Thursday, 1 October 2009 - Monthly Climate Summary for Western Australia - Product code IDCKGC21R0

Western Australia in September 2009
Cool and Wet in the South, Hot and Dry in the North

  • Above to very much above average rainfall for most of the south of WA.
  • Mean maximum temperatures 2nd coldest on record in the southwest of WA.
  • Very much above average maximum temperatures in the north of WA.

An archive of previous monthly summaries for Western Australia is also available, as are summaries for other states and many other climate summaries and diagnostics.

Details

Rainfall

Rainfall over Western Australia in 2009 was mainly above to very much above average for the south of the state, apart from patches of below average rainfall in the Gascoyne, Goldfields and eastern parts of the Southwest Land Division (SWLD) (see September rainfall decile map). Persistent cold fronts throughout the month resulted in Denbarker (in the South Coastal) observing it's highest September total on record, while several stations in the west of the SWLD observed their highest September rainfall for over 30 years.

In the north, rainfall was below average through most of the Pilbara and Kimberley, however rainfall during September is typically low. Thus, when averaged over the state as a whole, September 2009 rainfall was near average.

Maximum temperature

September 2009 saw above to very much above average daytime temperatures throughout the Kimberley and most of the Interior, with areas of up to 3°C warmer than normal (see September maximum temperature anomaly map). Several stations in the northeast of the state broke their highest daily and monthly maximum temperatures, and a particularly hot stretch in the middle part of the month culminated in Wyndham Aero (in the North Kimberley) recording 42.0°C on the 22nd which is their hottest September day in 9 years of record (previous record for September was 41.0°C on 27th September 2002 and 25 September 2007).

In contrast, the southwest of the state was below to very much below average, in terms of maximum temperature, with patches in the SWLD up to 3°C cooler than average (see September maximum temperature anomaly map). Persistent frontal activity and westerly flow over the south of the state during the month resulted in the lowest mean daily maximum temperature for over 30 years at several stations in the Southwest and Lower West. September 2009 in the Lower Southwest (southwest of a line from approximately Jurien Bay to Bremer Bay) was the 2nd coldest September since comparable records began in 1950, coming in at 1.6°C cooler than the long term mean (the coldest September for this region was in 1992 which was 2.3°C below normal). A cold airmass in the wake of a front on the 30th ensured that Meekatharra (in the Gascoyne) broke it's lowest daily maximum temperature record for September .

The warm conditions in the north and cool conditions in the south meant that when averaged over the state as a whole, the mean maximum temperature for September 2009 was near average.

Minimum temperature

Minimum temperature over WA during September 2009 was below to very much below average for most of the southwest half of the state contrasting with above to very much above average overnight temperature in the northeast (see September minimum temperature anomaly map). Halls Creek (in the Kimberley) recorded it's warmest overnight temperature on the 20th with 27.4°C, while in contrast many stations in the south of the state observed their coldest September for over 30 years with Meekatharra (in the Gascoyne) and Dalwallinu (in the Central Wheat Belt) breaking their lowest mean minimum temperature records for September.

When averaged across WA, mean minimum temperature was near average.

Further information

Western Australia Climate Services Centre
Bureau of Meteorology
Phone (08) 9263 2222
Email climate.wa@bom.gov.au

Extremes

Hottest day
Highest temperature
42.0°C at Wyndham Aero on the 22nd
Warmest days on average
Highest mean daily maximum temperature
38.8°C at Wyndham Aero
Coolest days on average
Lowest mean daily maximum temperature
14.1°C at Rocky Gully
Coldest day
Lowest daily maximum temperature
9.8°C at Rocky Gully on the 5th
Coldest night
Lowest temperature
−4.3°C at Eyre on the 9th
Coolest nights on average
Lowest mean daily minimum temperature
3.3°C at Southern Cross Airfield
Warmest nights on average
Highest mean daily minimum temperature
26.2°C at Troughton Island
23.9°C at Argyle Aerodrome (mainland)
Warmest night
Highest daily minimum temperature
28.1°C at Warmun on the 18th
Wettest overall
Highest total rainfall
283.4 mm at Mount William
Wettest day
Highest daily rainfall
42.6 mm at Karnet on the 12th
Highest wind gust
119 km/h at Busselton Jetty on the 10th

