Sydney Monthly Climate Summary: September 2006
Warmest September on record in Sydney

Tuesday 3 October, 2006

In Brief

September 2006 - Main Points:

  • A month of contrasting conditions - cold and wet early in month followed by hot, dry and windy weather.
  • Warmest September in 147 years of record.
  • 9 days exceeding 25°C, second highest ever recorded for September.
  • Well above average rainfall, ranking 8th wettest on record.
  • The 7 days 7th −13th was wettest week in September since 1879.
  • Plentiful sunshine averaging 8.5 hours per day.
  • Windy month with 8 strong wind days (average 5).

Details

Temperatures:    Well above average temperatures were recorded in Sydney during September,  making it the 9th consecutive September with above average temperatures.   The average monthly mean temperature (the average of the daily maximum and minimum temperatures) of 18.3°C was 2.4°C above the historic average1 of 15.9°C, making it the warmest September since records commenced in 1859.  The previous warmest September was in 1998 (average temperature 17.8°C).  

Except for one cool, wet week (7th to13th) nearly all days were above the historic average with extended periods of warm to hot and dry weather. The average maximum day-time temperature of 23.1°C at Observatory Hill was nearly 3°C above the historic average1 of 20.4°C and the second highest ever recorded, the highest being 23.3°C in 1980.  There were 9 days over 25°C, the second highest on record for September. The highest was 10 days in 2002 (historic average 3 days over 25°C).  During the hot spell from 18th to 24th there were 7 consecutive days when the temperature exceeded 25°C, the longest ever recorded in September. The unseasonally warm conditions were caused by a series of intense low-pressure systems near Tasmania directing persistent warm to hot and dry N-NW winds over Sydney.

Nights were also very mild with the average minimum temperature at Observatory Hill of 13.5°C, the highest ever recorded in September.  The previous highest was 13.4°C in 1998.  However, nights were progressively cooler in suburbs further from the coast with Richmond recording an average minimum of 8°C, which is only slightly above the historic average.

The highest temperature at Sydney (Observatory Hill) during September was 33.6°C on the 24th, the 4th highest temperature ever recorded in September.  The lowest temperature was 9°C on the 7th.          Corresponding extremes across the Sydney metropolitan area ranged from 34.6°C at Sydney Airport on the 24th to 2.9°C at Richmond on the 6th.

Rainfall:   Historically, September is Sydney's driest month, however the total rainfall of 192.2 mm was well above the historic average of 69 mm and the wettest September since 1995 when 226 mm was recorded.   There were only 7 rain days during the month which is below the historic average of 10 rain days.   All of the rain fell during the week from 7th to 13th making this the wettest week in September since 1879.  Heavy rain on the 7th totalled 107 mm, Sydney's wettest September day since 1883.  The rain was caused by an intense low-pressure system in the Tasman Sea, persistent, moisture-laden SE winds and significant thunderstorm activity.

Unlike the patterns over recent months,  the heavy rain penetrated inland to Sydney's western suburbs with some significant and welcome falls around Parramatta and Richmond.   The monthly rainfall of 151.4 mm at Richmond was the 3rd highest on record for September and nearly four times the historic average of 40 mm. Richmond also had its wettest 6-day period on record for September with a total of 151.2 mm from 7th to 12th (records since 1928).  There was minor flooding in and around Sydney on the 7th including the Audley Weir in Sydney's south. Metropolitan rainfall for September ranged from 219 mm at West Pymble and Marsfield in Sydney's north to 82 mm at Badgerys Creek and Glenmore Park in the far west.

Rainfall - Warragamba catchment:  September rainfall totals over the catchment area were much lighter than the Metropolitan area, ranging from about 40 - 70 mm.  Recent rainfall over Sydney's catchments can be found on the Sydney Catchment Authority web site http://www.sca.nsw.gov.au/dams/rainfall.html

Other phenomena:    Generally sunny conditions prevailed during the month with an average of 8.5 hours of sunshine per day which is considerably above the historic average of 7.8 hours per day.   There were 4 thunderstorms during the month (historic average 2 storms) with thunderstorms contributing to the majority of the month's rainfall from 7th to 11th.  Winds were stronger than usual with 8 windy days during September compared to an average of 5 windy days. Wind gusts reached 109km/h at Camden and 98km/h at Sydney Airport on the 24th, causing widespread damage and power failures in western Sydney.  Several major bushfires in and around the Metro area on the 24th destroyed at least 6 houses and burnt out thousands of hectares of bushland.

