Spring Thunderstorms for Canterbury

[gllitz]

Showers and rain for today, more than likely, but no storms...just can't see it happening...tomorrow looks pretty promising, though...

[Storm Struck]

Looking rather unstable out there at the moment CU forms towering everywhere in the last hour or so, looks good for some isolated thunderstorms somewhere today whether it be inland or coastal.
Cheers
Jason.

[gllitz]

For sure, Jason...things are looking a bit unstable out there...just wondering if that band moving up the coast on the SAT loops is anything, or just high cloud...radar doesn't seem to show anything, so assuming it is the latter...hmmm...I thought it was supposed to be nice and sunny for the next few days....we'll see! (and of course, DIDN'T bring my camera in today...)

[kiwisk8er]

We've been having rain showers on and off today. Just had a very light hail shower come through here in Tainui, Dunedin.

[Razor]

It was certainly bumpy flying into ChCh last night around 11pm! But dry on the ground

[Storm Struck]

Just got back home from town and it certainly is looking good out there for a thunderstorm to flare up any time soon, wind has swung NE so the clouds are towering much higher.
Already precipitation falling inland near the Foothills and some to the NE of here.
Cheers
Jason.

[mikestormchaser]

Looked very thundery this morn, has been all day, but particularly this morning.. i reckon its just a little tease mother nature is playing atm but is certainly getting close to thunderstorm.
Nothing suggests to me any thunder will happen tonight.. think we have had that chance this morning and again nothing has flared up to be much.
HOPE IM WRONG THOUGH! hehe i always like to be in this situation.

[NZ Thunderstorm Soc]

Driving to work this morning I did notice a couple of castellaTus lines around the back of BP which usually indicate thunder, or a chance of thunder development later in the day... BUT I was surprised that MetService had no chance on thunderstorm on their daily chart for today when I thought , judging by this, if the NE kicked in, a low chance may be of a thunderstorm somewhere.
Anyway, on saying this, the thunderstorm risk would be low anyway because of the factors.
About today's thunderstorm risk,I mention this because on Tuesday when MetService had a high chance of thunderstorm development, especially inland, I thought, 'no chance' ,well not really, mainly because the right conditions weren't in play although thunderstorms did occur further south as a result of some convergence activity down south around the Dunedin area. Could Paul fill me in on this?

JohnGaul
NZTS

[spwill]

thunderstorms did occur further south as a result of some convergence activity down south around the Dunedin area. Could Paul fill me in on this?

Yesterday, those Storms were all out to sea, there was some brief weak activity near the south coast otherwise the SouthIsland TS activity was in the West with a few strikes on the Canterbury foot Hills.

[mikestormchaser]

now shes looking bit unstable out this beautiful evening. turnd NE

[NZstorm]

Quite a nippy air mass crossing the South Island today and the forecast sounding for Canterbury suggested a few cu/cb tops upto 4000m. For thunderstorms there needs to be deeper layer instability, so not the instability in the mid levels of the atmosphere for thunder down there today.

[NZ Thunderstorm Soc]

Here are a few shots of a weak convergence line that developed quickly and dissipated quickly as well as the sun set slowly towards the west.

JohnGaul
NZTS

[Storm Struck]

Nice photo's there John, those first two photo's that weak CU was not far from me actually at around 6pm.
It certainly is good to see these chances popping up in early October and hopefully means an interesting season ahead if you look forward positivly.
I see there was a crop of showers that developed inland from Timaru at around 6pm, thought this may have been the weakoning trough coming up.
Perhaps after our first storm we can finally have our next CWW meeting somewhere .
Here's a photo i took looking west at around 3:30pm of the unstable skies.
Cheers
Jason.

weak instability oct 9th 003.JPG

[Paul Mallinson]

Driving to work this morning I did notice a couple of castellaTus lines around the back of BP which usually indicate thunder, or a chance of thunder development later in the day... BUT I was surprised that MetService had no chance on thunderstorm on their daily chart for today when I thought , judging by this, if the NE kicked in, a low chance may be of a thunderstorm somewhere.
Anyway, on saying this, the thunderstorm risk would be low anyway because of the factors.
About today's thunderstorm risk,I mention this because on Tuesday when MetService had a high chance of thunderstorm development, especially inland, I thought, 'no chance' ,well not really, mainly because the right conditions weren't in play although thunderstorms did occur further south as a result of some convergence activity down south around the Dunedin area. Could Paul fill me in on this?

JohnGaul
NZTS

Hi John,

Yes, I started the ball rolling on this one with my day 2 outlook which had the high risk of TS in Cny as you say. The guidance didn't really change much for the 'today' threat chart (for Tuesday 7th) and so Chris issued much the same forecast.
I wasn't working on the Tuesday and I'm still not quite sure why nothing happened. In looking back at the guidance used, the only thing I can think of is that the forcing aloft wasn't strong enough. That is, there should have been a stronger short wave trough going over (which would have more cyclonic vorticity advection, which promotes upward motion, and therefore cools the depth of the atmosphere more and so destabilise things more - sorry about all the jargon).
Anyway, one of the indicators we use is the Total Totals Index (for instability - and others). This had a centre of 55 migrating from the west coast to over north Cny by late afternoon (threshold is around 50 for TS). Along with this was the southerly change getting into the area about that time. Using T= 15C and Td = 7C on forecast soundings (tephigrams) indicated about 500 J/kg CAPE and a Lifted Index of -3.4C - so reasonable looking instability... but nothing happened.
I see the following day Waipara got to T= 19C and Td= 9C so you would think this would have helped things to fire.

Overall, I think there was a timing issue between the various parameters. If this had been more into the summer, the longer days and stronger heating probably would have produced something. Oh well, its a tricky business and its our job to try and pick the less obvious days!

Cheers,

Paul

[spwill]

so reasonable looking instability... but nothing happened.

No thunder but some heavy rain/showers did develop inland in the afternoon.

[Paul Mallinson]

Yes spwill, I just had a look at the radar data and 4 heavy cells did develop as you say in inalnd/more northern Cny bwteen 6 and 7pm.

Paul

[NZ Thunderstorm Soc]

Cheers, Paul and thanks for your reply. There also was an abundance of cloud cover across the plains which would of hindered any development of surface warming.

JohnGaul
NZTS