First major storm of year may strike New Zealand in early January

The country could be hit by its first major tropical storm in the second week of the new year. Photo / Weatherwatch

The country could be hit by its first major tropical storm of the season in the second week of the new year.

WeatherWatch said the changeable spring-like weather would likely continue into the first half of the month.

It comes as parts of the North Island experience a drier than average start to summer with no prospect of significant rain in the next seven days.

However, the weather in the tropics around northeastern Australia and the tropical islands north of New Zealand was heating up and storms and downpours are increasing.

Some long-range models were showing a potential ex-Australian low rapidly deepening over New Zealand and bringing a storm to the country in the second week of January.

"We have to look for a trend to form - clearly the data is seeing a low near Aussie so that's what we'll be monitoring," said head weather analyst Philip Duncan.

But the problem with even reliable long-range models is the storm may be replaced by a high in the space of a day.

Duncan said the pattern of temperatures dropping 10C from one day to the next was not the norm in a La Nina summer.

He said a change was likely and may be sudden if it came from across the Tasman.

Computer modelling was picking up a link to more La Nina-like-low near Australia.

"So while the next couple of weeks do see more of the same changeable, unsettled, weather, all eyes are looking north and northwest for the first signs of a breakaway system from La Nina-affected Australia and the South Pacific tropics," he said.

At the moment Australia was facing intense weather connected to La Nina as heavy tropical downpours delivered record-breaking rains to Uluru.

But in New Zealand the weather pattern and shape of the highs was keeping the tropics out and bringing west to south-west winds across the country.

"It's this airflow that is giving New Zealand the odd southerly injection - bringing in cloud, wind and cooler weather but keeping many in the east sunny," he said.