Chaotic weather system behind weirdly-shaped hail

Tuesday, 13 August 2019

North Taranaki residents woke to a dramatic Monday, with a tornado, hail and high winds wreaking havoc across the region.

There's been plenty of big winds, heavy rain, deep snow and even a tornado or two - all of which might be expected from a stormy period at the end of winter, but what's with the strangely-shaped hail?

The spiky hail - some pieces several centimetres long - had a big impact in Taranaki on Monday, and there were other reports of irregularly-shaped large hail from Auckland and Wellington.

It was thought that during the time the hail was falling there had been some melting and pieces of hail had collided, Ferris said.

MetService meteorologist Lewis Ferris said the strangely-shaped hail was new to him. 'Usually they'll be spherical,' he said.

'They were in these strange-looking shapes because they had collided at some point.'

The particularly chaotic nature of the weather system on Monday was thought to be a factor in the strange hail shapes.

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'They were in these strange-looking shapes because they had collided at some point,' MetService meteorologist Lewis Ferris said of the strangely-shaped hail.

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Normally hail grew in strong updrafts in a cloud. 'It goes up and up and gets larger, then it falls out so you get a more spherical shape,' Ferris said.

But the system on Monday was particularly chaotic.

'What we think yesterday, was they were going up, fell out, then because of the chaotic nature of the system and how strong the winds were, the hail stone was blown back into the very strong updraft.'

It was thought that during the time the hail was falling there had been some melting and pieces of hail had collided, Ferris said.

Then when it was blown back into a strong updraft there could have been some re-freezing.

'That could have happened a couple of times', he said. 'That's what we think has happened.'