Aucklanders get out into the spring sunshine on September 25. Niwa is picking widespread warm temperatures for New Zealand over the next three months. Photo / Alex Burton
Aucklanders get out into the spring sunshine on September 25. Niwa is picking widespread warm temperatures for New Zealand over the next three months. Photo / Alex Burton
Meteorologists will be keeping a sharp eye on drought conditions forming in parts of the country over the final months of 2022 – even after our wettest winter on record.
In its just-issued three-month outlook, Niwa is picking above-average temperatures across New Zealand, with a marine heatwave helping to crank up the warmth.
The agency was forecasting a "very likely" chance of hotter temperatures across the North Island and west and north of the South Island - and "most likely" in the east of the South Island.
Air pressure was forecast to be higher than normal around New Zealand - especially near the South Island and east of the country - with less frequent westerly winds, more northeasterly winds, and the potential for longer dry spells in western areas.
In the short-term, however, we could expect weeks more of spring variability.
Forecaster Ben Noll said October's conditions might look somewhat like those of this month, which has seen temperatures track near-average for the first time since September 2021.
Source / Niwa
"That means more ups and downs, hot days and brief cooler spells, and the continuation of subtropical lows that we've grown accustomed to over winter."
Much of the variability we could expect in October owed to the fact two main drivers were at the steering wheel of our climate, Noll said.
They are La Niña and another ocean-driven system called the Indian Ocean Dipole, which has been locked in a strongly negative phase for months.
Toward the back-end of spring, however, La Niña was expected to intensify and become the dominant player – setting up our third La Niña summer in as many years.
"So, as we look to November and December, we may see a different pattern emerge, with highs becoming quite strong – especially in and around the South Island.
"These will be deflecting incoming lows and keeping them right up toward the top of the country – and we'll be watching what regions begin to dry out," Noll said.
Source / Niwa
There was an elevated risk of dryness in the southwest of the North Island and also in the west of the South Island.
Elsewhere, the odds for drier conditions were below or near normal in the west of the North Island, and the north and east of the South Island.
While it was too early to predict droughts this far off, Noll pointed out that last summer's La Niña culminated in medium-scale drought events in Otago, Southland and Rakiura/Stewart Island.
"There was also a late drought in Waikato over autumn: so it's those western and southern regions we do need to keep a close eye on, temperature-wise."
Over what's been a largely dry September for the south, remnant soil moisture from the wettest observed winter in 50 years of measurements had likely delayed this happening.
"We haven't yet seen any substantial soil moisture deficits so far – but we know that this won't last forever," Noll said.
"If we string together three or four dry months, then no matter how wet it was in winter, you'll be running into some issues."
A dry-out could also have implications for fire risk: last summer's La Niña coincided with several major blazes in the south, including one that scorched 280ha of farmland and bush on the shores of Lake Wanaka.
Meanwhile, Noll said widespread marine heatwave conditions that have persisted throughout the year would likely worsen over late spring and early summer – and perhaps even influence earlier than normal tropical cyclone activity in our region.
Source /Niwa
"The marine heatwave conditions, combined with the north-easterly winds and fewer southerlies we can expect under La Niña, gives us higher confidence for above-average temperatures as we head toward summer."
The year has already brought a slew of concerning milestones.
Winter 2022 was also our warmest for the third year in a row, while the first half of the year was also the second-hottest ever recorded – trends that will only continue as our planet warms.
