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Why is NZ so windy? We explain the Roaring Forties!

New Zealanders shouldn’t be so surprised how often it’s windy here. After all, we’re basically a few mountainous islands stuck partially in the Roaring Forties.

But to many people, that doesn’t mean a lot and doesn’t clearly explain the set up. So we’ll give it a go!

No offence to our small country but…we are very small! We look huge compared to our island friends to the north, but compared to Australia, North America, Asia, Europe, Africa, South America…we are tiny. Our small size means the weather basically barrels over the top of us.

Which brings us to the “The Roaring Forties”.

This is the belt of wind at latitude 40 (south to latitude 50) over the Southern Ocean that sailors centuries ago named. Unlike the northern hemisphere, which has a lot of land at this latitude, the Southern Hemisphere in the 40s is mostly ocean with just tips of land – like Tasmania, New Zealand’s South Island and the very southern portion of South America the only areas that briefly jut out into this area. With a lack of land to slow things down the wind whips up across the sea, fuelled by storms these strong winds swirl around Antarctica quickly.

These westerly winds blast over the South Island and the lower portion of the North Island. In fact, the Roaring Forties stops northwards at about Whanagnui. North of that you’re outside of the Roaring Forties.

This link here from NOAA (US Government) explains how the Roaring Forties are created.

So when you’re a few islands in the middle of no where, surrounded by ocean and more than half of your country juts out south directly into the Roaring Forties belt of strong westerlies, it’s no real surprise that NZ keeps getting shots of wind when we think it should be calmer.

OUR MOUNTAINS MAKE IT WORSE – AND BETTER
New Zealand’s mountains have a giant impact on our weather. They create floods and droughts by holding up rain clouds in one region and blocking rain from reaching the next region. This process also makes for some spectacular high clouds and ‘UFO’ clouds in our east and central parts.  The winds coming over the Southern Alps and our main ranges also speed up – giving us those gale nor’westers which are so well known in Canterbury or Wellington.

These same mountains and ranges also make other areas very calm and sheltered, like Nelson and Bay of Plenty. Inland areas away from the sea are often much calmer too, like Taumarunui in the north and Alexandra in the south.

NZ HAS THREE MAIN WIND TUNNELS:

  1. Foveaux Strait
  2. Cook Strait / Wellington
  3. Auckland City – which is just over 1km wide at its narrowest point between Tasman Sea (west) and Pacific Ocean (east). 

These three areas can often have windy weather lingering longer all year round (especially coastal areas or exposed areas) simply due to the effect the Roaring Forties has around NZ and surface winds looking for the path of least resistance. (A bit like how water flows through the lowest points on land, like valleys, the wind flows through our wind tunnels between islands like the Straits, or at our lower/narrow points like Auckland, and to some degree Manawatu and Wairarapa partially fuelled by the Cook Strait tunnel but also the low gap in the Manawatu Gorge).


FORGET THE ROARING FORTIES, HOW ABOUT THE FURIOUS FIFTIES AND THE SCREAMING SIXTIES?!
The closer you get to Antarctica the worse those winds get and the bigger those Southern Ocean storms are. The creative names given by sailors centuries ago clearly sums up just how terrifying this part of the planet is. There is no where else on earth that is anything like the Roaring Forties, Furious Fifties and Screaming Sixties.

And remember, lil ol’ New Zealand has half of itself parked in those Roaring Forties forever. (well, maybe in millions of years NZ might have moved on!).


A DIFFERENT PERSPECTIVE:
On maps North is always straight up. But if we flip the map of New Zealand so that “up” looks directly towards where our predominant wind (W to SW) comes from it paints a different picture in your mind about where we sit on the planet. It helps understand why we get so many windy events, sometimes for weeks – even months – at a time.

WeatherWatch.co.nz often says NZ only has a two month winter and a two month summer – the other eight months are windy west to south west times – or an extended spring and autumn if you like.

– By WeatherWatch.co.nz head forecaster Philip Duncan.

Comments

Guest on 6/01/2020 8:23pm

Could I ask a question my daughter asked me. She believes this year has been the windiest yet that she remembers is this true. Has this year been extra windy?

WW Forecast Team on 6/01/2020 9:22pm

We will always have years where it’s quite windy and others where it isn’t as bad. This summer so far has certainly been fairly windy. But it will eventually calm down again.

As to whether it’s the windiest year ever that information I don’t have at my finger tips unfortunately, would require a message through to NIWA or Metservice.

Cheers
WW

Paul on 6/01/2020 5:08am

Hi there.
Thanks for the interesting article on the roaring forties and why NZ is so windy. Your comment that you believe NZ effectively has 2 months of summer and 2 months of winter caught my eye. Given that we’re approaching the halfway mark of the official summer and it hasn’t really felt like summer yet, I was wondering what are the two months that you consider to be summer and the same for the two months of winter
Thanks
Paul

WW Forecast Team on 6/01/2020 5:14am

Hi there Paul, thanks for the comment. We usually go with mid Jan to mid March. Some years it’s Jan/Feb. Every now and then we do get all 3 months (Dec, Jan, Feb), but more often than not NZ (nationally) has a fairly short summer – but likewise a fairly short winter too.

Cheers
Phil D

 

Lou on 6/01/2020 4:53am

Great article thanks! I particularly liked your note about our three wind tunnels. It’s only when you live in Auckland you understand how windy it is (especially today).

WW Forecast Team on 6/01/2020 5:15am

Thanks very much – and yes! Definitely today (and Tuesday too…sigh!)

– WW

Anthony Baker on 4/01/2020 8:18pm

It’s interesting what the Met Service says about the roaring Forties. I read a book about the climate of New Zealand a few years back and haven’t forgotten it once.
Thank you for the information.

WW Forecast Team on 6/01/2020 5:15am

Hi Anthony, you’re very welcome. 🙂

– WW

Tracey on 4/01/2020 7:35pm

I’m glad I took the time to read this!! It was interesting because it was clear and easy to understand and I appreciate the visuals too. I’m going to include this site in my (primary) class teaching. Good job and thank you!

WW Forecast Team on 6/01/2020 5:16am

Thanks very much! And we look to provide more eductation pieces like this in 2020 🙂 

– WW

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