Perth in spring 2011: Above average rainfall

This statement was prepared before all data for the period were available. This may affect some of the statistics presented.
  • Rainfall: Above average.
  • Maximum temperature: Near average for most sites.
  • Minimum temperature: Above average for most sites.
This statement was prepared before all data for the period were available. This may affect some of the statistics presented.

Rainfall

Rainfall across the Perth metropolitan area during spring 2011 was generally above average, with cold fronts and middle level disturbances bringing consistent rainfall during September, October and early November. Perth Metro and Jandakot Aerodrome observed their wettest spring for 12 years whilst it was Perth Airport's wettest spring for 15 years, since 1996.

Significant rainfall events for spring 2011 in Perth:

  • A strong westerly flow with embedded cold fronts produced moderate rainfall across the Perth area, with daily rainfall totals in the range of 10 to 30 mm recorded on 2 September. The daily rainfall of 35.4 mm at Mundaring in the Perth hills was the highest daily rainfall of spring 2011 in the Perth metropolitan area.
  • A number of cold fronts moved through the Perth area in the second half of September resulting in seven consecutive rain days between 16 and 22 September, the longest wet spell for spring 2011.
  • A thunderstorm with hail estimated to 3cm in diameter and heavy rainfall was reported from Lynwood in the southern suburbs of Perth on 9 October, whilst Jandakot reported 24.6 mm of rainfall between 0551 WST and 0816 WST on the morning of the 9th.
  • A number of cold fronts and an unstable onshore flow produced six consecutive rain days between the 4th and 9th November, the second longest wet spell for spring 2011. The daily rainfall of 34.0 mm at Mundaring during this spell was the second highest daily rainfall of the spring in the Perth area.

Perth Metro recorded 202.4 on 33 rain days during spring 2011, which was the wettest spring for 12 years, since 206.6 mm was recorded on 20 rain days in 1999. Last spring (2010), Perth Metro recorded 75.8 mm on 14 rain days, which was the driest spring for 41 years.


Maximum temperature

Mean daily maximum temperatures were near average for most sites during spring 2011, with mean maxima typically between 21 and 24 °C. The hottest day of spring 2011 came on 24 November when hot northeastely winds caused many sites to record maxima in the 36 to 38 °C range, and Medina Research Centre recorded 38.7 °C, the highest temperature for spring in the Perth Metro area.

Perth Metro's mean daily maximum temperature in spring 2011 was 23.6 °C, which was close to the average of 23.2 °C. Last spring (2010) was Perth Metro's warmest spring on record with a mean daily maximum temperature of 25.3°C. Daily maxima across spring ranged from a cool 17.1°C on 2 and 27 September to a very hot 37.2°C on 24 November.

Minimum temperature

Mean daily minimum temperatures during spring 2011 were above average for most sites, with all sites between 0.8 °C and 1.6°C above average. Mean minima were generally between 11 and 14 °C across the Perth metropolitan area.

Pearce RAAF observed its warmest spring nights for 29 years, whilst Medina in the southern suburbs observed its warmest spring in 24 years of record, and Bickley in the hills recorded its warmest spring nights in 17 years of record.

Perth Metro's mean daily minimum temperature in spring 2011 was 12.4 °C, which was above the average of 11.6 °C, and Perth Metro's warmest spring for 5 years, since a mean of 12.5 °C was recorded in 2006. Daily minima across spring ranged from a cold 4.9°C on 29 September to a warm 20.5°C on 3 November.

Wind and Sunshine

There was only one occurrence of severe wind gusts during spring 2011. A cold front crossed the Perth region on 18 September as Bickley observed the strongest wind gust for the season with 100 km/h. Severe gusts were also reported at Rottnest Island and Garden Island, and minor damage was reported in the Perth area, with the most serious damage in the southeast suburbs of Maddington and Westfield where trees fell on houses.

