NZ Weather Forum

http://www.stuff.co.nz/stuff/0,2106,3136702a10,00.html

It sure is storm season!

This photo is looking toward Penrose/Mt Wellington area at around 8.30am this morning.

I was in the Mt Wellington area about 8.15am, not far from the affected area, visiting a builders merchant. Weather was very dark with a threatening cb arcus cloud over the area followed by very heavy rain.
I didn't observe any wind. Spwill's photo captures the weather scene.

That is a wicked photo! Where's it taken from?

Awesome shot .... looks like something out of Day After Tomorrow

Pretty awsome Spwill!!

Good rain and like that base on the leading edge.

Have been looking back over the mornings photo's for shots taken in the direction of Penrose/Mt Welington but I had deleted most of them before I heard the Twister story.
This photo was taken about 7.45am and the cloud in the photo would have been moving toward Penrose/Mt Welington.

I had just got home about 8:25, and looking across to auckland, about the penrose area, there was a very dark area of cloud dipping down lower than the normal cloud base....but you see that ...the cloud base is not always level....so I didnt think anything of it much...must have been the source of the mini twister (it was on the trailing edge of the squall line Spwill, which would have been behind the rain , and so you would not have seen it!

Mini-twister or downburst? That picture by Spwill and the descriptions of very heavy rain accompanying the wind ("The wind struck without warning amid heavy rain about 8am and disappeared almost as fast" - Stuff) sound to me more like an intense downburst, not a tornado.

Yes, more likely a microburst. However, as Brian observed, there was considerable lowering of the cloud over that area. So a tornado possible.
Although upper soundings suggest only weak steramwise vorticity over the Auckland area this morning.

Weather Watcher wrote:Mini-twister or downburst? That picture by Spwill and the descriptions of very heavy rain accompanying the wind ("The wind struck without warning amid heavy rain about 8am and disappeared almost as fast" - Stuff) sound to me more like an intense downburst, not a tornado.

If it was a micro-burst how then do you explain the eye-witness accounts??
http://www.stuff.co.nz/stuff/sundaystar ... 16,00.html

Because as far as im aware a tornado differs from a downburst in that tornadoes lift their winds, (explains why debris were thrown up into the sky ie: wheelie-bin) downbursts are quick bursts of wind.

University of Chicago storm researcher Dr Ted Fujita ...The microburst, on the other hand is confined to an even smaller area, less than 2.5 miles in diameter from the initial point of downdraft impact. An intense microburst can result in damaging winds near 270 km/hr (170 mph) and often last for less than five minutes.

03 Stormchaser wrote:University of Chicago storm researcher Dr Ted Fujita

Yay, it's Uncle Ted

i go for a small tornado too (re reports of lots of debri in the air)
going back to the CB that dumped all the hail from port waikato to the city,i caught up with some locals tonight, and in Pollok, south of me here, they had 20mm hail (it was bouncing off things high in the air), and there was a funnel cloud that developed but did not reach the ground.,..now I just happend to take a photo that morning, and the cloud system sure was impressive.....see photo

Found this photo taken a few minutes before the other photo.
Ruawai Rd and Bean place are located just to the right of the small Mount to the left of the Photo. Thats Mt Welington. They are not quite in the heavy rain.
Whether it was a Twister or a Microburst I would say this photo captures the moment before it was about to strike. Photo was taken from Mt Eden

There looks like a lowered part of the cloud base just over Mt Wellington in that last shot.

Judging by what you guys have put up, I say it was a micro-burst, nothing tornadioc about it it, if there's such a word

JohnGaul
NZTS

a microburst will not send wheelie bins up into the sky

tornadoes occur quite often in this part of the city.....the Waitekere ranges are the ingredient

spwill's photos look to be after 8.30am. The timing of the wind event was 8.10am. Judging by reports in the NZ Herald, I am thinking an F0-F1 tornado.

that was the same protusion from the bottom of the cloud, me thinks, that i can could see from over this side of the manukau
it probablky went as quick as it came
with all this cold air aroudn and Cb's and a much warmer than the air manukau harbour (it does not take much sun to warm it up as it is so shallow), it does not surprise me

going back to the CB that dumped all the hail from port waikato to the city,i caught up with some locals tonight, and in Pollok, south of me here, they had 20mm hail (it was bouncing off things high in the air), and there was a funnel cloud that developed but did not reach the ground.,..now I just happend to take a photo that morning, and the cloud system sure was impressive.....see photo

Thanks for the report. Yes, the storm looked quite threatening into the south. Hail over Auckland that morning must have woken most of the city. Stones 1cm here with a light coating on the ground.

In todays NZ Herald an eye witness to yesterdays Tornado/Microburst said, "It was just like a path of wind about 50m wide with heaps of leaves gathered up there, swirling about 20m in the air above my head". This would suggest a Tornado rather than Microburst.
NZStorm was in the area at the time and said he experienced no wind. I think a Microburst would be more likely to show up in the above photos than a small Twister which probably lasted a minute or two.
Looks to me like it was a Tornado.

Maybe it was a whirlwind or small-scale eddy associated with the leading edge of the down-burst?

Sounds very localised and yes it sounds like a tornado to me!

The wheely bins thing up in the air makes it sound like a tornado to. A microburst would affect a larger area would it not?

But that's all I know, I wasn't there so can't be absolutely sure but it sounds like something whirley!

Now, was that Rakaia one a tornado is the question?

there was roofs lifted off houses and trees uprooted, from reports I heard on the radio...
more than a whirlwind
it was a small tornado
also, it was after the main squall line/rain band me thinks too?

I agree Brian.