7 Jan 2019

Cool respite in the south likely to be short-lived

2:31 pm on 7 January 2019

There's a break from the heat for southern parts of New Zealand today as a cold front moves north.

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Photo: RNZ / Richard Tindiller

Australia has claimed pavlova, Russell Crowe and jandals from New Zealand, but this country is getting a lot of hot air in return.

Niwa meteorologist Chris Brandolino said hot air off the Australian continent, further enhanced by the foehn effect - hot, gusty winds from the west - is responsible for high temperatures seen here this week.

A föhn or foehn is a type of dry, warm, wind that occurs in the lee of a mountain range, such as the Southern Alps.

"When those winds move down in elevation, they warm even further. That, in a nutshell, was the reason behind the warmth," Mr Brandolino said.

He said Canterbury's record temperatures on Saturday now top the charts so far this summer.

"Up until the weekend the warmest summer temperature so far this year was Cromwell on 32.8 (degrees Celsius) but that was beaten on Saturday - 33.8 at Wakanui in eastern Canterbury, just south-west of Christchurch

"Then on Sunday we had some very warm temperatures reaching pretty close to 33 degrees in Blenheim," Mr Brandolino said.

For South Islanders who have endured a blistering heat in recent days, he recommends making the most of the current cooler break because it is not going to last.

MetService is showing today's warmest spot to be Kerikeri in Northland, expected to reach almost 27 degrees, while those in the eastern suburbs of Christchurch will be pulling out the jerseys with an expected low of just 16 degrees.

Mr Brandolino said the respite is due to a cold front moving north, but it does not plan on hanging around.

"So, a puff of cooler air has worked its way into the South Island - I don't think it will quite make its way further north, but it will be short-lived.

"I think by Wednesday we'll be looking at a return to very warm conditions across the South Island, once again temperatures flirting with, if not exceeding 30 degrees across the eastern part of the South Island, particularly around Canterbury and south to Otago."

Mr Brandolino said beyond Wednesday, the warmer temperatures are expected to shift north towards Marlborough, and then cooler temperatures again on Friday and Saturday.

"That too will be relatively short-lived as it warms again early next week, and that could signal a period of more persistent warm, but we'll see. It's a bit too early to say, but either way the theme over the remainder of January will be warm days.

"The cooler days will be the exception and certainly not the rule."

Mr Brandolino said sea temperatures around the New Zealand coastline were above average.

"All coastal regions are experiencing sea temperatures anywhere from as little as one degree above average to (the long-term average for the time of year), to as much as three degrees above average."

Mr Brandolino said the bottom line is that sea temperatures, while not as warm as last year, are above average all around the country. He added the trend extends far out into the Tasman Sea.

"It's a critical ingredient in understanding our air temperatures," he said.

Mr Brandolino said it's too early to say if warmer seas around New Zealand are an indication of what the cyclone season might bring in late summer.

"At the moment there are some unusually cool waters to the north of New Caledonia, basically from Fiji south. So in between New Zealand and Fiji and west towards New Caledonia and Queensland, the ocean temperatures - while warmer than they are here, are cooler than average for the location and the time of year."

He said tropical cyclones need warm water of least 26 degrees Celsius to sustain them, but the water cooler temperatures in their typical breeding grounds could yet change, and the window might open to such storms making their way south to New Zealand.

"But it's not the state of play at the moment, across the tropical north," Mr Brandolino said.