Tornado, storms for North

Northlanders were expected to wake up this morning to the aftermath of small tornadoes that were forecast to spin across the top of New Zealand overnight.

The tornadoes, described as small, isolated and not uncommon in springtime, were expected to be joined by thunderstorms and heavy rain.

Wind gusts of up to 110km/h were also expected overnight.

Severe weather forecaster Erick Brenstrum told the Advocate such tornadoes could last just a few minutes but could be strong enough to uproot trees and disrupt power lines.

He said there was a danger of large items, such as trampolines and garden furniture, being picked up and thrown about.

Mr Brenstrum said up to 30 lightning strikes had also been recorded about 150km west of Northland yesterday afternoon.

He said the cold front was moving over the Tasman Sea and was expected to make landfall in New Zealand on the west of Northland last night, crossing at around midnight, with the system moving down towards Coromandel and the Bay of Plenty today.

"These tornadoes have the power to uproot trees, and lift roofs on vulnerable farm buildings."

The country was in the grip of a cold southwesterly flow, he added.

The moderate storm and tornado risk applied to Northland last night, then eastern parts of Northland and Auckland, and the Coromandel Peninsula before dawn, spreading to the Bay of Plenty this morning.

A trough expected to move across the central and northern North Island this afternoon was expected to bring scattered heavy showers and possible hail from Auckland to Taranaki.

Meanwhile, the south was also due for a wintry swipe.

A MetService spokesman said: "A very cold southwest flow will spread over southern South Island areas [today] bringing a brief return to wintry conditions."

Snow showers were expected down to 100m or 200m, followed by sleety showers down to sea level in the evening.

About five centimetres to 10cm of snow could accumulate above about 200m.

Southwest winds were also likely to rise to gale force about the coast and hilltops.

"Farmers and other outdoor workers are advised to prepare for strong winds and snowy conditions and shelter any vulnerable livestock," the MetService spokesman said.