Thursday, 1 May 2014 - Monthly Climate Summary for Western Australia - Product code IDCKGC11R0

Western Australia in April 2014: wet start and finish

Frequent thunderstorms in the first two weeks of April in the northern and eastern WA resulted in above average rainfall in these regions, and a significant rainfall event in the last week of the month ended a long dry spell in western parts of the state with heavy rainfall causing flash flooding, particularly in the west Pilbara, and numerous April daily rainfall records. Below to very much below average rainfall was reported in the southern Southwest Land Division (SWLD), east Gascoyne, and east Pilbara. Day-time and overnight temperatures were generally near average or above average across the State.

• A thunderstorm on the 6th brings record April daily rainfall to Nalyerlup in the South Coastal district. 
• Slow moving thunderstorms in the west Pilbara on the 26th cause record daily rainfall, flash flooding, and extensive damage to the Exmouth region.
• A cloudband associated with ex-tropical cyclone Jack off the WA west coast brings widespread rainfall to much of the SWLD on the 26th and 27th, with record high April daily falls reported at numerous locations in the northern and central SWLD, and flash flooding and minor damage reported in the eastern Lower West and northern Great Southern.
•  Severe tropical cyclone Jack develops well off the northwest WA coast and has no direct impact on WA, though the decaying ex-tropical cyclone helps bring some significant rainfall to the State. Jack was the fifth tropical cyclone in the Western Region for the 2013-14 season.
• Record 186 day dry spell comes to an end at Kalbarri in the Central West on the 24th

Rainfall

April 2014 rainfall was above average in the west Pilbara, western and southern Gascoyne, northern and eastern SWLD, and Kimberley, as well as a broad area of eastern WA. A few sites in the west Pilbara and Great Southern recorded their wettest April on record, largely due to a significant rainfall event over the ANZAC day weekend late in the month, whilst Giles Meteorological Office in the Southern Interior also recorded its wettest April on record as the result of the rainfall early in the month. The Lower Southwest (southwest of a line from Jurien Bay to Bremer Bay), eastern Southeast Coastal, east Pilbara, and east Gascoyne saw below to very much below average rainfall.

Averaged across WA as a whole, rainfall in April 2014 was above average. The SWLD recorded near average rainfall when averaged across the region, however below average rainfall was observed in the Lower Southwest.

A weak cold front moved across southern WA at the start of April bringing light showers to SWLD coastal parts.

A surface trough extending from the Kimberley to the west coast coincided with a middle level trough moving eastward across the State from the 4th to the 8th and produced showers and thunderstorms across much of WA. Moderate to heavy rainfall was recorded in the Kimberley, Northern and Southern Interior, and South Coastal districts. Giles Meteorological Office (Southern Interior) recorded its monthly rainfall total of 124.8 mm during this event, making this month the wettest April in 58 years of record. Daily rainfall of 50.0 mm at Nalyerlup (South Coastal) on the 7th was the wettest April day in 31 years of record at the site, exceeding its previous record of 43.6 mm on 17 April 1998.

Sunny and warm weather was experienced for most of WA through middle parts of the month, but a middle level trough combined with tropical moisture associated with ex-tropical cyclone Jack off the northwest coast to produce an extensive cloudband with widespread rainfall over the west Pilbara, Gascoyne, Goldfields, and SWLD from the 24th to the 27th, whilst a weak cold front in the wake of the trough brought light to moderate rainfall to western parts of the SWLD from the 27th to 29th.

Significant rainfall occurred on the 26th in the west Pilbara as a result of slow moving thunderstorms with daily rainfalls ranging from 50 mm to over 200 mm, with a few sites breaking April daily rainfall records. Exmouth Town recorded 206.0 mm in the 24 hours to 9 am on the 27th, exceeding its previous highest daily rainfall in April in 43 years of record of 136.4 mm on 20 April 1980. Ningaloo Reef, a unofficial observing site in Cape Range National Park, recorded 237.7 mm during the event, and anecdotal evidence suggests close to 400mm may have fallen in the Cape Range area to the west of Exmouth.The deluge caused significant localised flooding within the Exmouth town site, including inundation of some properties in low-lying areas, damage to local roads and causeways, and damage to a water main. The Cape Range National Park was extensively damaged and the caravan park was inundated to the extent that the residents were taken to an evacuation centre in Exmouth.

