This rare phenomenon – observed in our hemisphere only four times in the satellite era – happens when temperatures in the polar stratosphere heat up while wind speeds drop. It is one of a series of weather events in the southern hemisphere affecting temperatures and weather.
As for spring, NZ Herald science reporter Jamie Morton told The Front Page that, from his discussions with Niwa, it was going to be more of the “rocky, unsettled” weather we associate with spring.
“For the early part of spring, they tell me that we can expect more of those sort of westerly flows that we’ve seen over the last few weeks, which have been coming in off the Tasman and bringing those rainy fronts into the West Coast. Some of those winds have the potential to be quite strong over the next few weeks.
“I think we can keep expecting to see the influence of that event down in Antarctica, and also those lows to the southwest coming in, bringing that drizzly weather, sometimes on the cooler side.
“But on the east, places like Napier and Hastings, which are seeing temperatures in the double digits this week, can expect more of that sort of weather where things are almost sort of pushing it into November temperatures.
“So it’s a bit of a scrambled, messy picture, as it always is as we go into spring, but this year there’s some interesting factors in the mix, some sort of wildcard factors.”
The big question for spring is whether La Nina – the cooling of surface ocean water along the tropical west coast of South America, resulting in humid northeasterlies – will return for the fourth time this decade.
Morton said it was still expected to happen but meteorologists had downgraded their expectations and thought it would not be particularly strong.
“So if we remember how crazy things got between 2020 and 2023, when we had three La Nina years in a row, back-to-back record warm winters, and you had all that extreme weather last summer, that’s what we might think about when we think of La Nina weather: constant northeasterly flows coming down from the tropics and just spoiling the holidays of people in Auckland and Coromandel.
“The indications are this system is not going to be quite as strong as was earlier anticipated, which might weaken its usual signal.
“But I think, nonetheless, that could change if we see a couple of big bursts and trade winds in the Pacific, so there’s a fair bit of uncertainty there, but at this point it’s probably not going to be as strong as previous ones.”
Listen to the full episode for more on the spring outlook, looking towards summer – and if record-breaking temperatures in the northern hemisphere spell trouble for us.
The Front Page is a daily news podcast from the New Zealand Herald, available to listen to every weekday from 5am. The podcast is presented by Chelsea Daniels, an Auckland-based journalist with a background in world news and crime/justice reporting who joined NZME in 2016.
You can follow the podcast at iHeartRadio, Apple Podcasts, Spotify, or wherever you get your podcasts.