http://www.stuff.co.nz/national/115384287/rare-weather-heads-towards-new-zealand
https://twitter.com/NiwaWeather/status/1167575078466248704
-> Onderste draadje voor uitleg
Opwinding bij onze collega-weerfreaks in Nieuw-Zeeland. Een SSW vindt plaats en kan mogelijk effect hebben op het weer op de grond. Zie hieronde voor de tekst van
Niwa said the first impact of the SSW could reach New Zealand late next week, as a feature moved in from the Southern Ocean near Antarctica. Before that, by the middle of next week, a sub tropical low moving south could start affecting mainly the North Island.
It was possible those two features could join forces and affect the weather in New Zealand late next week and into the second week of September.
"Next weekend is ... when we could see that first wave of unusually cold weather and unsettled weather," Brandolino said.
There could be snow to low levels, mainly in the South Island, and strong winds. Similar periods of unsettled weather could be repeated during the first half of spring because of the SSW.
Noll said the SSW could weaken the structure of the polar vortex - a swirl of very strong winds in the stratosphere that typically encircled Antarctica and tended to keep cold stormy air locked up over the pole.
For now it was centred neatly and cleanly over Antarctica, but in the next 10 days it was expected to weaken, become displaced and oblong, Noll said.
"And this structure, as it weakens, can enable air masses from the pole, as it becomes weaker, to escape outward."
By the middle of October the effects of the SSW were expected to begin to fade, Brandolino said.
He thought it likely that in one of the next three months the nationwide monthly temperature would be be below average. The last time that happened was 31 months ago in January 2017.
Minor SSW -> forse temperatuurstijging op 10 hPa. Ik zie geen reductie tot oostelijke wind op 10 hPa.