Storms & gales Eastern SI, Oct 24th

[gopolks]

more lighting and thunder

[gopolks]

temp has droped 7 degrees in one hour in chch.

[Andrew Massie]

Just been out chasing.. It's still going on out there, 2 cells passed directly over me heading North, got plenty video, photos, will post tomorrow (camera issue). 12mm Hail and lightning every 20 odd seconds. A third cell inland, will prob be over Jase in Kaiapoi now...
AHhhhhhh.. That'll shut me up for a while!

My station info here: http://www.wunderground.com/weatherstat ... ICANTERB16

[dogmelon]

This thunderstorm just proves that you can get thunderstorms on a sw change when there is a warm w/nw wind blowing before it.

[NZ Thunderstorm Soc]

Thunderstorm moving over Christchurch.
It stalled my internet
This was a bit of a surprise? even for me

JohnGaul
NZTS

[David]

Chch airport winds at 8pm S26kts gusting to 41kts (76km/h)
Sounds like some pretty well developed cells down there - hopefully when the action finishes us up here can at least see some images to bring some cheer out of the boredom of our weather pattern for the next week.
A pretty sharp temperature decreases a drop of 9 degrees in some places
http://weather.northcott.co.nz/images/s ... hrtemp.png

[Inny Binny]

Well I was out just delivering my junk mail, small hail pelting down before really hurting too saw plenty of lightning everywhere and very,very windy and cold too.

[Andrew Massie]

Well.. I have to say, I'm not that impressed with the tracker accuracy.. We need more SI ones, obviously.. <checks bank account>

[David]

Strange how MS never forecast a thunderstorm risk for Canterbury today.

[Willoughby]

Well.. I have to say, I'm not that impressed with the tracker accuracy.. We need more SI ones, obviously.. <checks bank account>

Here's where you need correlation, not another Chch one... a boltek based in Ashburton/Kaikoura would track storms a lot better over the Canty Plains than it is so currently.

[mikestormchaser]

yes got very windy, thunder and lightning, with sporadic rain and also some hail, id say 10mm in diameter size. first storm for the season, so heres to it! wasn't just one storm this evening either!

[NZstorm]

That storm developed under the radar. No one forecast it! But looking at todays model run the 500mb -30C air gets right up the Canterbury coast.

[Storm Struck]

WOW first storm I watched over CHCH moving out into Pegasus some absoulute cracker CG's coming down.
I tried getting some lightning pics from that one not sure how well they came out just yet.
Just as i was beginning to give up and think that we wernt going to get any storms....
A nice flash from a completly different cell light up the sky in front of me to the W-SW then BOOOOM.
Out comes the video camera and a CG comes down towards the SW, and one of the most hairaising closest Bolts ive ever seen light up the sky kind of sprited across then hit the ground .
Not sure on the quality of the video as the council decided to turn the street lights on early because of the storm and I didnt realise so there was abit of out of focus.
Still you can hear the thunder and me cursing .
Will post pictures later, and here is why thunderstorms went through this evening in a W-SW flow.
See how the cold front has shunted the ridging of the NW flow inland, which has therefore given time for the trough inbehnind it to develop thunderstorms.
Going to keep this map for the next time we have a simular situation and compare.
Ye harr bring on storm season.
Cheers
Jason.

Thunder SW flow map.gif

[TonyT]

That storm developed under the radar. No one forecast it! But looking at todays model run the 500mb -30C air gets right up the Canterbury coast.

Actually, it probably developed almost over the top of the radar (at Rakaia)!

We did have "SW change in the evening with a few showers" in our forecast, shame we left out the word "thundery".

A very strong SW change here, no hail or thunder, but winds just as gale force from the S (not SW) for 10-15 mins as they were from the NW during the afternoon. Reminiscent of some of the SW changes I can remember from the 1980s. Reports of thunder and hail in Rangiora earlier, the power was off there for around 20 minutes, and a comment that there was a "cloudburst with torrential rain" just before the power went off.

Interesting to piece together some of the reports - seems like a (at least partial) meso-cyclonic system generated over the Plains late afternoon - the skies were very clear all through the time of the mid afternoon gales, so there was some ground heating, plus there was probably some fairly major vorticity on the southern side of the jet which brought the gales - line that lot up with a cold change moving up from Otago, the cold upper air Steven has mentioned, and bang, off it goes. A lot of our best SW changes come from this sort of scenario - unstable strong westerly flow for several days prior, then a combination of upper jet and weak cold front, which seems to allow storm development on its leading edge as it propagates northwards, especially if its late afternoon across the Plains. These weak, ill-defined fronts are often more "productive" than the stronger, more clearly defined ones.

[TonyT]

200710240600Z_cny.gif

Evidence of a well defined squall line right across the Plains on this 7pm radar scan with hail embedded in it. See how it curves back into the more complex area of heavy showers about to hit the Peninsula.

[NZstorm]

I have found once the 500mb temps get -30C or colder Thunderstorms can form more easily if there is good forcing as the surface dp only needs to be about 8C or 7C for deep convection.

[gllitz]

The GFS models from weatherzone were showing a LFTX of around 0 - -2 for the Canty coast near BP from last night's/today's runs...

[NZ Thunderstorm Soc]

I think Paul has definately lost an earning of a NZTS T-shirt on this one?

JohnGaul
NZTS

[Willoughby]

Leeward forcing coming onto the Cook Strait is leading to a few nice storms nearing Ngawi/Cape Palliser now!

[Andrew Massie]

Well.. I have to say, I'm not that impressed with the tracker accuracy.. We need more SI ones, obviously.. <checks bank account>

Here's where you need correlation, not another Chch one... a boltek based in Ashburton/Kaikoura would track storms a lot better over the Canty Plains than it is so currently.

There's a weather station in Ash Vegas.. Maybe we should coerce "In the interest of science"!

I can't afford anyway...!

[mikestormchaser]

wooo what a night! unexpected thunderstorms come in! well... i got two nice photos of the roll cloud that came up before the actual big storms, some nice lightning and some very strong winds with the change, about time we got something. wahooooooo oh and thanks for the txts and updates as those cells were moving in Andrew massie

[03Stormchaser]

Saw a few cg's, hail probably up to 10mm.

Nice little clip here my mate took of the lightning. http://bebo.com/watch/4917644571

[David]

Nice little clip here my mate took of the lightning

Well I would watch it, but there's nothing there when the page loads except text.

[Michael]

You may need adobe flashplayer v9

Nice little clip here my mate took of the lightning

Well I would watch it, but there's nothing there when the page loads except text.

[spwill]

Good clip there Steve.