Heavy western rain, heavy southern snow, strong eastern and northern gales – and some sunshine in the mix too. Welcome to the first full week of September and the forecast isn’t flash, especially if you’re kicking off lambing right now. While NZ has stormy weather until this coming weekend, Australia is far more settled under a high pressure system so large it is wider than Aussie itself (and Australia is 4000km across!). This large high will also add to the windy spring westerlies impacting NZ.
Spring is all about winter slowly fading away and hints of summer slowly coming in. This weather is normal for September, even if there are plenty of severe weather risks people should be aware of.
The Situation: Stormy lows out of the Southern Ocean coupled with a cold change out of southern Australia combine to bring a wet Tuesday to NZ, followed by a much colder Wednesday with severe gales off and on. A powerful high pressure zone out of Australia will contribute to NZ’s windier westerlies later this week.
Rain: Heaviest on the West Coast, especially from Hokitika southwards where over 200mm is likely in the coming days.
Snow: Heaviest through the Southern Alps with over 1 metre expected in the week ahead. Lower level snow flurries (light and unlikely to settle long) will also impact low levels of Southland, potentially into places like Lumsden, Balfour and Gore.
Sunshine/Dry: Eastern NZ looks driest – and sorry Hawke’s Bay, that definitely includes you. Hawke’s Bay will get very little from this rain event – but instead will have gales, possibly damaging over 150km/h by Friday in the ranges.
Severe Gales: New Zealand has three main surges of severe gales this week.
Nor’westers today and Tuesday ahead of Wednesday’s main cold change.
A classic spring set up on Wednesday with Sou’West gales impacting Auckland City with gusts over 100km/h and perhaps over 140km/h in the very west (like the Manukau Heads).
On Friday another W to NW surge moves through and impacts Central NZ the most (upper South Island/lower North Island). Exposed ranges will have gusts up to 150km/h, perhaps even higher in more extreme elevations.
FULL DETAILS: Rounds of rain, snow and damaging winds…Cold change Wednesday
A low and associated cold front pass over New Zealand from Monday to Wednesday producing rain or snow and strong winds across much of New Zealand.
The West Coast will generally receive 80-100 mm of total rainfall with heaviest amounts of 150-200 mm across the central and southern West Coast.
As temperatures plunge on Wednesday behind the cold front, rain will turn to snow across larger portions of the South Island, including low elevation areas as well as high elevation of the North Island.
Snowfall amounts will reach 100-150 cm across the Southern Alps.
The North Island’s Central Plateau will also receive 15-20 cm of snowfall from Tuesday night to Wednesday.
After the passage of the low and front, strong westerly to northwesterly winds will prevail over New Zealand from Thursday to Friday.
Rain and gusty winds will begin Thursday across the western South Island before expanding to much of New Zealand on Friday.
Heaviest hit will be the West Coast of the South Island again with 100-150 mm of rainfall and 50-80 cm of snowfall.
Also, portions of the North Island including Manawatu-Wanganui and Wellington will expect 50 mm of rainfall.
With regard to winds, 100-120 km of northerly gusts ahead of the front hit Fiordland and Southern Alps Monday to Monday night. Then damaging southwesterly winds behind the front will impact the North Island on Wednesday with gusts of 80-90 km/h common and locally 100 km/h to maybe even 140 km/h (like the Manukau Heads in west Auckland).
On Friday another surge of severe winds with gusts 120-150 km/h from the W to NW – especially in Central NZ (ie, upper South Island, lower North Island).
Temperatures will actually be above normal across New Zealand much of this week, except for notable cold change on Wednesday.