Seasonal rainfall update

Rainfall update 20 June 2018

The past week has seen lighter rainfall, mostly less than 10mm, for the bulk of the grainbelt. Some parts of the far northern grainbelt, as well as western parts of the central grainbelt have had higher amounts. The pattern of generally low rainfall has continued for south-eastern and southern regions.

Rainfall totals in the past week

Map of Western Australia showing coloured areas of rainfall levels in millimetres
Figure 1 Western Australian rainfall totals (in millimetres) for the week ending 20 June 2018 (source: Bureau of Meteorology, www.bom.gov.au/climate/)

For more information refer to the Bureau of Meteorology weekly rainfall table for the south-west.

Rainfall for the month to date

Western and south-western locations have received good rainfall to date, and may achieve close to average rain for the month. Rainfall over the south-eastern grainbelt remains well below average to date. The Gascoyne and Pilbara have had well above-average rainfall for the month to date, noting that this is a time of year when rainfall is usually low (Figure 2).

Map of Western Australia showing coloured areas of rainfall levels in millimetres for 1 to 19 June 2018
Figure 2 Western Australian rainfall totals (in millimetres) for 1–20 June 2018. (source: Bureau of Meteorology, www.bom.gov.au/climate/)

Monthly rainfall to date from DPIRD weather stations

Map of the northern grainbelt with DPIRD weather stations marked with monthly rainfall to date
Figure 3 Monthly rainfall to date (in millimetres), 1– 20 June 2018, from DPIRD weather stations in northern and central agricultural areas.
Map of the northern grainbelt with DPIRD weather stations marked with monthly rainfall to date
Figure 4 Monthly rainfall to date (in millimetres), 1–20 June 2018, from DPIRD weather stations in southern agricultural areas.

Seasonal rainfall to date

Map of Western Australia showing coloured areas of rainfall levels in millimetres for 1 April to 19 June 2018
Figure 5 Seasonal rainfall in millimetres (mm) from 1 April to 19 June 2018 (data source: Patched point dataset).

 

Map of Western Australia showing coloured areas of rainfall levels as a percentage of median seasonal rain to date
Figure 6 Season rainfall to date as a percentage of the median from 1 April to 19 June 2018 (data source: Patched point dataset)

Soil moisture

Soil water storage has improved in northern and western cropping areas, while far-eastern cropping and south coast regions still have low storage. Figure 7 shows the estimated root zone soil water storage from the Bureau of Meteorology landscape model, as relative storage for the time of the year.

Map of soil water storage relative to long term values at this time of year
Figure 7 Estimated root zone soil moisture 19 June 2018, relative to expected levels at this time of year (source: Bureau of Meteorology's landscape water balance model, www.bom.gov.au/water/landscape/)

Low levels of soil water remain in the eastern and south-eastern grainbelt. Figure 8 shows the estimated fallow soil water storage to 19 June 2018.

Map of soil water storage in millimetres at 19 June 2018
Figure 8 Estimated plant available soil water in millimetres at 19 June 2018 (data source: Patched point dataset).

Rainfall forecast for the next week

The second part of June is likely to see less rainfall because weather systems appear to be weaker and less frequent than early in the month. Rainfall forecast for the week ending 27 June 2018 appears to be confined to the south-west and west coastal areas (Figure 9). Relatively little rainfall is predicted for the eastern grainbelt and South Coast.

The ECMWF model is predicting a similar spatial pattern of rainfall over the coming week. Total predicted rainfall from the ECMWF model for the next 10 days is shown in Figure 10.

Map of rainfall forecast for the next week to 27 June 2018 in millimetres
Figure 9 Bureau of Meteorology forecast rain in millimetres for 20 to 27 June 2018 (source: www.bom.gov.au/jsp/watl/rainfall/pme.jsp). 
Map of forecast rain to 27 June 2018 from the ECMWF model
Figure 10 Total predicted accumulated rainfall from the ECMWF for 19 to 27 June 2018 (source: https://weather.us/model-charts/euro/western-australia).

Contact information

Ian Foster
+61 (0)8 9368 3954