The "enormous" weather system forecast to move over New Zealand this week will drag in chilly temperatures for the South Island.
A high pressure system thousands of kilometres wide and labelled "enormous" by Weatherwatch is slowly making its way towards Aotearoa from Australia and expected to cover New Zealand by the end of the week.
NIWA meteorologist Chris Brandolino told The AM Show that the South Island should prepare to wrap in blankets with "chilly" temperatures expected. He said while typically high pressure systems bring "happy weather", this high is "so strong" and coming in from the west, meaning cold weather.
"As the high comes in from the west, think of it like a cog, air flows anti or counter-clockwise, so as the high is coming in from Tasmania it is going to siphon some cold air from the polar regions, it is going to get us cold, the high comes over head, the air sinks, clear skies, a bit of snow on the ground, long nights," he said.
"As [the high pressure] moves in, it really drags in the cold air from the higher latitudes so that sets the scene for some really cold nights Saturday and Sunday morning."
The AM Show host Duncan Garner said he was initially confused because when he heard "high pressure" he thought "summer is coming". Brandolino replied that the area the weather system is coming from is key.
"High pressure, in the summertime, typically it would bring very warm weather because the air is clear, the sunshine is out longer, the days are longer, but it also depends where the high is coming from," he said.
"That high, think of a cog, if it is positioned to our west or coming in from the west, we are going to get cold at first. When that high goes away, to our east, we will get a warmer flow but that won't be until next week."
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