Western Australia in December 2009: A very warm month with wet north and dry south

  • Above average rainfall for WA, but very much below average in the southwest
  • Very much above average mean maximum temperature for WA (3rd highest on record)
  • Very much above average mean minimum temperature for WA (4th highest on record)

Rainfall

Rainfall was above to very much above average in the north and west Kimberley, and the east Pilbara in December 2009, whilst coastal districts of the Southwest Land Division (SWLD) saw below to very much below average rainfall.

Severe Tropical Cyclone Laurence produced moderate to heavy rainfall to the north and west Kimberley and the east Pilbara in mid-to-late December, with several sites in these regions registering their highest daily rainfall amount or highest monthly rainfall total on record for December (see December rainfall decile map). Conversely, seasonally dry conditions were experienced in western and southern parts of the SWLD, with numerous sites recording no rainfall for the month. Averaged over the state as a whole, rainfall in December 2009 in WA was above average.

Some sites had their highest total December rainfall on record. Some sites had their highest December daily rainfall on record.

Maximum temperature

With the exception of near average daytime temperatures in small parts of WA, including in the north Kimberley, December 2009 saw above to very much above average daytime temperatures across much of the state, with up to 4°C warmer than normal maxima in the southwest Gascoyne and Central West, and some records broken. (see December maximum temperature anomaly map).

Abnormally hot conditions were experienced in the early part of the month in the Kimberley and neighbouring regions as some daytime and overnight temperature records were broken, whilst in the parts of the SWLD on the 29th, with many locations registered their highest December temperature on record, and some experienced record high December minima.

When averaged over the whole state, December 2009 was the 3rd highest mean maximum temperature on record for December.

Minimum temperature

Mean minimum temperatures during December 2009 were above to very much above average over much of WA, with minima in parts of the Gascoyne up to 3°C above normal. Only small parts of WA recorded below normal mean minma, with the southern SWLD recording mean minimum temperatures to 2°C below average. (see December minimum temperature anomaly map). On the 9th, Eyre recorded a minimum temperature of 0.2°C, the second lowest temperature recorded in WA in December when 0.0°C was recorded at Bridgetown on 7 December 1953.

Overall, December 2009 saw the 4th highest mean minimum temperature on record for December when averaged across WA.

Some sites had their lowest December temperature on record. Some sites had their warmest December night (highest daily minimum temperature) on record. Some sites had their highest December mean daily minimum temperature on record.

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Extremes in December 2009
Hottest day 47.0 °C at Hyden on the 29th
Warmest days on average 42.1 °C at Marble Bar & Roebourne
Coolest days on average 20.8 °C at Albany
Coldest day 17.0 °C at Albany on the 16th
Coldest night 0.2 °C at Eyre on the 9th
Coolest nights on average 9.9 °C at Rocky Gully
Warmest nights on average 27.8 °C at Troughton Island
27.2 °C at Wyndham
Warmest night 32.9 °C at Wittenoom on the 31st
Wettest overall 717.2 mm at Troughton Island
641.2 mm at Truscott (mainland)
Wettest day 402.0 mm at Napier Downs on the 18th
Highest wind gust 187 km/h at Troughton Island on the 15th
100 km/h at Paraburdoo Aero on the 15th (mainland)

Record highest December daily rainfall
Highest daily rainfall
in December 2009 (mm)
Previous highest
for December
Years of
record
Kimberley Downs 310.6 on the 18th 162.0 on the 15th in 1996 91
Yarrie 140.0 on the 22nd 118.0 on the 19th in 1996 90
Warrawagine 244.5 on the 22nd 190.4 on the 15th in 1998 87
Napier Downs 402.0 on the 18th 237.7 on the 16th in 1950 83
Theda 176.0 on the 16th 161.0 on the 11th in 1998 43



Record highest total December rainfall
Total rainfall
for December 2009 (mm)
Previous highest
for December
Years of
record
Average for
December
Kimberley Downs 610.0 368.4 in 1998 99 99.9
Napier Downs 567.2 495.3 in 1950 86 114.3
Theda 632.1 524.2 in 1996 44 203.6





Record highest December temperature
Highest temperature
in December 2009 (°C)
Previous highest
for December
Years of
record
Average for
December
Kellerberrin 46.3 on the 29th 45.0 on the 19th in 1954 97 32.0
Carnamah 45.2 on the 29th 44.5 on the 26th in 2007 68 33.4
Kimberley Res.Station 44.0 on the 6th 43.9 on the 16th in 1985 57 37.6
Dalwallinu Comparison 44.6 on the 29th 44.0 on the 23rd in 1997 55 32.9
Bencubbin 45.3 on the 29th 44.6 on the 20th in 1987 51 32.4
Eucla 45.4 on the 15th 45.0 on the 9th in 1960 48 24.7
Warmun 45.7 on the 7th 45.1 on the 7th in 1986 47 38.5
Merredin 44.5 on the 29th 43.6 on the 23rd in 1997 44 31.9
Wongan Hills 45.0 on the 29th 43.5 on the 20th in 2002 43 32.4
Esperance 44.9 on the 29th 44.4 on the 11th in 1977 41 24.5
Narembeen 44.4 on the 29th 44.0 on the 27th in 2007 41 31.8
Hyden 47.0 on the 29th 45.2 on the 27th in 2007 37 31.7
Paynes Find 46.1 on the 29th 45.1 on the 31st in 1994 31 34.8
Goomalling 45.0 on the 29th 44.5 on the 22nd in 2002 30 31.9




Record highest December mean daily maximum temperature
Mean daily maximum
temperature
for December 2009 (°C)
Previous highest
for December
Years of
record
Average for
December
Roebourne 42.1 41.6 in 1961 90 39.0
Geraldton Airport 33.0 32.8 in 1999 67 29.4
Jurien Bay 30.9 30.5 in 1972 40 28.0
Kalbarri 34.3 33.6 in 2006 36 30.9




Record highest December daily minimum temperature
Highest daily minimum
temperature
in December 2009 (°C)
Previous highest
for December
Years of
record
Average for
December
Carnamah 29.2 on the 29th 29.1 on the 27th in 2003 68 15.9
Halls Creek Airport 31.8 on the 9th 31.6 on the 15th in 1985 64 24.7
Wiluna 31.0 on the 16th 30.5 on the 19th in 2005 51 21.0
Balladonia 27.1 on the 30th 23.7 on the 19th in 2005 45 13.2
Karnet 22.6 on the 29th 22.4 on the 17th in 1991 44 13.4
Brookton 24.8 on the 29th 24.0 on the 15th in 1989 43 13.4


Record lowest December temperature
Lowest temperature
in December 2009 (°C)
Previous lowest
for December
Years of
record
Average for
December
Eucla 6.9 on the 9th 7.0 on the 27th in 1977 48 15.0



Record highest December mean daily minimum temperature
Mean daily minimum
temperature
for December 2009 (°C)
Previous highest
for December
Years of
record
Average for
December
Yeelirrie 22.0 21.9 in 1977 34 19.8



Notes

This statement has been prepared based on information available at 11 am on Monday 4 January 2010. 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

Media
(03) 9669 4057
Enquiries