A large thundercloud crosses South and East Auckland last night.  Photo by weather watcher Foehn MacKenzie.

Rain is likely to continue across north eastern parts of the South Island Tuesday while the western half of the North Island sees a gradual return to showery sou’westers. Meanwhile the South Island’s West Coast should again enjoy an almost summer-like day with sunny, warm, weather.

So what’s happening overall?

Much of the North Island is still engulfed in the large centre of this low – the centre of the low itself is very large – about the size of New Zealand. Much of this centre lies over the North Island and out to the north east of East Cape. As the low slowly moves out eastwards into the Pacific Ocean the western side of the low (the area with all the isobars) will move on land onto the west coast. This means a south westerly flow will slowly move eastwards over the North Island – very slowly actually, it wont reach Hawkes Bay until Wednesday.

Meanwhile the South Island is in the squeeze zone between the Low up north and higher air pressure down south. The squeeze zone is just that – an area where the low and high push together, creating stronger winds. So that cold, wet, south easterly will continue over the north east part of the South Island.

For those in Christchurch worried about flooding, I’d say you can relax a bit today – the rain band has become very narrow and is mostly focused across the Kaikoura region and even then it’s pretty much north of Kaikoura. 

The wettest spots today will be from Kaikoura to Wellington, southern Wairarapa and East Cape, with patchy rain or showers possible right along the east coast from Christchurch to Gisborne. 

Showers – some heavy – are also possible from northern Auckland to Northland – mostly along the west coast.

It wont be until about Thursday when the low finally clears New Zealand and drifts out over the open waters of the Pacific Ocean. In the meantime, we’re still expecting a big friendly high pressure system to move in and give much of us some much welcome sunny weather.

But as luck would have it, initial thoughts on this high show it may be travelling quite quickly…that means while Friday to Sunday are looking fantastic for a number of areas, early next week may well see things going back downhill again. But that’s too far out to focus on just yet.

Story by head weather analyst Philip Duncan