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Friday, 30 April 2010 - Monthly Climate Summary for Perth - Product code IDCKGC21L0
Rainfall around the Perth area was generally near average, with totals generally in the 20 to 40 mm range. The only significant rainfall event was during the middle of the month when a deep low lingered off the southwest coast. The low produced almost all of Perth's April 2010 rainfall between the 12th and 16th, including the highest daily total for the month of 28.8 mm at Jandakot Aero on the 14th.
Perth Metro recorded 25.0 mm of rainfall on 6 days in April, compared with the average of 44.2 mm on about 7 days. Historically, April rainfall in Perth Metro has ranged from nil on 3 occasions, to 153.6 mm in 2008. Last April, Perth Metro registered 5.0 mm of rainfall on 2 days.
Daytime mean temperatures in the Perth area during April 2010 were near average. Daily maxima ranged from a cold 14.0 °C at Bickley on the 12th (which was also the lowest daily maximum temperature for WA in April 2010) to a hot 33.2 °C at Pearce RAAF on the 18th.
Perth Metro's mean daily maximum temperature in April 2010 was 25.0 °C, which is near the average of 25.7 °C, and was Perth Metro's coolest April since 2008. Last year, Perth Metro experienced its third warmest April on record with 27.6 °C, the warmest being 28.2 °C in 1978 and 1999. Daily maxima ranged from a hot 32.3 °C on the 18th to a cool 17.7 °C on the 12th, Perth Metro's coolest April day for four years since the 17.0 °C on 26th April 2006. Perth Metro's coldest April day on record was 13.6 °C on 16th April 1919.
Overnight mean temperatures were also near average across the Perth area in April 2010. The three lowest temperatures around Perth were observed consecutively at Jandakot Aerodrome where temperatures dropped to 6.0 °C on the 23rd; 5.8 °C on the 24th; and 4.6 °C on the 25th. Jandakot Aerodrome also recorded 6.0 °C on the 28th.
Perth Metro's mean minimum temperature in April was 13.7 °C, which is close to the average of 13.6 °C. Daily minima ranged from a mild 18.0 °C on the 3rd to a cool 7.8 °C on the 24th, which was Perth Metro's coolest night of the year so far and coolest since the 6.5 °C on 2nd October 2009. Perth Metro's coldest April night on record was 4.1 °C on 20th April 1914.
No severe winds (winds greater than 90 km/h) were observed in the Perth area during April 2010 and wind conditions were near normal for this time of year. Rottnest Island reported the strongest gust of 81 km/h on the 13th as a low deepened off the coast.
Perth recorded sunshine of 8.2 hours, which was equal to the long-term average.
|Extremes in April 2010|
33.2 °C at Pearce RAAF on the 18th|
|Warmest days on average||
26.6 °C at Pearce RAAF|
|Coolest days on average||
22.8 °C at Rottnest Island|
14.0 °C at Bickley on the 12th|
4.6 °C at Jandakot Aero on the 25th|
|Coolest nights on average||
11.8 °C at Jandakot Aero|
|Warmest nights on average||
17.0 °C at Rottnest Island|
20.3 °C at Champion Lakes on the 19th|
55.6 mm at Jarrahdale|
28.8 mm at Jandakot Aero on the 14th|
|Highest wind gust||
81 km/h at Rottnest Island on the 13th|
|Summary statistics for April 2010|
|Garden Island HSF||23.2||-0.3||28.3||1st||15.7||+0.1||11.4||24th||32.4||47.2||average||69%|
|Medina Research Centre||25.3||-0.2||32.6||18th||13.2||0.0||7.0||25th||30.6||40.3||average||76%|
|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|
|Garden Island HSF||-||-||-||-||0.2||0.2||0.4||-||-||-||-||0.2||3.4||19.6||7.6||0.8||-||-||-||-||-||-||-||-||-||-||-||-||-||-|
|Medina Research Centre||-||-||-||0.2||-||0.6||-||-||-||-||-||0.8||2.4||19.4||6.2||1.0||-||-||-||-||-||-||-||-||-||-||-||-||-|
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 10 am on Friday 30 April 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 5 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.