Jamie Morton is the NZ Herald's science reporter.

Want a sunny weekend? Head to Hokitika

Skiers enjoy snowy conditions at Mt Ruapehu's Turoa skifield this afternoon. Photo: Mtruapehu.com
Skiers enjoy snowy conditions at Mt Ruapehu's Turoa skifield this afternoon. Photo: Mtruapehu.com

Keen for sunshine this weekend?

Unless you live on the South Island's West Coast, you're probably out of luck.

An easterly flow that brought the recent rain to northern and eastern parts - more than 90mm fell in the Coromandel on Wednesday - strengthens again on Saturday as another low rolls towards the upper North Island from the Tasman Sea.

With the low comes warmer air, poised to bring a wet weekend to Auckland and the North Island's skifields. There's also the chance of heavy thundery falls over Northland.

Wellington has been in a showery southerly since Saturday and isn't looking at a change of scene until well into next week, completing more than a week of southerlies.

Christchurch, which has also experienced mainly southerly winds and overcast and drizzly conditions, will stay cloudy - but at least the wind will switch to a warmer northeasterly.

WeatherWatch.co.nz weather analyst Philip Duncan expected this weekend to be a "battle" of two air pressure systems.

A high was slowly spreading over the South Island while a low gently smudged over the upper North Island and southwards.

The two would combine to encourage more winds from the east - "and this means a lot of cloud the further north you go with sunniest weather the further south you go".

"On Saturday, most of the South Island will be under high pressure while the Tasman Sea low will push into the North Island gradually.

"This means more cloud, more drizzle and showers or patchy areas of rain spreading south into more regions."

Duncan said the low was so large that the rain clouds were definitely broken up.
"It's not one big widespread rain cloud but areas of rain, drizzle and showers broken up further by New Zealand's mountains and ranges.

"It's possible some wet weather may brush the upper South Island on Saturday too."

By Sunday, Duncan expected the big low in the north to start to push more into the South Island, while high pressure south of New Zealand retreated a little back over the Southern Ocean.

"The high will try to slide up the eastern side of the South Island on Monday but it looks as though the low will be more dominant for the country this weekend and next week - pushing drizzly patchy rain into Canterbury on Sunday too.

"The low will hang around the upper North Island for nearly an entire week - so get used to cloud, drizzle, showers as New Zealand has it's first taste of La Nina-like weather conditions - perhaps a hint of the potential humid and wet summer ahead, for North Islanders especially."

Meanwhile, the West Coast has been basking in an unseasonal dry spell.

Aside from one day of heavy rain last Friday, the region has been mostly dry since September 7.

So far this month, Milford Sound airport has received only 222mm of rain, 40 per cent of the monthly average, while Hokitika is also behind on the numbers with 155mm or 60 per cent of its monthly average.

With persistent easterlies for the next week, little additional rain was forecast for the area.

MetService meteorologist Tom Adams said this wasn't the "typical set-up" that could be expected with the spring equinox - the two days of the year when Earth's axis of rotation was pointing exactly towards or away from the sun, meaning the sun's rays fell on all latitudes for approximately 12 hours in the day.

"This time of year we normally see high pressure north of the country and strong westerlies, but what we are currently experiencing is the reverse of that," Adams said.

"Although the regular pattern should assert itself at some point, the odds are against that happening in the next few weeks."

- NZ Herald

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