Rainfall update 4 September 2018
Rainfall for the previous month
Given this update is very early in the month, Figure 1 shows rainfall deciles for August, which was above average for much of the grainbelt and South West.
Monthly rain to date is available from the DPIRD weather stations and radar page (select Month to Date from the drop-down menu).
While August was wetter than average for most of the grainbelt and South West, July was near-average or slightly wetter, and June was slightly drier than average. Rainfall for June to August was a mixed pattern of near-average, slightly wetter and drier regions. The dry start to the season means much of the South Coast remains at decile 2 or less for growing season rainfall to date (Figure 2).
For graphs of seasonal rainfall at individual locations refer to the Rainfall to date tool.
Figure 3 shows relative root zone soil water storage to 3 September 2018 from the Bureau of Meteorology’s Landscape Water Balance model. Good rain in August has improved soil water storage for much of the grainbelt and the South Coast. Parts of the south-eastern grainbelt remain with relatively low levels of soil water storage for this time of year.
For soil water estimates at individual locations with and without crop water use refer to the Soil water tool.
Potential crop yield is estimated using the French-Schultz relation, and uses seasonal rainfall from 1 April to date. Rainfall for the rest of the growing season (to 30 September) is assumed to be decile 5. This model does not account for crop diseases or soil constraints. There is little change in yield potential from the previous report, as most of the seasonal rainfall is unchanged
To estimate yields at individual locations refer to the Potential yield tool.
Rainfall forecast for the next two weeks
Rainfall forecast for the next week shows continuing rain for the lower west coast and south west of WA (Figure 5). Most of the grainbelt is expected to receive less than 10mm.
Beyond next week, the US NCEP model indicates only light rainfall for the second week. See Figure 6. Almost all climate models surveyed indicate September is more likely to be drier than normal, with most also expecting below normal rainfall in October. This appears to raise the risk of a drier than normal finish to the 2018 growing season.