The chance of a wetter than average winter is strengthening for parts of the State. The rainfall outlook for winter (June-August) shows most of Australia is very likely to have a wetter than average season. The strong chances, greater than 80 per cent, stretch all the way from northwest WA across and down to central Victoria. However, the wet signal isn't as strong east of the Divide, and parts of East Gippsland and the NSW coast have closer to a 50:50 chance of a wetter than average winter.
Daytimes are likely to be cooler than average in northwest Victoria and warmer than average in East Gippsland during winter. There are high chances (greater than 80 per cent) nights will be warmer than average across the north but there is no strong push towards higher or lower minimum temperatures in the far south.
But before winter, most of Victoria has roughly equal chance of being wetter or drier than average for the second half of May.
The tropical Pacific and Indian oceans can strongly influence south eastern Australia's seasonal weather. Both the El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) are currently neutral. However, all of the international climate computer models surveyed by the Bureau of Meteorology suggest the possibility of a negative IOD developing in the Indian Ocean from the middle of winter. And some models suggest a La Niña in the tropical Pacific Ocean is possible in early-to-mid spring.
A negative IOD typically brings above average winter-spring rainfall to the State. When ENSO is neutral, it has little influence on Australian climate, while La Niña typically means above average winter–spring rainfall for most of Victoria, with less influence over Gippsland.
Overall, the international climate computer models favour a negative IOD developing. But it is not guaranteed—they all show either a neutral IOD or negative IOD are possible. Also, the accuracy of IOD and ENSO forecasts for winter-spring are lower during autumn and improve during winter. This means that current ENSO and IOD forecasts should be used with some caution.