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Tuesday, 4 January 2011 - Monthly Climate Summary for Perth - Product code IDCKGC21L0
December 2010 saw near average rainfall in south and southeast parts of the Perth metropolitan area, but above average rainfall for the remainder. Rainfall totals generally ranged from 10 mm to 20 mm, though Rottnest Island received 46.2 mm which was highest rainfall total for the Perth area for December. Rainfall occurred on several days in the first week of December, however the highest falls occurred on the 20th and 21st as a result of a tropical low off the west coast that brought flooding rain to the Gascoyne a few days earlier.
Perth Metro recorded 17.4 mm of rainfall on 5 rain days in December 2010, which was the wettest December since the 18.0 mm on 7 rain days in 2007. The wettest day for Perth Metro in December 2010 was 9.6 mm on the 20th, which was the wettest December day since the 10.2 mm on 12 December 1996.
Daytime temperatures were near average to above average across the Perth metropolitan area during December 2010. Mean maximum temperatures ranged from the high twenties near the coast to the low thirties in the east, and were generally between 0.5 °C to 1.5 °C above the long-term average. The highest temperatures for the month were recorded from the 25th to the 27th, with Pearce RAAF recording 42.1 °C on the 27th.
Perth Metro's mean daily maximum temperature in December was 29.3 °C, which was near the average of 28.8 °C. Daily maxima ranged from a mild 21.1 °C on the 3rd to a very hot 40.0 °C on the 27th.
Minimum temperatures across the Perth metropolitan area were close to normal for most locations during December 2010 although a few sites recorded means over 1 °C above average. Mean minima ranged from near 14 °C in the hills to 17 °C near the coast. The coolest morning in December was on the 4th for most sites with Jandakot Aerodrome recording the lowest metropolitan minimum of 5.5 °C.
Perth Metro's mean daily minimum temperature in December 2010 was 16.6 °C, which was near the average of 16.1 °C. Daily minima ranged from a cool 9.4 °C on the 4th, to a warm 22.4 °C on the 23rd.
Very strong easterly winds were observed in the Perth metropolitan area over the Christmas period, with severe or near severe wind gusts (a severe wind gust is a gust greater than 90 km/h) recorded at a number of locations on Boxing Day (26th). Gale or near gale force easterly winds (gale force winds are 63 to 87 km/h) were observed at Perth Airport on the 26th for aproximately 5 hours until 0730 WST, with the highest wind gust of 98 km/h at 0704 WST. Maximum daily wind gusts at other locations on the 26th were, 91 km/h at Pearce RAAF at 0453 WST; 89 km/h at Champion Lakes at 0636 WST; 80 km/h at Bickley at 0912 WST; and 72 km/h at Jandakot 0909 WST.
Perth recorded a daily average of 10.8 hours of sunshine in December 2010, which was below the average of 11.6 hours and the least sunniest December since 10.6 hours per day in 2007.
|Extremes in December 2010|
|Hottest day||42.1 °C at Pearce RAAF on the 27th|
|Warmest days on average||31.7 °C at Gosnells City|
|Coolest days on average||25.3 °C at Rottnest Island|
|Coldest day||19.3 °C at Bickley on the 3rd|
|Coldest night||5.5 °C at Jandakot Aero on the 4th|
|Coolest nights on average||13.8 °C at Bickley|
|Warmest nights on average||17.5 °C at Rottnest Island|
|Warmest night||25.1 °C at Pearce RAAF on the 27th|
|Wettest overall||46.2 mm at Rottnest Island|
|Wettest day||20.0 mm at Rottnest Island on the 20th|
|Highest wind gust||98 km/h at Perth Airport on the 26th|
|Summary statistics for December 2010|
|Garden Island HSF||26.6||36.9||26th||17.3||13.5||10th||11.4||6.8||high||168%|
|Medina Research Centre||29.7||+1.8||40.5||27th||16.0||+1.1||7.5||4th||9.5||9.1||average||104%|
|Rottnest Island||25.3||+0.4||35.5||26th||17.5||0.0||13.8||3rd||46.2||6.8||very high||679%|
|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||-||-||-||-||1.4||-||0.4||1.0||-||-||-||-||-||-||-||-||-||-||-||6.4||2.2||-||-||-||-||-||-||-||-||-||-|
|Medina Research Centre||-||-||-||»»||»»||»»||2.2||-||-||-||-||-||-||-||-||-||-||-||-||3.6||3.0||-||-||-||-||-||-||-||-||-||-|
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 4 January 2011. 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.