Wet and wild the story of New Zealand’s extreme weather – Stuff.co.nz

Posted: November 7, 2021 at 12:13 pm

From wind strong enough to toss two train carriages, to seven-storey waves ripping buoys out of the Southern Ocean, New Zealand's weather is wildly changeable. And as a new book shows, it's only going to get wilder.

Wellington once had a spell of seven scorching days, clocking in at 25 degrees C or more.

The Department of Health published a column in The Evening Post recommending tepid baths and eating tomatoes and oranges to keep cool.

But good luck finding anyone who remembers that sweltering stretch it happened in 1934.

Thats one of the fun facts in a new book by New Zealands MetService, New Zealands Wild Weather, which explores the history and science behind our worst weather.

Mark Gee

Heavy rain falling from cumulonimbus cloud over Lyall Bay in Wellington.

READ MORE:* Residents leave homes, state of emergency declared in Gisborne amid flooding and rising river levels* Super tides tear up concrete and damage homes on South Coast* On a hot streak: Warming climate a wake up call

A week of warmth hardly seems wild, but as MetService meteorologist and weather communicator, Lisa Murray, points out, it does illustrate why Kiwis are so obsessed with the weather.

The thing I love about the weather, is how much it changes and how interesting it is... Its very rare in New Zealand that youd have a week of the same weather.

Thats unless you live in Hamilton, which in 1978 had 32 days straight of 25C or warmer.

On an international scale, our weather is mostly middling, with a chance of extremes. We get tornadoes, but not as destructive as Americas; we get hail, but not as big as Indias cricket ball-sized smashers; we get droughts, but not as badly as Australias sunbaked earth.

Cameron Burnell/Stuff

The changeability of New Zealands weather is what makes it interesting for meteorologist Lisa Murray. (File photo)

A long, skinny landmass, our weather is shaped by the ocean swirling around us, the breath of Antarctica blowing north, cyclones spinning down from the tropics and the mountainous seams that stitch together the wet west and drought-prone east coasts.

We get all sorts in New Zealand, Murray says. As a forecaster, if you can forecast in New Zealand, you can forecast anywhere. Its that kind of challenging environment. We get big snow dumps, along with heavy rain events, really strong wind events, and we have such a different terrain.

And when wild weather hits, it hits hard.

CIVIL DEFENCE

The Waiho Bridge taken out by the flooded Waiho River, in March 2019.

We started crossing over and people were looking at us as if we were crazy. We got over the other side and I said: That doesnt look too good. We parked up in the middle of the road so people couldnt go past, and we saw bits of the bridge hanging off... It was pretty dramatic. Within 20 minutes it was all gone. DOC operations manager for South Westland, Wayne Costello, on crossing the Waiho Bridge just before it was taken out by flood waters , in March 2019.

In Murrays 15 years at MetService, standout wild weather includes ex-cyclones Gita and Fehi, which slammed into New Zealand within weeks of each other, in 2018. She was working to get road workers in before the mayhem, so they could manage any damage.

We have to be on our top game. So you have the adrenaline running through you constantly, because this is really important. These forecasts are life and death.

Kent Blechynden/Stuff

Severe weather forecaster Erick Brenstrum on the job in 2006.

Retired severe weather forecaster, Erick Brenstrum, spent 43 years in the job, starting in 1974. He remembers ex-tropical Cyclone Bola stalling over Gisborne and Hawkes Bay in 1988, dumping rain for three days and causing catastrophic flooding and landslides.

That was one of the most damaging storms to have battered New Zealand in the 20th century, alongside the 1968 storm that wrecked the Wahine ferry and an unnamed howler in 1936.

Cropp River on the West Coast holds the record for the heaviest 12 months of rainfall, at 18,413 millimetres, from October 29, 1997, to October 29, 1998.

Grant Gillingham, 5, admires the view while his dad Roger surveys the damage after floodwaters submerged a cottage on their Waerenga-o-kuri farm, south of Gisborne, during Cyclone Bola.

Theres a weird atmosphere in the forecasting room when a massive event hits both relief and regret at the forecast proving accurate, Brenstrum says.

There's that funny, sad mixture, that it's awful that the weather is doing damage and destruction, but how wonderful that, with the technology we have, we've been able to tell people that this is the place it was going to happen with a day or two's warning.

In his four decades as a forecaster, Brenstrum noticed temperatures creeping up. That means wetter weather is coming. Warmer air can carry more water vapour, but its worse than that. Imagine a pot boiling on the stove. Turning water to steam takes heat, so when that vapour is turned back to water droplets, in clouds, that heat is released. That increases the upward motions in the storm, which increases the rate of rainfall.

It doubles the effect, basically. So thats why, around the world, and in New Zealand, rainfall records are being broken.

Ryan Anderson/Stuff

A house in Papatoetoe was destroyed by a tornado in June.

Something picked me up and landed me 150 metres away in another paddock and totally wrecked the bike...The thing went through so fast I didnt have time to think. By the time I came to my senses it was gone, it took the hay shed with it and then disappeared. Took part of the roof off the farm cottage and left the young couple inside looking at the blue sky above them. Manukau Heads farmer Lawrie Coe, on being tossed by a tornado in September 1990.

However you slice the numbers, the capital is New Zealands windiest city. From 2011 to 2020, Wellington airport recorded the strongest gust (146kmh), the highest number of days with gusts of 90kmh or more (22) and the longest distance wind travels past a point during a day, called the wind run (602km).

It also holds the unofficial record for the countrys worst wind ever a 267kmh gust measured during the Wahine storm, at an uncertified site on Wellingtons South Coast.

