Big seas, gales, snow to low levels as southwesterly flow batters New Zealand

Wednesday, 25 September 2019

Snow is expected to low levels across much of the South Island and central North Island during Wednesday.

Big swells are expected along the west coastline of New Zealand, along with snow to low levels and gusts approaching severe gale strength as a southwest flow, bringing cold air from far to the south, blasts the country.

MetService is forecasting snow falling on all the main high road passes, except the Remutaka Hill Road, at various times from Wednesday afternoon through to early Thursday.

Snow is expected to lower to 100 metres and be heavy in Fiordland from late Wednesday afternoon or evening. The snow level is also expected to drop to 100m elsewhere in Southland, to 300m and possibly lower in heavy showers in Dunedin, to 300m in Central Otago, to 100m and possibly lower in Canterbury, and 400m in Marlborough

In the North Island snow is expected to 600m in Taihape, affecting the Desert Road, on Wednesday evening, and to 600m in Hawke's Bay, affecting the summit of the Napier-Taupō Road.

* Auckland weather watch: gale force winds set to batter harbours**

MetService reported a 30-minute snow shower at the summit of the Crown Range Road mid-afternoon Wednesday and said more was expected through the afternoon and evening for alpine passes around the country.

It is also forecasting 6m swells for much of the west coast of New Zealand through to Sunday.

MetService meteorologist Tui McInnes said the stretch of coastline likely to be hit by the biggest swells would be from around Taharoa, southwest of Hamilton, northward.

'That's just because that's where the coastline turns to be really exposed to that direction (southwest),' McInnes said.

For most of the South Island the biggest swell would not be coming onshore because the coastline was parallel to the direction the swell was travelling.

But the forecast swell height was also a kind of average, so some waves higher than 6m should be expected.

'These swells are quite significant, generating off quite a long stretch to the southwest … all the way from south of Australia,' McInnes said.

'The best way to have a big swell is to have a prolonged period of wind from the same direction, at a reasonable speed, over a reasonable distance.'

The swell also had quite a long period - the time between wave peaks. 'It means the waves are quite strong.'

Along with the big swells, MetService is also expecting the sea along the west coast to be 'very rough'.

Winds are expected to reach gale strength in exposed places in many parts of the country, with a chance they could get to severe gale strength in Northland, Auckland, Coromandel Peninsula, Waikato, Bay of Plenty, southern Hawke's Bay and Banks Peninsula, and during Thursday in Dunedin, Clutha, Southland and Stewart Island.