Kiawaka, Northland Tornado? - Jul 12

[Nev]

I heard a report on Zb this morning of a house loosing part of its roof at Kaiwaka,Northland. Its was reported as a tornado..

Was also quoted in the NZ Herald... 'Tornado hits Northland houses overnight'

Edit: And a few more details from Stuff... ''Tornado' wrecks Northland house'

[Manukau heads obs]

I was right then to raise the awareness that those CB's had tornado potential

[03Stormchaser]

Any wind damage seems to be called a tornado these days. Need to see the proof before im happy to confirm it is one.

[NZstorm]

Any wind damage seems to be called a tornado these days. Need to see the proof before im happy to confirm it is one.

yes, it can sometimes be tricky to tell a tornado from a strong squall gust when the damage is extremely local like in Kaiwaka.
Structural failure of a roof can easily happen with a 70knot gust if the house is not that sturdy.

The Waikanae event looks very much like a tornado though.

[Manukau heads obs]

but when people describe the sound like a 747 jet, I think that more than just a squall...

[03Stormchaser]

The Waikanae event looks very much like a tornado though.

Yes not doubting that, a van being lifted, spun then dumped doesnt happen in squall. The Northland damage isnt tornado related and im sure the news who are reporting it as that have even less of an idea than I do, but the word tornado sells, because at the end of the day the news sell's advertising, its how they make there money, and word tornado is a money spinner.

[Manukau heads obs]

the northland one news story describes a trail of destruction though

and it arrived very suddenly without warning

and there were all the hall marks of CB's strong enough to produce a tornado that evening, as evident by rotation in CB's on the rain radar signatures

and there was 5oC temperature and DP boundaries with the CBs
(i.e from 15C to 10C...thats alot of forcing)

[03Stormchaser]

The "75m" path of destruction as they are calling it isnt exactly proof of a tornado.
Would be better if they shot more footage of related damage rather than just the roof.

[Manukau heads obs]

I do agree that just saying there was alot of debri on the road leading up to the house is not alot to go on
and also the trees around the house are still standing...could mean the wind was very isolated...ie a brief tornado touch down...
the article talks about it being a well maintained house...the roof looked like that off a haybarn if you ask me,..not that strongly built...

[NZstorm]

I would expect a tornado to break the roof into pieces but its in one big sheet in pic.

Photo sourced from stuff news.

[Nev]

Yes, I'm not really convinced by this one. The 1am radar doesn't really support any activity over Kiawaka at the time, although the 12am one might. Also that fact the resident who lost her roof made no mention of any heavy rain before or during the event, just distant lightning. And although the Herald ran the headline '75 metre trail of destruction', it sounds more like a trail of scattered debries, i.e. pink bats; other reports say destruction over just 5 metres. A good squall or gust-front can be incredibly loud; a resident way over near Whakatane earlier the same night said, "the noise of the wind was horrendous". And yes, looking at pics of the displaced yet relatively intact roof complete with purlins and undersize rafters suggests it probably wasn't adequately fastened to the main structure.

This story from the Northern Advocate is interesting... 'Tornado hits Kaiwaka home (+ video)'
.

[MadDog]

^Nev,

Could it possibly have been some form of Downburst? Considering the lack of rotational-like destruction and evidence of nearby electrical storms. On the other hand, there was a lack of heavy precip.

[Nev]

Hi MadDog and welcome to forum.

I think the other guys on this thread could probably answer that better than me , but a downburst or microburst also seems unlikely for the same reasons above, i.e. they'd have to be caused be a by a cb almost directly overhead and their associated straight-line winds generally only have range of a few km or less.

Not saying there wasn't any T-Storms over Kiawaka at the time, just that the available evidence so far tends to suggest otherwise.

More outages on the island today btw.

[Manukau heads obs]

the rain radar you posted above does show a CB up wind
the news articile said the occupant did notice lightning in the distance beforehand
so there was an approaching CB

[NZstorm]

Surface wind at Whangarei airport at 1am was 310Deg (WNW) 10kts G20kts. Temp 11C, Dp 8C. Those numbers don't point to a tornado. Generally for tornadoes I like to see a higher surface dewpoint and a surface wind more into the north. BTW 850mb wind was about 290Deg 40kts.

[Manukau heads obs]

Kaiwaka is pretty exposed to the WNW, being not far inland from the Kaipara harbour, and with a funelling effect beside the Brynderwyn ranges
so it could have been a particular nasty squall....downburst type thing?