By Alexa Cook of RNZ
Antarctica’s warm weather in September is driving the gale-force winds and hot temperatures being felt across New Zealand this week.
Temperatures could reach nearly 30C in Hawke’s Bay on Thursday and the region is under a strong wind watch as fire crews work to try and contain a huge bush fire near Porangahau.
Earth Sciences meteorologist Chris Brandolino told RNZ the weather patterns being experienced nationwide can all be traced back to what was happening in Antarctica in September, when the top of the atmosphere got really warm, really quickly.
“Because of that, there were flow-on effects ... that polar vortex weakened and became wobbly and oblong shaped.
“That low pressure that is frequently over the continent of Antarctica got displaced into the Southern Ocean ... that has really accentuated the pressure gradient,” he said.
Hastings and Havelock North are expected to hit 29C today, which is one of the factors that resulted in a total fire ban for the Hawke’s Bay District until October 27.
Brandolino is helping Fire and Emergency with their fire risk forecasting, and told RNZ the soaring temperatures and high winds can create problematic conditions.
“Conditions are dry, we haven’t had much rain in the Eastern part of the North Island, so that’s helping to set things up with high-end fire risk,” he said.
Three fires are burning in Porangahau, one is 250ha in size and hasn’t been contained yet because high winds have grounded helicopters.
Brandolino said parts of Napier and Hastings had already reached more than 20C by 8am this morning, and will keep climbing by nearly 10C throughout the day.
It’d be the second time for temperatures to reach those heights this month.
“It is certainly unusual but it is not unheard of,” he said.
Brandolino explained that we’ve seen low pressure favouring the southern ocean since September, and high pressure in the northeastern parts of New Zealand. Those two factors have created a steep pressure gradient, resulting in brisk winds.
“Spring usually features these changeable conditions that wind thrives off, but this has been next-level,” he said.
More ‘potent’ high winds and hot temperatures on the cards
Keep the trampoline tied down and the sunscreen handy as the hot windy weather is far from over, with more on its way at the end of the long weekend.
“Another warm surge of air comes down, probably Labour Day and the following day ... that could be potent as well.
“It’ll bring with it another surge of warmth, another surge of wind – and that’s something we need to be mindful of,” said Brandolino.
He’s warning Kiwis that we’ll see very changeable conditions over the next few weeks.
“We’ll get days where it feels like summer and then, a couple days later, it kinda feels like early Spring again.
“Don’t get too comfortable or complacent with the weather because it’ll likely be highly variable,” he said.
The chance for some more rainfall on dry regions will increase later in November.
“We’ll see a change in wind direction, and that could mean a change in rainfall patterns. Northern and Eastern parts of the North Island could have a wet lean,” said Brandolino.
-RNZ