Stormy outlook: Is the Bay's extreme weather here to stay?

By Cassandra Mason

New Zealand has been battered by one extreme weather event after another. With June the hottest on record, is our volatile climate an anomaly or a taste of what’s to come? Cassandra Mason investigates.

A man sails over flooded rugby fields in Greerton.
A man sails over flooded rugby fields in Greerton.

Multiple storms and widespread flooding in recent months have uprooted trees, cut power to thousands of homes, and cost one woman her life.

In some parts of the country blossom is already threatening to bloom, but unexpected cold snaps have Kiwis shivering indoors.

Ski fields and retailers have been feeling the sting of the unpredictable season, with little snow and winter clothing still clogging the shelves.

Wild weather's costly legacy

Severe storms and flooding in Northland and parts of Auckland early last month caused widespread damage to homes and infrastructure, and cut power to thousands of properties.

Flooding was so severe 28-year-old mother Talia Smith was killed when raging waters in the swollen Waitangi River pulled her under near Paihia.

It was one of the longest and most damaging storms to hit in years, and Northland faces a lengthy recovery phase, including repairs to roading, sewage treatment and water.

A month earlier damage caused by another storm between June 9 and June 11 cost insurers $30 million.

 Talia Smith died after being swept away in Northland floods. Photo / File
Talia Smith died after being swept away in Northland floods. Photo / File

The storm, which hit much of the Auckland region and east coast of the North Island, brought down trees and power lines and cut power to more than 80,000 residents.

It also caused surface flooding as far south as Marlborough and Canterbury.

Severe flooding in Nelson and the West Coast in recent months also pointed to an unusually active season.

The storms have taken their toll on agriculture too, which Federated Farmers national president William Rolleston described as "disruptive and expensive".

"The floods in Northland are continuing to have a pretty severe effect on agriculture up there, with feed having to be brought in with a huge amount of repairs to do now the water has subsided."

Extreme weather tests the resilience of farmers and livestock alike.

"Animals feel miserable in miserable weather, just like humans do."

However, while the warm winter has brought storms, there have been fewer frosts and higher temperatures, which are good growing conditions, Dr Rolleston says.

"Certainly areas like Hawke's Bay, which were in drought a year ago, have had a pretty good season."

A warmer world

According to the National Institute of Water and Atmospheric Research (Niwa), New Zealand experienced its warmest June since national records began in 1909.

Niwa forecaster Chris Brandolino says the warmer the temperatures, the wilder the weather. "June was the warmest on record for New Zealand. [In June] we had predominantly east and north-east winds so you're looking at winds coming from a place that cold air doesn't come from."

Irrigation dam overflow near Kaikohe. Photo / File
Irrigation dam overflow near Kaikohe. Photo / File

Ocean temperatures that have been running about 1C above average since January last year are a recipe for rainfall.

"When ocean water is a bit warmer than it usually is, that's fuel for rain.

"If you have two pots of water, one is at 40C and one's at 10C, the one that's warmer is going to give off a lot more steam and energy into the atmosphere."

Warmer water combined with warmer winds serve as "fuel" for storms.

"Typically those heavy duty downpours are more likely in warm, humid conditions."

While it's hard to pin a single flood, drought, storm or other weather event as a result of climate change, Mr Brandolino does believe extreme weather will only become more frequent as temperatures rise.

"One of the things we're expecting are more extreme rainfall events, [and] more significant weather events in general.

"It's one of the indicators of a changing climate."

A sombre warning

The State of the Climate in 2013 report, released last month by the American Meteorological Society, shows the planet is continuing to heat up.

The report, compiled by 425 scientists from 57 countries, shows the winter of 2013 was New Zealand's warmest ever, with the year turning out third-warmest overall.

Victoria University climate scientist Associate Professor James Renwick, who helped present the report, said climate change didn't mean "a few extra nice days in summer".

The weather that wreaked havoc in Northland last month showed what Kiwis could expect in the future, he told the New Zealand Herald.

"The region has had a number of very dry summers in recent years and has now experienced much higher than normal rainfall.

"Going from drought conditions to very heavy rain and flooding is exactly the kind of pattern we can expect from climate change."

The long-term effects of climbing temperatures are also making their mark. Recent research shows one-third of the permanent snow and ice on the Southern Alps has vanished in less than four decades.

Using Niwa aerial surveys, three Kiwi researchers calculated the alps' ice volume has shrunk by 34 per cent - a process that is accelerating.

However, some offer a more settling explanation for the turbulent climate.

A different perspective

WeatherWatch head analyst Philip Duncan says this year's weather hasn't been more extreme - it's just hit more populated areas.

"Anything that affects Auckland or Northland tends to make the headlines a lot more than something that affects Southland and Otago.

A man sails over flooded rugby fields in Greerton.
A man sails over flooded rugby fields in Greerton.

"A lot more of the news coverage this year from storms has been more because of where they've been rather than an increase in severe weather."

The South Island has been a long sufferer of extreme weather, with Southland, Canterbury and the West Coast frequently dusting themselves off after bouts with Mother Nature.

Many of this year's storms have been localised, affecting only small pockets of the country.

The flash flooding that soaked Nelson in June was a narrow strip of rain "as wide as Nelson itself", Mr Duncan says.

"A lot of this severe weather is created by our geography, not our lows and highs."

Rising temperatures undoubtedly spell more severe weather, but it's too soon to tell whether there's a direct correlation between recent spells and global warming, Mr Duncan says.

"A lot of [the severe weather] is to do with the warming of the planet, however, you can't necessarily say that our recent warm winters are a direct result of that.

"In time, it will almost likely show that, but at this stage there's not enough evidence to say that our warm winters over the last few years are due to climate change."

Kiwis can expect average to above average temperatures through August, Mr Duncan says.

"We see no end in sight of this warmer weather pattern.

"Even though we've got some cold snaps coming in it's not going to last."

Niwa predicts temperatures in August and September will be likely above average across all regions, while rainfall will be about normal.

- APNZ

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