Sluggish start to spring with high likelihood of El niño, and a dry summer


Temperatures averaged more than 27 degrees on Graham Hewett's  (background) parched Seddon farm during the last El niño.

KYLIE PINKER/STUFF

Temperatures averaged more than 27 degrees on Graham Hewett’s (background) parched Seddon farm during the last El niño.

Ah the good old Kiwi summer.

Walks on the beach, sipping on cold beers, and endless hours in the ocean.

And thanks to climate change, there’s a touch of El niño mixed in.

NIWA is seeing increasing El niño patterns forming, meaning a hot dry summer is probably coming to New Zealand’s East coast, NIWA principal scientist forecaster Chris Brandolino says. 

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The oscillations in the Pacific Ocean at the moment are causing heatwaves in the Northern Hemisphere – people have been dying in Japan.  Those same oscillations are pushing the El niño patterns for the Southern Hemisphere’s summer.

This means there will be “above average” temperatures, less rainfall on the east, and drier soil conditions.

The average annual rainfall in Rotomanu, West Coast, is 3.5 metres and close to 6m in El Nino years.

TONY BENNY/STUFF

The average annual rainfall in Rotomanu, West Coast, is 3.5 metres and close to 6m in El Nino years.

We still have to get there

Brandolino warns not to jump up and down just yet – New Zealand’s current climate conditions were sitting neutral, neither leaning towards El niño or La niña – two polar opposite weather patterns.

Weather is a science that forecasters don’t like to predict more than three months out, he says, it throws off the accuracy.

However, El niño is becoming increasingly likely as we progress through spring into summer, Brandolino says.

But don’t slip, slop, slap, just yet – we still have to make our way through a sluggish spring – despite daffodils and lambs already popping up over the country – in the middle of winter.

Spring would get off to a slow start as it works into the rhythm of warmer temperatures, he says.

August might be warmer than average or above average, but temperatures may be colder through September and October, Brandolino says.

In spring and autumn, south-westerlies tend to happen more often and are stronger, which gives a variety of both summery and wintry weather.

So, there will be lots of changing weather in the next couple of months if El niño does set in.

In the El Nino summer of 2015, a farmer's wife took a dip in the pool to escape the dry summer.

DAVID WHITE/STUFF

In the El Nino summer of 2015, a farmer’s wife took a dip in the pool to escape the dry summer.

What does El niño mean?

In New Zealand it’s a game of two halves. With the East and West Coasts in both islands separated by mountain ranges, each coast will have its own summer experience. The strong winds coming from the west will bring hot and dry weather to the East Coast, and it will be wet, wet, wet on the West Coast.

It also means that the warmest months will be January and February. December is more likely to be on the cooler side. 

In a nutshell, it does not guarantee a drought for the East Coast, but it is more likely to occur than in a non- El niño summer.

NIWA warns on its website that the likelihood of an El niño pattern is increasing with climate change.

El niño is a periodic weather phenomenon driven by changes in sea temperature around the Pacific Ocean, which in turn affects atmospheric circulation. The intensity of the atmospheric El Nino is measured by the Southern Oscillation Index, which roughly speaking is the difference in average air pressure between Tahiti and Darwin.

In an El niño, like this current event, average pressures are lower in Tahiti, resulting in a negative value of the index.

New Zealand’s set for a Modoki El niño, meaning “same but different” in Japanese.


 – Stuff



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