Tuesday, 31 August 2010 - Monthly Climate Summary for Perth - Product code IDCKGC21L0
Perth in August 2010: A dry month with many cold nights
- Very much below average rainfall across the Perth metropolitan area.
- Near average to above average mean maximum temperature
- Below to very much below average mean minimum temperature for most sites.
Fewer than normal cold fronts passing across southwest WA in August resulted in below average rainfall for the Perth metropolitan area, with totals ranging from about 45 mm at Gosnells City to around 90 mm at Rottnest Island.
An unusually dry start to August ended when a strong cold front and low pressure system crossed the Perth region on the 12th bringing useful rainfall, as well as the highest daily falls for the month. Swanbourne recorded the highest daily rainfall in the Perth metropolitan area for August 2010 with 28.4 mm on the 12th, whilst two-day totals including the 12th and 13th were typically 30 to 40 mm across the metropolitan area. Several weaker fronts moved through Perth in the remainder of the month though daily falls were modest.
Perth Metro recorded 63.0 mm of rainfall on 8 rain days in August, which was the driest August since the 27.8 mm in 2008. Historically, August rainfall in Perth has ranged from 11.8 mm in 1902 to 318.3 mm in 1945.
The total rainfall for the eight months from January to August 2010 at Perth Metro was 410.6 mm recorded on 46 rain days, which was the driest January to August period since the 340.4 mm in 2006, and the fourth driest since records commenced in 1876. The average for the January to August period is 684.3 mm on about 76 rain days while the total for the same period last year was 482.0 mm on 71 days. Perth Metro also experienced its least number of rain days for the eight months (January to August) on record. The previous record low being 59 days in 1902.
Mean daily maximum temperatures in the Perth area during August 2010 were close to average or above average, ranging from 16.5 °C at Bickley to 20.1°C at Gosnells City. Perth Airport saw the largest departure from the mean with an August mean daily maximum temperature of 19.6 °C, 1.2 °C above the long-term average.
August 2010 started quite warm with most sites reporting maxima over 20 °C in the first 4 days of the month, and the warmest day in the Perth metropolitan area in August was 24.9 °C at Gosnells City on the 3rd. The coldest day for the month was 12.5 °C at Bickley on the 18th as cold southerly winds predominated.
Perth Metro's mean daily maximum temperature in August was 19.1 °C, which is close to the average of 18.8°C. Daily maxima ranged from a warm 24.1 °C on the 2nd, to a cold 14.3 °C on the 31st, which was the coldest day in August for 6 years.
Mean daily minimum temperatures were below to very much below average for much of the Perth area with overnight temperatures generally about 2 °C cooler than normal. Pearce RAAF's mean minimum temperature in August was 6.2 °C, breaking the previous record of 6.3 °C set in August 2001, whilst Gosnells also recorded its lowest August mean minimum temperature.
The coldest night recorded in the Perth metropolitan area in August was -0.4 °C at Jandakot Aerodrome on the 9th as a high moved over southern WA following the passage of a weak front near the WA south coast. The warmest night was 14.8 °C at Rottnest Island on the 2nd in a prevailing northwesterly flow.
Perth Metro's mean daily minimum temperature in August was 6.3 °C, which was the second coldest August for Perth Metro on record behind the 5.6 °C in 2008. Daily minima in August 2010 ranged from a mild 12.3 °C on the 12th, to a cold 1.4 °C on the 9th, the equal second coldest August night on record at Perth Metro. Perth Metro's coldest August temperature of 1.3 °C occurred on 21st August 2000.
Wind & sunshine
The highest wind gust recorded in the Perth metropolitan area in August was 98 km/h at Rottnest Island on the 11th as a cold front crossed Perth.
