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Climate change is a factor in extreme autumn weather


Climate change was a factor with fall being the second hottest on record, but last season also brought extreme flooding, high winds, tornadoes and drought – while a marine heat wave hurt the aquaculture industry.

Flood damage in Tairāwhiti in March.
Photo: Tairāwhiti Civil Defense

The season also saw a new hourly record for rainfall, despite being the third hottest month of May.

Niwa said temperatures were above average or well above average in every region and one of the factors behind this was global climate change.

In May, dozens of places set record or near-record temperatures.

It was particularly hot at Castlepoint in Wairarapa, where the average temperature of 16.2 degrees Celsius was 3.5 degrees above average.

This means that the average temperature there was closer to that expected in December (16.4°C) compared to May (12.7°C).

In Middlemarch, Otago, the average daily high temperature was 16.6°C, 4.3°C above normal.

Many locations in the interior of the South Island recorded average daily high temperatures at least 3°C ​​above normal for the time of year.

Parts of Southland, Otago, Inland Canterbury and the West Coast had average temperatures more than 2C above average.

The very warm air temperatures were the result of more frequent airflows from the north, consistently warmer than average sea surface temperatures across the country, and climate change.

New Zealand king King Salmon hoped that the extension of his Te Pangu Bay farm would prevent salmon from dying in hotter summers.

NZ King Salmon has been forced to close farms due to warming water temperatures.
Photo: Supplied / NZKS

Meanwhile, a prolonged ocean heat wave continues with record temperatures for April – some places up to 5 degrees warmer than normal.

NZ King Salmon has been forced to close farms and will lay off more than 100 staff due to warming water temperatures caused by climate change.

The company reported a net loss of $55.7 million in fiscal 2022.

For the first time, there has been a massive bleaching of native sea sponges in Aotearoa.

Sea temperatures are almost certainly to blame, with scientists fearing what it could mean for the whole Fiordland ecosystem.

Fall had it all – tornadoes, record rainfall, droughts and floods

This month of March was the eighth hottest on record, April the ninth hottest and May the third hottest.

Middlemarch has had its driest autumn – with records dating back to 1896.

Invercargill experienced a dry spell from March 14 to 31, contributing to a meteorological drought in Southland.

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Flooding in central Hawke’s Bay in May.
Photo: RNZ / Jake McKee

But it was Wairoa’s second wettest fall on record, driven by two extreme rainfall events in March and April.

On March 21, rain fell at a rate leading to the second wettest hour on record in the Auckland region – North Shore recorded 76.8mm of rain in an hour between 8am and 9am.

At Maungatapere near Whangārei, 103 mm of rain was recorded from 4 a.m. to 5 a.m., making it the new national hourly rainfall record for a low-altitude station (less than 500 meters above sea level). ).

Whangārei also observed its wettest hour on record (64.4 mm) since at least January 1979.

On March 23, a state of emergency was declared in Tairāwhiti as the river level rose rapidly, prompting evacuations in a number of townships, destroying roads and bridges, and cutting off some communities.

There was another storm on April 13 which again caused flooding in Gisborne and Hawke’s Bay.

On May 20, a woman died after being struck by a windblown tree in Cambridge as a probable tornado struck Levin, damaging dozens of homes while a hailstorm in nearby Ōhau caused extensive damage to property and crops.

From May 8 to 9, heavy rains on the west coast caused several large landslides and surface flooding

There were at least two more likely tornadoes in Waikanae on the Kāpiti Coast earlier this week, with roofs ripped off at least four properties.

A tree affected by the probable tornado in Levin on May 20

Meanwhile, according to Niwa’s New Zealand Drought Monitor, dry weather conditions were present in the southern parts of Southland and Stewart Island throughout the second half of March.

Rainfall was below normal to well below normal in parts of Northland, Auckland, Gisborne, Hawke’s Bay, Wairarapa, Canterbury (south of Christchurch), Otago and South west of Southland.

Akaroa and Matamata were the driest places in New Zealand compared to normal, with just 24% of normal May rainfall recorded, respectively.

In Akaroa, it was the second driest May since records began in 1977.

Winter will be warmer and wetter than average

New Zealanders should expect this winter to be warmer and wetter than average.

Niwa’s seasonal climate forecast predicts above-average temperatures across the country this winter, alongside increased rainfall in many areas.

Niwa meteorologist Ben Noll said warm seas and subtropical winds would keep the country warm for most of the winter.

Cold snaps may keep this winter from being the hottest on record, but temperatures still trend higher, he said.

Niwa also suggests that increased rainfall and humidity could indicate more flooding.