Records

Record highest total September rainfall
Total rainfall
for September 2009 (mm)
Previous highest
for September
Years of
record
Average for
September
Denbarker 147.2 144.6 in 1996 38 85.9

Highest total September rainfall for at least 30 years
Total rainfall
for September 2009 (mm)
Most recent higher
for September
Years since
higher
Average for
September
Dwellingup 243.4 298.9 in 1971 38 130.8
Marradong 126.0 129.2 in 1971 38 72.0
Mundaring 205.8 251.7 in 1971 38 112.9
Balingup 161.4 169.3 in 1971 36 87.3
Carnamah 55.7 71.9 in 1973 36 28.4
Jarrahdale 195.6 251.3 in 1973 32 125.7



Record highest September daily maximum temperature
Highest temperature
in September 2009 (°C)
Previous highest
for September
Years of
record
Average for
September
Onslow 39.0 on the 25th 38.9 on the 2nd in 2007 49 29.1
Troughton Island 34.4 on the 24th 33.6 on the 27th in 1971 31 30.2



Record lowest September daily maximum temperature
Lowest daily maximum
temperature
in September 2009 (°C)
Previous lowest
for September
Years of
record
Average for
September
Meekatharra Airport 13.7 on the 30th 15.0 on the 1st in 1956 60 25.6
Yeelirrie 13.2 on the 30th = 13.2 on the 29th in 1992 36 25.8



Record highest September mean daily maximum temperature
Mean daily maximum
temperature
for September 2009 (°C)
Previous highest
for September
Years of
record
Average for
September
Halls Creek Airport 36.3 = 36.3 in 1995 61 34.0
Balgo Hills 35.8 35.5 in 2005 30 33.8



Record lowest September mean daily maximum temperature
Mean daily maximum
temperature
for September 2009 (°C)
Previous lowest
for September
Years of
record
Average for
September
Badgingarra Research Stn 17.7 18.5 in 1992 42 20.6
Karnet 15.3 15.4 in 1971 42 17.5

Lowest September mean daily maximum temperature for at least 30 years
Mean daily maximum
temperature
for September 2009 (°C)
Most recent lower
for September
Years since
lower
Average for
September
Donnybrook 17.1 16.3 in 1931 75 18.8
Cape Leeuwin 16.2 16.0 in 1971 38 17.0
Dwellingup 15.5 15.2 in 1971 35 17.2



Record highest September daily minimum temperature
Highest daily minimum
temperature
in September 2009 (°C)
Previous highest
for September
Years of
record
Average for
September
Halls Creek Airport 27.4 on the 20th 27.3 on the 30th in 1992 62 18.9



Record highest September mean daily minimum temperature
Mean daily minimum
temperature
for September 2009 (°C)
Previous highest
for September
Years of
record
Average for
September
Troughton Island 26.2 25.8 in 2005 30 24.5



Record lowest September mean daily minimum temperature
Mean daily minimum
temperature
for September 2009 (°C)
Previous lowest
for September
Years of
record
Average for
September
Meekatharra Airport 9.5 9.7 in 1992 59 11.5
Dalwallinu Comparison 6.3 6.4 in 1966 53 7.9
Esperance 8.4 = 8.4 in 1973 40 9.5

Lowest September mean daily minimum temperature for at least 30 years
Mean daily minimum
temperature
for September 2009 (°C)
Most recent lower
for September
Years since
lower
Average for
September
Lake Grace Comparison 5.0 4.7 in 1969 40 6.7
Carnamah 6.9 6.5 in 1966 37 8.1
Merredin 5.1 4.8 in 1973 36 6.7
Bencubbin 6.2 5.8 in 1973 34 7.2
Salmon Gums Res.Stn. 4.6 3.9 in 1969 34 5.8
Carnarvon Airport 12.8 12.6 in 1977 32 13.9
Hyden 4.7 4.2 in 1975 31 5.9
Roebourne 15.7 15.7 in 1978 30 16.8



Notes

This statement has been prepared based on information available at 10 am on Thursday 1 October 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 30 years of record, as they cannot then be calculated reliably.
The median is sometimes more representative than the mean of long-term average rain.

Further information

Western Australia Climate Services Centre
Bureau of Meteorology
Phone (08) 9263 2222
Email climate.wa@bom.gov.au