Thunder/Hail Storms for Sth Is. - Sunday, Mar 25

[Thunder]

Went out with Mikey and Jase, didn't see any tornadoes. Met up with Ben south of Ashburton for a time. We were on that main big cell as it developed somewhere south of Ashburton. We got some resonable hail, 10 maybe 15mm at the most where we were. Saw a fair amount of lightning, maybe the other guys got some on video. I was trying to muck around with my trigger but it was very difficuilt with alot of rain about so didn't get any lightning. We saw the cell move north but figured it would be going to fast, infact it sort've stalled a little as it got just south of the Peninsula, we should've gone after it but didn't.

Got some nice photo's of it as it went into the distance, another we cell developed around 7pm in the area south of Tinwald but unfortunately didn't give out any lightning. Gave a nice hail shower though and looked good as it moved east. Saw that mammatus where Steve was at Birdlings flat from our location, looked fantastic but we were too far away for a good photograph. Look forward to Steve's pics. We waited for the trough that hit bridlings around 11pm. It hit with vengence! Saw a few flashes of lightning but that was it really, the winds must've been a real gale or something. Very strong as it hit.

Will right up a report this week. Here's a few pics anyway.

[Manukau heads obs]

Nice, love the white/blue contrast

[Paul Mallinson]

Very nice pics 'Thunder'.

You may be interested to know that we got a call from a reporter last evening who said a tornado had been reported near Leeston which caused minor damage to a house and paddock

Paul

[Nev]

Yes great pics Aaron. And thanks for the updates Paul.

Yes, seems John got call about the tornado too. I initially thought it may've been pyro-cu they saw.
Did the reporter mention a time btw?

[spwill]

Good reports/photos.

[Michael]

The 3rd one down looks the best

[Nev]

Here we are (was about 4:30pm)...

'Tornado' downs trees in Leeston - The Press (Stuff)
Last updated 08:01 26/03/2012

What was believed to be a tornado tore a path through a Leeston property yesterday, downing trees and hurling branches up to 50 metres.

Leeston farmer Alan Manhire, 43, was shifting sheep just before 4.30pm yesterday when "everything went white". "It was unreal," he said. "A band of rain and hail came p...... down and then it just blew like sh.., but the wind wasn't making any noise, it was bizarre."

A decade-old willow tree, taller than a lamppost, was brought to the ground, along with about 20 other trees on his property. Some branches were snapped off and thrown about 50m, he said.

Manhire thought his car was going to turn over. A friend, who was trying to drive a four-wheel- drive with eight sheep on a trailer could barely move.

The tornado lasted about three minutes and then "everything went dead calm".

Manhire estimated the winds would have reached up to 200kmh. "It was about three times stronger than one of Canterbury's strong nor'westers. I was sh...... myself," he said. ...

MetService forecaster Hordur Thordarson ... predicted isolated winds could have reached about 100kmh. ...

(more...)

[spwill]

Probably straight-line winds rather than tornado , others have also reported the showers to have been very gusty.

[Manukau heads obs]

yeah, I would have gone with a particulary nasty squall with the southerly change?

[spwill]

03Stormchaser was at Birdlings near Leeston and thought the wind gusts were up to 100kmph there.

[Lacertae]

I really like your first shot Aaron !

[Richard]

great photos you fella's,love that second one

[03Stormchaser]

I left home at 4pm, would have got to lincoln about 430, I stopped there and watched the storm over leeston for 5min. In true steve fashion I didnt take any photos duh! But on hearing this report I would agree with spwill that it was more a very strong gust or downburst as the area being hit was almost completely white like it was being belted with heavy hail. I then made my way to birdlings to get in front of the storm. When it hit there it was so intense, probably the most powerful storm ive encounted in Canterbury so im not surprised there was damage.

[Storm Struck]

That storm was very intense it started at midday near Fairlie and was still firing off lightning way off the coast at midnight,so something was keeping it going and on the radars there looked to be a possible hook offshore at one stage.
Even once we had sat through the storm just west of Ashburton with marble hail, the back end which was feeding the storm looked to have some possible rotation but i am not sure if the photos would do it justice.
But i certainly think it was just a really strong squall, the southerly was only asociated with the isolated storms as it was light to no wind elsewhere even away from the storm.
Infact i think there was no wind when we were under the hail core to the west of ashburton, but further back initially where we stopped the southerly picked up which was more closer to the coast side.
As Aaron mentioned we did watch a weaker cell which dropped a decent heavy hail shower near zero visability on the road but no thunder or lightning from that one.
The wind at Birdlings when the southerly hit was fairly strong at a guess around 70-80kmh perhaps which is hard to stand up in when in the open right at the ocean.
It did seem to flare up briefly as it got close to the coast and the enhancement of the peninnsula, which put out two bright purple flashes lighting up the whole CB, but it soon seemed to die down and clip more the southern tip of the peninnsula.
Photos later on, not a bad birthday gift really

[03Stormchaser]

Didnt take alot of photos, mostly take video now days.
Below photo of Mammatus:

MAMA.JPG

Il get a video up in on thursday when Aaron is free to upload it on his comp.