Perth recorded an average daily sunshine of 7.9 hours in August, which is the equal fourth sunniest August on record. The long-term average is 7.1 hours per day, whilst the sunniest August on record saw 8.5 hours per day in 2008.
|Extremes in August 2010|
|Hottest day||24.9 °C at Gosnells City on the 3rd|
|Warmest days on average||20.1 °C at Gosnells City|
|Coolest days on average||16.5 °C at Bickley|
|Coldest day||12.5 °C at Bickley on the 18th|
|Coldest night||-0.4 °C at Jandakot Aero on the 9th|
|Coolest nights on average||4.5 °C at Jandakot Aero|
|Warmest nights on average||12.0 °C at Rottnest Island|
|Warmest night||14.8 °C at Rottnest Island on the 2nd|
|Wettest overall||92.0 mm at Rottnest Island|
|Wettest day||28.4 mm at Swanbourne on the 12th|
|Highest wind gust||
98 km/h at Rottnest Island on the 11th
|Record highest August daily rainfall|
Highest daily rainfall
in August 2010 (mm)
|Rottnest Island||27.2||on the 12th||25.4||on the 22nd in 2006||20|
|Record lowest August mean daily minimum temperature|
Mean daily minimum
for August 2010 (°C)
|Pearce RAAF||6.2||6.3||in 2001||49||8.2|
|Gosnells City||7.1||7.3||in 2002||17||8.8|
|Summary statistics for August 2010|
|Garden Island HSF||17.9||21.7||4th||10.0||6.2||5th||83.8|
|Gosnells City||20.1||+1.0||24.9||3rd||7.1||-1.7||3.2||19th||50.0||126.1||v low||40%|
|Jandakot Aero||19.4||+1.0||23.9||4th||4.5||-2.4||-0.4||9th||74.6||125.0||v low||60%|
|Medina Research Centre||19.6||+1.0||24.2||2nd||6.4||-1.6||2.0||8th||76.1||115.6||low||66%|
|Pearce RAAF||19.1||+0.9||24.7||28th||6.2||-2.0||0.7||23rd||52.8||104.3||v low||51%|
|Perth Metro||19.3||+0.5||24.1||2nd||6.3||-1.8||1.4||9th||63.0||134.1||v low||47%|
|Central Coast (09)||1||2||3||4||5||6||7||8||9||10||11||12||13||14||15||16||17||18||19||20||21||22||23||24||25||26||27||28||29||30||31|
|Garden Island HSF||0.2||-||-||-||-||0.2||-||-||-||-||-||27.0||11.0||3.6||-||-||-||8.0||-||8.0||4.6||9.0||-||0.8||-||-||-||-||-||4.8||6.6|
|Medina Research Centre||-||-||-||-||-||-||-||-||-||-||-||24.0||18.2||1.5||-||-||-||3.0||-||1.8||0.6||8.6||-||-||-||-||-||-||-||4.2||14.2|
Most values are the precipitation in the 24 hours to 9 am on the day indicated.
Days marked with »» are part of a longer accumulation, which is marked like this on the final day.
Values over 100 mm have been rounded to the nearest whole millimetre.
Days marked with - have a rainfall report of zero;
days left blank have no rainfall report (which often indicates no rain fell).
This table is very wide; you may have to scroll sideways to see all the days, and you may need to set the paper to 'landscape' to print.
A Monthly Climate Summary is prepared to list the main features of the weather in Perth using the most timely and accurate information available on the date of publication; it will generally not be updated. Later information, including data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review, usually published in the fourth week of the month.
This statement has been prepared based on information available at 4 pm on Tuesday 31 August 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 10 years of record.
The median is sometimes more representative than the mean of long-term average rain.
The Rank indicates how rainfall this time compares with the climate record for the site,
based on the
(very low rainfall is in decile 1, low in decile 2 or 3,
average in decile 4 to 7, high in decile 8 or 9
and very high is in decile 10).
The Fraction of average shows how much rain has fallen this time as a percentage of the long-term mean.
Records in this summary are based on sites with at least 10 years of data.
*Official Perth observations have been recorded at several different sites with varying instrumentation over the years, and these changes can affect the continuity of the climate record. For the current Mt Lawley site, the most significant changes of this kind relate to temperature and rain days.
For that reason, current mean temperature and rain-day data quoted here are based only on readings from the Mt Lawley site, which commenced observations in 1993. Sunshine recordings are from Perth Airport and for similar reasons current means use only Perth Airport data, which commenced in 1993.