Warm weather has sting in the tail

Melissa Wilson and her son Ni, 3, make the most of the sunshine yesterday at Hardinge Rd playground, Ahuriri. Photo / Warren Buckland

While temperatures are set to rise across Hawke's Bay this weekend they come with a sting in the tail - gale-force wind gusts and bursts of rain are also forecast.

While the Wellington region and western and exposed regions are set to get the worst of it, most of the North Island will be affected in some way and could lead to dangerous conditions on some roads.

"Motorists heading home from holidays are strongly urged to check the forecasts and plan ahead," MetService meteorologist Tom Adams said.

Gusts may reach 120km/h in exposed areas.

The wild weather is a result of a strong northwest flow over the country between a departed high and a deep low over the Southern Ocean. It will drag in tropical air, rain and wind.

Those high winds, more reminiscent of what Hawke's Bay traditionally gets in early spring, as well as unusually warm spells, has led to the creation of a new meteorological term for the region, and much of New Zealand as a whole.

Weatherwatch head analyst Philip Duncan has dubbed the weather of recent days, and what is effectively forecast to continue until the end of July, as "sprinter".

A combination of spring and winter, and going into the weekend it suits the Bay well.

"Once we get to Saturday we have warmer winds from Australia and the sub-tropics with showers and patchy rain," Mr Duncan said.

Today, after a forecast 1C overnight temperature for the twin cities, the temperature is set to reach 17C with mainly fine skies although cloud will increase through the day.

Then tomorrow and into Sunday the daytime temperatures are forecast to nudge their way into the 20s - although they will arrive accompanied by the strong to potentially gale force winds tomorrow before things start easing up on Sunday.

Tomorrow and Sunday are forecast to hit 21C, with the possibility of some patches of light rain also.

It will begin to cool from Sunday and into next week, with daytime temperatures of 15C on Tuesday then up to a sunny 17C on Friday.

Mr Duncan said next week would see a lot of westerly winds coming through, with some potentially gale-force blows around some coastal areas "off and on".

While rain looks likely in western areas, eastern areas, including Hawke's Bay, are likely to remain mainly dry.

"The final days of July look like another cold south-west change but the jury is still out on when the country might face a significant southerly this winter."

He said strong westerlies in the Southern Ocean were cutting the southerlies "off at their knees", meaning the really cold air around Antarctica could not escape northwards and onto New Zealand.

"It's a bit like trying to go directly across a very busy motorway without a lane or over-bridge ... so it just sits and waits for a gap in the traffic."

It would only be such a gap in the present westerly systems which would drag truly cold air onto the whole country.

Mr Duncan said past winter records and tracking showed that while the days were clearly getting longer, the greatest chances of a hard-hitting cold snap was between around now and the first half of August.

However, possible cold snaps after that time were likely to be short-lived as the spring weather patterns of September began to take over.