Start to Season 15/9/2005

03Stormchaser · Unread post by **03Stormchaser** » Sun 11/09/2005 22:05

First 'real' chance of thunder down south for the New Season. Although not overly great, there is still something in it to get abit excited over!

A brief southerly change will make its way up the country reaching Christchurch around dusk, hopefully accompanied by a thunderstorm.

A quick scan over the models suggest good temp through out the day and dewpoint of at least 8C, anything lower and all possiblites are out the window. Heating shouldn'e be a problem, cloud cover will be patchy, cape is bording on ok, but we have had thunderstorms before with bugger all cape, I wouldn't really worry to much about that. Tottot of around 55-50 around canterbury, Negative Li's of around -1 -2, 500mb temp at -25C and good vorticity tracks across the East coast. Little sheer to talk about.

Wether or not storms happen in chch or south of christchurch im undecided, probably a higher percentage chance around Ashburton.

Overall, the setup looks 'ok' Probably our best setup in a while!!
*Of course closer to the time the models may change, hopefully in our favour!!

03Stormchaser · Unread post by **03Stormchaser** » Wed 14/09/2005 13:22

Damn I should have gone with the orignal outlook I had done 2 days before I posted above, as I had Otago in the forecast!!

03Stormchaser · Unread post by **03Stormchaser** » Thu 15/09/2005 17:34

Well I actually sort of got this right!! A couple of strikes were picked up Lee's Valley way, and also inland from Dunedin. Cu was spotted around Canterbury plains, and I did notice larger build up from CHCh in North Canterbury in the Lees Valley area.

Thunder · Unread post by **Thunder** » Thu 15/09/2005 22:11

Good on ya steve, a very marginal day but just enough to produce a few isolated showers and a few strikes. A bit more down south by the looks and yes I remember you mentioning to me about the possiblilty of something happening that way so good stuff. I figured Cu would be possible but just didn't think that cloud would clear to allow enough heating, looks like it did in Less Valley for the temp to get up enough. Horay!

Right, tomorrow! We've got un unstable upper atmosphere with cold air moving over / -28 C at 500mb, we've got an area of 55 tottot on the plains at 3pm which is getting very nice for this time of year! Should be fine with no cloud so heating will be good. What will dewpoints be? Hmmm, well from what I gather even if we get dewpoints of 5 degrees storms will still be allowed to happen if air temp's get to 15 degrees which seems highly likely. That brings LI's of -3! which is cool. However storms would be high based. My ideal situation is 15 degree temps and 8 degree dewpoints which brings -4 LI's, if we get higher dewpoints I'll be very happy! And if we get higher surface temps that's cool and means we'll get really good CAPE but higher based storms are more likely.

Things that make me uneasy are we are in NW flow but I've seen storms here in NW flow so it's not all bad, NW shouldn't make it over here anyway so it shouldn't be a prob. With afternoon heating an area of low presure could build up on this side and even enduce a SW up the coast which would be cool if it converged with a NE but I can always dream. Anyway, so yeah. Tomorrow could be our turn on the plains!

As for this Monday evening, it just screams thunderstorms!!!! Hopefully the models stay the way they are.

Cheers

NZ Thunderstorm Soc · Thu 15/09/2005 22:16

Aaron J Wilkinson wrote:
As for this Monday evening, it just screams thunderstorms!!!! Hopefully the models stay the way they are.

Cheers

I don't think so, it'll be strong cold S to Sw winds and grey skies, possibly up to 50mm of rain in some areas in Canterbury and other places.
As Fogy suggests, it will probably be about 6C. If the wind is less severe and the temp drops to 2C around 3pm. then we should be in for some snow.

JohnGaul
NZTS

Thunder · Unread post by **Thunder** » Thu 15/09/2005 22:20

But look at beloved ECMWF for Monday! Shows some nice advection there. The skew t profile for this day looks really good! We'll see.

NZ Thunderstorm Soc · Thu 15/09/2005 22:35

Aaron J Wilkinson wrote:[quote="NZ Thunderstorm Soc

A very informative post John, couldn't of said it better myself.

Cheers

soory, I was trying to edit it, for a message, and then it went and posted itself, by itself??

