Moist NW flow and severe weather, Upper NI, 5 Dec -

[littleheaven]

Far out, this is a bit scary! Just before that last lot of terrible rain I looked out the back door to the west and saw debris flying up over the hill behind the house. I spent 10 minutes hiding under the house. Back out again now but the thunder has really cranked up again.

[jamie]

Radar showing auckland is really getting punded by some bright colours.

I havent seen a warning from MetService yet.

[Manukau heads obs]

seems to be
whenever you get a NE wind at the surface ahead of a NW wind change behind a fontal line
like today
and when there is a high dew point
there is a tornado /funnel in the auckland area

[Tornado Tim]

ssued by MetService at 02:08 pm Thursday 06 December 2012.
Valid until 02:52 pm Thursday 06 December 2012.
This warning affects people in the following local government areas:
AUCKLAND CITY, THAMES COROMANDEL, MANUKAU CITY, NORTH SHORE CITY, FRANKLIN and RODNEY.
At 01:52 pm, MetService weather radar detected severe thunderstorms near AUCKLAND, OREWA, ALBANY, INNER HAURAKI GULF, DAIRY FLAT, WHANGAPARAOA and SILVERDALE.
These severe thunderstorms are moving towards the eastsoutheast, and are expected to lie near WAIHEKE ISLAND at 02:22 pm and near TAPU and FIRTH OF THAMES at 02:52 pm.
These thunderstorms are expected to be accompanied by very heavy rain, damaging wind gusts and possible tornadoes.
Very heavy rain can cause surface and/or flash flooding about streams, gullies and urban areas, and make driving conditions extremely hazardous.
Very strong wind gusts can break branches from trees, damage roofing, and make driving hazardous especially for high-sided vehicles and motorcycles.
Tornadoes can blow out windows, lift roofs, break large branches off trees, generate dangerous flying debris and blow vehicles off the road.
A Severe Thunderstorm Watch remains in force for AUCKLAND, NORTHLAND and WAIKATO.

[David]

david give it time, the rain just hit takapuna 15 minutes ago, and looks like theres more to come

Yep 7mm at home now
Pouring again at uni

[Powermad]

Photo deleted

[Willoughby]

Topic split.

[Tornado Tim]

Thunder still going strong, nice storm this

12:00 Auckland radar showed 3x potential hooks..

I wouldn't bother trying to see if a hook exists in a 300 KM radar image, the detail is far too poor.

I am still not sure if it was a Tornado, the video so far that I have seen makes it looks like a severe straight-line wind.

[Orion]

Posting on phone from Geraldine, just checked Stuff news and read 3 killed, 7 hurt by tornado in Hobsonville around 12.15pm. Truly tragic event.

[Manukau heads obs]

powermad, no, those are not tornado signature hooks at all
(they actualy hook the other way for starters)
the kaipara harbour entrance looks like that simply because the radar beam has a clearer path right out the heads

M/S have missed the boat...the horse has already bolted...
one problem is, the rain was very dense, but the drops were not particulary big..hence the rain was actualy heavier , for as far as rain totals went, than what the rain radar was showing...i.e just relying on the rain radar alone was not enough...
ground spotters would have been better today, or keeping up with reports of how heavy the rain was (e.g on this forum..reports of torrential rain)

[Tornado Tim]

M/S have missed the boat...the horse has already bolted...
one problem is, the rain was very dense, but the drops were not particulary big..hence the rain was actualy heavier , for as far as rain totals went, than what the rain radar was showing...i.e just relying on the rain radar alone was not enough...
ground spotters would have been better today, or keeping up with reports of how heavy the rain was (e.g on this forum..reports of torrential rain)

Hence why dopplar velocity data should be released to the public,and the data that is provided goes in to a higher resolution!, Rain Radar alone to detect these events is worthless esp at 300KM resolution.

Metservice can say what they want but they are putting the public safety at risk for the sake of profit.

