Perth Winter 2012

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Perth Winter 2012

Postby @weather_wa » Sun Sep 02, 2012 4:00 pm

Perth in winter 2012: A warm and very dry winter. ... erth.shtml


Rainfall across the Perth metropolitan area during winter 2012 was very much below average at most sites, mainly due to the driest July on record at most locations, with June totals being close to average, and August totals being near average to below average. Winter rainfall totals were generally in the 250 mm to 300 mm range, grading to 400 mm to 500 mm in the Perth hills.

Significant rainfall events during winter 2012 in Perth:

A slow moving trough off the west coast, associated with a near stationary low to the southwest of the state, brought showers and thunderstorms with moderate falls to Perth on 6 June. The trough moved gradually eastward over land during the morning of the 7th, with severe thunderstorms developing over Perth in the late morning and early afternoon, and a tornado was reported close to midday in the suburbs of Dianella and Morley, causing substantial damage.

A rapidly deepening tropical low off the northwest coast of Western Australia moved south-southeastward close to the west coast during the morning on 10 June and crossed the Southwest district during the afternoon, bringing severe wind gusts and moderate rainfall to the Perth area.

A cold front moved through the Perth metropolitan area on 11 June bringing further rainfall and more severe wind gusts before a rapidly developing cold front and deep low pressure system moved through the Southwest Land Division (SWLD) during the afternoon and evening of the 12th, bringing moderate to heavy falls and more severe winds to the Perth area.

A persistent westerly flow was maintained over the Perth region from 12 to 18 June, bringing consistent, though generally light, rainfall. Cold fronts on the 19th and 20th brought moderate falls.

July 2012 saw only a handful of light rainfall events in the Perth area, with daily rainfall totals generally less than 10 mm.

A strong cold front and pre-frontal trough brought moderate to heavy falls to the Perth area on 12 August. Mundaring in the hills received 53.0 mm in 24 hours to 9am on the 13th, the highest daily fall recorded in the Perth metropolitan area during winter 2012.

Perth Metro recorded 262.6 mm of rainfall on 42 rain days during winter 2012, well below the average of 478.7 mm on 48 rain days and was the 4th driest winter on record behind 2006 (230.4 mm), 2010 (256.4mm), and 1940 (260.0 mm). Rainfall records commenced at Perth Metro in 1876. Rainfall totals at Perth Metro for the individual months in winter 2012 were: June: 140.8 mm (average 175.7 mm), July: 34.6 mm (average 169.6 mm), and August 87.2 mm (average 133.4 mm).

Maximum temperature:

Mean daily maximum temperatures for winter 2012 were very much above average across the Perth region and in the 18 °C to 20 °C range, with most sites 0.5 °C to 1.0 °C above normal. The very much above average winter mean maxima were the result of slightly above average maxima in June, very much above average maxima in July, with some sites registering a record high July, and an above average August. Consequently, Swanbourne recorded its highest winter mean maximum temperature in 18 years of record.

A high in the Bight directed warm northeasterly winds over the Perth area during early June, and again in mid-August, with all Perth sites observing their warmest winter days on either 3 June or 10 or 11 August. A maximum temperature of 25.5 °C at Gosnellls City on 3 June was the highest temperature recorded in the metropolitan area during winter. The lowest maximum temperature for winter was 11.3 °C at Bickley on 20 June in southerly winds after the passage of a cold front.

Perth Metro's mean daily maximum temperature for winter 2012 was 19.7 °C, which is 0.9 °C above the winter average of 18.8 °C and the equal second warmest winter on record with 1976 and 1983 (comparable temperature records commenced in 1897). Perth Metro's warmest winter was in 2006 when a mean maximum temperature of 19.8 °C was observed.

Minimum temperature:

Mean daily minimum temperatures during winter 2012 were generally near average across the Perth region, with mean daily minima close to 8 °C for inland sites, but were generally in the 10 °C to 13 °C range near the coast. The near average winter was the result of an above average June, a very much below average July, with record low mean minima at some sites, and a slightly above average August.

Cool to cold nights were observed throughout most of July 2012, with generally clear skies throughout much of the month. A particularly cold night was observed on the 25th when Perth Airport, Pearce RAAF, and Jandakot Aerodrome registered sub-zero overnight temperatures and most sites observed their coldest night for winter 2012. The mildest night for winter 2012 for a number of metropolitan sites occurred on 3 and 4 June in a northerly flow as a strong low pressure system sat to the southwest of WA. Rottnest Island recorded a minimum temperature of 17.7 °C on the 4th, the highest for winter in the Perth metropolitan area.

Perth Metro's mean daily minimum temperature for winter 2012 was 8.0 °C, which is close to the average of 8.2 °C.

Wind and Sunshine:

Perth’s mean daily winter sunshine was 6.5 hours per day in 2012, which is close to the long term average of 6.4 hours per day

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