La Nina climate systems traditionally bring more rain and warmth to Auckland and other northern and eastern spots. Photo / Michael Craig
It’s goodbye El Nino, hello La Nina - but what does it all mean?
Forecasters have called time on the El Nino of 2023-24 - the first El Nino we’d experienced in nearly a decade.
The climate pattern describes the unusual warming of surface waters in the eastern Pacific Ocean - while La Nina is the cooling of surface ocean water along the tropical west coast of South America.
NZ Herald reporter Jamie Morton told The Front Page that they are on opposite ends of what you could call an “ocean-atmosphere seesaw” that influences a fair chunk of our seasonal weather.
“These set-ups also happen to come with certain pressure and circulation patterns for New Zealand.
“In El Nino, we get low pressure to the south of the country, and high pressure to the north and this acts like two cogs that drive warm westerlies over New Zealand in summer and cold south-westerlies in winter.
“In La Nina, obviously you get the contrasting set-up which means we’re more exposed to those humid north-easterlies.
“And that’s why for the first three years of this decade when we were in three years of La Nina, much of the North Island had to put up with muggy weather and regular visits from big rainmakers. Whereas with this El Nino, a lot of the east has dried out, with those constant westerly flows acting like a bit of a blow dryer,” he said.
The effects of this system referred to as the El Nino-Southern Oscillation (ENSO), while unpredictable, has attracted climate scientists worldwide.
Some say it “is the most important climate phenomenon on Earth”.
Morton says there is some debate amongst climate scientists about what climate change means for La Nina or El Nino.
“There’s one school that basically thinks climate change means we get more El Nino-type weather and that’s according also to the latest United Nations climate report. But, there’s another school that thinks climate change means we’ll get more La Nina.
“But, it’s fair to say that there’s broad consensus that whether we get either El Nino or La Nina the effects of either of those are going to be more amplified and pronounced and potentially more extreme as our planet heats up,” he said.
When it comes to New Zealand’s winter - a colder-than-average season appears unlikely, with sea temperatures predicted to be average to above average for the coming months.
“Over the next few weeks at least, forecasters are telling me it will be a bit colder than average over New Zealand. So that’s the result of basically the last gasp of El Nino.
“As we move into winter proper though it’s hard to tell. But, last time I checked, the odds of a colder winter weren’t so high.
“And if you get La Nina starting to form up kind of towards the end of winter, moving into spring, then that’s going to shift things to the warmer side,” Morton said.
Listen to the full episode to hear more about what La Nina means for weather in the coming months.
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.
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