NZ Weather Forum

I came across this write up on a website. I have read this before smewhere. Its amazing how little has been written about tornadoes in NZ. I won't credit the author as I don't know who it is.


"Tornadoes of New Zealand
New Zealand experiences, on average, about 20 damaging tornado events each year. The tornadoes are typically very narrow and have short tracks. Most are in the F0 to F2 range.

Most tornadoes in New Zealand have been reported in the North Island, particularly around the Bay of Plenty and down to Auckland. About 17 tornadoes have been reported in this small but populated region. Another concentration of tornadic activity is found on the western coast of Taranaki near New Plymouth, where 12 tornadoes struck between 1961-1975.

New Zealand's worst tornado struck the community of Frankton then moved into neighbouring Hamilton on 25 August 1948. The twister killed 3 and injured 80 others. The tornado winds lifted buildings, snapped off chimneys, unroofed houses, and uprooted trees. The air was reportedly filled with flying corrugated iron, branches of trees, timber and other debris. Rated an F2, the tornado damaged or destroyed 163 buildings and 50 businesses."

In the last few years there have been significant tornado events at Cambridge, Kaitaia, Opunake Taranaki , Ramarama South Auckland , Albany Auckland. Any others?

Auckland might be a good indicater of tornado frequency over western NZ as the region is well populated so Tornadoes tend to get noticed.

I would call that water spout off the cost of Tauranga/the Mt a couple of years ago. Im sure that would have been tornado if it was over land. That storm was amazing and was rotating

I also think the use of camera phones etc, means events like tornadoes will get captured more often. But yes there is very little written about tornadoes or reported unless it hits a populous area.

spwill wrote:In the last few years there have been significant tornado events at Cambridge, Kaitaia, Opunake Taranaki , Ramarama South Auckland , Albany Auckland. Any others?

The Greymouth and Waimate tornadoes down here plus the one I captured on tape near Halswell in 2002.

JohnGaul
NZThS

I think Taranaki might be the hot spot for tornadoes in NZ.
For the east side of NZ would Canterbury have the highest frequency ?.

spwill wrote:For the east side of NZ would Canterbury have the highest frequency ?.

Possibly.
I haven't heard of reports of tornadoic activity in other eastern areas. eg. Marlborough or Eastern Otago, although unobserved observations of such activity may have occured in the past with active cold fronts moving over those areas.

JohnGaul
NZThS

spwill wrote:IFor the east side of NZ would Canterbury have the highest frequency ?.

I overlooked Bay of Plenty. I see MetService have Westland as having the highest frequency in NZ.

jamie.haultain wrote:I would call that water spout off the cost of Tauranga/the Mt a couple of years ago. Im sure that would have been tornado if it was over land. That storm was amazing and was rotating

There were multiple vortices in that event, I watched, photographed and recorded over 20 minutes and I missed the start, not sure how long it went on for. A very good thing it was so far out to sea.

That was almost 2 years ago, I've got heaps of photo's & some video I've never posted. I even took some photo's in the lead up to that event. I've been pretty slack not posting those photo's or the Darwin video/photo's.

There are two seasons for tornadoes in NZ,

Winter season (April to October) which affects the west and north of the country.

Summer season which affects Southland to Canterbury and also the inland North Island.

Over 90% occur in the winter season. The winter season is the season for strong upper levels systems crossing NZ. In the summer, the strong upper level systems tend to be confined to the south.

There have been 4 other deadly tornado events in NZ besides the recent Albany tornado.

Frankton, Waikato 25 August 1948, 3 fatailities

Opunake, Taranaki 22 April 1973, 1

Albany Auckland 24 April 1991, 1

Motonui, Taranaki 15 August 2004, 2


There was a fatality in Onehunga, Auckland in 1980 caused by thunderstorm winds but can't confirm it was a tornado.
The insurance council say it was a tornado.

NZ Thunderstorm Soc wrote:unobserved observations

NZstorm wrote:There are two seasons for tornadoes in NZ,

Winter season (April to October) which affects the west and north of the country.
Summer season which affects Southland to Canterbury and also the inland North Island.
Over 90% occur in the winter season. The winter season is the season for strong upper levels systems crossing NZ. In the summer, the strong upper level systems tend to be confined to the south.

Yes, I tend to agree in general with this scenario. I recently went through out severe thunderstorm log and the majority of events are certainly in the west of the country and across the north of the North Island. There are about 10 events of one intensity or another each year. There are clusters of reports showing up in places like Auckland and Tauranga. One finding I thought was really impressive is the number reported from places on the South Island West Coast. Over the last few years Greymouth, Hokitika and Westport (not sure about the latter) have reported almost one per year and I think it was in 2007 (would have to check) Greymouth had 3! These West Coast locations are very small sample points and what these reports suggest is that there are many tornado events up and down the West Coast. The ones that occur in Southland, Otago and Canterbury are often associated with supercells in the summer.