Widespread heavy rainfall was also reported on the 26th and 27th in the Gascoyne, Central West, Central Wheat Belt, and Great Southern, and numerous sites observed their wettest April day on record. Minor water damage was reported in Toodyay (Lower West) and Quairading (Central Wheat Belt) where daily rainfall totals in the 60 mm to 70 mm range were reported.

Kalbarri recorded 51.8 mm on the 27th, its highest daily rainfall total in April in 44 years of record. This rainfall event came only two days after Kalbarri ended a record long dry spell of 186 days with only 0.8 mm, from 21 October 2013 to 24 April 2014. The previous the longest dry spell at Kalbarri with a total of 0.8 mm or less was 170 days from 3 December 2008 to 21 May 2009.

Maximum temperature

Mean maximum temperatures in April 2014 were above to very much above average in most of the SWLD and across much of the northern half WA, with means 2 to 3 °C warmer than normal in the southwest Gascoyne. Below average mean maximum temperatures were confined to small parts of the west Pilbara, eastern Interior, and Goldfields, with means up to 2 °C cooler than normal in the northern Goldfields.

Averaged across the state as a whole, the mean maximum temperature for WA in April 2014 was above average, whilst the Lower Southwest was also above average. The above average month in the Lower Southwest continued a run of 13 consecutive months above the long-term average, with only three months since October 2009 (three in the past 55 months) being below average.

In the north, hot days with maxima in the high thirties to low-forties were observed in the Kimberley and east Pilbara on the first four days of April. Derby Aerodrome recorded a maximum of 40.7 °C on the 2nd, its warmest April day in 30 years of record, whilst the highest temperature recorded in WA in April 2014 was 41.0 °C at Fitzroy Crossing Aerodrome on the 2nd and at Bidyadanga on the 3rd. Much of the Gascoyne and southern Pilbara experienced hot days with maxima in the mid-to-high thirties on the 3rd and 4th, and from the 12th to 15th, whilst mild days with maxima in the mid-to-high twenties were observed in the Gascoyne on the 6th and 7th, and from 25th to 30th.

In the south, warm to hot days with maxima in the mid-twenties to low thirties were experienced in parts of the SWLD on the 4th and 5th. and from 8th to 15th. High temperatures in the low thirties were recorded in the northern Goldfields from the 15th to 20th. Cool to cold days with maxima in the high teens were reported near the south coast on the 1st and 2nd, 20th and 21st, and across large parts of the SWLD from the 28th to the 30th. The lowest maximum temperature recorded in the month was 13.6 °C at Mount Barker on the 28th.

Minimum temperatures

Mean minimum temperatures in April 2014 were above to very much above average across much of the southern half of WA, as well as areas in the north and east Kimberley, with means up to 3 °C warmer than normal in parts of eastern WA. Mean minimum temperatures were near average for most of the northern half of the State and near the west coast.

The mean minimum temperature averaged across WA in April 2014 was above average, and the Lower Southwest (southwest of a line from Jurien Bay to Bremer Bay) also recorded above average mean overnight temperatures. WA has recently seen a run of consistently above average months, in terms of mean minimum temperatures, with only one month in the past 20 being below the long-term average. Similarly the Lower Southwest has been above average for the past nine consecutive months.

In the north, nights were mostly mild, though a few warm nights with minima in the mid-to-high twenties were observed in the Kimberley and Pilbara region on the first seven days and last three days of the month. Troughton Island recorded the warmest night in WA in April 2014 with a minimum of 29.3 °C on the 3rd.

Warm nights with minima in the high teens to low twenties occurred between the 10th and 15th in parts of the SWLD. In contrast, cold nights with minima below 10 °C were observed in the SWLD mostly from the 2nd to 4th, on the 17th, from the 21st to 23rd, and from the 28th to 30th, whilst cold nights in the southern Goldfields were mostly confined to the last two days of the month. Jarrahwood in the Southwest district recorded a minimum temperature of 0.9 °C on the 22nd, the lowest temperature recorded in April 2014 in WA.

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

Click on a map to show it full size in a pop-up window

* 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