The flash flood triggered by a record-breaking downpour left debris scattered across a farm northwest of Whangārei. Photo / supplied
The flash flood triggered by a record-breaking downpour left debris scattered across a farm northwest of Whangārei. Photo / supplied
A deluge in Maungatapere, just west of Whangārei, has set a national record for the biggest dump of rain in a single hour.
The 103mm downpour between 4am and 5am on March 21, broke the half-century old record for a low-elevation weather station.
It also triggered flash floods that destroyed fences, triggered slips, carved out gullies and scattered debris across farmland.
Niwa image of the weather system that brought a record-breaking deluge to Maungatapere. Image / Niwa
Rebekah Sulman, of the Northland Rural Support Trust, said farms in Riponui, Pipiwai, Purua and Ruatangata to Titoki and Maungatapere were worst affected.
Seven or eight farms had borne the brunt of the deluge with some recording as much as 320mm of rain during the five-hour downpour.
The trust was seeking volunteers to help clear debris and reinstate farm infrastructure at the worst-hit properties.
Anyone able to lend a hand with the clean-up this weekend could call her on 021 538 6866.
Niwa's principal forecasting scientist, Chris Brandolino, said the record rainfall was caused by a low-pressure system in the Tasman Sea siphoning moisture from the humid tropics towards the upper North Island.
About 3000 lightning strikes were observed in Northland that same morning.
The thunderstorm increased the rainfall, and an ongoing marine heatwave around New Zealand may have also contributed.
Brandolino said rising global temperatures meant more extreme weather.
"In the future, it's likely such events will become even more common and more extreme."
Silt and flood debris left on farmland by the record-breaking deluge. Photo / supplied
The same weather system had caused significant flooding in Auckland and Tairāwhiti, and sank the fishing charter boat Enchanter off North Cape with the loss of five lives.
Brandolino said Maungatapere's 103mm wasn't the highest hourly rainfall in New Zealand but it was the highest for a station up to 500m above sea level.
The record for any New Zealand weather station was held by a gauge next to the Cropp River, near Hokitika, which recorded 134mm in an hour on January 8, 2004.
Between 3.30am and 4.30am the 60-minute total at Maungatapere was even higher: a staggering 123.3mm.
However, that didn't count as an hourly rainfall record because those were calculated from top-of-the-hour to top-of-the-hour.
It had taken a week to announce the record because any new records had to go through a rigorous checking process, which included a site inspection.
