Jamie Morton is the NZ Herald's science reporter.

Downpours predicted in warm winter

Forecaster suggests similarities with 2011 — when snow fell in city after mild season.

It's going to be a warmer winter - but with plenty of moisture.

That's the prediction climate scientists have made for the official cold season.

The latest outlook issued by the National Institute of Water and Atmosphere (Niwa) projects temperatures are "very likely" to be above average in all regions over the next three months, with a probability of between 65 per cent and 80 per cent.

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"Even though we were expecting this, 80 per cent is unheard of - that's a huge level of confidence," Niwa principal scientist Chris Brandolino said. "But even still, it doesn't mean there won't be cold snaps. It's important to remember there will still be some outbreaks of cold weather, bringing frost and snow."

And the picture didn't quite mean all the country would get the buffet of sunny, warm days unusually dished up by autumn this year.

Rainfall levels, too, were likely to be above normal in the north and west of the North Island and the west of the South Island, and either near or above normal in the east of the North Island and the north and east of the South Island.

"Big downpours and more severe weather - that's something that will still be on the table over winter, and more so than usual."

A warmer winter would follow a run of abnormally balmy months for the year which meteorologists have put down to a high number of northerlies, an absence of southerlies and unusually warm seas around the entire country.

Driving the milder conditions over winter would be above-normal sea surface temperatures, especially to the west of the country, and a "general flavour" of westerly or northwesterly wind flows.

What that meant for skifields was unclear. As of yesterday, most skifields were reporting healthy snow bases, with season opening dates just weeks away.

WeatherWatch forecaster Philip Duncan expected a "neutral" winter that, without the effects of El Nino or La Nina, meant more chaotic weather and the odd potential for subtropical winds chased up by southerly blasts.

He said the season could prove similar to winter 2011, when record-breaking warm months were followed by a snow storm in mid August that saw snow falling in downtown Auckland and the hills of Northland.

- NZ Herald

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