Your weather: Fine end to week before tempest arrives Friday

Fine weather is on the cards over the next few days. File photo / Ben Fraser

A fine few days are in store for most of the country before a Tasman tempest arrives Friday to spoil the weekend plans.

A ridge of high pressure has spread from the North Island across the South Island, kicking out a front that brought strong winds and a severe drop in temperatures yesterday.

Fine and warm conditions were forecast across most of the North Island today, MetService duty forecaster Mickey Malivuk said.

Auckland is in for another cracking day and a high of 20C. Tauranga looks to be the pick of the bunch though, with a high of 22C forecast.

Satellite loop of NZ this afternoon

THE VIEW FROM ABOVE THIS AFTERNOON Whilst the North Island has seen settled weather today under the influence of a ridge, the South Island has been abit more exciting for the MetService Meteorologists. In the gif below you can see a sharp cold front moving onto the SW of the country. The front has been very active with over 300 lightning strikes in the in the last 2 hours down south, and 22.5mm of rain falling at Manapouri this morning. Rain and thunderstorms aren’t the only weather impacts as northwesterly winds over the lower South Island ahead of the front have been strong and gusty – up in the mountains Mid Dome recorded a gust of 210km/hr! An interesting phenomenon to see on the satellite gif below is the Northwest Arch cloud, formed by vertically propagating mountain waves, slowly peeling away to the northeast from the mountain range divide which runs through the centre of the South Island. Mountain waves can develop in strong northwesterly flows where the wind at the mountain tops is perpendicular to the range. As the front approaches in the gif below, the wind direction aloft subtly changes, becoming more westerly and the Mountain waves can no longer propagate so the wave disappears! If you want to know more about Mountain waves, check out our blog at https://blog.metservice.com/Turbulence. ^JM

Posted by MetService New Zealand on Monday, 7 May 2018

The South Island is joining the fine weather party too, enjoying temperatures in the late teens to 20C, and fine weather forecast in most areas.

The settled conditions bring a change from yesterday, when a quick cold snap brought gusty winds, thunderstorms and a rapid drop in the mercury.

Temperatures near Invercargill dropped more than 8C in just 50 minutes yesterday afternoon.

The front brought over 300 lightning strikes in a two-hour period a wind gust of 210km/h was recorded in the mountains at the Mid Dome station.

This image shows observations from Tisbury (near Invercargill) this afternoon, with the red line indicating air temperature.

⬆️At 1:50 pm, the temperature was 18.7°C
⬇️At 2:40 pm, the temperature was 10.3°C

🌡️That's a decrease of 8.4°C in only 50 minutes! pic.twitter.com/ZsYvLkNBMz

— NIWA Weather (@NiwaWeather) May 8, 2018

On the flats, winds in Gore got to 110km/h, and 90km/h in Invercargill and Queenstown.

Those same wind gusts are behind a "rare" southern ocean swell lashing the bottom of the South Island.

The swell was peaking this morning, when waves will reach heights of 8-9m around the coasts of Southland and Fiordland.

"Those areas are used to big waves, but this is pretty rare," Malivuk said.

In the open ocean, waves could be double the height double of those on the coast, he said.

The swell was forecast to head southwest today, banging head on into the Chatham Islands.

Additionally, the wind will generate large seas as waves near/more than 10 m will impact west coast of Stewart Island & Foveaux Strait late tonight & early tomorrow morning. Waves of 6-8 m will impact lower west coast of the SI from Haast/southward. Mariners take note!

~Chris pic.twitter.com/xd1nW7z8Z6

— NIWA Weather (@NiwaWeather) May 7, 2018

Fine weather is forecast across New Zealand tomorrow before a low developing in the Tasman Sea arrives in the South Island Friday morning bringing rain, and moving over the North Island in the evening.

Most areas will get rain from Friday across the weekend, some heavy.

"Western areas of both islands will experience the worst, but it is hard to pinpoint exactly where at this stage," Malivuk said.

Up to 100mm could fall in 24 hours in northwest Nelson from Friday through to Sunday and in Westland on Friday, possibly triggering warnings.

Rain could also get heavy about Nelson, Buller and northern Marlborough on Saturday and Sunday, and Westland on Sunday.

On Sunday in the North Island, Mt Taranaki, the Tararua Range and Gisborne ranges could get heavy rain.

Today's weather

Whangarei Fine. Southwesterly breezes. 21C high, 10C overnight.

Auckland Fine, apart from isolated morning showers. Southwesterly breezes. 20C high, 11C overnight.

Hamilton Some morning cloud otherwise fine. Southwesterly breezes. 21C high, 8C overnight.

Tauranga Fine, could get some morning cloud. Southwesterlies dying away. 22C high, 11C overnight.

New Plymouth Morning cloud then fine from afternoon. Westerly breezes. 19C high, 9C overnight.

Napier Fine, some high cloud at first this morning. Westerlies dying out by midday. 21C high, 8C overnight.

Wellington​ Fine, some morning high cloud. Northerlies easing in the morning. 18C high, 12C overnight.

Nelson​ Fine. Light winds. 20C high, 8C overnight.

Christchurch​ Fine. Light winds this morning. Northeasterlies by evening. 17C high, 4C overnight.

Dunedin​ Fine. Westerlies dying away and northeasterlies developing this evening. 17C high, 7C overnight.