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


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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

Roaring Forties

Know someone who experienced all this sailing to the Ice on the Navy's old Antarctic Supply Ship Endeavour in the 50s. The Roaring 40s was the scene of an incident in 1895, when the NZ Shipping Line sailing vessel the Turahina overhauled and passed the Steamer Ruapehu, of the same company, on route to Dunedin. This was the old trade route for sailing ships from Europe to the East Indies (now Indonesia,) and Australasia.

Wow that would've been a

Wow that would've been a terrifying boat trip to take. I know my parents had to briefly sail through the Roaring Forties when they travelled from England to NZ in the 1960s and 70s but that only skimmed the Roaring 40s as it docked in Wellington, not further south. Cheers for the update!
Phil D

Great story thanks! was just

Great story thanks! was just wondering about all of us in the north Island who are not in the roaring forties, why is it so windy for us? do the thirties have a phenomenon like the 40's, 50's, 60's?

Thanks very much for the

Thanks very much for the feedback and questions. To put it simply, the windy weather doesn't know the latitude lines are there. It's really just a way of showing the further south you go the worse the winds get. So it doesn't magically stop at 40 degrees, it fades out northwards. The air flow over the upper North Island is often W to SW...but just north of NZ it tends to flow SE towards Queensland. So this windy Southern Ocean airflow basically fades out over NZ like a wave does as it goes up a beach.
Cheers
Phil

Roaring 40's

I learnt about the roaring 40's from my seafaring dad. Your story is great!

Thank you Zelda! Did he

Thank you Zelda! Did he venture down that way? Scary if so!

Cheers
Phil