Tasman weather warning: Heavy rain, flood risk as storm hits South Island

The South Island is set to be hit with “serious” weather as the subtropical storm battering the North Island moves down the country – with Tasman, in particular, in line for some of the “more extreme” impacts.

MetService meteorologist Mmathapelo Makgabutlane says the “large weather system” bringing heavy rain and strong winds to much of the north is also impacting the South Island.

An orange heavy rain warning, with a high chance of being upgraded to red, is in place for the Tasman region northwest of Motueka, with about 24 hours of rain expected from 4pm today – up to 250mm of downpours, with 15-25mm/h at its peak.

The subtropical storm lashing the North Island is set to move south. Image / Windy.com

Heavy rain warnings are also in place for the Westland District, Richmond and Bryant ranges, North Otago and parts of Canterbury.

“What we’ve seen so far is quite a wet Thursday over the South Island and we’re expecting a prolonged period of rain,” Makgabutlane said.

“We have an orange warning up towards the Tasman area, and that is an area that we’re keeping a close eye on. It looks like quite a prolonged period of rain, and we’re still expecting further rain tonight and into tomorrow as well. So quite a wet area out there.

“But apart from that, we also have a lot of other areas that have orange heavy rain warnings.”

The Tasman District Council’s hydrology team said the weather “is now shaping to have high potential to be a significant event for areas around Golden Bay and Tākaka Hill”.

“In the lower Tākaka River, we can expect at least an annual flood, with a five-year flood being likely and maybe even a 10-year flood possible (although unlikely at this stage).”

The heaviest rain for those areas is set to hit early Thursday evening and Friday morning.

Makgabutlane advised people from “anywhere that is currently under either a watch or a warning for heavy rain and strong winds” to “keep a close eye on the forecast and how things are developing in your area”.

“That rain is looking quite persistent, and on Friday in that western part – so all the way from Tasman, Buller, down towards kind of Grey, Westland – we could see some thunderstorms in the morning as well.

“In addition to the rain, we’re also seeing a good possibility of strong winds, so lots to keep an eye on over the next day or so.”

Affected areas should expect surface flooding, possible slips and difficult road conditions, while “strong gusty winds” could cause damage to trees and power lines.