NZ Herald
  • Home
  • Latest news
  • Video
  • New Zealand
  • Sport
  • World
  • Business
  • Entertainment
  • Podcasts
  • Quizzes
  • Opinion
  • Lifestyle
  • Travel
  • Viva
  • Weather forecasts

Subscriptions

  • Herald Premium
  • Viva Premium
  • The Listener
  • BusinessDesk

Sections

  • Latest news
  • New Zealand
    • All New Zealand
    • Crime
    • Politics
    • Education
    • Open Justice
    • Scam Update
  • Budget 2025
  • On The Up
  • World
    • All World
    • Australia
    • Asia
    • UK
    • United States
    • Middle East
    • Europe
    • Pacific
  • Business
    • All Business
    • MarketsSharesCurrencyCommoditiesStock TakesCrypto
    • Markets with Madison
    • Media Insider
    • Business analysis
    • Personal financeKiwiSaverInterest ratesTaxInvestment
    • EconomyInflationGDPOfficial cash rateEmployment
    • Small business
    • Business reportsMood of the BoardroomProject AucklandSustainable business and financeCapital markets reportAgribusiness reportInfrastructure reportDynamic business
    • Deloitte Top 200 Awards
    • CompaniesAged CareAgribusinessAirlinesBanking and financeConstructionEnergyFreight and logisticsHealthcareManufacturingMedia and MarketingRetailTelecommunicationsTourism
  • Opinion
    • All Opinion
    • Analysis
    • Editorials
    • Business analysis
    • Premium opinion
    • Letters to the editor
  • Sport
    • All Sport
    • OlympicsParalympics
    • RugbySuper RugbyNPCAll BlacksBlack FernsRugby sevensSchool rugby
    • CricketBlack CapsWhite Ferns
    • Racing
    • NetballSilver Ferns
    • LeagueWarriorsNRL
    • FootballWellington PhoenixAuckland FCAll WhitesFootball FernsEnglish Premier League
    • GolfNZ Open
    • MotorsportFormula 1
    • Boxing
    • UFC
    • BasketballNBABreakersTall BlacksTall Ferns
    • Tennis
    • Cycling
    • Athletics
    • SailingAmerica's CupSailGP
    • Rowing
  • Lifestyle
    • All Lifestyle
    • Viva - Food, fashion & beauty
    • Society Insider
    • Royals
    • Sex & relationships
    • Food & drinkRecipesRecipe collectionsRestaurant reviewsRestaurant bookings
    • Health & wellbeing
    • Fashion & beauty
    • Pets & animals
    • The Selection - Shop the trendsShop fashionShop beautyShop entertainmentShop giftsShop home & living
    • Milford's Investing Place
  • Entertainment
    • All Entertainment
    • TV
    • MoviesMovie reviews
    • MusicMusic reviews
    • BooksBook reviews
    • Culture
    • ReviewsBook reviewsMovie reviewsMusic reviewsRestaurant reviews
  • Travel
    • All Travel
    • News
    • New ZealandNorthlandAucklandWellingtonCanterburyOtago / QueenstownNelson-TasmanBest NZ beaches
    • International travelAustraliaPacific IslandsEuropeUKUSAAfricaAsia
    • Rail holidays
    • Cruise holidays
    • Ski holidays
    • Luxury travel
    • Adventure travel
  • Kฤhu Mฤori news
  • Environment
    • All Environment
    • Our Green Future
  • Talanoa Pacific news
  • Property
    • All Property
    • Property Insider
    • Interest rates tracker
    • Residential property listings
    • Commercial property listings
  • Health
  • Technology
    • All Technology
    • AI
    • Social media
  • Rural
    • All Rural
    • Dairy farming
    • Sheep & beef farming
    • Horticulture
    • Animal health
    • Rural business
    • Rural life
    • Rural technology
    • Opinion
    • Audio & podcasts
  • Weather forecasts
    • All Weather forecasts
    • Kaitaia
    • Whangฤrei
    • Dargaville
    • Auckland
    • Thames
    • Tauranga
    • Hamilton
    • Whakatฤne
    • Rotorua
    • Tokoroa
    • Te Kuiti
    • Taumaranui
    • Taupล
    • Gisborne
    • New Plymouth
    • Napier
    • Hastings
    • Dannevirke
    • Whanganui
    • Palmerston North
    • Levin
    • Paraparaumu
    • Masterton
    • Wellington
    • Motueka
    • Nelson
    • Blenheim
    • Westport
    • Reefton
    • Kaikลura
    • Greymouth
    • Hokitika
    • Christchurch
    • Ashburton
    • Timaru
    • Wฤnaka
    • Oamaru
    • Queenstown
    • Dunedin
    • Gore
    • Invercargill
  • Meet the journalists
  • Promotions & competitions
  • OneRoof property listings
  • Driven car news

