New rainfall record set in New Zealand with 1 086 mm (42.7 inches) in 48 hours

The atmospheric river event affecting New Zealand over the past 3 days has set the country's new 48-hour rainfall record. The storm caused major infrastructural damage, including destroyed Waiho Bridge in South Island's Westland District. At least one person has died during the event.

Cropp waterfall recorded 1 086 mm (42.7 inches) of rain in 48 hours to March 27, setting the country's new 48-hr rainfall record. This is 176% of average annual rainfall in Christchurch, 147% in Dunedin, 97% in Hamilton and Auckland, 91% in Tauranga and 89% in Wellington.

Extremely heavy rain caused a rapid rise of West Coast rivers to near-record levels. The Haast River at Roaring Billy, for example, recorded a water level of 7.423 m (24.35 feet), making it its 2^nd highest water level at the station since 1968 (the highest was 7.580 m / 24.86 feet) recorded in 1978. In less than 48 hours, this location has recorded 548 mm (21.57 inches) of rain, or nearly 10% of its yearly normal.

The Waiho Bridge was destroyed by the rising and rough floodwaters of the Waiho River near Franz Josef on March 26, forcing authorities to declare a State of Emergency for the Westland District. The river was running as high as 7.6 m (24.93 feet).

According to the New Zealand Transport Agency (NZTA), hours of torrential flood waters carrying large amounts of rock and material downstream battered the bridge's support piers until it collapsed. However, one of the residents said he warned authorities three days before the collapse that the northern end of the bridge's abutment was missing rocks and needed strengthening.  

According to police reports, one woman has been found dead after her body washed up on a riverbank north of the town of Hokitika. It appears she got out of the vehicle she was driving and tried to cross floodwaters on foot. 

Atmospheric river event over New Zealand on March 27, 2019. Credit: NASA/NOAA Suomi NPP/VIIRS

The front which brought heavy rain to the west of the South Island on Tuesday, March 26 moves north onto the lower North Island this afternoon to lie over the central North Island at night, New Zealand's MetService said March 27. This front is likely to bring a period of heavy rain to the northern South Island and southern/western North Island.

Although thunderstorms are considered unlikely with the front as it passes over the northern South Island this morning, and southern North Island in the afternoon, there is a low risk of a few embedded thunderstorms with the front about Taranaki and coastal Waitomo from this afternoon. If any thunderstorms do occur, they will boost local rainfall rates.

A southerly change is expected to affect Canterbury from about the Banks Peninsula southwards and also North Otago and Dunedin this afternoon. 

Featured image credit: NASA/NOAA Suomi NPP/VIIRS. Acquired March 26, 2019