Weather: That 'giant storm' now a low pressure system - but cold temperatures still coming

The giant storm that has been the centre of differing views among weather experts is now being dubbed a low pressure system.

The weather system developing in the Southern Ocean was this week tipped to be associated with one of "the world's largest storms and would bring an Antarctic blast to the country", according to WeatherWatch.

Other weather experts - MetService and Niwa - suggested the storm was unlikely to even be near the country and that there was no reason for people to be alarmed as a result.

WeatherWatch has now backed down on its giant storm forecast - calling it not a storm, but an enormous low pressure system that will still alter the country's weather pattern.

"The enormous area of low pressure we talked about earlier this week is still forecast for next week and is still likely to influence our weather with a colder, windier, sou'wester.''

No storm over #NewZealand next week, but enormous low nearby will alter our #weather pattern, especially the south https://t.co/zCKya4wOLT via @weatherwatchnz

— WeatherWatch.co.nz (@WeatherWatchNZ) August 8, 2019

WeatherWatch released a situation statement early today, saying the storm "well south" in the Southern Ocean will send up a pulse of cold air early next week - making for wintry conditions in the lower South Island.

"Latest data continues to suggest it will pull away east enough to just spare the South Island from a major blast.

"But next week - especially for those in calving - should be aware of a likely cold southerly wind and biting wind chills for a time early next week, peaking on Tuesday.''

In a forecast video for this weekend's weather, head analyst Philip Duncan smiled slightly as he acknowledged that "big Southern storm we've all heard about in the news".

He pointed out: "We never said that was coming directly into the country. We said, very clearly, it would influence our weather over the New Zealand area."

Pointing to the weather systems in front of him, he said: "And hey, guess what? These two [lows] are merging and there's a big southerly change coming in across the country on Monday."

MetService meteorologist Amy Rossiter said there had been some confusion among members of the public about which weather systems were affecting different parts of the country and when.

A low pressure system developing in the Tasman Sea would affect the central North Island - bringing wintry weather conditions - but would move away by early next week.

The low in the Southern Ocean, however, is expected to pass just south of the South Island and would affect areas on the south-east.

Although it would not pass directly over the country, it would bring colder temperatures and showery conditions, Rossiter said.

To add to the confusion, a cold front that extends from that Southern Ocean low may, however, move across parts of the South Island - again bringing wintry weather with it.

InfoGraphic: The Big Picture for #Friday - more rain or the north.. https://t.co/pylETqGLT3 via @weatherwatchnz #NewZealand #weather

— WeatherWatch.co.nz (@WeatherWatchNZ) August 8, 2019

SEVERE WEATHER WATCHES:

The MetService has a number of severe weather watches in place for parts of Northland, the Bay of Plenty and Gisborne, where heavy rain is a possibility.

Northern and eastern parts of Northland have a watch in place until at least 11am. Rainfall amounts may approach "warning criteria", MetService said.

Gisborne north of Tokomaru Bay and Bay of Plenty east of Te Kaha may also see heavy rainfalls today. The severe watch in these areas are in place until 6pm.

The MetService said wintry conditions are forecast for the weekend, with a low approaching from the Tasman Sea expected to cross the South Island.

Weather experts would be monitoring the low closely as road snowfall warnings were likely to be issued for higher roads and passes in the South Island in particular.

"People should keep up-to-date with any severe weather watches and warnings that may be issued,'' the MetService said.

That would cause winds to turn easterly over Canterbury and Otago and onshore winds would bring rain to those areas. Snow levels are expected to lower early tomorrow. Most parts of the country can expect a wet weekend; save for Fiordland, which uncommonly is forecast to be the driest spot in the coming days.

There is also a watch for heavy rain in Northland and Gisborne today.

"A possibility of heavy snow above 400m has been flagged on the severe weather outlook for several days and we could see smaller amounts to lower levels," MetService said.

"Inland parts of Canterbury and Otago are likely to see the most snowfall."

TODAY'S FORECAST:
- Whangārei: Rain, possibly heavy, easing to a few showers morning. Showers frequent evening. Northwesterlies. High 16C, Low 11C
- Auckland: Rain, possibly heavy, easing to a few showers this morning. Showers becoming frequent tonight. High 15C, low 11C.
-Tauranga: Rain, possibly heavy, clearing afternoon. Northerlies changing westerly afternoon.High 15C, low 10C
- Rotorua: Rain, possibly heavy, clearing afternoon. Northerlies changing westerly afternoon. High 13C, low 8C
- Hamilton: Rain, possibly heavy, easing to a few showers this morning. High 15C, low 9C.
- Whanganui: Few showers, chance heavy, clearing this afternoon, but returning at night. Northwesterlies. High 17C, Low 8C.
- Gisborne: Occasional rain developing this morning, clearing this afternoon. High 14C, low 7C.

- Napier: Cloudy periods, chance morning shower. Northerlies changing southerly in the afternoon.High 16C, low 7C
- Wellington: Cloudy periods, few morning showers in the north. High 13C, low 8C.
- New Plymouth: Rain, possibly heavy, easing this morning. High 14C, low 9C.
- Nelson: Fine spells and a few evening showers. High 14C, low 6C.
- Christchurch: Fine day, then cloudy this evening. High 15C, low 5C.
- Queenstown: Fine at first then cloud and rain developing this evening. High 8C, low 0C.
- Invercargill: Occasional showers. High 8C, low 1C.