Heavy rain, severe gales and snow are forecast to hit the country this weekend, with warnings of power cuts just as the school holidays kick off.
Key messages for the #SeptemberStorm— MetService (@MetService) September 25, 2020
- Peak winds overnight SAT to SUN morning
- Heaviest rain/largest amounts in Fiordland/Westland
- Snow may affect many high roads and is likely to lower to near sea level in far south overnight SUN
- Heavy swells expected next week
MetService is forecasting one of the most widespread severe weather events this year with a blast of cold Antarctic air following downpours and high winds.
"There's quite a significant event which is developing, virtually the entire country will see some impact from this system," MetService meteorologist Andy Best said.
Lines company Vector is also warning Aucklanders about potential for strong winds and rain that could cause power cuts.
Head of Network Field Services Marko Simunac warned people to stay away from fallen powerlines or damaged electrical equipment and watch out for falling tree branches which could cause damage to power lines.
"If the weather causes damage to powerlines, we'll aim to restore power as quickly as possible while ensuring the safety of our crews and the public. This means that we may need to remotely shut down power to an affected area as a public safety precaution until crews arrive on site."
Simunac said there may be circumstances when it was unsafe for crews to begin or continue to fix outages, for example during high winds, and he asked that the public be patient.
Meanwhile, this afternoon the Transport Agency issued a high wind warning for strong winds on the Remutaka hill as the weather system began to have an impact and it was warning people driving high-sided vehicles or motorcycles to take extra care.
Winds gusting up to 130km/h will hit the South Island and lower North Island from tomorrow afternoon, and the rest of the North Island on Sunday.
The West Coast of the South Island will have heavy rain over the weekend.
MetService warns transport disruptions are likely, along with challenging conditions for livestock in the South Island early next week as heavy snow falls to low levels
#SeptemberStorm - See how the low pressure that shoots across the Tasman deepens rapidly, and the gales (yellow arrows) increase. The rapid deepening is due to strong support in the upper atmosphere including the exit of a jet stream. It will be windy! https://t.co/qHyE5zhh6X ^TA pic.twitter.com/thFJ2A9tmW— MetService (@MetService) September 24, 2020
The low pressure system will head across the Tasman Sea on Saturday, dragging warm air ahead of it.
"A strong jet stream deepens this low, which brushes past the far south early Sunday morning," MetService forecaster Tom Adams said.
"That low is expected to be around 970hPa when it passes us, the deepest low in our neck of the woods for a long time."
The warm air will bring widespread rain which will be heavy in some areas, but Adams said it was the wind that had the greatest risk of causing widespread disruption.
Gales will hit many parts of the country, including areas that don't often see strong wind, he said.
"Saturday morning will be a good time to prepare for windy weather. The public are advised to secure their properties and boaties should check moorings before strong winds arrive.
"There's going to be a lot of wind around this weekend. The places that are going to get heavy rain, to be fair, are the places that quite often get heavy rain.
"The places that are going to see wind are those that regularly see wind, but also those that don't. So places like Taupo, places like Northland and the Bay of Plenty. Places that don't normally see high winds are going to see high winds."
The low is fast moving, and the band of rain will be short-lived for many northern and eastern areas.
The winds also start easing on Monday, but the "sting in the tail" is cold Antarctic air dragged up to New Zealand behind the low.
That will leave snow on most alpine passes, and Ruapehu, and large southerly swells with the risk of inundation on both coasts.
Snow is expected in Southland and Otago down to 200m to as low as sea level which could cause headaches for farmers during lambing season.
"We are expecting to see a lot of road snow warnings, a lot of alpine passes closed due to snow and then even when that has gone through there's going to be a big swell in behind this as well, so as we go Monday through to Wednesday there's going to be big waves out there on both coasts which could run some risks for coastal roads as well," Adams said.
MetService was warning farmers that conditions from Sunday evening through to Tuesday could cause stress to livestock.
It said people travelling for the school holidays should check its website today for updates on the worst-hit places.
"It's not just the weekend ... by Monday morning down through Fiordland, Southland and lower and interior Otago winds will be hustling again, in exposed areas getting up to 100 kilometres [an hour].
"By midday Wellington will be getting strong west and north-west gusts, and we'll do it all again."
As of Friday morning, this low is near Tasmania, and will continue to strengthen over the coming days. pic.twitter.com/3Z2TB917A3— NIWA Weather (@NiwaWeather) September 24, 2020