Spring is just weeks away and the early signs are that weather wise it’s going to be a literal damp squib.
A collection of climate drivers are teaming up to bring rain, and quite a bit of it, to eastern states. Flooding is a very real risk.
More rain is great news for farmers, flooding is not.
It’s also likely to be warmer than average in Australia’s north and south east.
“For September to November 2021, we can expect a negative Indian Ocean Dipole to continue during spring bringing above average rainfall for the eastern half of Australia,” stated the Bureau of Meteorology (BOM) in its latest climate outlook.
That soggy spring was also more likely because of the increasing chance of La Nina making a comeback.
Both the Indian Ocean Dipole (IOD) and La Nina, the shorthand term for the neutral phase of the El Nino Southern Oscillation (ENSO) are measures of sea surface temperatures aided by powerful trade winds.
The two brood in the oceans on either side of Australia and when they crank into action it can have a powerful effect on the continent’s climate for months on end.
A negative IOD, which is currently in place in the Indian Ocean, generally aids in the creation of rain over southern and eastern Australia.
La Nina sees warmer seas pushed towards Australia’s east which brings more clouds and also adds to the rainfall.
It hasn’t kicked in yet, but several long-range forecasts suggest that La Nina will. Even if the ENSO doesn’t quite slip into neutral, it could still be powerful enough to bring more moisture to land.
Not everywhere will see more rain though. The BOM has stated that Western Australia, despite being lapped by the Indian Ocean where the IOD is located, is looking at having a dry spring – as is western Tasmania.
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Spring days are looking at being warmer than average in the north of the country and the far south east, so cities such as Melbourne, Hobart, Darwin and Cairns.
But it could be a cooler spring in central and eastern areas including Brisbane, Alice Springs and potentially Sydney.
Overnight, expect spring to be warmer than average almost everywhere in the country with the exception of southern Western Australia including Perth.
The BOM has also warned that a relatively wet winter has meant catchments are already sodden. That means if persistent wet weather does occur, flooding is a real possibility.
Australia’s climate has warmed by around 1.44C for the 1910–2019 period, the Bureau has said, while southern Australia has seen a reduction of 10–20 per cent in cool season rainfall in recent decades.