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The dramatic stats behind history-making weather system

Jamie Morton,
Publish Date
Tue, 14 Feb 2023, 3:42pm

The dramatic stats behind history-making weather system

Jamie Morton,
Publish Date
Tue, 14 Feb 2023, 3:42pm

Meteorologists have tallied dramatic weather totals to find what would’ve been obvious to anyone caught in Gabrielle’s destructive path – this ex-tropical cyclone is a history-maker.

Between midnight Sunday and 11am today, a whopping 568mm had fallen at Raparapaririki in the ranges of Tairāwhiti, where scenes of heavy flooding have emerged amid a communications blackout.

Those numbers were approaching some of the incredible values recorded in 1988′s Bola – one of the costliest cyclones in New Zealand’s history – in which 419mm fell at Te Puia in 24 hours, while Glenross Station recorded a mammoth 917mm over four days.

“We’ve had stations in that region recording half a metre [of rainfall] – so we’re talking about a shorter duration than Bola, but just as intense,” Niwa forecaster Ben Noll said.

At Niwa’s Fernside station in the Gisborne district, 375mm fell between Monday and Tuesday morning, while 345mm was recorded at Whangarei, where yesterday was the city’s wettest February day on record.

“Since Sunday, Whangarei is now sitting at three and a half times its monthly normal.”

Elsewhere in Northland, the climate station at Trounson measured 305mm over that one and a half day period, while the Brynderwyn Hills were saturated with 299mm.

At Napier – where emergency services ordered the evacuation of multiple suburbs today – the 175.8mm of rainfall registered at the city’s airport in the 24 hours from 9am Monday proved its second-wettest day since 1950, and eclipsed the 56mm usually recorded there in an average February.

Extensive flooding at Awatoto seen from above the Napier Golf Course. Photo / Photography by Corena

Extensive flooding at Awatoto seen from above the Napier Golf Course. Photo / Photography by Corena

Other standout totals included the 200mm that a station at Maunganui, north of Napier, recorded in just 12 hours to 7am Tuesday.

In that same period, climate stations measured 191mm at Pukeorapa southwest of Gisborne, 160mm in Waitakere in Auckland, 152mm in southern Coromandel’s Golden Valley and 133mm at Wallers, northwest of Auckland.

“At Western Springs, we saw two times the monthly normal in just under 24 hours.”

Incredibly, Auckland had now received around half of its annual rainfall, just 45 days into 2023.

MetService reported other huge totals for yesterday, including 160mm at Whangarei Airport, 151.8mm at Gisborne Airport, 125.8mm at Tolaga Bay and 83.2mm at Mahia.

Gabrielle has also brought seriously strong wind speeds.

“Wind gusts over 140km/h have been recorded at many exposed coastal locations, but urban areas have been affected too, with New Plymouth airport gusts reaching 128km/h, with wave heights close to 11m recorded off the coast of the Bay of Islands,” MetService meteorologist Andrew James said.

The highest peak wind gust measured by one of Niwa’s stations was at Dargaville, measuring 127km/h, while Metservice had observed gusts as powerful as 140km/h in Northland, along with 135km/h in the Hauraki Gulf.

Near the recently shuttered Chateau Tongariro Hotel at the base of Mt Ruapehu, Niwa recorded gusts as heavy as 125km/h - along with 269mm of rainfall.

Noll said Gabrielle had been expected to reach record low values for air pressure in New Zealand overnight – but Whitianga’s station was knocked out just after 9pm.

At that point, the barometer had already plunged to 973hPa – at least putting Gabrielle’s central pressure in the same ballpark as the July “weather bomb” of 2008.

“At the same time, other locations like Leigh in north Auckland had their lowest pressure on record,” Noll said.

At noon today, MetService was estimating pressure at the system’s centre, to the north of East Cape, to be as low as 965hPa.

All told, Noll expected Gabrielle to go down as a historic weather event.

“When you’re talking two or three months worth of rain in single days, along with the winds we’ve had, and flooding, waves and coastal hazards, it all comes together to create this situation.”

Such was the extent of Gabrielle’s destruction that the Government declared a national state of emergency for only the third time in history – and the first for severe weather.

This afternoon, tens of thousands across the North Island were without power, pockets of Napier and other parts of Hawke’s Bay were underwater and entire communities in the Coromandel and East Coast were cut off.

State Highway 5 after heavy flooding during Cyclone Bola in 1988. Photo / Warren Buckland

State Highway 5 after heavy flooding during Cyclone Bola in 1988. Photo / Warren Buckland

Some have already drawn comparisons with Bola, which damaged houses, roads, railway lines and bridges with widespread flooding along the East Coast.

It forced the evacuations of thousands of people, cost more than $70m in insured losses, and claimed the lives of seven people in flooding.

Noll said Gabrielle wasn’t yet finished with New Zealand, but conditions were expected to ease over the next two days.

Today, rain was forecast to ease in the upper North Island, but continue in Tairāwhiti/Gisborne and northern Hawke’s Bay until tonight, with rain also affecting the lower North Island and parts of Marlborough.

“A continuing focus will be wind,” James said.

“We are still expecting gusts in excess of 120km/h over parts of the upper North Island, Taranaki and central New Zealand, and warnings are still in place.”

Chatham Islands, 850km offshore from Christchurch, was expecting heavy rain and strong winds from this afternoon, with the system passing to the north on Wednesday.

This would be tied with large easterly waves, an unusual direction for the islands.

While Gabrielle takes a southeast track moving away from New Zealand from early tomorrow, the impacts would be felt for much longer.

Tomorrow, rain was forecast to continue into the capital – with a few showers around central and northern North Island – and dry breaks across Waikato and Bay of Plenty.

Following that, there was some more wet weather from Thursday, but apart from Wellington and Wairarapa, most areas would only receive showers.

For the South Island, wet weather continued for Canterbury and Marlborough tomorrow, while conditions elsewhere would be generally dry.

“There is some light at the end of the tunnel – MetService is forecasting a ridge over the North Island bringing a spell of settled weather from this weekend onwards.”

Region-by-region warnings

As of 1pm Tuesday, MetService has weather warnings/watches in place:

  • Northland: Red strong wind warning until 9pm tonight
  • Auckland including Great Barrier Island and other islands in the Hauraki Gulf: Red strong wind warning until midnight Tuesday
  • Coromandel: Orange strong wind warning until midnight Tuesday
  • Gisborne: Orange heavy rain warning until midnight Tuesday; strong wind watch until 2am tomorrow
  • Hawke’s Bay (especially about the ranges): Orange heavy rain warning until 2am tomorrow
  • Taranaki: Red strong wind warning until 10pm tonight
  • Mt Taranaki: Orange heavy rain warning until midnight Tuesday
  • Wairarapa including the Tararua District, Wellington, Horowhenua, and the Kapiti Coast: Orange strong wind warning until midnight Tuesday
  • Wairarapa including the Tararua District: Orange heavy wind warning until midnight Tuesday
  • Wairarapa - Turakirae Head to Mataikona: Heavy swell warning until 3pm tomorrow
  • Marlborough and Nelson southeast of Mapua including Nelson Lakes: Orange strong wind warning until 2am tomorrow
  • Canterbury Plains and the foothills north Rakaia River: Heavy rain watch until midnight tomorrow
  • Chatham Islands: Strong wind watch until 2am tomorrow


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