Australians are in for a soggier than usual winter with cooler than average daytime temperatures but warmer nights.
That’s the forecast from the Bureau of Meteorology which released its outlook for the winter months today.
Winter officially kicks off on Monday.
“Most areas of mainland Australia are showing a better than 70 per cent chance of having a wetter than average winter,” said Dr Andrew Watkins, the Bureau’s manager of long-range forecasting.
That’ll be good news for vast areas of the country still affected by drought and it will also cause some relief for firefighters as a good soaking of moisture over winter should lead to a more manageable bushfire season.
It will be a step change from the current rainfall which nationwide is 20 per cent below average, driven by particularly dry conditions in Western Australia.
Dr Watkins said the outlook was being largely driven by warmer than average ocean temperatures in the waters to the north of Australia, as well as warm ocean temperatures in the western Pacific.
“When warm sea surface temperatures occur closer to Australia, weather patterns shift towards us too, favouring more cloud and rainfall across the country.
“We last saw this happen in 2016, when a strong negative Indian Ocean Dipole (a major climate driver) formed to the west of Australia. This was the last time we saw tropical moisture from the northern Indian Ocean deliver good winter rainfall to large parts of Australia.”
Neither the Indian Ocean Dipole nor the El Nino/La Nina climate driver are expected to fully shift out of neutral during winter. However the IOD is expected to head towards a neutral phase which would increase moisture levels on Australia while depriving eastern Africa of rainfall.
For rain to form it, of course, needs clouds which then act as something of a blanket during the winter months. In the daytime, that can lead to cooler temperatures as the sun struggles to reach the ground.
“Conversely, it means our nights are more likely to be warmer than average, because that cloud cover will prevent heat from escaping during the evenings,” he said.
But residents in some of Australia’s most populated areas — east of the Great Dividing Range — may miss out on the extra rain with the BOM saying it could be far drier.
That extends to eastern Victoria and Tasmania and parts of south west Western Australia. All could have more usual winter conditions as wetter conditions peter out.
“Parts of Northern Australia are also showing no strong push towards wetter than average conditions, but this is typically the dry season anyway.”
Looking back at Autumn, the BOM has released preliminary data that showed much of northern and Western Australia had a warmer than average season albeit interspersed with periods of very cold weather.
Yet most of south eastern Australia has had a cooler than average season.
Autumn rainfall is likely to have been above average through most of the south east, and parts of Central Australia and northern WA. Conditions have been drier than average through most of southeast Queensland and parts of northeast NSW.
Large parts of WA were drier than average for autumn but recent and expected rainfall in the coming days could push some areas of WA closer to average rainfall for the period.