9

+0.5 28.6 28th

12.6

+1.1 8.8 23rd

41.2

69.4

normal 59%
Parramatta

21.5

normal 28.6 28th

9.7

+0.4 5.8 10th

53.8

53.6

normal 100%
Richmond

21.8

normal 28.3 28th

8.0

+0.3 3.4 23rd

11.4

54.4

low 21%
Springwood*

20.0

26.8 27th

8.0

3.5 23rd

15.4

56.1

low 27%
Camden Airport

21.5

-0.3 28.0 28th

7.2

+0.5 2.3 23rd

26.6

39.7

normal 67%
Terrey Hills*

19.7

27.2 28th

10.7

7.3 23rd

37.0

 

* new stations, no historic average temperatures available and no historic average rainfall available for Terrey Hills

Additional climate data for Sydney (Observatory Hill) for September 2007
 

September 2007

Normal for September

Number of rain days

 9

 10

Average sunshine hours per day*

 8.1

7.8

Average humidity at 3pm (%)

 47

51

Number of thunderstorms

 1

2

Number of windy days*

 8

5

* recorded at Sydney Airport


Notes

This statement has been prepared based on information available at noon on Tuesday 2 October 2007. The data has been quality controlled, but it is possible that results will change as new information becomes available.

1Averages:  historic average temperatures for Observatory Hill and Richmond are based on the period 1961 to 1990 which is a convention of the World Meteorological Organisation.  Average temperatures for Parramatta are based on all available data, 1968 - 2006 and Camden 1972 - 2006.  Rainfall averages and extremes for Observatory Hill are based on all years of record 1859 - 2006.

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 "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.