The maps displayed in the drought section of the Weekly Rainfall Update show how much rainfall as a percentage of mean rainfall for that period, has been received for specified periods. The time periods are determined by the most recent Drought Statement. The rainfall percentages maps have the same start date as the periods discussed in the Drought Statement, but the end date is the date of issue of the latest Weekly Rainfall Update. Percentages that are below 100% are below the mean rainfall for that period. About percentages of mean rainfall.
The Drought Statement discusses areas of Australia which have recorded either serious or severe rainfall deficiencies rainfall (i.e. rainfall in the lowest 10% and lowest 5% of historical observations). The Drought Statement is updated at the start of each month; the time periods analysed may be changed for a new Drought Statement.
The Weekly Rainfall Update tracks the percentage of mean rainfall received, to date, for each of the periods defined in the Drought Statement. Each week, the effect of rainfall or dry conditions in areas experiencing serious or severe rainfall deficits is evaluated and changes in rainfall deficits compared to the previous week are discussed.
Figure 1 shows the rainfall deficiencies map for the 8 months starting 1 July 2014 and ending 28 February 2015. Figure 2 shows the rainfall percentage map also starting 1 July 2015, but ending on Tuesday 24 March 2015.
Figure 1 shows that for the 8 months ending 28 February 2015 much of the south of Southern Australia and western Victoria received rainfall in the lowest 10% of observations since records commenced in 1900 for similar July to February periods. Serious (lowest 10% of observations) to severe (lowest 5% of observations) rainfall deficits are shown in pink and red shading on the map, and also cover parts of far northern Queensland and the coast of the Pilbara and Gascoyne. Figure 2 shows that by Tuesday 24 March, large areas of South Australia away from the northeast had recorded less than 60% of their mean rainfall for 1 July to 24 March. Some sites in central northern South Australia and on the coast near Ceduna had recorded less than 40% of mean rainfall. In Western Australia, the map shows that while parts of the coast of the Gascoyne had reached at least 100% of mean rainfall, deficits on the Pilbara coast near Karratha indicate totals for the period less than 50% of mean rainfall for similar periods.