After a near-record wet March in the south-east, we’ve just had a near-record dry April

New South Wales has just experienced one of its driest Aprils on record, after wading through its second-wettest March since records began in 1900, according to the Bureau of Meteorology.  

The ending of the La Niña climate phase has combined with typically settled autumn weather to bring clear skies to the south-east over the past month.

This dry spell saw New South Wales record its eighth-driest April and South Australia its seventh-driest April on record.

“Autumn is a time when you do tend to see quite a lot of stability in weather systems. So that can make for quite prolonged dry periods, or conversely quite prolonged wet periods,” said Dr Blair Trewin, a senior climatologist with the Bureau of Meteorology.

The Murray Darling Basin just had its 10th driest April, the least rain since 2005. This followed its fourth wettest March in more than 120 years.

“We certainly had no systems feeding moisture from the north-west and just about the only meaningful rain in a lot of inland New South Wales came out of localised thunderstorms,” Dr Trewin said.

Rainfall for April was above average for Queensland’s Cape York Peninsula and the northern parts of the state, as well as around most of the west and north-west coast of Western Australia.

The clear skies also brought cold nights to the south-east.

Canberra had a record low average minimum April temperature of 3.7 degrees Celsius. It was one of several locations in the region with record low average minimum temperatures.

Canberra’s previous record average minimum was 4.0C in April 1949. 

Wetter-than-average winter forecast

Despite the recent dry conditions in the south-east, the Bureau of Meteorology predicts a wetter-than-average winter for southern Australia.

 

This comes despite the major climate drivers like ENSO (El Niño/La Niña) and the Indian Ocean Dipole being in a neutral phase.

“Whilst we speak of the broad-scale climate drivers being in the neutral phase, that doesn’t mean that everything around Australia is completely normal,” Dr Trewin said.

“You’ve got relatively warm waters around most of the Australian coastline, but particularly off the coast of WA. That does point towards heightened availability of moisture from that direction.”

Trend of drier winters

The warm waters may help buck the trend of southern Australia increasingly experiencing drier than average winters.

“In the last 20 years we’ve had particularly dry cool-season conditions in southern Australia,” Dr Trewin said.

“We’ve only really had three years [in that period] where we’ve seen significantly above average cool-season rainfall through inland southeast Australia, for example.

“And those were the years when we had a La Niña in place or significant negative Indian Ocean Dipole in place.”

But Dr Trewin cautions against seeing the dry April as the beginning of a new cycle of drought.

“A single dry month in Autumn is not a particularly unusual thing to happen,” Dr Trewin said.