Thunderstorms possible coastal Otago/Canterbury 30/11/13

[Storm Struck]

Ive been sitting out on this day for awhile as its been very flip flop in the models and I am not keen on this NW wind, but with such cold upper air coming through this evening of -28C I am picking something could happen but just very coastal.
Cape and LI's have turned for the better today too, so I am picking late afternoon and into this evening or tonight for some isolated thunderstorms along the coast from Oamaru up to Birdlings Flat.
Onshore breezes should sneak in further south later once the westerly pulls back towards the mountains, so this for me suggests the risk is much less for inland areas and along the foothills.
Will be out for a chase later should something eventuate

[Lacertae]

Been keeping an eye on the models too, I'll be out in a couple of hours and fingers crossed something interesting happens ! I'm dying to try my new lens …

[Storm Struck]

Abit of a weak CB has popped up just south of Ashburton on the coast with hail, but they will be weak until later on anyway when the colder air moves up.

[NZ Thunderstorm Soc]

Cumulus forms are bubbling up to the south of here at the moment, although a bit flat.
The persistent high cloud layer (Jet) to the north of us gradually moving away allowing the sun to become "more sunnier?"
Could be a clap or two later this afternoon as long as we don't get nay hail with it


EDIT: Transferred from my GNW posting.

[Orion]

A vast and bubbly cloud to my east, with precipitation of some kind trailing away from it.
The wind aloft seems to be pushing clouds in several different directions depending on altitude.

[Storm Struck]

Yes several converging winds today/tonight could mean we see a funnel or two in any storm development, also hail around 20mm in diameter I am bordering 25mm at the largest.
The latest from BSCH suggests upper air of -30C for the lower south island around 4pm so looking good , quite bulky widespread shower activity over south Canterbury/north otago stretching inland too.

[NZ Thunderstorm Soc]

The NW here is starting to "urinate me off"

[Chris Raine]

Cb's all around us at Oamaru currently

[Chris Raine]

Just seen some lightning and had a clap of thunder from cell NW of Oamaru town

[Orion]

Showing on the Canterbury radar, 120km radius - a curious line of whatever moving in briskly from the south-east. Meanwhile the rest of the weather crosses from the west.
Someone who knows more than I might like to 'capture' the image and post it here?

[jamie]

Showing on the Canterbury radar, 120km radius - a curious line of whatever moving in briskly from the south-east. Meanwhile the rest of the weather crosses from the west.
Someone who knows more than I might like to 'capture' the image and post it here?

Thats very interesting. I wonder what that is . The only time I have ever seen a line like that is the dry line in the midwest.

[Storm Struck]

That's the dry southerly wind change signature Orion, I think this is a good thing as it boots out this westerly wind and shouldn't last too long before letting lighter onshore winds in.
Storms are firing down north otago/south Canterbury and in the line offshore from banks peninsula.
Still plenty of time for the second wave to hit tonight

[jamie]

That's the dry southerly wind change signature Orion

ahh so it is the dry line? I didnt think anywhere in NZ would get that type of phenomenon strong enough to be picked up on radar.

[mikestormchaser]

yes i am also picking a thunderstorm or two along the coast this evening, very coastal.. birdlings flat area and up to or just passed akaroa/BP the dry howling westerly is an absolute no no for canterbury thunderstorms though, and the trouble is even when you get onshore winds at the surface the upper level winds can still bw W-NW but we'll see

[Weather Watcher]

The line is a clear-air southerly wind change. They are reasonably common on the Canterbury radar on warm days in summer, and are the result of a higher concentration of insects showing in the convergence between the northwesterly and the southerly. Small insects are swept into the convergence zone with the converging winds, and have trouble getting out. These lines show on several of the radars in summer, particularly on the sea breeze front. The Bay of Plenty radar often shows these, however the reflectivity values are generally quite weak (less than 5-10 dBZ).

Here's an image from 4pm showing the line...

Southerly_ClearAirChange.PNG

[Razor]

Still blowing hard from the NW here in town. I don't imagine there is any chance left here.

[Orion]

Thanks for putting up that 4pm radar image, Weather Watcher.

[Orion]

Just heard a rumble of thunder.

[Skywatcher]

The southerly has just arrived here marked by a ragged line of convergence cloud.

[Storm Struck]

Southerly has gone through but look at that sharp purple line to the south, its lightning active too will wait to see if the one near Rakaia does the same.

[NZ Thunderstorm Soc]

Hooray. The southerly has finally gone through, illuminating that awful, horrible and nuisance NW wind. Some glaciating CB cells to the south. Bring on the action

[Storm Struck]

Look at that storm coming up just about to hit Ashburton, some good white showing on the radars.
Me and mike are about to head out to I think Birdlings Flat soon will be the best option as i dont think it will hit Christchurch, but if it was me i would have a severe thunderstorm warning MS .
I think Aaron might be out there at the moment near Ashburton.

[Orion]

Bright lightning, booming thunder (window-rattling!) rain and a brief fall of small hail. 12.4 deg.

[Orion]

About 8 seconds between lightning and the whacking big peal of thunder a minute ago.

[NZ Thunderstorm Soc]

Nice line of "Cb-ness" from TC, out to the east, observed from here
Lots of unstableness within