12-Month Rainfall Forecast
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Darling Downs 12-month Rainfall Forecast
Apr
25May
25Jun
25Jul
25Aug
25Sep
25Oct
25Nov
25Dec
25Jan
26Feb
26
10
50
977766551076Rainfall deciles
10Well above normal8 - 9Above normal4 - 7Near normal2 - 3Below normal1Well below normalIssue Notes
Issued 28 Mar 2025ENSO status: Weak La Niña-like conditions. IOD status: Neutral. SAM status: Neutral. The El Niño Southern Oscillation (ENSO) is in a weak La Niña-like pattern. The US declared a La Niña event this summer, but this event has not met the BoM definition, and will likely end in the coming weeks. A La Niña typically increases rainfall over northern and eastern Australia, while reducing rainfall over southern coastal Australia and western Tas. The Indian Ocean Dipole (IOD) is in a neutral phase and does not play a part in Australia's climate during this time of year. The Southern Annular Mode (SAM) is in a neutral phase. Forecasts show a tendency towards the positive phase in autumn, with the long-wave pattern indicating that cold fronts are a bit less likely for Australia's longitudes over the next few months. During autumn, a positive SAM increases rainfall over most of eastern Australia, and decreases rainfall for SA, Vic and western Tas. Rainfall outlooks are showing above average rainfall across much of northern Australia in April due to lingering monsoon activity. Above average rainfall is expected for the NSW coast through autumn, with wetter conditions also developing over western WA from late autumn. SA, Vic and Tas are expected to be average to slightly below average, with average conditions elsewhere.
Forecast ExplanationNotes on the concept of deciles
If all the data in a record are ranked from lowest to highest they can then be divided into 100 equal blocks. These blocks are known as percentiles. The values that fall into the lowest 10% range (from 0 to 10%) are said to be in the first decile, those in the group 10+% to 20% are in the second decile, and so on. Those in the group 90+% to the maximum value recorded are in the 10th decile. The 50% value is a special one known as the 'median'. It is noteworthy since there is the same number of records above and below its value.
Deciles have been found to be very useful for analysing rainfall in particular as its distribution is not the normal bell-shape distribution but is skewed towards many low values with only a few high values. The deciles can be described in qualitative terms. A table is provided in the accompanying results.
