A rare mesocyclone was captured above Auckland yesterday. Photo / NIWA
A rare mesocyclone was captured above Auckland yesterday. Photo / NIWA
A rarely-seen meteorological phenomenon - and one linked to tornadoes - has been caught on camera over Auckland.
Amid humid, showery conditions in the city last night, Niwa’s live cameras picked up a strange, swirling pattern within the dense cloud.
This was a mesocyclone - a spinning vortex of rising, converging air that often formed within the same convective storm clouds that produce hail, thunder and lightning.
Sometimes spanning just a kilometre or two across, they’re also known to spawn twisters.
Niwa meteorologist Ben Noll said last night’s mesocyclone was spotted above the CBD just before 7pm, on the western edge of a shower that passed over the Hauraki Gulf.
Hamish McCourtie snapped the mesocyclone from his boat just offshore from Auckland, shortly before 7pm. Photo / Hamish McCourtie
“It likely came about from a combination of shifting winds, from the surface up to a few kilometres in the atmosphere.”
Those converging winds – which included sea breezes, but also those within the cell of the storm cloud itself – caused a “frictional” effect that resulted in the rising air rotating around a vertical axis, ultimately creating a swirling, moving mass.
“I don’t think we see these all too often – it’s definitely an unusual kind of cloudscape.”
Aucklander Gina Boniolo spotted last night’s mesocyclone in the skies over Ellerslie and Newmarket while driving home from Tauranga. Photo / Gina Boniolo
Forecasters had earlier that day advised of possible severe thunderstorms in Auckland and other areas.
While no lightning occurred over the city, Noll said the convective clouds the mesocyclones formed within were similar systems to those that generated thunder.
“It’s the same principles, in that you need warm, rising air, and in this case we had those winds coming together.”
Karl McGhie photographed the mesocyclone from the Post Malone concert at Auckland's Western Springs Stadium last night. Photo / Karl McGhie
Last night’s spectacle would be a much more common sight in places that routinely experienced severe thunderstorms and tornado activity.
“We do of course get our fair share of strong to severe thunderstorms in New Zealand, and because a lot of people live in Auckland, I guess there’s potential for a lot more eyeballs to see them.”
Forecasters are expecting more dramatic weather this week, with near record-breaking spring temperatures set to sizzle parts of the country before a polar blast sees the mercury plunge a chilly 10C in 24 hours.
MetService forecasts Twizel, Wānaka, and Timaru could be some of the warmest spots today, reaching 27C, 26C, and 25C.
Niwa said the warm temperature is a result of an overhead air mass from eastern Australia, which may even bring Aotearoa’s first 30C this spring.
