Friday, 1 June 2012 - Monthly Climate Summary for Western Australia - Product code IDCKGC11R0

Western Australia in May 2012: A dry month for WA

• Rainfall: 5th driest on record for WA; below average for southwest WA
• Maximum temperature: above average
• Minimum temperature: 5th coolest on record for WA; near average for southwest WA

Extremes Maps Records Summaries Important notes the top

Rainfall

Rainfall during May 2012 was below average throughout much of WA, with areas of very much below average rainfall scattered throughout the state. The only area of WA to observe above average rainfall during May 2012 was in the northeast Kimberley; however, monthly totals in this area were less than 10 mm, which reflects the fact that May is typically a dry month in the north of the state. When averaged across the state as a whole, May 2012 rainfall was very much below average and ranked as 5th driest on record. The Lower Southwest (southwest a line from Jurien Bay to Bremer Bay) observed below average rainfall for the month, whilst for the wider Southwest Land Division (SWLD), rainfall averaged across the region during May 2012 was very much below average and ranked as 12th driest on record. Comparable rainfall records commenced in 1900.

A low and trough moved through the southwest of the state from the 3rd to the 6th, bringing the first rainfall for May 2012 for much of the SWLD. On the 5th, showers and thunderstorms were observed through much of western WA, with reports of a tornado on Little Pidgeon Island in the Abrolhos. A cold front moved across the SWLD on the 7th and 8th, bringing further rainfall and some strong gusts to coastal parts of the Southwest and Lower West districts. A westerly flow over the south of the state maintained a few isolated showers in mostly coastal parts of the southwest in subsequent days, before a strong high moved into the Bight on the 11th forcing showers to contract to the south coast. A cold front and low crossed the SWLD on the 13th, with showers and thunderstorms observed in southern and eastern parts of the SWLD and the adjacent southern Goldfields, with reports of large hail to the north of Albany in the South Coastal district. A series of weak cold fronts crossed southern WA from the 14th through to the 18th, with generally light falls near the south coast and showers and thunderstorms in central parts of the state. A strong ridge developed over the south of the state from the 19th, with rainfall contracting to southeast coastal parts, before a very strong high estabilshed in the Bight from the 24th through to the end of the month. A slow moving cold front moved over the western parts of the Southwest District late on the 30th and into central parts of the SWLD on the 31st, with some heavy falls observed in the Southwest district. Cape Leeuwin recorded 67.2 mm in this event, thus registering the highest daily fall in May 2012 in WA.

For the year to date (January to May), the Lower Southwest has observed its 10th driest start to the year on record, and interestingly has seen a drier start to the year than 2010, which was the driest year on record in the region. The dry start to 2012 was primarily due to a very dry autumn which ranked as 7th driest on record.

Maximum temperature

Much of WA saw above to very much above average maximum temperatures in May 2012, though the east Kimberley and northeastern Interior saw below normal daytime temperatures. Mean daily maxima were up to 2 °C warmer thon normal throughout much of WA, away from the northeast and far south, grading to up to 3 °C above average in the west Pilbara, Gascoyne, northern SWLD, and central Interior. Areas up to 3 °C cooler than normal were evident in the east Kimberley. When averaged across the state as a whole, the mean maximum temperature for WA during May 2012 was above average. For the Lower Southwest (southwest a line from Jurien Bay to Bremer Bay), daytime temperatures were also above average. Comparable records commenced in 1950.

Consistently warm temperatures over the northwest of WA throughout much of May 2012, associated with the lack of rainfall and clear skies, resulted in Cararvon Airport, Onslow Airport, Learmonth Airport, and Geraldton Airport Comparison all observing their hottest May on record. Of note were hot days from the 2nd to the 4th where temperatures were up to 10 °C above normal in the west Gascoyne and west Pilbara.

Very much above average mean daily maximum temperatures have been observed through the January to May period in the Lower Southwest, apart form February 2012 which is in fact one of only two months since September 2009 that have seen below average mean maxima. Consequently the region has observed its 6th warmest start to the year on record.

Minimum temperature

May 2012 saw below to very much below average minimum temperatures in the Kimberley, east Pilbara, and northern and eastern Interior, with overnight temperatures up to 3 °C cooler than normal, grading to up to 5 °C cooler than normal in the central Kimberley. Most of central and southern WA reported close to average mean minimum temperatures. When averaged across the state as a whole, the May 2012 mean minimum temperature was very much below average and ranked as 5th coolest on record, whilst the Lower Southwest (southwest a line from Jurien Bay to Bremer Bay) observed near average overnight temperatures. Comparable records commenced in 1950.

Warm overnight conditions were evident across western of WA durnig the first week of May, particularly in on the 3rd to 5th, as a slow moving trough over western parts directed warm northerly winds and cloud over the area. Warm nights were evident in eastern parts of the state from the 8th and 9th as the trough moved eastward through the state. Cold overnight conditions were observed in the western Eucla on the 10th under a developing ridge and Eyre observed -2.0 °C. Cold conditions developed over the south of the state from the 17th through to the end of the month as a ridge developed over the south of WA. A strong high moved over the southwest on the 24th and 25th, resulting in very cold nights in the SWLD and the adjacent southern Goldfields, with a number of sites observing their coldest May night on record. The strong high pushed cool air over the north of the state over the following days, resulting in cold overnight temperatures, particularly in the Kimberley. Broome Airport observed its coolest temperature in 73 years of record on the 28th, whilst Mount Elizabeth observed -0.9 °C on the same morning which was the first recorded sub-zero temperature in May in the Kimberley. Mount Elizabeth broke its May record of 3.7 °C (set on 28 May 1998) on six consecutive days, with minimum temperatures (26th to 31st) of 3.1 °C, 0.5 °C, -0.9 °C, 2.5 °C, 2.8 °C and 1.7 °C respectively.

WA as a whole has observed its 3rd coolest January to May period on record in terms of minimum temperature, with every month so far this year seeing a below average mean minimum. In contrast, above average mean daily minimum temperatures have been observed through the January to April period in the Lower Southwest, with May 2012 being the first month since October 2010 to record a below average monthly minimum. As a result the Lower Southwest has observed its 8th warmest start to the year on record.

Extremes Maps Records Summaries Important notes the top

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

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Extremes Maps Records Summaries Important notes the top

Extremes Maps Records Summaries Important notes the top

Extremes Maps Records Summaries Important notes the top