Heavy rain building, sparking flood warnings

Monday, 16 December 2019

Storms and heavy rain are forecast for much of the country on Tuesday.

Warnings are in place for motorists in Nelson, Taranaki and Marlborough to watch out for surface flooding and slips, as heavy rain builds.

All three regions are set for more than 100mm of rain as brutal weather looks to hammer the country throughout Tuesday.

MetService warned that streams and rivers may rise, causing flooding and dangerous driving conditions.

But they are not alone. MetService was watching for potential heavy rain around most of the central North Island, Buller, Canterbury and Otago.

Flooding and road damage on the West Coast last week.

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Late on Monday evening showers started to ramp up in intensity, which would continue into Tuesday, reaching a peak in the afternoon.

Nelson and Taranaki were projected to be the worst hit.

MetService forecasted up to 140mm of rain for Mt Taranaki in the 24 hours from 6pm Monday.

The Nelson region could get up to 150mm in the 24 hours from 7pm Monday, with the heaviest falls about the western ranges.

The week ahead was looking 'very unsettled', MetService meteorologist Andy Best said.

'It's very spring-like, rather than beginning-of-summer-like. All of these mobile systems are moving across the Tasman very rapidly.'

A power pylon is just twisted metal after being torn down by the effects of the nearby flooded Rangitata River.

South Canterbury was drenched just over a week ago, with major flooding of the Rangitata River forcing the closure of both highways through the area.

The region was facing the possibility of another drenching, with MetService expecting heavy rain in the Canterbury High Country, Canterbury Plains south of the Rakaia River, and the ranges of Westland from Tuesday morning to Wednesday afternoon.

Auckland was forecast to have showers, possibly heavy on Monday night, then periods of possibly thundery rain with gusty northwesterlies on Tuesday. Wednesday was forecast to have strong southwesterlies but only a few showers.

Wellington was forecast to have occasional and possibly heavy rain with strong northerlies on Tuesday, showers with a southerly change on Wednesday, then mostly fine on Thursday, but northerlies could reach gale strength.

In Christchurch rain on Tuesday becomes more frequent in the afternoon with a strong southwesterly change and gales about Banks Peninsula.

Rain was forecast to ease on Wednesday morning but southwesterlies were expected to stay strong and could be gale strength in exposed places, while Thursday was expected to have rain from evening and strengthening northerlies.

The rough weather in the next few days was linked to a major low pressure system.

'This low eventually moves onto the country during the course of [Monday night] and [Tuesday]', Best said.

'It's a very complicated low and splits into two. It's a very difficult thing to get a handle around at the moment'.

Winds were expected to change to strong southeasterlies in the east of the South Island on Tuesday afternoon or evening, with gales about the coast.

'Whether those gales will be severe … it will still be very, very windy and it will be a lot cooler as well,' Best said.

For much of the central and lower South Island, temperatures were expected to be around 8 degrees Celsius below normal for the time of year.

Further out into the week, MetService was indicating the possibility of gale northwesterlies in Wellington and Wairarapa on Thursday, while most of the South Island is expected to have rain, with a gale or severe gale strength northwesterly developing.

On Friday, rain is forecast for most of the North Island, while in the South Island showers were expected to become isolated.

There could be another brief respite on Saturday, but on Sunday another low was expected to cross the country.