Monday, 2 September 2013 - Monthly Climate Summary for Western Australia - Product code IDCKGC21R0

Western Australia in August 2013: Second warmest August on record

• Rainfall: below average rainfall for WA, near average for southwest WA
• Maximum temperature: 2nd warmest for WA, 4th warmest for southwest WA
• Minimum temperature: above average for WA, 3rd warmest for southwest WA

Extremes Maps Records Summaries Important notes the top

Rainfall

Rainfall in August 2013 was below to very much below average over most of the Pilbara, Gascoyne, Goldfields, Northern and Southern Interior, and Eucla. Much of the Kimberley and Southwest Land Division (SWLD) reported near average August rainfall, although very light rainfall in the far north Kimberley in the middle of the month brought above average totals, given it rains rarely in the region in August. Small areas of the SWLD also recorded above to very much above average rainfall, particularly near the west and south coasts.

For WA as a whole, rainfall in August 2013 was below average, however averaged across the the Lower Southwest (southwest of a line from Jurien Bay to Bremer Bay), as well as for the wider SWLD region, rainfall during August 2013 was near average.

A weak cold front brushed through the southwest corner of WA on the first day of August, bringing generally light showers to parts of the SWLD, with some moderate falls in the Southwest, Lower West, and South Coastal districts. Northwesterly winds over the SWLD from the 4th to the 8th along with a slow moving cloudband and a cold front brought persistent showery conditions to much of the SWLD, with moderate to heavy falls reported in the Lower Southwest (southwest of a line from Jurien Bay to Bremer Bay) intially and extending through the SWLD on the 7th and 8th. Daily rainfall of 80.2 mm at Bickley (Perth hills) on the 8th was the highest daily rainfall of the month in WA, and it was the second wettest day in August at Bickley in 45 years of record, and the wettest day at the site for any month for over 12 years, since 137.0 mm was recorded on 30 July 2001. Gingin in the Lower West recorded a daily total of 52.8 mm, also on the 8th, which was the wettest day in August at the site in 107 years of record. The previous record at Gingin was 52.3 mm on 11 August 1944.

Light to moderate rainfall continued in the southwest of WA between the 9th and 14th under a persistent westerly airstream with embedded weak cold fronts. A strong cold front moved through southern WA on the 15th and 16th brining widespread rainfall to the SWLD and neighbouring parts of the Gascoyne, Goldfields, and Eucla. Esperance in the Southeast Coastal recorded a daily total of 47.2 mm on the 16th, the wettest August day in 45 years of recording at the site, exceeding the previous record of 40.2 mm on 27 August 2002, whilst Merivale Farm (Southeast Coastal) recorded a daily rainfall of 52.4 mm on the 16th, exceeding the previous highest August daily fall in its 31 years of record of 38.0 mm. A complex low pressure system and upper level trough moved through southern WA on the 25th and 26th bringing widespread rainfall to much of the SWLD, southern Gascoyne, and Goldfields, with moderate to heavy falls in the Central West, Lower West, and Southwest, followed by another low pressure system on the 27th and morning of the 28th, that brought further widespread rainfall to the SWLD and southern Gascoyne. A westerly stream prevailed over the SWLD from the 29th for the remainder of the month as weak cold fronts moved through the region bringing widespread rainfall with some moderate falls to western parts of the Division.

Maximum temperature

Very much above average mean maximum temperatures were observed across almost all of WA in August 2013, with areas over 4 °C warmer than normal in the southeast Northern Interior and the eastern coastal Eucla. Carnarvon Airport in the Gascoyne and a few sites in the Lower West observed their warmest or equal warmest August on record, including Perth Metro and Rottnest Island, with 116 and 115 years of record respectively. Only parts of the Pilbara coast recorded a near average August in terms of the mean maximum temperature.

Averaged across the state as a whole, the mean maximum temperature for WA in August 2013 was the second warmest from comparable records commencing in 1910. For the Lower Southwest (southwest of a line from Jurien Bay to Bremer Bay) the mean maximum temperature was the fourth warmest on record.

