After the heat, there comes rain, wind and flooding fears

Tuesday, 30 January 2018

Much of the country has been sweating through another scorching day.

The temperature in Christchurch reached 29C, Auckland 28C and Dunedin hit 27C, as it hit a baking 36C in Alexandra on Tuesday - the hottest place in the country.

But the days-long heatwave is set to finally break for many of us (Wellington has already had some respite, getting up to a more pleasant 23C on Tuesday).

MetService's severe weather outlook forecasts rain and wind for parts of New Zealand.

Stormy weather is moving in, with stark changes on the way for the South Island in the coming days.

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The 1984 floods in Invercargill came after a period of dry, sunny weather.

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While Christchurch's forecast high for Wednesday is 34 degrees Celsius, the temperature is expected to fall to 17C on Saturday. The temperature in Alexandra is forecast to fall to 16C on Friday - a 20 degree drop.

A weather system brings the risk of flooding to parts of New Zealand after a week of baking heat - while temperatures are expected to plummet from the mid-30s to the mid-teens in places.

Environment Southland councillor Neville Cook.

On Tuesday, MetService issued a severe weather warning for a storm which developed as Tropical Cyclone Fehi and is tracking towards the west coast of the South Island. MetService says it should approach New Zealand overnight Wednesday and cross the South Island during Thursday, then move away from the country on Friday.

The storm will bring significant heavy rain to the west and south of the South Island from late Wednesday to early Friday, with possible damaging gales for parts of the South Island, especially in the the west and north.

In Southland, some fear that conditions could be similar to 1984, when devastating floods hit the region after a spell of fine weather.

A severe weather watch, with warnings for heavy rain for Southland, Otago and Canterbury high country, was issued on Tuesday. There is the possibility of rainfall accumulations reaching warning amounts in those areas.

MetService meteorologist Philippa Murdoch said the cyclone would be downgraded to a mid-latitude low by the time it hit the country.

But flooding was a possibility in Otago and Southland, Murdoch said. 'We are expecting a lot of rain, and it has been quite dry in those areas.'

The rain would spread to the North Island from Thursday.

SO COLD WE COULD GET SNOW

Snow could even come as part of the cooler front - but Murdoch said it would only noticeably affect the Southern Alps and the Canterbury high country.

'The snow is not likely to fall at a low level or affect where people are living, but people will definitely notice the drop in temperatures in the South Island from Thursday and Friday,' she said.

Temperatures would start to fall in the South Island on Thursday, spreading to the North Island on Friday.

Wind was expected to pick up on Thursday, and Murdoch said there could be northerly gales.

MetService meteorologist Tom Adams said at least 100mm of rain is predicted between 7pm Wednesday and midnight Thursday in Southland.

'There's heavy rain due,' Adams said. 'I would strongly expect a heavy rain warning to be issued sometime Wednesday for Thursday.'

100mm in the timeframe predicted 'is the sort of rain where you get flooding', he said. 'You get slips and damage associated with heavy rainfall.'

FLOODING RISK BEING MONITORED

Emergency Management Southland group controller Angus MacKay said weather prediction models for the storm were changing by the hour and EMS was watching them closely.

'We know there is going to be significant rain in Westland on Thursday but whether it is just a regular rain event or something more serious than that in other regions remains to be seen.'

EMS could activate its emergency coordination centre if the situation develops. He urged Southlanders to keep an eye on forecasts and the EMS webpage and Facebook page for updates.

Environment Southland councillor Neville Cook said he 'hopes' a repeat of the devastating 1984 floods in the region does not occur.

Cook said Southland also experienced fine weather to the end of January in 1984 before it 'rained and rained', with flooding occurring in Invercargill and across Southland.

The 1984 floods, on January 26 and 27, included a one-day total of 85mm of rain. More than 5000 people were forced to leave their homes and there were huge losses in livestock and damage to buildings and services.

'It was a concentrated rainfall when the ground was dry. It just runs off and doesn't soak in,' Cook said.

Southland needs rain, but not too much, Cook said. 'We want the rain, we want the water … but we don't want too much too quickly.'

Adams said Cook was right. 'The ground is dry … there is a lot of rain coming. There's the potential for flooding, definitely.'

The rain would be gone after little more than a day, he said. There would be no more significant rain in Southland 'at least until the second week of February', Adams said.

Environment Southland deputy chairman Lloyd McCallum said a lot of flood protection work had been done since the 1984 floods. 'It's similar conditions but hopefully we have done a lot of work that will stop this one.'