"The first week to 10 days of September are looking particularly warm as we get a flow of air from Australia - and maybe even some temperatures in the 20C to 25C range."
Noll said that, broadly speaking, the climate set-up should result in below normal rainfall for swathes of the country — the North Island and northern and eastern South Island in particular.
"Some parts of the country, such as Auckland, have experienced below normal winter rainfall, so this may not be welcome news for things like dam level recharge," he said.
"Western and southern parts of the South Island may find rainfall that is closer to normal thanks to a westerly air flow."
The flavour could also bring lighter winds, sunny and milder afternoons, but chilly, sometimes frosty mornings.
Why?
Similar to this time last year, a La Nina climate system was currently developing in the tropical Pacific.
The negative phase of another major climate driver, called the Indian Ocean Dipole, was also unfolding northwest of Australia.
"This feature is lowering the pressures in the north of Australia, which is pumping up a ridge of high pressure in the mid-latitudes to the south, where New Zealand is."
Added to that, the Southern Annular Mode (SAM) - a ring of climate variability that encircles the South Pole, but stretches far out to our own latitudes - had been positive for around three-quarters of 2021 so far.
"A positive SAM tends to be associated with more settled weather around New Zealand," Noll said.
"The SAM has been trending more positive in recent decades, explained by changes in hemispheric ozone levels as well as climate change.
"There will of course be some week-to-week variability, so predictions like this are only meant to provide a high level overview for the coming weeks rather than a specific forecast for a town on a certain day."
Noll pointed out the weather was reminiscent of the tranquil conditions of last year's autumn lockdown period, along with sunny stretches that Auckland had spent under level 3 since.
"It's just co-incidence, of course, but over the last two years we've had this certain propensity for higher than normal pressure - and now here we go again."