Puzzles & Quizzes

  • Puzzles
    • All Puzzles
    • Sudoku
    • Code Cracker
    • Crosswords
    • Cryptic crossword
    • Wordsearch
  • Quizzes
    • All Quizzes
    • Morning quiz
    • Afternoon quiz
    • Sports quiz

Regions

  • Northland
    • All Northland
    • Far North
    • Kaitaia
    • Kerikeri
    • Kaikohe
    • Bay of Islands
    • Whangarei
    • Dargaville
    • Kaipara
    • Mangawhai
  • Auckland
  • Waikato
    • All Waikato
    • Hamilton
    • Coromandel & Hauraki
    • Matamata & Piako
    • Cambridge
    • Te Awamutu
    • Tokoroa & South Waikato
    • Taupล & Tลซrangi
  • Bay of Plenty
    • All Bay of Plenty
    • Katikati
    • Tauranga
    • Mount Maunganui
    • Pฤpฤmoa
    • Te Puke
    • Whakatฤne
  • Rotorua
  • Hawke's Bay
    • All Hawke's Bay
    • Napier
    • Hastings
    • Havelock North
    • Central Hawke's Bay
    • Wairoa
  • Taranaki
    • All Taranaki
    • Stratford
    • New Plymouth
    • Hฤwera
  • Manawatลซ - Whanganui
    • All Manawatลซ - Whanganui
    • Whanganui
    • Palmerston North
    • Manawatลซ
    • Tararua
    • Horowhenua
  • Wellington
    • All Wellington
    • Kapiti
    • Wairarapa
    • Upper Hutt
    • Lower Hutt
  • Nelson & Tasman
    • All Nelson & Tasman
    • Motueka
    • Nelson
    • Tasman
  • Marlborough
  • West Coast
  • Canterbury
    • All Canterbury
    • Kaikลura
    • Christchurch
    • Ashburton
    • Timaru
  • Otago
    • All Otago
    • Oamaru
    • Dunedin
    • Balclutha
    • Alexandra
    • Queenstown
    • Wanaka
  • Southland
    • All Southland
    • Invercargill
    • Gore
    • Stewart Island
  • Gisborne

Media

  • Video
    • All Video
    • NZ news video
    • Business news video
    • Politics news video
    • Sport video
    • World news video
    • Lifestyle video
    • Entertainment video
    • Travel video
    • Markets with Madison
    • Kea Kids news
  • Podcasts
    • All Podcasts
    • The Front Page
    • On the Tiles
    • Ask me Anything
    • The Little Things
    • Cooking the Books
  • Cartoons
  • Photo galleries
  • Today's Paper - E-editions
  • Photo sales
  • Classifieds

NZME Network

  • Advertise with NZME
  • OneRoof
  • Driven Car Guide
  • BusinessDesk
  • Newstalk ZB
  • What the Actual
  • Sunlive
  • ZM
  • The Hits
  • Coast
  • Radio Hauraki
  • The Alternative Commentary Collective
  • Gold
  • Flava
  • iHeart Radio
  • Hokonui
  • Radio Wanaka
  • iHeartCountry New Zealand
  • Restaurant Hub
  • NZME Events

