Wednesday, 1 June 2011 - Monthly Climate Summary for Western Australia - Product code IDCKGC21R0

Western Australia in May 2011: A dry month in WA

• Rainfall: Below average for both WA and southwest WA;
• Maximum temperature: Below average for WA; but above average for southwest WA.
• Minimum temperature: Below average for WA; near average for southwest WA.

Details Extremes Records Summaries Important notes the top

Rainfall

May 2011 rainfall was below average in the eastern Kimberley, eastern Interior, northern Goldfields and eastern Gascoyne. Parts of the Southwest Land Division (SWLD) also observed below average rainfall, with an area of very much below average observed in parts of the Southwest district and adjacent parts of the Great Southern. Above average rainfall was confined to patches in the central Pilbara, Western Gascoyne, northern Central west, western South Coastal and coastal Eucla (see May 2011 rainfall totals & deciles).

When averaged across the state, rainfall during May 2011 was below average for both WA and the Lower Southwest (southwest of a line from Jurien Bay to Bremer Bay).

A cloudband produced moderate to heavy rainfall in the Pilbara, Gascoyne and northern Central West on the 16th, with Karratha Airport recording daily rainfall total of 77.0 mm, exceeding its previous May record of 74.0 mm set on the 22 May 1972. Hines Hill in the Central Wheat Belt broke its May daily rainfall record on the 18th due to thunderstorms ahead of a cold front moving through the SWLD while

A cold front brought the first significant season rainfall to the Lower Southwest on the 20th, with daily rainfall totals mostly in the 20 mm to 50 mm range in the Lower West and Southwest districts, grading to around 10 to 20 mm in the Central West and Central Wheatbelt. Donnybrook in the Southwest observed a daily rainfall total of 52.0 mm on the 20th, while Tamaru in the South Coastal broke its highest May daily rainfall with 54.6 mm in the 24 hours to 9am on the 21st.

A strong cold front moved through the SWLD and adjacent Gascoyne late on the 29th and during the 30th with a number of heavy falls observed. 24 hour rainfall totals to 9am on the 30th were generally between 25 and 50 mm along the west coast and adjacent inland areas from Shark Bay to Busselton, with isolated heavier falls in the 50 to 70 mm range. Mandurah in the Lower West observed 28.0 mm in 60 mins (2117 WST to 2217 WST), which has an Average Return Interval (ARI) of between 10 to 20 years. Nabawa in the Central West recorded the highest 24 hour total with 64.0 mm in the 24 hours to 9am on the 30th.

Maximum temperature

May 2011 maximum temperature was below to very much below average over a large area from central to eastern WA, with areas of lowest on record in the central and western Pilbara, northwest Interior, eastern Kimberley and eastern Eucla. Mean maxima was up to 3 °C cooler than normal in those areas, with a patch of up to 4 °C cooler than normal in the northwest Interior and far east inland Pilbara. In contrast, above average mean maxima were observed over much of the SWLD and adjacent western Gascoyne, with an area of very much above average in the western Lower West and western Southwest districts where mean maxima was with up to 2 °C warmer than normal (see May 2011 mean maximum temperature decile & anomaly maps).

When averaged across the state as a whole, mean maximum temperature during May 2011 was below average; however, the Lower Southwest (southwest of a line from Jurien Bay to Bremer Bay) observed above average mean maximum temperature. Comparable records began in 1950.

Minimum temperature

Mean minimum temperature during May 2011 was below to very much below average in most of the northern half of WA, with up to 4 °C cooler than normal mean minima in the eastern Kimberley. Above average to very much above average overnight temperatures were observed in the Eucla, southern Goldfields and eastern parts of the SWLD (see May 2011 minimum temperature decile & anomaly maps).

When averaged across the state as a whole, mean minimum temperature during May 2011 was below average, whilst the Lower Southwest (southwest of a line from Jurien Bay to Bremer Bay) observed near average mean minima.

Other Phenomena

Waterspouts were reported offshore from Yallingup in the afternoon of the 4th, with a narrow convergence line was located off the southwest Capes. The Perth (Serpentine) radar showed strong reflectivities in the low levels.

A low off the Pilbara coast combined with ridging over central Australia to produce strong to gale force easterly winds over coastal parts of the Pilbara. Varanus Island observed a severe wind gust of 91 km/h at 1748 WST on the 4th.

A cold front crossed the SWLD during the morning of the 20th with roof and powerline damage reported in Canning Vale around 0800 WST. Severe wind gusts were observed at Rottnest Island from 1200 to 1300 WST, and a maximum wind gust of 96 km/h was observed at 1235 WST High tides, well above the Highest Astronomical Tide (HAT), were observed at Bunbury (1.63 m), Busselton (1.88 m), Fremantle (1.88 m), Barrack Street (1.73 m), and Geraldton (1.45 m).

The passage of a cold front across the southwest corner was accompanied by a tornado in Bunbury at around 0900 WST on the 29th with house and tree damage confined two streets in the Bunbury suburb of Usher.

Extremes Records Summaries Important notes the top

Extremes Records Summaries Important notes the top

Extremes Records Summaries Important notes the top