 

Climate summary for Sydney, September 2006

 

Sydney Observatory Hill   (Elev 39 m)

 

September 2006

Historic average1

September 2005

Average maximum
temperature (°C)

 23.1

 20.4

 21.0

Average minimum
temperature (°C)

 13.5

 11.5

 12.1

Mean
temperature (°C)

 18.3

 15.9

 16.5

Monthly rainfall
(mm)

 192.2

68.6#

 51.2

Number of
rain days

 7

10

 11

Average daily
sunshine (hours)

 8.5

7.8

 7.7

Average relative humidity at 3pm (%)

 51

51

 51

Number of days of thunderstorms

 4

2

 0

Number of windy days*

 8

5

 5

#  median September rainfall is 53 mm..

* windy day defined as average wind speed of 40km/h or greater at synoptic times.

 Climate summary for Sydney metropolitan and lower Blue Mountains, September 2006

 

  Parramatta

(Elev 55 m)

   Richmond  

(Elev 19 m)

     Camden    
 
(Elev 79 m)

Terrey  Hills # (Elev199 m)

Springwood #

(Elev 362 m)

 

September 2006

Historic average1

September 2006

Historic average1

September 2006

Historic average1

September 2006

September 2006

Average maximum
temperature (°C)

 23.8

 21.5

 23.4

 21.8

 23.8

 21.8

 21.6

 22.1

Average minimum
temperature (°C)

 10.5

 9.2

 8.0

 7.7

 7.9

 6.7

 12.3

 9.0

Mean
temperature (°C)

 17.1

 15.3

 15.7

 14.8

 15.9

 14.2

 17.0

15.6

Monthly rainfall (mm)

 192.2

 50.2

 151.4

 40.2

 83.8

 38.4

 139.4

 72.8

Number of
rain days

 8

 8

 6

 8

 6

 8

 8

 7

#  new station, historic averages not yet available

Climate averages for Sydney are available, here

Daily Extremes for September - Sydney metropolitan and lower Blue Mountains

 Observatory Hill (CBD)ParramattaRichmond

Terrey Hills #

Springwood #

 

September 2006

All years

September 2006

All years

September 2006

All years

September 2006

September 2006

Highest temperature (°C) and date
Warmest day

  33.6
(24th)

  34.6   (1965)

 33.8
 (24th)

35.4  (2003)

32.9
 (24th)

35.9  (1980)

 32.7
 (24th)

 31.4
(24th

Lowest temperature (°C) and date
Coldest night

9.0
 (7th) 

  4.9   (1945)

 6.4 
(5th)

1.4  (1995)

2.9
 (6th) 

−1.2  (1945)

 7.5  
(7th)

 5.5
(14th)

Lowest maximum temperature (°C) and date
Coldest day

16.7  
(9th)

  9.5   (1869)

  15.8
 (9th)

12.7  (1970)

13.9
 (9th) 

11.7  (1943)

 14.5
 (9th)

 11.0
(10th)

Wettest 24hours (mm) and date

 107.2
(7th)

144.5  (1879)

 103.4
(7th)

164.1  (1970)

 89.4
 (7th)

97.8  (1970)

 52.6
 (7th)

 41.6
(7th)

Maximum Wind Gust (km/h) and date

NW @ 98  (24th)*

W @ 131  (1968)

-

-

 NNW @ 100  (24th)

  W @ 117 (1945)

 S @ 76  (7th)

-

 * recorded at Sydney Airport              # new station, extremes not yet available

This statement has been prepared based on information available at noon on 03/10/06. Although every effort has been made to check them, it is possible that results may change as new information becomes available.

A note about deciles: Deciles are used to give an element (in this case rainfall or temperature) a ranking. Deciles are calculated by arranging the totals in ascending order (from lowest to highest) then splitting them into 10 equal groups (thus the groups are called deciles). The first group would be in decile range one, the second group in decile range two, etc up to the highest annual totals (highest 10 per cent) being in decile range 10.

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 - 2005 and Camden 1972 - 2005.  Rainfall averages and extremes for Observatory Hill are based on all years of record 1859 - 2005.

Further information: Contact Mike De Salis 02 9296 1542, email: reqnsw@bom.gov.au

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The latest rainfall and temperature maps are available here
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