[NZstorm]

Excellent photos guys.

Re the tornado report, I agree, a southerly buster. It didn't look like a tornado set up yesterday but then again, I'm surprised such a strong squall developed.

[NZstorm]

Photo here off trademe of the squall line over Sth Canterbury.

http://images.trademe.co.nz/photoserver ... 8_full.jpg

[03Stormchaser]

It was very warm before the front/squall moved thru about 21C. Dropped to 9C (probably went lower but I didnt check when the hail/gusts were hitting) as the front had already moved over then back up to 13 when I left. So probably all with 30-40min period.

[NZ Thunderstorm Soc]

Very nice pics 'Thunder'.

You may be interested to know that we got a call from a reporter last evening who said a tornado had been reported near Leeston which caused minor damage to a house and paddock

Paul

Yes Paul, I was rang up from her and Paul Gorman from THE PRESS regarding this.
It was the first I had heard of this.
I was watching the cloud as it moved away to the east and possibly because of the persistent westerly or NW maybe pyro-cumulus forms from burn-offs may have added to the instability or possibly could of contributed to this?

[Lacertae]

Very interesting sat pic captured by Aqua at 02:30 UTC (14:30 or 15:30 local time ?) : http://lance-modis.eosdis.nasa.gov/imag ... 5.aqua.1km
You can display the coast line via the vector options.

If you look at the IR pics you can see the cell survived a long long long time ... quite special conditions required ? Centre of a low carrying it away, or feeeding it ?

[Paul Mallinson]

John, I think the energy in the pyrocumulus clouds would be small bickies compared to the energy in that thunderstorm.
With regard to the tornado, there were some good ingredients indicated in the forecast information such as good CAPE to 3kms and shear through the storm. I agree with NZStorm that low level shear/inflow may have been a little on the weak side. However, we did see a very nice hook echo on this and a couple of other cells. The profile of the storms on radar did display a bounded weak echo region BWER at times but in the instances I saw, they weren't all that strong (I didn't see the profile for the storm in the Leeston area). So there may have been a weak tornado but it would have been nice for the reports to have actually mentioned seeing a funnel. I remember the gust potential was about 40-45kts so that would square with some of your comments about estimated gust front speeds of 100km/hr. So there is also a good chance that the damage reported was due to very strong gust front winds.
The reason the cell kept going out over the sea was probably because of the temperature and available moisture held up over the sea relative to how very unstable/cold aloft it was. The whole thing was being driven by a pretty strong short wave trough aloft.

Paul

[mikestormchaser]

I think what Aaron and Jase said sums what i would of said, i thought the hail was 20mm in size in some stones but i think i was just abit overly excited, they were reasonable though.
When we sat out at birdlings flat and that trough hit, man did she blow! and it wasnt gusting either out that way, she was constant!! i filmed one big flash that lit up the CB behind some other CU infront of it but the whole thing pretty much died.
Great day though and fantastic photos Aaron and steve.

[Thunder]

Thanks guys. That second photo is right when the cloud is over the Leeston area at 4.34pm, it did look intense there. Here's another few pics, when travelling through Ashubrton we saw more of this burn off cloud and there was a wind change moving through it at the time. Gave a good idea of what a wind change looks like in the atmosphere as displayed by the smoke. The second photo is of the "Leeston cloud of anguish" at 4.14pm.

I've blown these images up to 100% but can't see anything that odd about the base, apart from one or two photos there may be a decending area sort've but it looks too far to the left of the updraft unless the anything rotating if it was there at all was on an angle going up towards the right? I'll include a cropped photo of that to, taken at 4.24pm. Looking at the second photo in my first post above I'd say at a guess that possible lowering is just above that tiny white shed in the picture, I had moved so the perspective of the picture is a bit different. The lowering looks to of moved aswell perhaps. But realistically can I take a photo of something like that, that far away? It would've been 40km away as the crow flies perhaps, it is those clouds though.......lol

[Nev]

Interesting reports thanks guys.

Below are a few readings around the time of those late arvo gust fronts.
Note that some sites recorded similar speeds again just before midnight and although not so strong at Leeston, Sugar Loaf (30km away @ 600m) got up to around 95 km/hr (51 kt)...

Code: Select all

 Peak gusts to the hour - Mar 25
>hr   km/h  kt    Site
5pm    76   41    Sugar Loaf
5pm    72   39    Leeston 
6pm    69   37    Lyttelton Harbour 
6pm    68   37    Akaroa 
6pm    54   29    Christchurch Aero 

Also here's a cropped sequence of radar images from around 4:30pm showing just the tip of that large cell brushing Leeston in the centre of the image, next to Lake Ellesmere...

[Manukau heads obs]

that lowering is not at all
you are just seeing the edge of the hail curtain