NZ Weather Forum

I recall the last one. I'm pretty sure that was Aaron's famous Tornado Whisperer day. There is a stand of historic genetic pinus radiata near Kawerau it went through, heaps of trees were snapped off at a uniform height, rotation obvious in the way they fell.

I now think this event in Central Otago a couple of years back was likely was a landspout tornado rather than a devil.

http://www.odt.co.nz/the-regions/centra ... -buildings

Yes i would agree with you,as Dustdevils are more to do with summer land heating

Could it have been caused by a NW gust and local topography. Central Otago Cb clouds tend to be spill over showers in decay.

The vortex will have been triggered by an orographic eddy. To become a landspout there would need to be some surface based lift. There was a cold upper trough crossing the area with steep lapse rates. Would be interesting to know what the temperature got to in Cromwell on this day.

^ High was 13.9C in Cromwell that day, 12-13C around the time of the event (DP 5C) with a max NE gust of 59km/h, no rain until later that arvo (although the event was about 15 km NNE of Cromwell).

Satellite pic
http://satellite.landcareresearch.co.nz ... d21079.txt

Twister seen in Waipu
http://tvnz.co.nz/national-news/twister ... witterfeed

7 tornadoes reported in the media this year since March.

2010 was an uneventful year for tornadoes in NZ due to La Nina.(warm upper air).

There is an article is Stuff today http://www.stuff.co.nz/national/5352968 ... y-to-track - Metservice say a database on NZ tornadoes would be useful to them

Barrow said there was no database that recorded tornados in New Zealand, but such a database would prove useful.

"It would really help us quite a lot, but you need a good observational network that just doesn't exist," he said.

"There's a real difficulty in confirming a tornado has occurred."

Maybe they could make use of the forum?

I've plotted a chart of tornado damage occurrences for Taranaki since the year 2000. I have found 18 days with events and plotted them on a chart. The region in the vicinity of New Plymouth certainly looks like NZ's tornado alley although maybe waterspout alley is a better term. Other regions that stand out for waterspout occurrence are Westland, Kapiti Coast and Bay of Plenty. Exposure to the N or NW is the important factor.

Some more tornado trivia, NZ's highest rated tornado was F3 which was the Motonui,Taranaki August 2004 event. The longest track tornado was possibly the one that went through Awhitu Peninsula, south Auckland in September 1990. Looks to have traveled 25km.

Mention here of a tornado in Huntly back in 1975:

A tornado struck near Huntly, in the Waikato, knocking over a line of power poles and destroying a hay barn, parts of which flew over the heads of children playing nearby. A service station at Waerenga was ripped apart and a number of houses damaged. Fallen trees cut roads and brought down power and phone lines in many other parts of the country.
http://blog.metservice.com/2011/10/rugb ... -the-rain/

No surprises that is was a winter tornado.

Mention here of a tornado in Huntly back in 1975:

There was an F1 at Huntly in August 2000 as well.

Yes, here's a couple of NZ Herald stories about that 2000 Huntly 'tornado'...

'Huntly cleans up following mini tornado'
'Twister's lash wakes Huntly'


Also came across this compelling account from 94 years ago, c/o the NZ National Library archives...

'TORNADO AT HUNTLY' - Ashburton Guardian, 19 June 1917.

NZstorm wrote:NZ's highest rated tornado was F3 which was the Motonui,Taranaki August 2004 event.

I would challenge that, from my understanding the Frankton Tornado was not EF documented (due it being 1948) and looking at the historic photos of the damage I bet would have met or have exceeded the damage of that tornado in 2004.
References: 1 and 2

I tend to agree Tim, the volume of damage at Frankton was far greater than the Motonui tornado, the later being a rural tornado.
There are photos of the Frankton tornado damage in the NZ herald which I have viewed a couple of times at the Auckland library.

The Motonui tornado did get rated and I think it was NIWA who gave it the F3. The farm house that was hit was reduced to kindling. Very rarely see that kind of damage in NZ. I think it was a case of the house being the first sizable obstruction the tornado hit, which meant the house took the full force of it. I did visit the area about 5 days after the event and did a bit of a survey.

The little blue bcnz book from 1978 depicts several in january 20th 1975 with a low over central n.z with an anticyclone over the far south providing colder air and westerly flow where they occured,mostly wiakato guess most have the book.

Picture here from the NZ Herald of the left overs of the house at Motonui August 2004.

The tornado season for the North Island is finished now. There is a clearly defined season from April to October, about 90% of the NI tornadoes reported occur within this time frame.

The season for landspout tornadoes is during the summer months when we get cold air masses being heated. I have noticed in Auckland/Waikato they seem to occur with weak easterly flows converging with sea breezes.

Landspouts are formed by stretching upwards of surface vorticity.

1953 Friday 3rd Apri
A man was killed from a collapsing bus shelter that was struck by a tornado that formed in the North Shore suburb of Bayswater which then swept over the harbour and struck Remuera.

More here:
http://news.google.com/newspapers?id=4d ... 1932&hl=en

Another mention here of another Tornado that looks like it took much the same path but way back in 4th November 1863!

http://paperspast.natlib.govt.nz/cgi-bi ... --0--&st=1

Fascinating articles, thanks so much for those links, 03Stormchaser

Thanks for those reports 03Stormchaser.