...anyway...in a previous post, I did have a low chance of thunderstorm development for today as I knew that there would be a slack low trough over the country and with sunshine, if the day was fine, could trigger something which would be of interest ....but alas there was no sunshine and a persistent cloud layer. Winds were variant but mostly SW so that also hindered deveopment of anything substantial. there have been one or two patchy showers but nothing really significant to really wet the ground.
A shower around 9:45pm here did wet the ground, 0.6mm recorded here.

JohnGaul
NZTS

Thunder · Unread post by **Thunder** » Thu 15/09/2005 22:45

I should've put lol behind it, I was playing silly buggers! my fault! I've deleted that message anyway.

Yeah, I was worried about that cloud cover to, I did see patches of sunlight late in the day to the West so it looks to of been just enough.

Cheers

NZstorm · Unread post by **NZstorm** » Fri 16/09/2005 06:44

This is an interesting sounding Aaron.

Taken at Christchurch Aiport on the day of the Halswel tornado. Surface dewpoint was just 2.8C yet LI was -2.5. Add a coastal breeze with dp10C to that sounding. No wonder there was golf ball sized hail over Christchurch that day.

TonyT · Unread post by **TonyT** » Fri 16/09/2005 07:49

The Halswell tornado storm formed on a cold front moving north along the east coast of the South Island. The actual storm which brought the tornado formed well south of Chch, probably in North Otago/South Canty, and was already bringing hail there earlier. The tornado formed as this cloud approached the NE/SE convergence line inland from Banks Peninsula, pushed along by a pretty vigorous SW change. This is a common area for storm enhancement in these situations, and frequently marks the point at which storms start producing hail.

Quite a lot of data was collected about this event, including a continuous strip chart wind record from the anemometer on the roof of the Geography building in the University, which was just a few km from where the tornado dissapated around Wigram. Peak gust was over 80 knots from memory. Ian Millar wrote a report on it (I know as I helped collate some of the data).

Fujita Phil · Unread post by **Fujita Phil** » Fri 16/09/2005 14:16

Good Spring hail falling in Dunedin around 2pm today. Not much but more may fall... have to get outside....

Storm Struck · Unread post by **Storm Struck** » Fri 16/09/2005 14:24

Hail? is there any thunderstorms about Phil? some weak CU popped up to south before but then fizzled out and had a few spits of rain before with some instability in the upper level scrappy nvil looking clouds drifting over.
I don't think Thunderstorms will happen today now as we do have a NW wind now but if the NW wind dies away before evening there migt be something

.
Cheers
JASON.

Thunder · Unread post by **Thunder** » Fri 16/09/2005 14:29

Yes Jason, my thoughts on the NW were wrong and it's become a big prob so looks unlikley for storms today. Oh well.............. I saw that Cu to the south to and it made me get a bit more hopefull but it's pratically gone now. Despite the no storms situation I can always take something from this and learn. I can see a pattern with the different pressure systems and can see now when that area of low pressure forms here on the coast.

Cool to hear you got some hail Phil, air is cold enough.

Cool skew-t Steven. Yeah, definately looks unstable. When I was talking to a guy who still lives on Kennedy's Bush Hill he said that there were NW winds, NE winds and a Big SW (or S?) coming up the coast on that day. All converging I guess! What a bugger he had a VHS video camera sitting in the room right next to him and he didn't record it, he said he sat there watching the torndoes (there was atleast two touching down at the same time) for a while and didn't think to grab the video camera. Grrr!! Oh well..

Where's that report Tony? Might be interesting!!!

Cheers

TonyT · Unread post by **TonyT** » Fri 16/09/2005 16:46

Aaron J Wilkinson wrote:Where's that report Tony? Might be interesting!!!

Cheers

I must still have a copy somewhere, in one of those cardboard boxes we leafed through a few months back. If I find it I'll let you know.

Fujita Phil · Unread post by **Fujita Phil** » Fri 16/09/2005 17:56

Missed a nice cb out to sea tonight. Time I got home, go the camera, raced to the top of the hill, another low frontal cloud have passed between us. Spherics on the radio here, just a couple, far apart

GreggWard · Unread post by **GreggWard** » Fri 16/09/2005 18:25

Just had a thunderstorm pass through Palmerston North with two very big flashes of lightning and a 3-4 minute shower of hail with stones up to 10mm in size.