Back to the West Coast events... we have found that the circumstances that they occur under in New Zealand are very much like the conditions described in a paper (from memory) called "Cold Season Tornadoes of california and Western Australia" by Hansen, Dosewell et al back in about 2003. A year of so later, a related paper was published about about the Shear Environment for Tornadoes in California. (I can look up the title of this paper if anyone is interested. These two groups collaborated and we have found that the same phenomemna is happeing in the west of N.Z.

Paul

In summer waterspouts seem to be "common" in the north though often in reasonably stable weather/convergence.

Cold Season Tornadoes

They seem to occur on days with moisture levels more typical of the warmer season, eg 18C dewpoint on the day of the recent Albany tornado.

They seem to occur on days with moisture levels more typical of the warmer season, eg 18C dewpoint on the day of the recent Albany tornado.

The low level warm moist advection is certainly a key factor with the cool season tornadoes.

Cold Season Tornadoes of california and Western Australia" by Hansen, Dosewell et al back in about 2003

I have read that paper, very interesting. The California papers are interesting and they emphasize topography as a cause of enhanced shear there.

Actually, they tend to occur in the cooler months - March to November or thereabouts and are associated with fronts moving north over the country.

In addition to the presence of a front, necessary thresholds for forecasting are:

1. Lifted Index with respect to 700 hPa (from memory) less than -0.5C (lifted index with respect to 500 hPa can be around 0C or even a little positive - but if negative then so much the better)

2. Surface to 2km negative shear greater than 20kts. (If the Surface to 1km shear is >= 20kts then so much the better). The winds need to back with height. This is common on the South island west coast because in the low levels a northeasterly barrier jet is often present (flows parallel to the coast) and then winds aloft turn more northwest or westerly with height.

3. Need significant low level wind convergence (I forget the value). We use moisture convergence which is always present in the wind convergence zone at a front (typically a northwest wind just ahead of the front converges with a more westerly wind to the rear of the front).

We also look at the storm relative helicity (needs to be about -150 (forget the units) or less) and the surface to 6km shear.

You don't always need lightning in the cloud to have it spawn a tornado. A cumulonimbus cloud is often present but as we all know, waterspouts can be associated with towering cumulus. The Albany tornado cell didn't have any lightning as I recall. The Cambridge tornado of a few years ago had very little. In the case of the Albany tornado, the Whenuapai sounding at midday had very little helicity but plenty of bouyancy (about 1100 J/Kg CAPE). The distortion of the low level flow by the terrain must have created enough storm relative helicity (twistiness) to kick off the tornado. I seem to recall the Greymouth tornado of about 2007 didn't have any lightning either.

This seems logical since the Australia and Californian results don't call for a Lifted Index (wrt 500 hPa) to be -2C or lower (thunderstorm). What we are relying on for 'Cold Season Tornadoes' is very modest bouyancu but lots of wind shear.

Paul

I do remember hearing one account of some lightning with the Albany Tornado. A person who was trying to get video of the lightning and instead filmed the tornado from the motorway..
Replaying my lightning detector logs shows some activity of about the right strength from that direction, though probably mostly intra-cloud.

i have found in all the storms in the USA, probably 70% of the tornadoes ive seen have come from cells that are strangly not very lightning active.

spwill wrote:In the last few years there have been significant tornado events at Cambridge, Kaitaia, Opunake Taranaki , Ramarama South Auckland , Albany Auckland. Any others?

Auckland might be a good indicater of tornado frequency over western NZ as the region is well populated so Tornadoes tend to get noticed.

Good point, about Auckland.
Re other significant events: One could add one in Oakura, on the western edge of New Plymouth, around four or five years ago, I think. Plus another on the edge of New Plymouth's CBD , for which silly old TVNZ news used a fake photo to illustrate it as it came in off the sea.

This link describes a tornado experienced in Ashburton in 1903:
http://paperspast.natlib.govt.nz/cgi-bi ... --1----0--

and this one mentions the "Ruapuna Tornado" - I've been racking my brains to remember when it happened:
http://weatherforum.org.nz/phpBB3/viewt ... 3&start=50
- maybe someone here remembers better than I? - guessing between 10 - 15 years ago?

Orion wrote:...and this one mentions the "Ruapuna Tornado" - I've been racking my brains to remember when it happened:
http://weatherforum.org.nz/phpBB3/viewt ... 3&start=50
- maybe someone here remembers better than I? - guessing between 10 - 15 years ago?

Think it was March 11, 1999.

Thankyou! thought it was a March, and about then. I should have known - it was only a few miles from here.

Not sure if its been mentioned but the Waimate Tornado
http://www.weatherforum.org.nz/phpBB3/v ... =12&t=1721

Methven tornado:
http://www.ashburtonguardian.co.nz/news ... -farm.html

And this on Youtube, Just North of Dunedin in wakawaiti:
http://youtu.be/Sc_Xiempnps

Smaller but brief ones in the past, there was a tornado in Oxford 15th August 2004 a day before heavy snow fell to sea level across the region.
Ive been trying to find the article online through the press but cant find it, it ripped a garage to shreds and tore a spoiler off the back of a car.
Also the Parklands brief tornado back in November 2009.
The Methvan one ocurred on a day when several funnels came down including the waterspout off Sumner and the funnel cloud we encountered while chasing.