An explosive low pressure system is today rapidly deepening over the waters of the Tasman and will peak in intensity tomorrow morning out at sea shortly before reaching New Zealand.

The low has already become highly visible in the satellite imagery and by Saturday morning the air pressure would have fallen from around 1005hpa into the late 970s.

“The low will thankfully be at its nastiest out at sea, which has been our prediction all week, but it will still hit the country with severe gales, heavy rain and some snow.  It has more energy than the low we saw last week” says head weather analyst Philip Duncan.

Mr Duncan says the forecast couldn’t be more spring-like this weekend with heavy rain, severe gales, heavy snow and the risk of sunburn all in the weekend forecast.

“This is a very complicated system, by that we mean it’s not as straight forward as other lows – this one will be constantly evolving and changing shape across the weekend as it moves over New Zealand, transferring the energy from the Tasman Sea to our west, to the Pacific Ocean in our east”.

“This means we’ll see heavy rain falling on both the west and eastern coastlines and strong winds will affect a number of regions, especially the north and east of the North Island”.

Those in the north, due to the strong winds, will likely still get some sunny weather too – and it should be warm or mild in the north of New Zealand once the main fronts moves through on Saturday.

Heavy Rain
Heaviest rain is likely to be on the West Coast of the South Island, the north west of the South Island (Nelson) and also the lower North Island from Mt Taranaki southwards.  Heavy rain is also expected in the north of New Zealand but should be fairly short lived compared to regions further south, closer to the centre of the storm.

Because we’ll see a new low rapidly developing east of NZ on Saturday this means the rain energy will also transfer over to the east coast – which means Canterbury may have increased river flows from the West Coast deluge then localised heavy rain moving in on Saturday too.

Gales
Many parts of New Zealand will have strong winds this weekend.  The strongest most widespread winds look to be on the northern half of the low – which will impact the top half of the North Island and east of the North Island.

But as with any storm the winds wrap around the centre – and the centre is relatively calm.  The centre of this storm will cross central New Zealand/top half of the South Island during Saturday afternoon.  That means some areas may have fairly calm conditions as the low moves through tomorrow, especially some central and southern areas.

Warnings
At the time this story was written there were already several heavy rain warnings in force by MetService for the South Island.  We anticipate more warnings for others parts of New Zealand as this low moves closer.  

– WeatherWatch.co.nz