Monday, 3 May 2021 - Monthly Climate Summary for Western Australia - Product code IDCKGC11R0

Western Australia in April 2021: wet in the west; warm in the south

April rainfall was above average in western parts of Western Australia, largely due to the passage of severe tropical cyclone Seroja and a cold front at the end of April, though rainfall was below average in the eastern half of WA. The state's monthly rainfall overall was below average. Mean maximum temperatures were above average for most of the southern two-thirds of the state, as well as in the north and west Kimberley. Mean minimum temperatures were above average in the west and south of WA, in contrast to the north-east with below average mean minima.

Wet in western parts of WA

• April rainfall was 38% below average for Western Australia as a whole.
• Rainfall was above average in western parts of the state, due to the passage of severe tropical cyclone Seroja, and a cold front at the end of April; monthly rainfall totals were up to 100–120 mm at some sites in the state's south-west, and Porongurups in the inland South Coastal District had the highest recorded total of 125.6 mm.
• Several sites in the inland Central West, South West and inland west Pilbara districts had their wettest April for at least 20 years.
• The eastern half of the state saw below average rainfall, with little or no measurable rainfall was recorded throughout the month at some sites.
• Severe tropical cyclone Seroja and its remnants produced moderate daily rainfall in the western parts of the state from North West Cape down to the South Coastal and South East Coastal district, with locally heavy daily rainfall up to 100 mm at sites near the passage of Seroja and to its far south; more than a dozen sites had their highest April daily rainfall on record on the 12th.
• A trough over north-west WA produced thunderstorms with moderate rainfall in the east Pilbara on the 14th.
• At the end of April, a cold front moved across the South West Land Division to produce widespread moderate rainfall up to 40 mm on the 30th.
• The northern wet season (October 2020-April 2021) rainfall was 19% above average, and wettest since 2016-17, for northern Australia (north of 26°S, including areas in WA from Shark Bay northward); much of the Kimberley region and western Gascoyne had very much above average wet season rainfall.
• During the 2020-21 tropical cyclone season to the end of April, 8 cyclones formed or tracked within the Australian Region; 4 tropical cyclones were in the Western Region, including 2 (Marian and Seroja) reaching severe (category 3) strength: Seroja made landfall in the Central West District.
• There were three notable tropical lows impacted Western Australian coast and further inland during the 2020-21 season.

Warmer temperatures in the south, cooler nights in the north-east

• The mean maximum temperature was 1.69 °C above average, although 2018, 2019 and 2020 were even warmer for Western Australia.
• The mean minimum temperature was 0.05 °C above average, and the coolest since 2017 for Western Australia.
• Daytime temperatures were 8–12 °C above average across southern WA except the far south-west coast at the start of April, and the heat remained in the south-east until the 7th; a dozen sites in the South West Land Division and Eucla District had their highest April temperature on record
• Eyre (a mid-point along the Eucla coast), recorded 3 days with temperatures of 40 °C, and 41.7 °C on the 7th equalled its April temperature record, and the month being a record warm April as a result.
• Kalgoorlie-Boulder Airport reported a mean maximum temperature of 28.3 °C, which was its equal third-warmest April on record, and warmest for 40 years since 1981 (a record with 29.5 °C ).
• Broome Airport recorded 10 consecutive cool nights with temperatures below 20 °C between 18th and 27th, the longest such run in April since 1999 (15 consecutive cool nights); 12.8 °C on the 20th was the third-lowest April temperature on record at Broome Airport, and the month was the coolest April since 2001.

Severe tropical cyclone Seroja

• Tropical cyclone Seroja formed in the Timor Sea on 5 April, the eighth-cyclone of the 2020-21 season in Australian Region.
• Seroja moved south-west well offshore parallel to the Kimberley and Pilbara coast then interacted with another tropical low (which briefly intensified into Tropical Cyclone Odette) before taking a sharp turn moving south-east towards the west coast from the 10th.
• Seroja intensified to a category 3 cyclone on the 11th and made landfall just south of Kalbarri in the Central West District in the evening, a rare occurrence of a severe cyclone tracking so far south.
• Wind gusts over 100 km/h to 120 km/h were recorded in locations between Carnavon in the Gascoyne coast to Dalwallinu in the Central Wheat Belt on the 11th or 12th; Meanarra Tower east of Kalbarri, a non-bureau site, recorded a gust of 170 km/h (92 knots) on the 11th.
• Kalbarri and the nearby town of Northampton sustained significant damage, with 70% buildings with roofs lost or structures destroyed.

Extremes Maps Records Summaries Important notes the top

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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* note: there are gaps in the historical record at this site, so it is possible a higher value has gone unreported

Extremes Maps Records Summaries Important notes the top

Extremes Maps Records Summaries Important notes the top