SubscribeSign In
Advertisement
Advertise with NZME.
Home / New Zealand

Weather: Why NZ's spring is about to get wet - but not warm

Jamie Morton
By Jamie Morton
Multimedia JournalistยทNZ Heraldยท
5 Oct, 2019 11:40 PM6 mins to read

Subscribe to listen

Access to Herald Premium articles require a Premium subscription. Subscribe now to listen.
Already a subscriber?  Sign in here

Listening to articles is free for open-access contentโ€”explore other articles or learn more about text-to-speech.
โ€Œ
Save

    Share this article

Central and lower parts of both island could be in for big bouts of rain over the next three months - partly thanks to a climate driver called the Indian Ocean Dipole. Photo / NZ Herald
Central and lower parts of both island could be in for big bouts of rain over the next three months - partly thanks to a climate driver called the Indian Ocean Dipole. Photo / NZ Herald

Central and lower parts of both island could be in for big bouts of rain over the next three months - partly thanks to a climate driver called the Indian Ocean Dipole. Photo / NZ Herald

Just as a rare and dramatic event high above Antarctica eases its icy influence on our weather, forecasters are warning another climate phenomenon is taking centre stage.

What's called the Indian Ocean Dipole, or IOD, could mean big bouts of rain in some parts of the country, in a lead-up to summer likely to lean on the cooler side.

New Zealand has only just seen the effects of the strongest stratospheric warming event ever observed in the Southern Hemisphere.

At its peak, this natural phenomenon lifted temperatures in the stratosphere above the South Pole - that's 30km to 50km above ground - to an incredible 70C above average.

The result was a disruption to the polar vortex which swirls around Antarctica, normally keeping its cold effectively locked up.

Advertisement
Advertise with NZME.
Advertisement
Advertise with NZME.

Niwa forecaster Ben Noll said the vortex was displaced toward South America, bringing bitterly cold conditions to Chile and Argentina - and with knock-on effects for New Zealand.

"In weather circles, we use a term called 'teleconnection' - that's where an event being observed some distance away is also having an influence on the weather patterns where you are," he said.

"So what we saw was that displaced cold being teleconnected to us here. What that meant for us was more southerly winds, frequent cold snaps, several rounds of snow and the fourth coldest September since the turn of the century."

Advertisement
Advertise with NZME.

September came in at 0.1C below the 30-year average - breaking a streak of more than 30 months above average temperatures - with parts of the South Island like Nelson and Marlborough seeing the biggest shifts.

While the dissipating event wasn't quite done with our weather, Noll expected that any further cold blasts it created would come within the first half of this month.

As it was fading, New Zealand would begin to feel a greater influence from what's being described as one of the strongest IOD events ever.

An oceanic seesaw

The IOD typically had three phases: neutral, positive and negative.

Discover more

New Zealand

Climate change: How hard will extreme weather hit NZ?

21 Sep 10:12 PM
New Zealand

Holi-yay: Sunshine on way after bleak week

05 Oct 07:01 AM
New Zealand

Rain forecast for most and heavy rain warnings for the south

17 Oct 09:53 PM

Events usually kicked off around May or June, peaked between August and October and then rapidly decayed when the monsoon arrived in the Southern Hemisphere around the end of spring.

Have 2๏ธโƒฃ minutes to spare?

Learn about one of New Zealand's primary climate drivers for the upcoming season, the Indian Ocean Dipole ๐Ÿ‘ฉโ€๐Ÿ”ฌ ๐Ÿ‘จโ€๐Ÿ”ฌ pic.twitter.com/6HhaBV0NTB

โ€” NIWA Weather (@NiwaWeather) October 5, 2019

In a positive phase, westerly winds weakened along the equator, allowing warm water to shift towards Africa.

