Polar jet stream pushing freezing temperatures across New Zealand
Winter-like weather is hitting New Zealand this week and Niwa says the polar jet stream is playing a key role in the freezing temperatures.
Niwa meteorologist Ben Noll said it looked like the polar jet stream would send the coldest airmass of the year northward across New Zealand in the coming days.
“No matter if you are in Cape Reinga or Bluff, you will certainly notice the chill in the air quite sharply right across the country in the next couple of days,” Noll said.
According to MetService, temperatures are expected to go below 0C, such as -3C in Christchurch and -2C in Taupō tomorrow.
Noll said the jet stream was a fast-flowing wind in the upper portion of the atmosphere that pushed weather systems along.
There was both a polar jet stream, which sat closer to the South Pole, and a subtropical jet stream,which tended to sit further north, closer to the subtropics.
Noll said there were occasions when the subtropical jet stream would blow across New Zealand and bring with it warm or unsettled, rainy weather.
Or conversely, the polar jet stream could blow across New Zealand.
“As we have experienced in the last couple of months, the polar jet can be located north of where it typically would blow,” Noll said. “Over autumn, the polar jet has been displaced north of its average position and has more commonly blown across New Zealand.”
This had brought several cold air masses and continued to play an important role in our weather patterns, he said.
Noll said the polar jet stream’s location over New Zealand had contributed to a cold autumn.
March this year was the coldest March since 2012 and it had been a cold start to May.
Noll said it would be interesting to see if any cold temperature records for May were broken. Although, it was challenging to break those cold temperature records these days due to the long-term warming trend across the planet.