An unusual atmospheric phenomenon is amassing in the stratosphere above Antarctica, called a Sudden Stratospheric Warming.

There have only been 2️⃣ such events on record & number 3️⃣ is possible next week!

It may contribute to unsettled, chilly weather across NZ in Sep-Oct ❄️ pic.twitter.com/LnZxMjVtUT

— NIWA Weather (@NiwaWeather) 22. August 2019