Changes in the winds also allowed cool water to rise up from the deep ocean in the east.

This ultimately set up a temperature difference across the tropical Indian Ocean, with cooler than normal water in the east and warmer than normal water in the west.

Auckland's skyline, blanketed in spring rain this month. Photo / Michael Craig
Auckland's skyline, blanketed in spring rain this month. Photo / Michael Craig

Noll described it as a "seesaw" of sea surface temperatures.

"That seesaw creates a dipole that brings high pressure over the cool waters in the east - and low pressure over those warm seas in the west."

Advertisement
Advertise with NZME.

In Australia, this had already contributed to the unusual dryness much of the country had been experiencing.

The Indian Ocean Dipole is up to +1.76C above normal. This is the 16th strongest IOD weekly value since the archive began in 1981. In terms of years, 2019 ranks now as the third strongest IOD event in the archive. The strongest +IOD was Oct 1994 (+2.57C), second Nov. 1997 (+2.5C) pic.twitter.com/XdOMYtqHZ2

โ€” MJVentrice (@MJVentrice) October 2, 2019

"And here in New Zealand, it's been linked to what was still quite a dry September for the South Island specifically. We've seen storage in the hydro lakes there decline quite dramatically."

As spring marched on, Noll said we could expect to see the IOD play a more noticeable role, by driving increase in westerly winds.

"What that means is those western areas of the South Island which have been quite dry will likely turn wet as the season unfolds. Obviously, that's not ideal for those folks who are caravaning around the south."

A strongly positive Indian Ocean Dipole will suppress convection
across the Maritime Continent over the next few months.

The MJO will ๐—ฎ๐˜ƒ๐—ผ๐—ถ๐—ฑ phases ๐Ÿฏ-๐Ÿฐ but ๐’‡๐’‚๐’—๐’๐’“ phase 1.

What does that mean for where you live? [Oct-Feb ๐Ÿ‘‡] pic.twitter.com/2paNXwItIy

โ€” Ben Noll (@BenNollWeather) September 27, 2019

In November wet weather was likely for the central and lower parts of both islands, including Raglan, Hamilton, Rotorua down to Ohakune and northern Taranaki.

The wet trend would continue into December with more rainfall than average in the South Island and the west and upper north of the North Island.

Advertisement
Advertise with NZME.

Noll pointed out that a positive IOD observed last year - and weaker than the current system - was linked with an extreme rainfall event that hit Otago.

"That gives you an idea that we may need to be vigilant or on high alert about the strong driver that we have in the climate system now, and how it might influence rainfall and westerlies as we go through the next three months."

The wet didn't necessarily come with warmth: when the IOD was strongly positive, temperatures historically hedged in the cooler direction.

Cooler trend

Added to that was the fact New Zealand's coastal sea temperatures were all sitting at below average - another departure from the past two years' balmy trend.

"It doesn't mean we won't see warm weather at times, but when you have warm seas, often the air temperature tends to paddle in the same direction."

Forecasters say the coming months could be on the wetter side - and there's little in the mix to make things warmer. Photo / Paul Taylor
Forecasters say the coming months could be on the wetter side - and there's little in the mix to make things warmer. Photo / Paul Taylor

Several models also indicate the polar region below New Zealand will be characterised by higher than normal pressure over the next three months, allowing for a ring of low pressure to develop around the mid-latitudes.

Advertisement
Advertise with NZME.

That meant that, although seasonal temperatures would still climb from October through December, the door to the Southern Ocean might remain ajar, allowing air masses from the south to continually influence our weather.

And out in the equatorial Pacific, oceans were sitting in an ENSO-neutral state - or in neither La Nina or El Nino conditions.

Noll said a subtle hint of the latter over the final months of 2019 - but not the conventional type of El Nino that brought hotter conditions to eastern areas.