[Tornado Tim]

Waikato now got a STW:

Issued by MetService at 02:21 pm Thursday 06 December 2012.
Valid until 03:07 pm Thursday 06 December 2012.
This warning affects people in the following local government areas:
SOUTH WAIKATO, MATAMATA PIAKO, WESTERN BAY OF PLENTY, WHAKATANE and ROTORUA.
At 02:07 pm, MetService weather radar detected severe thunderstorms near MATAMATA, WAHAROA, SOUTHERN KAIMAI RANGES, TE POI, THE KAIMAI RANGES and HINUERA.
These severe thunderstorms are moving towards the southeast, and are expected to lie near ROTORUA, THE MAMAKU PLATEAU, MAMAKU, NGONGOTAHA and OTANEWAINUKU at 02:37 pm and near ROTORUA, WAIOTAPU, WAIKITE VALLEY, ROTOITI and LAKE TARAWERA at 03:07 pm.
These thunderstorms are expected to be accompanied by very heavy rain, damaging wind gusts and possible tornadoes.
Very heavy rain can cause surface and/or flash flooding about streams, gullies and urban areas, and make driving conditions extremely hazardous.
Very strong wind gusts can break branches from trees, damage roofing, and make driving hazardous especially for high-sided vehicles and motorcycles.
Tornadoes can blow out windows, lift roofs, break large branches off trees, generate dangerous flying debris and blow vehicles off the road.
A Severe Thunderstorm Watch remains in force for AUCKLAND and WAIKATO.

[Powermad]

(they actualy hook the other way for starters)

http://forum.weatherzone.com.au/ubbthre ... nderstorms

"As regards to storm cells: the Coriolis force isn't, however, omnipotent, compelling all currents great and small to spin counterclockwise when north of the equator and clockwise to its south.
However, according to research meteorologist Richard Rotunno of the U.S. National Center for Atmospheric Research in Boulder, Colo., the opposite has also occurred. There has even been the occasional appearance of both counterclockwise and clockwise rotating tornadoes under the same thunderstorm. These deviations undercut the common misperception that the direction of a tornadoes' spin results from the Coriolis force."

[xealeel]

was wondering when the met service warning system would kick in:
SEVERE THUNDERSTORM WARNING:
This warning affects people in the following local government areas:
SOUTH WAIKATO, MATAMATA PIAKO, WESTERN BAY OF PLENTY, WHAKATANE and ROTORUA.

At 02:07 pm, MetService weather radar detected severe thunderstorms near MATAMATA, WAHAROA, SOUTHERN KAIMAI RANGES, TE POI, THE KAIMAI RANGES and HINUERA.

These severe thunderstorms are moving towards the southeast, and are expected to lie near ROTORUA, THE MAMAKU PLATEAU, MAMAKU, NGONGOTAHA and OTANEWAINUKU at 02:37 pm and near ROTORUA, WAIOTAPU, WAIKITE VALLEY, ROTOITI and LAKE TARAWERA at 03:07 pm.

[GraemeWi]

Interesting video on the Stuff website from Hobsonville / Whenuapai, unfortunatly it cuts to another video as the heaviest rain and wind is hitting the houses

[03Stormchaser]

Video so far doesnt support it being a tornado...

[littleheaven]

Just got a text from a friend working in West Auckland who claims he saw a funnel.

[spwill]

Have been out around NW Auckland today, occasional Thunderstorms out there.
Came across the property damage at Hobsinville, photos. The damage path was wider than 100m, some one told me they saw low cloud swirling as the wind came in. Some of the tree damage looks Tornado. I later heard the terrible news of three people being killed

[Manukau heads obs]

powermad:
the hook signature of a tornado is of the mesocylone
that will always rotate the correct way
but yes sometimes a tornado can spin up the wrong way

even so,what you have highlighted on the rain radar is just the leading edge of the rain band,which is not a straight line

good photos there spwill
building NW wind here now

[Willoughby]

This mornings's Whenuapai sounding does show a little veering supportive for rotating structues.

Good photos there spwill, a big shame about the deaths and injuries.

[Rogue]

http://www.youtube.com/watch?v=tuq5hiJh4q0

tornado or not, that is some sick wind!

[Manukau heads obs]

tornado or not, that is some sick wind!

especialy considering how little wind there was in other parts of the area...at the time we had virtualy no wind here!
I see Ricky recorded strong wind and a drop in the barometer and 5mm in 2 minutes from the same CB cell

[bmo]

Have recorded 50mm of rain today

[Nev]

Here's a close-up of the Ak radar about the time of the alleged tornado ('+' marks Hobsonville Point)…
.

[Tornado Tim]

Jacqui Bridges aka Metservice PR team..... has set up a Blog post about today events so far......
It contains a hi-res Radar Image of when the Tornado occurred, to little to late in my opinion.
Link: http://108.179.233.133/?p=4564

Image Curtesy of Metservice....