El Nino brings warmer-than-normal waters in certain parts of the tropical Pacific Ocean, whereas La Nina brings colder-than-normal waters.
But, while La Nina has only just ended, why are we seeing such a rapid flip from one extreme to another?
Earth Sciences New Zealand and MetService meteorologist Jon Tunster told the Front Page that there aren’t too many historical comparisons for the speed of moving from one to the other in the same year.
“When you go back and look around, there aren’t a huge number of what we would call historical analogues for a switch that occurs in the same year, and certainly not for one that occurs as quickly as this.
“So, we’re running quite light on analogues, to be honest. When we searched through the record, we were able to find 1976 possibly as one, and 2023 to 2024 was another one.
“But the trouble is, when you look at these historical analogues, there’s a whole bunch of other variables that change within them. It can’t necessarily be the case that we just follow history and we know what’s coming in the future,” he said.
The big picture from the models is a dramatic increase in sea surface temperatures in the tropical Pacific.
For New Zealand, El Nino generally brings more westerlies, often stronger or more persistent, with rainfall tending to be concentrated in western areas and reduced in northern and some eastern areas.
“Perhaps one easy comparison is that probably this winter will be different from last winter. Last winter was quite wet for a lot of places.
“There were a decent number of northerly sourced northeasterly rain events. One good example was the Nelson-Tasman flooding that happened in late June or early July last year.
“That was sort of characteristic of that type of winter, and I think that what people might start seeing on the ground is that if you’ve become accustomed to seeing a lot of these kind of humid rain-bearing events coming down from the north, maybe we just start to see far fewer of those than what we’ve become accustomed to in the last year,” he said.
Listen to the full episode to hear more about:
What El Nino could mean for New ZealandIts global impactsWhat models are showing How forecasters judge strength.
The Front Page is a daily news podcast from the New Zealand Herald, available to listen to every weekday from 5pm. 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.
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