Overall, Niwa's latest climate outlook predicted little chance of above-average temperatures anywhere between now and December.

It remained to be seen what the would mean for 2019's hitherto hot run in the record books.

The January to August period had come in at 0.96C above average โ€“ second only to the corresponding stretch in 2016, which was 1.10C above average.

Advertisement
Advertise with NZME.
Save

    Share this article

Latest from New Zealand

New Zealand

Five people injured in crash involving car and pedestrian in Christchurch

24 May 04:00 AM
New Zealand

Pork crackling snacker breaks tooth on birthday, leading to small claims clash

24 May 04:00 AM
New Zealand

Afternoon quiz: In karate, what does 'kata' refer to?

24 May 03:00 AM

The Hire A Hubby hero turning handyman stereotypes on their head

sponsored
Advertisement
Advertise with NZME.
Recommended for you
Make the most of feijoa season with roasted feijoa, bacon and feta salad
Lifestyle

Make the most of feijoa season with roasted feijoa, bacon and feta salad

24 May 04:00 AM
Pork crackling snacker breaks tooth on birthday, leading to small claims clash
New Zealand

Pork crackling snacker breaks tooth on birthday, leading to small claims clash

24 May 04:00 AM
Boeing to pay $1.9b to settle criminal probe into fatal plane crashes
World

Boeing to pay $1.9b to settle criminal probe into fatal plane crashes

24 May 03:31 AM
Black Ferns v USA: Pacific Four Series test
Black Ferns

Black Ferns v USA: Pacific Four Series test

24 May 03:25 AM
Afternoon quiz: In karate, what does 'kata' refer to?
New Zealand

Afternoon quiz: In karate, what does 'kata' refer to?

24 May 03:00 AM

Latest from New Zealand

Five people injured in crash involving car and pedestrian in Christchurch

Five people injured in crash involving car and pedestrian in Christchurch

24 May 04:00 AM

The Serious Crash Unit has been notified and traffic management is in place.

Pork crackling snacker breaks tooth on birthday, leading to small claims clash

Pork crackling snacker breaks tooth on birthday, leading to small claims clash

24 May 04:00 AM
Afternoon quiz: In karate, what does 'kata' refer to?

Afternoon quiz: In karate, what does 'kata' refer to?

24 May 03:00 AM
'Salt in the wound': Anger as ex uses legal aid to fight case he lost in Family Court

'Salt in the wound': Anger as ex uses legal aid to fight case he lost in Family Court

24 May 02:00 AM
Gold demand soars amid global turmoil
sponsored

Gold demand soars amid global turmoil

NZ Herald
  • About NZ Herald
  • Meet the journalists
  • Newsletters
  • Classifieds
  • Help & support
  • Contact us
  • House rules
  • Privacy Policy
  • Terms of use
  • Competition terms & conditions
  • Our use of AI
Subscriber Services
  • NZ Herald e-editions
  • Daily puzzles & quizzes
  • Manage your digital subscription
  • Manage your print subscription
  • Subscribe to the NZ Herald newspaper
  • Subscribe to Herald Premium
  • Gift a subscription
  • Subscriber FAQs
  • Subscription terms & conditions
  • Promotions and subscriber benefits
NZME Network
  • The New Zealand Herald
  • The Northland Age
  • The Northern Advocate
  • Waikato Herald
  • Bay of Plenty Times
  • Rotorua Daily Post
  • Hawke's Bay Today
  • Whanganui Chronicle
  • Viva
  • NZ Listener
  • What the Actual
  • Newstalk ZB
  • BusinessDesk
  • OneRoof
  • Driven CarGuide
  • iHeart Radio
  • Restaurant Hub
NZME
  • About NZME
  • NZME careers
  • Advertise with NZME
  • Digital self-service advertising
  • Book your classified ad
  • Photo sales
  • NZME Events
  • ยฉ Copyright 2025 NZME Publishing Limited
TOP
search by queryly Advanced Search