The highest official reading was 250kmh, at Mt John in Canterbury, on April 18, 1970. Thats about as fast as a Porsche Cayenne at full throttle.

The nations biggest wind trap, however, is Fiordlands Puysegur Point, where lighthouse keepers apparently gave up farming sheep because they kept being blown onto the rocks below.

Angry air has claimed lives in New Zealand, including four children who died in 1880, when a mighty gust blew two train carriages off the Remutaka Incline north of Wellington, on an exposed stretch appropriately known as Siberia.

While New Zealand doesnt have tornadoes of the magnitude whipped up by Americas great plains, they can still be fatal. The worst happened in 1948, cutting a 180-metre swath of devastation through the Hamilton suburb of Frankton, killing three people, injuring 80 and damaging 150 houses.

Murray Clarkson

New Zealand gets about 47,000 lightning strikes on land every year.

I was enveloped by the brightest light I have ever seen I felt an instant of heat all over my body, similar to when you open up a very hot oven and get blasted by the hot air. Then the loudest explosive crack of thunder that literally vibrated my entire body. Fisheries officer Martin Williams, on being struck by lightning at Sponge Bay near Gisborne, in 2013.

The heat inside a lightning bolt is about 30,000C five times the temperature of the suns surface.

New Zealand gets about 47,000 strikes on land every year, but more than double that if you include our coastal waters. The South Islands west coast is the most frequently lightning-lit, but most strikes actually fire from cloud to cloud, rather than cloud to ground.

Supplied

The stages of thunderstorm formation. Stage 1 (left): the Cumulus stage is when warm, moist air rises forming cloud. Stage 2 (middle): the updraft strengthens and the cloud becomes a towering cumulus. When the updraft rises to the top of the troposphere, the top of the cloud freezes and spreads out into an anvil shape. This is the Mature stage. The cloud is now a cumulonimbus. A strong downdraft has formed with heavy rain, and moving air builds up electric charges, bringing thunder and lightning. Stage 3 (right): the Dissipating stage is when the downdraft dominates the updraft. The storm weakens, and the rain and electrical activity dissipate.

For a forecaster, thunderstorms are a bit of a nightmare. As New Zealands Wild Weather puts it, its like making popcorn. You know those kernels are going to burst, but you dont know in which order.

The accuracy of forecasting leapt ahead in Brenstrums 43 years. A few years before he started, someone in Christchurch would put the one daily satellite photo on a plane to Wellington airport, from where it would be sent in a taxi to the national office in Kelburn.

Temperature readings only came from land-based observation stations where weather balloons were sent up and you might get one ships observation a week from the ocean between Antarctica and Australia, where a lot of New Zealands weather comes from.

Now, high-resolution satellite images arrive at least every hour. Technology can estimate temperature anywhere, including over the ocean, and estimate wind strength from tiny waves on the sea surface.

Forecasters can even see inside thunderstorms. While theyre amazing creatures, with their ability to birth tornadoes, lightning and hail, thats about as close to them as Brenstrum cares to get.

Ive seen enough of what they can do that I really dont want to get anywhere near them.

While floods dominate the headlines, droughts generally hurt more. Between mid-2007 and mid-2017, droughts caused about $720 million of economic loss, compared with $120 million for flood damage.

Long dries and parched forests also make for fire weather and that will increase with a warming climate. High fire risk days are expected to double in some fire-prone areas.

New Zealands hottest day ever was February 7, 1973, when the North Canterbury town of Rangiora hit 42.4 C.

Barry Harcourt/Stuff

A heavy Southland snowfall making life difficult for new lambs. (File photo)

There was no sun, and any water on the roof would come down and form icicles right round the house. Anything steel like a waratah, if you tried to bend it, it would just snap off, thats how cold it was. It went on for four or five days; we were in a deepfreeze situation. I remember going to Omakau in the tractor for diesel and we ran into a warm wind which was actually blowing at about 2 C and we just thought it was summertime. Ophir farmer Sam Leask on the July 1995 freezing spell.

When Brenstrum was forecasting in Christchurch in about 1976, he opened the curtains to a world of white.

My heart leapt. Id grown up where it didnt snow and I was just overjoyed it snowed. It was a foot deep. Then after about 2 seconds of joy, my brain said That wasnt in the forecast yesterday... In terms of me experiencing weather that was not what I said it would be the day before, Ive never had a more dramatic example than that.

New Zealands coldest temperature was often cited as the -21.6C recorded in the Central Otago town of Ophir, on July 3, 1995. However, a forgotten record sheet revealed the chilliest day a bracing -25.6C actually occurred in Eweburn, Ranfurly, on July 17, 1903.

That unexpected Christchurch dump wasnt the biggest snow of Brenstrums career, though. That happened in Canterbury in 1992, when two storms hit within weeks, in July and August. More than a million lambs died.

While that was unusual in his time, incredible snows were not uncommon in the 1800s and early 1900s. One in 1895, with snow 1-2m deep in inland Canterbury and Otago, particularly stood out.

The real thing that made me fall off my chair when I read it, was this snow stayed on the ground continuously for more than four months, and that's just absolutely unheard of. To me, that's the mark of climate change, without a shadow of a doubt.

Although its been fun doing weather forecasting all these years, Im now almost crushed and appalled by the magnitude of the problem were facing with global warming... The world is staring down the barrel of really, really bad things, and we need action really fast.

New Zealands Wild Weather, by MetService (Penguin, RRP $45, Publishing 9 Nov)

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Wet and wild the story of New Zealand's extreme weather - Stuff.co.nz

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