Perth's average sunshine hours in spring 2011 was 8.7 hours per day, the least sunniest spring for 18 years since a mean of 8.5 hours per day was recorded in 1993. The long-term average sunshine for spring is 9.3 hours per day. Last year (2010), Perth experienced its sunniest spring since records commenced in 1898 with an average of 10.1 hours sunshine per day.

Further information

Media
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Extremes in spring 2011
Hottest day 38.7 °C at Medina Research Centre on 24 Nov
Warmest days on average 24.3 °C at Gosnells City
Coolest days on average 20.7 °C at Bickley
Coldest day 12.7 °C at Bickley on 27 Sep
Coldest night 3.4 °C at Jandakot Aero on 29 Sep
Coolest nights on average 10.6 °C at Bickley
Warmest nights on average 14.9 °C at Rottnest Island
13.4 °C at Swanbourne
Warmest night 24.0 °C at Pearce RAAF on 24 Nov
Wettest overall 330.2 mm at Mundaring
Wettest day 35.4 mm at Mundaring on 2 Sep
Highest wind gust 100 km/h at Bickley on 18 Sep

Highest total spring rainfall for at least 10 years
Total rainfall
for spring 2011 (mm)
Most recent spring
this high or higher
Years since
higher
Average for
spring
Perth Airport 205.2 231.4 in 1996 15 142.6
Jandakot Aero 205.0 260.8 in 1999 12 164.1
Perth Metro 202.4 206.6 in 1999 12 152.2



Record highest spring mean daily minimum temperature
Mean daily minimum
temperature
for spring 2011 (°C)
Previous highest
for spring
Years of
record
Average for
spring
Bickley 10.6 10.5 in 2006 17 9.7



Summary statistics for spring 2011
Maximum temperatures
for spring
(°C)
Minimum temperatures
for spring
(°C)
Rainfall
for spring
(millimetres)
Mean for
spring
2011
Diff
from
average
Highest for
spring
2011
Mean for
spring
2011
Diff
from
average
Lowest for
spring
2011
Total for
spring
2011
Average
for
spring
Rank of
spring
2011
Fraction of
spring
average
Bickley 20.7 -0.4 34.0 24 Nov 10.6 +0.9 4.7 28 Sep 311.8 229.4 high 136%
Champion Lakes 22.6   35.1 24 Nov 12.9   4.3 28 Sep
Garden Island HSF 21.8   36.9 24 Nov 14.2   7.8 28 Sep 116.6 116.1 average 100%
Gosnells City 24.3 +0.3 38.2 24 Nov     5.9 23 Sep 208.1 156.0 high 133%
Jandakot Aero 23.3 +0.4 37.3 24 Nov 11.2 +1.2 3.4 29 Sep 205.0 164.1 high 125%
Medina Research Centre 23.4 +0.5 38.7 24 Nov 12.3 +1.5 4.7 28 Sep 149.5 149.9 average 100%
Pearce RAAF 23.4 0.0 37.8 24 Nov 11.4 +1.0 4.6 28 Sep 153.8 128.7 high 120%
Perth Airport 23.7 +0.9 37.2 24 Nov 11.7 +1.1 3.8 28 Sep 205.2 142.6 high 144%
Perth Metro 23.6 +0.4 37.2 24 Nov 12.4 +0.8 4.9 29 Sep 202.4 156.7 high 129%
Rottnest Island 21.1 +0.5 32.2 23 Nov 14.9 +0.8 10.3 28 Sep 149.4 112.9 high 132%
Swanbourne 23.2 +0.9 36.0 24 Nov 13.4 +0.9 6.8 28 Sep 179.6 149.2 high 120%

Notes

This statement was prepared before all data for the period were available. This may affect some of the statistics presented.

A Seasonal 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 5 pm on Wednesday 30 November 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 decile ranking (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 minimum 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.

For PDF files of Perth Metro climate statistics for other months, please click here for extremes and here for averages.

Further information

Media
(03) 9669 4057
Enquiries