Capricornia 12-month Rainfall Forecast

10 5 0
No forecast available for this district.
Rainfall deciles
10 Well above normal
8-9 Above normal
4-7 Near normal
2-3 Below normal
1 Well below normal

Issue Notes

ENSO status: Neutral.
IOD status: Neutral.
SAM status: Positive. Trending positive.

The El Niņo Southern Oscillation (ENSO) has returned to neutral conditions, after a short and weak La Niņa pattern. Neutral conditions are likely to persist through autumn and early winter.

The Indian Ocean Dipole (IOD) is in a neutral phase, but the Indian ocean overall is much warmer than average. The IOD is forecast to become more negative from late autumn, and is a higher than normal chance to develop in 2025. A negative IOD typically increases the amount of northwest cloudbands that cross Australia, increasing rainfall from northwest WA through to southeastern Australia during winter and spring.

The Southern Annular Mode (SAM) is in a positive phase, meaning cold fronts are further south than they typically would be at this time of year. Forecasts are indicating a positive phase to be more dominant during autumn, aligned with most autumns in the last decade. During autumn, a positive SAM increases rainfall over most of eastern Australia, and decreases rainfall for SA, Vi, western Tas, and southwest WA.

Rainfall outlooks are showing below average rainfall for much of Australia during May, then generally returning closer to average by June. There is a increased chance of wetter than average conditions over western WA and eastern NSW with very warm sea surface temperatures near both coasts.

Issued Apr 22

Forecast Explanation

Notes 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.

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Anzac Day dawn service weather forecast around Australia

14:41 AEST Anzac Day is this Friday, 25 April, so how’s the weather looking around each capital city for those attending the dawn service? Looking at the synoptic image below, showers and storms are possible over parts of Tasmania and Victoria with a low pressure trough and cold front, and eastern NSW with moist onshore winds.

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