AUTUMN and winter could bring a change with the weather bureau forecasting wetter than average conditions likely for most of Australia.
The exception is parts of the tropical north and along the eastern seaboard, where outlooks have roughly equal chances of being wetter or drier than average, according to the Bureau of Meteorology’s latest climate outlook.
Little surprise here but days are likely to be warmer than average from May to July across northern Australia and the eastern seaboard extending into northeast Tasmania.
Elsewhere, May to July days have roughly equal chances of being warmer or cooler than average.
Nights for May to July are very likely to be warmer than average nationwide.
A warmer than average eastern Indian Ocean is currently the main influence on Australia’s climate, increasing moisture feeding into weather systems as they sweep across the country.
BoM’s rainfall outlook for May to July at Lismore predicts an equal likelihood for the chance of above median rainfall (recorded at 340mm), although past accuracy is low.
Tenterfield will likely exceed the median of 124mm for this period, and Casino has an equal likelihood of exceeding its median of 176mm.
Wetter May to July for most of Australia
In the shorter-term, the fortnight of April 20 to May 3 is likely to be drier than average along the eastern seaboard and for much of northern Australia, meaning a drier end to the northen wet season (mostly 60–75 per cent chance).
The three months May to July are also likely to be wetter than average for most of Australia (mostly 60–75 per cent chance).
The likelihood of a wetter or drier May to July is roughly equal across the far north NT and Queenland, along the coastlines of southeast Queensland, along NSW and into eastern Victoria, and southern Tasmania.
Similarly, June to August is also likely to be wetter than average for most of Australia (mostly 60–75 per cent chance, with chances slightly higher towards central Australia).
- A warmer than average eastern Indian Ocean is increasing the likelihood of northwest cloudbands interacting with fronts and troughs bearing rain as they sweep across the country during late autumn and into early winter.
- While the Indian Ocean Dipole (IOD) is currently neutral, the Indian Ocean is expected to approach, or even exceed, negative IOD thresholds later in the outlook period. However, caution should be exercised with using IOD forecasts made during autumn, as they are less accurate than forecasts made at other times of the year. While all other international models surveyed by the Bureau approach or exceed negative IOD thresholds during 2020, the individual models have only moderate confidence at this time. Negative IOD events typically increase the likelihood of above average winter-spring rainfall across southern Australia.
- The El Niño–Southern Oscillation (ENSO) is most likely to remain neutral over winter, though a weak La Niña cannot be ruled out for later in 2020.
- The Southern Annual Mode (SAM) is currently neutral, and likely to remain neutral for the coming three weeks. At this time of the year, SAM has little influence on Australian rainfall.
- Australia’s temperature and rainfall variability are also influenced by global warming caused by human activities, BoM said.
- Australia’s climate has warmed by around 1.4 °C since 1910, while southern Australia has seen a reduction of 10–15 per cent in cool season (April–October) rainfall in recent decades.