Smoke from Australia's bushfires set Auckland's Sky Tower against a dramatic orange-tinged sky yesterday. Photo / Luke Kirkness
Smoke from Australia's bushfires set Auckland's Sky Tower against a dramatic orange-tinged sky yesterday. Photo / Luke Kirkness
Our skies could soon glow orange again, as long as Australia's bushfires continue to burn.
But it would take the same mix of certain weather ingredients to get a repeat, a forecaster says.
Yesterday's sepia-toned haze came from a northwesterly flow that ferried smoke from Eastern Australia more than 2000kmacross the Tasman Sea and on to a broad swathe of the North Island.
Headlights switched on mid-afternoon, temperatures plunged and many people scrambled to call 111 about the colour of the sky. Police issued a plea to the public to save the line for emergencies.
That followed a separate plume that blanketed much of the South Island at the start of the month, giving 2020 a somewhat ominous opening.
Neither event, of course, could compare with the hellish conditions where the fires are raging, turning skies in areas like New South Wales South Coast a dark, blood red in daytime, and effectively creating their own weather.
Niwa forecaster Nava Fedaeff said while there was nothing to suggest Aucklanders would be seeing amber skies again in coming days, it was possible there might be another episode in the longer term.
"The fires have been burning for several weeks now, and it basically depends on the pressure set-up, and whether there is going to be a link between the eastern coast of Australia and New Zealand, in terms of how the winds are steered," she said.
"Every now and again, those conditions come together and mean that we get smoke drifting us. It happened over Otago on January 1, and we've seen the exact same thing over Auckland and the upper North Island yesterday.
"We are just getting these episodic events and we are expecting these to continue as long as the fires are burning."
Yesterday's proved the most significant to date – something put down to the scale of the plume itself, and the strength of the trans-Tasman flow.
"The northwesterly winds provided almost a highway from Australia, and the smoke was travelling ahead of that front."
While a southwesterly change had driven much of the smoke away, she said there was still some lingering over the upper North Island.
Forecasters say New Zealand's skies could bear the orange tinge of smoke plumes as long as Australia's wildfires keep burning. Photo / Angie Hari-Billing
"If we look at the next few days and what we can expect, I'd say there may still be some hazy skies around the likes of Northland tomorrow afternoon," she said.
"But, while there has been a big [high pressure system] affecting Australia, which has been doing a lot of the steering, we've got low pressure south of us that is now driving southwesterlies.
"So, a lot of the smoke that's coming off Australia over the next few days is going to be travelling east of the fires, and not coming down south enough to affect New Zealand."
The plumes also weren't expected to pose any significant health risk to Kiwis.
While the smoke that travelled over the South Island last week pushed levels of pollution indicator PM10 to three to five times above normal in places, the effect was short-lived.
And where it was monitored, the smoke was neither thick enough nor persistent enough to breach National Environmental Standards for Air Quality – which are expressed as an average over 24 hours.
To put that in context, the average concentration of smoke that impacted South Island were at most a third of the levels that had regularly been recorded in urban Sydney over the last month.
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"Averaged out over 24 hours, you're not even close to breaking what you'd get on a winter's night in somewhere like Arrowtown or Rangiora," Fedaeff said.
Average temperatures across Auckland dropped by about 2C yesterday as the haze covered the city.
A Metservice weather station in Whangaparaoa logged a fall from 19.9C to 16.9C, while one Waiheke resident's weather station logging a 4.6C drop in 40 minutes.
Lux (light levels) also fell from 510 to 18 over the same time, Waiheke man Peter Mangin said.
MetService reported the southwesterly change would bring slightly cooler than average temperatures this week, with some weather watches and warnings early in the week.
Another front would move on to the South Island on Saturday, potentially bringing stronger winds and rain.
The Tararua District and Hawke's Bay south of Napier could expect strong west - northwesterly gales till midnight, with gusts up to 120km/h.
Dunedin could expect westerly and southwesterly gales until 10pm, potentially reaching 130km/h. The bottom of the South Island and Stewart Island could also expect 120km/h gusts till tonight.
