Weather: Rainmaker to bring heavy downpours to parts of North Island

Forecasters say a subtropical low will bring downpours to the North Island over coming days – with “warning” amounts of rainfall possible for eastern regions.

MetService forecaster Dom Barry said the system was due to form to the northeast of New Zealand during Monday and a heavy rain watch was already in place for Hawke’s Bay and Tairawhiti, from Tuesday morning to Wednesday evening.

“It’ll bring rain to the likes of Northland, the Coromandel Peninsula and the Bay of Plenty – but at this stage, we’re expecting the most significant impacts to be felt in those areas that have heavy rain watches at the moment.”

That news would be welcome for rain-starved farmers in Hawke’s Bay and Gisborne, where, even at the doorstep of winter, soil levels are running dry to very dry.

Niwa data showed some areas had received just 20 to 40 per cent of their normal autumn rainfall – and could finish the season with near-record deficits.

“It’s really crept up as an issue,” Federated Farmers’ Hawke’s Bay president Jim Galloway said.

“If we get an average winter, we’ll still be going into a spring with probably less feed than is ideal.”

Barry said the coming rain might indeed offer some relief to farmers – but there was also a risk it could cause flash flooding if too much fell on hardened ground.

“With regard to what we’re going to be seeing for Gisborne and Hawke’s Bay, there is still uncertainty in the models as to the preciseness of the [heavy rain] location,” he said.

“As we move closer to this event, people should keep updated, as those areas will be refined.”

More generally, Barry said the North Island’s weather for the week was a messy picture, with widespread cloud and showers out to Friday.

But much of the South Island was in for fine spells, courtesy of a ridge of high pressure.

“Temperature-wise, it’s going be chilly down south because of that ridge, and we’re expecting frosts in a lot of places in the deep south, as well as inland.”

For most of New Zealand, the MetService was forecasting single-digit overnight lows for the week ahead, and highs reaching only the mid-teens.

It comes after a weekend that brought widespread chilly temperatures and snow to the lower and central South Island, with up to 40cm settling on Aoraki/Mt Cook.

Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.