Rare Thunder activity 2nd January!!

[Storm Struck]

This is from the Press about yesterdays situation.


Loud booms that echoed across parts of Christchurch early yesterday were thunder caused by a rare phenomenon, the MetService says.

Several reports were received from coastal residents, from New Brighton to Redcliffs and Sumner, of noises like thunder or explosions about 6am.

There have been frequent rumbling noises over the past few months since the September earthquake.

However, the GNS Science seismograph drums showed no sign of quake activity.

MetService severe weather forecaster Allister Gorman confirmed it was thunder that had woken people.

He said it was due to a "very rare" occurrence.

The unstable atmosphere needed to form thunderclouds was rarely present above Canterbury when warm, stable, north-westerly winds were also blowing.

"It is a very rare event. There was a very odd occurrence of instability in the wave clouds that actually managed to make a thunderstorm.

"According to one or two people on duty here, they've only seen it happen before once or maybe twice in 10 years," Gorman said.

The strong nor'west winds probably meant the thunder was heard more loudly in the eastern part of the city, he said.

Four lightning strikes were detected by MetService above Sumner and eight over the Rangiora-Oxford area.

The Christchurch Airport webcam showed an amazing mixture of thunderclouds and a nor'west arch, Gorman said.



http://www.stuff.co.nz/the-press/news/4 ... of-thunder

[spwill]

Lightning will be from old anvil cloud originating from storms which formed over the Tasman Sea/Southern Alps rather than storm formation over east Canterbury .

[Manukau heads obs]

or maybe there were elevated storms, with elevated instability, sandwiched in, by the NWer above and NE below, or something along those lines....or a conversion line from the NWer and NEer?

[Michael]

The day before I remember someone writing the NW was there in the day and a SW change arrived late in the day so it could be a result of that??? and the map on the 2nd had a strong NW flow again there.

[Weather Watcher]

This storm was an elevated thunderstorm which formed in the high level wave cloud over Christchurch around 6am. Radar imagery showed the convective cell embedded within the wave cloud, with a base around 4km high. Radar also showed most of the precipitation falling from the cell evaporated in the dry norwesterlies, but some did reach the ground near the coast (around New Brighton). There were about 4 or 5 negative CG lightning strikes recorded.

It was a very interesting storm. I have only ever seen one other elevated thunderstorm develop in northwesterly wave cloud which was just off the coast near Ashburton a couple of years ago. It also showed on radar, produced a few CG lightning strikes, and had little precipitation reaching the ground.

There were also a couple of strong convective cells in the wave cloud over North Canterbury yesterday around 8am. These didn't produce lightning, but an aircraft flew through one reporting severe icing conditions.

[NZstorm]

The upper level air was unsually unstable, you can see the upper level instability on the Invercargill 12Z sounding on the 1st. I thought the whole episode was interesting as we don't see such good set ups for elevated thunderstorms in NZ very often. The storms started in Fiorldand on the 1st.

[NZ Thunderstorm Soc]

A similar occurence happened on the 8th of January 1994 when from 3:30am to about 5:30am, a thunderstorm passed over from the NW.
According to my weather diary, there was irratic lightning with long rolls of thunder, with the storm moving away to the east and there was no droppage in temperature with it remaining warm and close.
Again at 11am, it clouded in again from the NW with 'one or 2 claps of thunder' as the rain settled in again from the NW. Accodrding to my diary, the West Coast was getting "Feast" of thunderstorms and some of these were probably an 'overthrow' from the west.
The next day produced a thundersorm also from the NW but that was just before the SW change came through around 6pm, with a change of weather.


JohnGaul
NZThS

[tich]

From an old Met Society newsletter article, there was a similar thunderstorm at Sumner in January 1991. It was during a light northwesterly flow, and a strike hit a tree. Interestingly, this wasn't an 'overflow' storm from the Alps, as there was only drizzle in Westland.

[Richard]

A similar occurence happened on the 8th of January 1994 when from 3:30am to about 5:30am, a thunderstorm passed over from the NW.
According to my weather diary, there was irratic lightning with long rolls of thunder, with the storm moving away to the east and there was no droppage in temperature with it remaining warm and close.
Again at 11am, it clouded in again from the NW with 'one or 2 claps of thunder' as the rain settled in again from the NW. Accodrding to my diary, the West Coast was getting "Feast" of thunderstorms and some of these were probably an 'overthrow' from the west.
The next day produced a thundersorm also from the NW but that was just before the SW change came through around 6pm, with a change of weather.


JohnGaul
NZThS

Yes i remember that one,i was living at the time out the back of Amberley.I drove out the back of the farm to the top of a large hill to get a better view of it,like the other day also it came from NW arch cloud and was all sheet lightening,this being the reason for the long rolls of thunder,what was amazing was it could be seen all the way from Kaikoura to Timaru.
A night i'll never forget