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Thursday, 1 September 2011 - Monthly Climate Summary for Western Australia - Product code IDCKGC21R0
August 2011 rainfall was above average in the inland Gascoyne and northern Goldfields, as well as in small pockets of the Kimberley and Southwest Land Division (SWLD). In contrast, below average rainfall was evident in parts of the Pilbara, Interior, Eucla, South Coastal and Southeast Coastal districts (see August 2011 rainfall totals & deciles).
When averaged across the state, August 2011 rainfall was near average. It was also near average for the Lower Southwest (southwest of a line from Jurien Bay to Bremer Bay).
Widespread rainfall was evident over much of southern WA in the first few days of August, due to a strong westerly flow with embedded fronts crossing the region. Daily rainfall totals up to 30 mm were recorded in the Lower West and Southwest. The Central West and northern Central Wheat Belt districts received significant falls on the 7th, with daily totals generally in the 20-30 mm range. Lynton in the Central West recorded 45.0 mm in 24 hours to 9am on the 8th, the highest daily total for that day. A series of cold fronts brought further moderate to heavy rainfall to southwest and central WA from the 13th to 15th. Cape Leeuwin observed its second wettest August day since records commenced in 1907, and the highest daily total for August 2011 in WA, with 79.0 mm to 9am on the 14th. Most of this rain fell in the afternoon of the 13th as a slow moving line of heavy showers moved over the region and Cape Leeuwin registered 49.2 mm in just two hours, which equates to a one in over 100 year event. Widespread heavy falls occurred in the SWLD on the 21st and early morning on the 22nd, when a strong cold front moved across southwest WA. Many locations registered daily totals over 50 mm, and several sites in the Southwest district experienced their wettest August day on record.
With the exception of much the central and eastern Kimberley, mean maximum temperatures in August 2011 were above to very much above average for most of WA, with a broad area of up to 4 °C warmer than normal in the southern Pilbara and northern Gascoyne (see August 2011 mean maximum temperature decile & anomaly maps).
When averaged across the state, August 2011 was the 4th warmest August on record, and the 3rd warmest August on record for the Lower Southwest since records commenced in 1950. This continues the trend in the Lower Southwest that has seen all of the first 8 months of 2011 registering above average mean maxima. As a result, the January to August mean maximum temperature for the Lower Southwest is the highest on record.
During the first week of August, parts of southwest WA experienced cold days (a cold day is when a daily maximum temperature is less than 15°C) due to a persistent and strong westerly flow causing wet weather. Katanning in the Great Southern recorded a daily maximum temperature of 11.2 °C on the 3rd, the lowest temperature of the month for WA.
In the last week of August, northwest WA experienced abnormally hot daytime temperatures. Curtin in the west Kimberley observed 5 consecutive days (27th to 31st) with a daily maximum temperature over 35 °C, which was the longest run of 35 °C or greater days for August at Curtin since 1998, whilst 37.0 °C recorded on the 29th at Curtin was the highest temperature of the month for WA. The unusually high temperatures also had an impact in the Pilbara as the daily maximum temperature of 35.5 °C recorded at Onslow in the Pilbara on the 28th was its hottest August day in 51 years of record. at Whilst at Bidyadanga, the mean maximum temperature of 33.5 °C was its highest August mean maximum temperature on record, exceeding the previous record of 33.1 °C set in August 2006. The Lower West also reported unseasonally high day-time maximum temperatures in August as Perth Metro recorded its equal 2nd warmest August since 1897, and Jurien Bay recorded its warmest August in 41 years of record.
Mean minimum temperatures in August 2011 were below to very much below average over much of the Kimberley, with up to 4 °C cooler than normal mean minima in northeastern parts. In contrast, much of southern, central, and western WA saw above to very much above mean minimun temperatures, with parts of the eastern Interior experiencing mean minima up to 4 °C above normal, whilst the western Pilbara, northwest Gascoyne and parts of the Goldfields experienced up to 3°C above normal mean minima (see August 2011 minimum temperature decile & anomaly maps).
When averaged across the state, August 2011 was near average, however, the Lower Southwest register an above average mean minimum. Similar to maximum temperatures, all of the first 8 months of 2011 have seen above average mean minima for the Lower Southwest, and thus the Lower Southwest has recorded its warmest January to August period in terms of mean minimum temperature.
A few chilly nights with sub-zero overnight temperatures were experienced in some locations in the southern half of WA during the early and the latter parts of August. Eyre, in the Eucla, recorded -3.5 °C on the 26th, the coldest night of the month for WA. In contrast, large parts of WA experienced very warm nights during the middle part of August with daily minima over 15 °C. Onslow, Emu Creek and Learmonth Airport in the Pilbara all registered their warmest August night on record on the 14th, whilst Jarrahwood in the Southwest and Ravensthorpe in the Southeast Coastal also recorded their warmest August nights on record on the 21st and 22nd respectively. Pemberton in the Southwest experienced its warmest nights for August on record with a mean minimum temperature of 9.2 °C, exceeding the previous record of 9.1 °C set in August 1941.
