Friday, 30 September 2011 - Monthly Climate Summary for Perth - Product code IDCKGC21L0

Perth in September 2011: A wetter than average month

• Rainfall: Average to above average.
• Maximum temperature: Near average.
• Minimum temperature: Near average.

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Rainfall

Rainfall across the Perth metropolitan area during September 2011 was near average at most locations, however some sites in the eastern suburbs and hills saw above average rainfall. Rainfall totals on the metropolitan plain were generally in the 80 to 130 mm range, while Mundaring in the hills was the wettest in the Perth area with 175.0 mm. Perth Airport, Jandakot Aerodrome and Perth Metro observed their wettest September in 10 or more years.

A strong westerly flow across the south of WA, with embedded cold fronts, brought wet weather to Perth during the first few days of September. Moderate rainfall was registered across the Perth area, with daily totals in the 10 to 30 mm range on the 2nd, with lighter falls observed on subsequent days. After a lengthy break due to a very strong high pressure system, a number of cold fronts brought moderate falls across the Perth area during the second half of the month. Bedfordale observed 47.2 mm in the 24 hours to 9am on the 16th which was their highest daily total in its 18 years of record, and was also the highest daily total of September 2011 in the Perth area.

Perth Metro recorded 109.2 mm on 16 rain days in September 2011 which is above average and the wettest September since the 115.2 mm on 18 rain days in 2001. The average for September is 80.6 mm on 15.3 rain days with September rainfall totals ranging from 8.7 mm in 1916 to 199.1 mm in 1923. Last September (2010), Perth Metro recorded 43.6 mm on 6 rain days.

Perth Metro recorded 691.8 mm of rainfall on 86 rain days in the first 9 months of 2011 (January to September) which is below average, but still the wettest since the 700.0 mm on 88 rain days in 2008.

Maximum temperature

Mean daily maximum temperatures were near average across the Perth area during September 2011. Two consecutive warm days were experienced on the 11th and 12th, with daily maxima across Perth in the low to mid 20's, which is 3 to 4 °C warmer than normal. The daily maximum temperature of 26.2 °C at Perth Airport on the 12th was the highest temperature of the month in the Perth region. A few cool to cold days were experienced at the beginning and latter parts of the month due to cold fronts crossing the region. During this time, daily maxima were generally in the low to mid teens, which is 2 to 4 °C cooler than normal for most sites. The daily maximum temperature of 12.7 °C at Bickley on the 27th was the lowest temperature of September 2011 in the Perth area.

Perth Metro's mean daily maximum temperature in September was 20.5 °C which was close to the average of 20.1 °C. Daily maxima ranged from a cool 17.1 °C on the 2nd and the 27th to a warm 24.5 °C on the 12th.

Perth Metro's mean daily maximum temperature for the first 9 months of 2011 (January to September) was 25.3 °C, which was the warmest year to date since records commenced in 1897, breaking the record of 24.7 °C set in 1976 and 1978. The average for the 9 month (January to September) period is 24.0 °C.

Minimum temperature

Minimum temperatures across Perth during September 2011 were near average. A few warm nights were experienced in the middle of the month, with daily minima in the low to mid teens for most sites. The daily minimum temperature of 16.5 °C recorded at Gosnells City on the 21st was the highest minimum temperature of the month for the Perth area. Cold nights (daily minima less than 5 °C ) were observed near the end of the month at most inland sites. Jandakot Aerodrome observed the coldest night in the Perth area during September 2011 with 3.4 °C on the 29th.

Perth Metro's mean daily minimum temperature in September was 9.4 °C, equal with the long term average. Daily minima ranged from a cold 4.9 °C on the 29th to a mild 14.4 °C on the 16th.

Wind and Sunshine

A strong cold front crossed the Perth area on the 18th and caused severe wind gusts at Bickley (100 km/h), Rottnest Island (98 km/h) and Garden Island (91 km/h). Widespread though 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 recorded an average daily sunshine of 7.6 hours in September 2011, close to the average of 7.7 hours.

ails Extremes Records Summaries Important notes the top

Details Extremes Records Summaries Important notes the top

Details Extremes Records Summaries Important notes the top

Details Extremes Records Summaries Important notes the top

Details Extremes Records Summaries Important notes the top

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.

Details Extremes Records Summaries Important notes the top