Monday, 1 November 2010 - Monthly Climate Summary for Perth - Product code IDCKGC11L0
October 2010 saw below average rainfall across the Perth area, with several sites receiving well below half their October average. A strong ridge of high pressure persisted over the south of WA for much of October 2010 causing the generally dry conditions in Perth, with the only rainfall coming from cold fronts during the middle and latter parts of the month.
Perth Metro recorded 20.6 mm of rainfall on 5 rain days in October, compared with the average of 52.4 mm on 9.1 rain days. Historically, October rainfall in Perth has ranged from 1.0 mm in 1969 to 199.9 mm in 1890. Last October (2009), Perth Metro recorded 6.8 mm on 5 days. The wettest day in October 2010 was 8.4 mm on the 21st.
2010 has been a particularly dry year in the southwest of WA, including the Perth region with Pearce RAAF, Gosnells City and Bickley all breaking their driest January to October records. Total rainfall for the ten months from January to October 2010 at Perth Metro was 474.8 mm recorded on 57 rain days, which is the third driest January to October period since records commenced in 1876, and the driest since the 445.4 mm in 2006, Perth Metro's driest year on record. The average for the January to October period is 817.6 mm on 101.4 rain days whilst the total for the same period last year was 590.0 mm on 104 days (ranked 10th driest on record). Perth Metro has also experienced its least number of rain days for the ten months (January to October) on record with 57, breaking the previous record of 80 days in 1969.
Daytime temperatures were well above average across the Perth area during October 2010, as a result of a strong ridge over the south of the state for much of the month, with several sites breaking their October mean daily maximum temperature records.
Hot days were experienced throughout the Perth area on the 8th, 18th and 26th, with most stations observing maximum temperatures in excess of 30 °C. Pearce RAAF observed the hottest day for October 2010, with 34.9 °C on the 26th.
Perth Metro's mean daily maximum temperature in October was 24.6 °C, which was the second warmest October on record behind the 25.8 °C observed in 1969 (records commenced in 1897). The average for October is 22.9 °C. Daily maxima during October 2010 ranged from a hot 33.8 °C on the 26th to a mild 19.3 °C on the 11th.
Minimum temperatures across the Perth area were close to normal during October 2010, with most metropolitan sites recording mean minima within 1 °C of their long-term mean. Jandakot Aerodrome experienced both the coldest night during October 2010, on the 29th with 2.6 °C, as well as the coolest nights on average, with a mean of 8.9 °C.
Perth Metro's mean daily minimum temperature in October was 10.6 °C, which was the coolest October since the 9.7 °C in 2005, but is close to the average of 11.2 °C for October. Daily minima ranged from a cool 6.3 °C on the 12th to a warm 17.8 °C on the 27th.
No severe wind gusts (a severe wind gust is a gust greater than 90 km/h) were recorded during October 2010, with the highest wind gust of 76 km/h observed at Rottnest Island early on the 14th in the wake of a cold front as a strong ridge developed over the south of the state.
Perth recorded average daily sunshine of 10.5 hours in October, which was the third sunniest October on record behind the 10.9 hours in 2000 and the 10.6 hours in 1978. The average daily sunshine for October is 9.6 hours.
|Extremes in October 2010|
|Hottest day||34.9 °C at Pearce RAAF on the 26th|
|Warmest days on average||25.6 °C at Pearce RAAF|
|Coolest days on average||21.6 °C at Rottnest Island|
|Coldest day||16.3 °C at Bickley on the 21st|
|Coldest night||2.6 °C at Jandakot Aero on the 29th|
|Coolest nights on average||8.9 °C at Jandakot Aero|
|Warmest nights on average||14.3 °C at Rottnest Island|
|Warmest night||17.9 °C at Rottnest Island on the 27th|
|Wettest overall||31.8 mm at Jarrahdale|
|Wettest day||17.2 mm at Jarrahdale on the 21st|
|Highest wind gust||76 km/h at Rottnest Island on the 14th|
|Record highest October mean daily maximum temperature|
| Mean daily maximum
for October 2010 (°C)
| Previous highest
|Medina Research Centre||24.3||23.8||in 2000||23||22.4|
|Jandakot Aero||24.8||24.2||in 2008||20||22.4|
|Gosnells City||25.5||25.1||in 2006||15||23.6|
|Summary statistics for October 2010|
|Garden Island HSF||21.9||27.8||8th||12.7||7.0||18th||18.0|
|Gosnells City||25.5||+1.9||34.7||26th||11.6||+0.1||5.8||29th||15.0||46.7||v low||32%|
|Medina Research Centre||24.3||+1.9||32.3||26th||10.0||-0.2||4.5||29th||20.6||41.4||low||50%|
|Pearce RAAF||25.6||+2.4||34.9||26th||9.0||-1.1||3.0||29th||8.8||36.7||v low||24%|
|Perth Metro*||24.6||+1.7||33.8||26th||10.7||-0.5||6.3||12th||20.6||52.4||v low||39%|
|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||-||-||-||-||-||-||-||-||-||2.4||2.0||-||-||-||-||-||-||-||-||0.2||10.8||0.2||-||-||-||-||-||2.2||0.2||-||-|
|Medina Research Centre||-||0.4||-||-||-||-||-||-||-||5.2||2.4||-||-||-||-||-||-||-||-||-||11.2||-||-||-||-||-||-||1.4||-||-||-|
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 10 am on Monday 1 November 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, as they cannot then be calculated reliably.
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.