"A little unusual" - Extreme weather in New Zealand

White, wet - and a little weird

Unusual weather system dumps soft hail over Auckland region and has some fearing a tornado

NZ Herald,

11 August, 2015

Is that snow? Was that a tornado?

A day that started off fine and clear for most areas of Auckland yesterday quickly turned into something a "little strange".

Reports of tornadoes and snow came around 3pm when a cloud opened above State Highway 1 on the North Shore and downpours began.

Hail fell all around the Auckland region, covering some areas in a blanket that resembled snow.

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A funnel cloud appeared on the North Shore, fooling some that it was a tornado.

Impressive lightning displays were captured in some areas, and thunder booms shook houses.

MetService meteorologist Claire Flynn said the unusual weather was caused by a weather system that more commonly appears in summer.

"There's really cold air sitting aloft over Auckland, and in the afternoon when the ground heated up a little ... the warm air rises and that's what is causing these showers.

Pics: Hail storm hits Auckland

"It is more common in the summer because the ground heats up so much more. This was a little strange because the air aloft was so much colder than it usually is it just didn't take that much heating ... to set them off."

Aucklanders were excitedly taking photos of what appeared to look like snow falling and collecting on the ground from about 3pm yesterday.

However, Ms Flynn said it was actually soft hail called graupel.

It was definitely not cold enough for the real white stuff, she said.

"The temperatures in Auckland were around 6C and 7C. So, it's not snow, you need less than 2C or 1.5C for snow."

Graupel is formed like hail, but hail is cycled through thunderstorms multiple times, which lets it firm up and grow large.

"Poppy Rowe, 2, of Grey Lynn, on her white deck. Photo / Julie Clothier

Graupel tends to drop a lot quicker than hail, and is softer and smaller than hail.

"Because of the intense precipitation, a lot of [graupel] can drop in a short amount of time," Ms Flynn said.

At the same time as the hail and showers were falling, North Shore residents may have looked to the west and seen a funnel cloud appearing in the sky.

The funnel cloud led to many reports of a tornado forming, but it was another case of mistaken identity, Ms Flynn said.

"I wouldn't go so far as to call it a tornado."

The funnel cloud was caused by converging winds and was amplified by the other weather activity, she said.

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Ms Flynn said the cloud didn't appear on any radars and would have been harmless.

Ms Flynn said the pool of very cold air was moving away and showers would ease overnight.

Last night WeatherWatch.co.nz said the heavy hail and graupel downpours over Auckland had eased by about 8.30pm.

Below average temperatures

Aucklanders are waking up to a chilly and frosty morning today.

MetService meteorologist Nick Zachar said it was chilly in Auckland this morning.

"It looks like temperatures of between 3C and 4C right around the Auckland region, there is likely some light frost in some places, but there shouldn't be hard frost anywhere, and certainly no severe frosts.'

Mr Zachar said skies across the region were clearing, and a fine day with a high of 12C could be expected.

"The skies are clearing quite nicely after the showers that we had yesterday.

"There might be the odd shower in the very far west but overall, it should be quite a nice fine day in the Auckland area."

These chilly temperatures were below average for this time of year, Mr Zachar.

"In Auckland city on average, there is a low of around 5C for August, so it is a little bit cooler than normal. After the mild week we had last week it is going to feel quite chilly this morning."

Meanwhile, most of the rest of the country was also looking fine today, he said.

"There is a nice large ridge moving over the country slowly, so the places to be are pretty much the whole South Island, and especially the West Coast."

Things in the North Island were also looking fine today, with the exception of the Hawkes Bay and Wellington.

"There is a fair amount of showers with the southwesterlies [in these areas], and that should eventually ease over the next 24 to 48 hours as that ridge pushes on the whole island, and we are expecting pretty nice weather for the next couple of days overall."

Grappling with graupel
•Rain is liquid precipitation.
•Hail is frozen precipitation that is cycled through thunderstorms.
•Graupel is soft hail.
•Snow is ice crystals stuck together.
•Sleet is snow that melts before hitting the ground.