|Extremes in August 2011|
37.0 °C at Curtin Aero on the 29th
|Warmest days on average||33.8 °C at Curtin Aero|
|Coolest days on average||16.1 °C at Katanning|
|Coldest day||11.2 °C at Katanning Comparison on the 3rd|
|Coldest night||-3.5 °C at Eyre on the 26th|
|Coolest nights on average||3.9 °C at York|
|Warmest nights on average|| 22.4 °C at Troughton
18.4 °C at Truscott (mainland)
|Warmest night|| 24.1 °C at Troughton
Island on the 19th
23.3 °C at Argyle Aero (mainland) on the 9th
|Wettest overall||213.9 mm at Northcliffe|
|Wettest day||79.0 mm at Cape Leeuwin on the 14th|
|Highest wind gust||109 km/h at Cape Leeuwin on the 2nd|
|Record highest August daily rainfall|
Highest daily rainfall
in August 2011 (mm)
|Westbourne||69.8||on the 22nd||41.7||on the 4th in 1964||105|
|Ferguson Valley||67.0||on the 22nd||60.0||on the 23rd in 1982||40|
|Frankland||64.0||on the 22nd||41.6||on the 3rd in 2003||38|
|Record highest August temperature|
in August 2011 (°C)
|Onslow||35.5||on the 28th||34.0||on the 30th in 1988||51||26.5|
|Record highest August mean daily maximum temperature|
Mean daily maximum
for August 2011 (°C)
|Jurien Bay||21.3||21.2||in 2006||41||19.8|
|Record highest August daily minimum temperature|
Highest daily minimum
in August 2011 (°C)
|Onslow||21.8||on the 14th||20.3||on the 9th in 1992||51||12.5|
|Ravensthorpe||18.4||on the 22nd||17.0||on the 7th in 2006||49||6.6|
|Emu Creek Station||21.9||on the 14th||21.3||on the 6th in 1993||39||12.2|
|Learmonth Airport||20.8||on the 14th||19.7||on the 6th in 1993||37||12.2|
|Jarrahwood||15.5||on the 21st||14.3||on the 13th in 1976||32||5.1|
|Record highest August mean daily minimum temperature|
| Mean daily minimum
for August 2011 (°C)
| Previous highest
|Summary statistics for August 2011|
|North Kimberley (district 01)|
|Wyndham Aero||33.7||-0.1||36.7||30th||14.9||-1.5||11.2||24th||0||0.1||v low||0%|
|East Kimberley (district 02)|
|Argyle Aerodrome||31.5||-0.5||33.9||29th||16.3||-1.2||11.6||20th||0||0.3||v low||0%|
|Halls Creek Airport||29.7||-0.3||32.8||16th||13.6||-1.2||9.8||2nd||0||1.9||lowest||0%|
|West Kimberley (district 03)|
|Curtin Aero||33.8||+0.8||37.0||29th||14.9||-1.1||11.0||2nd||0||1.8||v low||0%|
|Fitzroy Crossing Aero||32.9||-0.4||35.5||31st||12.0||-2.0||9.4||2nd||0||1.3||v low||0%|
|West Roebuck||33.6||+1.4||36.6||30th||13.0||-0.3||10.1||26th||0||2.9||v low||0%|
|De Grey (district 04)|
|Marble Bar||31.8||+2.0||36.0||30th||13.2||0.0||9.6||6th||0||0.3||v low||0%|
|Port Hedland Airport||30.8||+1.7||34.4||29th||13.3||+0.1||10.0||2nd||0||4.9||lowest||0%|
|Roebourne Aero||31.0||+1.0||35.8||29th||11.6||-1.2||8.2||2nd||0||1.1||v low||0%|
|Fortescue (district 05)|
|Barrow Island Airport||26.4||+1.5||30.5||30th||17.6||-0.2||14.7||7th||2.6||3.1||high||84%|
|West Gascoyne (district 06)|
|Emu Creek Station||30.0||+2.7||34.6||29th||14.4||+2.2||10.3||19th||0.4||11.6||average||3%|
|Shark Bay Airport||24.2||+0.3||27.9||20th||11.6||+0.8||8.1||6th||23.2||21.2||average||109%|
|East Gascoyne (district 07)|
|Murchison (district 07A)|
|Meekatharra Airport||23.5||+2.2||30.2||29th||10.1||+1.6||3.6||5th||28.0||11.5||v high||243%|
|Mount Magnet Aero||22.0||+1.1||29.1||21st||9.0||+1.4||2.3||5th||17.8||17.4||average||102%|
|North Coast (district 08)|
|Geraldton Airport Comparison||20.5||+0.4||24.4||21st||9.0||+0.1||3.0||26th||59.4||64.7||average||92%|
|Central Coast (district 09)|
|Badgingarra Research Stn||18.5||+0.3||23.7||21st||8.3||+1.4||4.8||27th||92.0||83.8||average||110%|
|Garden Island HSF||18.7||24.1||21st||12.0||8.4||5th||71.6||88.3||low||81%|
|Medina Research Centre|
|South Coast (district 09A)|
|Busselton Aero||18.4||+1.3||21.7||29th||8.7||+1.7||1.5||5th||55.2||105.0||v low||53%|
|North Central (district 10)|
|South Central (district 10A)|
|Lake Grace Comparison||17.8||+1.4||26.6||21st||6.3||+0.8||1.0||5th||26.8||39.9||average||67%|
|Newdegate Research Station||17.1||+1.0||26.1||21st||4.3||+0.2||-1.2||26th||36.6||43.7||average||84%|
|Eucla (district 11)|
|Red Rocks Point||20.3||30.8||22nd||9.3||4.3||26th||33.0|
|South East (district 12)|
|Salmon Gums Res.Stn.||19.6||+2.3||30.8||21st||5.2||+0.6||-2.8||26th||26.2||33.2||average||79%|
|Southern Cross Airfield||19.5||+1.2||28.9||21st||5.1||+1.9||-1.2||5th||37.6||29.0||high||130%|
|North East (district 13)|
|Giles Meteorological Office||25.3||+2.8||30.4||31st||9.5||+0.8||2.1||6th||0||10.4||lowest||0%|
A Monthly Climate Summary is prepared to list the main features of the weather in Western Australia 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 11 am on Thursday 1 September 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.
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 30 years of data.