A high moving over WA from the west in the early days of August 2013 produced a warming trend near the west coast, which resulted in unusually high temperatures in the west Gascoyne on the 3rd. Carnarvon Airport recorded its equal warmest day in August on record with a maximum of 31.6 °C, equal with the same maximum recorded on 11 August 1988. The unusually warm conditions extended through the southern half of WA on the 4th, and persisted until the 9th when the unusually high temperatures became confined to eastern central parts of the State where they continued until the 12th. Unusually hot days were reported in parts of the Kimberley and Northern Interior from the 12th to the 21st with daily maxima in the mid-to-high thirties at times. Warmun in the east Kimberley recorded a daily maximum of 39.5 °C on the 20th, which was the highest temperature in August 2013 in WA, and the highest August temperature at Warmun in 52 years of record, exceeding the previous record of 39.0 ºC on 31 August 2009. It was also the equal fourth highest temperature recorded in August in WA, only behind 40.0 ºC at Kalumburu Mission on 27 August 1970, 39.7 ºC at Wyndham Aerodrome on 31 August 2009, 39.6 ºC at Wyndham on 31 August 1985, and equal with 39.5 ºC at Derby Post Office on 24 August 1989.

Unusually warm days were evident in parts of the west Gascoyne and western SWLD from the 22nd to the 24th, whilst very warm days were reported in the Southern Interior and Eucla from the 25th to the end of the month.

Minimum temperatures

Most of the southern half of WA, west Gascoyne, west Pilbara, and Northern Interior saw above to very much above average mean minimum temperatures in August 2013 with a number of sites in the SWLD recording their highest mean minimum on record . Mean minima up to 3 °C warmer than normal were recorded in the southern half of the SWLD and parts of the Northern Interior. Cape Leeuwin in the Southwest recorded a mean minimum of 13.5 °C, which was its highest August mean minimum in 116 years of record and 0.5 °C higher than the previous record in August 2006, as the result of warmer than normal sea surface temperatures near southwest WA. In contrast, below to very much below average mean minimum temperatures occurred in parts of the Kimberley, with means up to 3 °C cooler than normal reported.

Averaged across the state as a whole, the mean minimum temperature for WA in August 2013 was above average, whilst averaged across the Lower Southwest (southwest of a line from Jurien Bay to Bremer Bay) the mean minimum temperature was the third warmest on record.

Cold nights were reported at various sites in the north and east Kimberley under clear skies and in very dry air between the 4th and 10th, with daily minima below 10.0 °C. Kununurra Aerodrome recorded a minimum of 7.0 °C on the 6th, overtaking its previous lowest temperature in August in 26 years of record of 7.3 °C registered on both 3 and 14 August 2012.

Mild nights were observed across large parts of the SWLD from the 5th to the 8th due to generally northwesterly winds and cloudy skies. Several sites in the Lower West and neighbouring Great Southern and Central Wheat Belt recorded their highest August minimum temperature on record on the 7th or 8th as a result. Perth Metro recorded a daily minimum 17.1 °C on the 7th, which was its warmest night in August since records commenced in 1897. The previous August record of 17.0 °C was observed exactly seven years previously on 7 August 2006.

Cold nights were experienced in parts of southern WA from the 11th to the 25th as a result of clear skies and light winds, with daily minima below 5.0 °C and a number of sites recording sub-zero temperatures. Eyre recorded the lowest temperature in the State on the 21st with a minimum of -1.8 ºC.

Other Phenomena

A suspected waterspout crossed the Perth metropolitan coast near North Coogee on the 6th, causing injury to 6 people (two serious) when scaffolding on a building site collapsed. Buildings were damaged and a heavy concrete building slab was lifted up.

Extremes Maps Records Summaries Important notes the top

xtremes Maps Records Summaries Important notes the top

Maps

Maps
	Observed	Anomaly	Decile rank
Total rainfall
Mean daily maximum temperatures
Mean daily minimum temperatures

Extremes Maps Records Summaries Important notes the top

Extremes Maps Records Summaries Important notes the top

Extremes Maps Records Summaries Important notes the top