Trough with thunderstorm chances 2-3 October NZ wide.

NZstorm · Unread post by **NZstorm** » Sat 01/10/2016 07:39

Active polar trough inbound.

A front crossing the North Island tomorrow with thunderstorm potential.
Moist low level air and directional shear could favour an isolated tornado.

Convergence over the South Island from eastern Canterbury to Southland with thunderstorm risk.
Light upper winds promote the risk of local heavy falls for inland Southland/eastern Otago.

Monday looks convective as well in the east.

GFS 500mb chart for 1pm tomorrow.

03Stormchaser · Unread post by **03Stormchaser** » Sat 01/10/2016 16:12

Monday will be a repeat of yesterday I think in Canterbury and prob the best chance here. Sunday currently although not great is showing a possible storm around Timaru. Will make the call in the morning if I bother heading down.

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Tornado Tim · Unread post by **Tornado Tim** » Sat 01/10/2016 16:13

Yes, some Low level shear, CVA for Auckland and lower to mid-Northland on that frontal passage, so yes the isolated weak twister cant be ruled out.
Some fairly good instability numbers coming in from the models.

spwill · Unread post by **spwill** » Sat 01/10/2016 18:30

I'm hoping those good instability numbers showing in the GFS for tomorrow can deliver some Tstorm action to Auckland, as always these systems can be hit or miss.

NZstorm · Unread post by **NZstorm** » Sat 01/10/2016 20:11

For Canterbury tomorrow the upper levels are good with lapse rates 7C, a good number for convection.
Will come down to surface moisture and how that mixes with daytime heating.

For Auckland it seems like a frontal cloud band crossing in the morning and then a wind change early afternoon.

Manukau heads obs · Sun 02/10/2016 07:19

in coming thunder storm I see !

edit..there was...I see its weakening..typical,lol

Richard · Unread post by **Richard** » Sun 02/10/2016 08:29

Surface winds are light here this morning so that will be helpful, looks also that heating shouldn't be a problem from later this morning onward.

spwill · Unread post by **spwill** » Sun 02/10/2016 08:37

There is currently isolated thunderstorm activity over North Auckland,
I'm at Owera, heavy rain with some lightning /thunder observed here.

Nev · Unread post by **Nev** » Sun 02/10/2016 08:47

Isolated strike and thunder over Waiheke just now…

Nev · Unread post by **Nev** » Sun 02/10/2016 09:31

This morning's T-storm Outlook update for the rest of today…

MetService Thunderstorm Outlook

Valid to: Midnight Sunday 2 Oct 2016
Issued at: 9:24am Sunday 2 Oct 2016

A front moving across Northland, Auckland and Waikato late morning is expected to move across the Bay of Plenty this afternoon and evening. From Northland to Waikato there is a moderate risk of thunderstorms embedded in the front this morning and for a time in the afternoon following the passage of the front. While for the Coromandel Peninsula and the Bay of Plenty there is a moderate risk of thunderstorms associated with the front in Coromandel Peninsula from this morning and for the Bay of Plenty from afternoon. These thunderstorms if they occur have the potential to produce heavy rain with intensities of 15 to 25mm/hr. However about Northland and Auckland this morning and the Coromandel Peninsula from this morning until afternoon, there is a low risk of SEVERE THUNDERSTORMS producing localised downpours of 25 to 35mm/hr.

About inland areas of the central North Island there is a moderate risk this afternoon and evening of isolated thunderstorms producing rain of 10 to 25mm/hr.

Additionally about western coastal areas from Waitomo to Taranaki, there is a low risk of thunderstorms.

For the South Island, instability is expected to increase this afternoon and there is a moderate risk of isolated thunderstorms in the afternoon and evening for western areas from northwest Nelson to Fiordland. Afternoon heating and moisture convergences also bring a moderate risk of thunderstorms to Southland and Otago during the afternoon and evening, and a low risk of thunderstorms to Canterbury, as depicted on the chart. These thunderstorms have the potential to bring heavy rain with intensities of 10 to 25mm/hr and hail.

No thunderstorms or significant convection expected elsewhere.

MetService T-storm Outlook map - Is. Oct 2, 9.24am.gif

spwill · Unread post by **spwill** » Sun 02/10/2016 09:42

Ongoing thundery rain here at Owera, very loud thunder just now with a strike that must have been nearby.

NZstorm · Unread post by **NZstorm** » Sun 02/10/2016 09:53

I am on the line at Warthworth. Occasional flashes/thunder.

03Stormchaser · Unread post by **03Stormchaser** » Sun 02/10/2016 10:17

Models don't seem as favourable as they did yesterday for Canterbury. An isolated weak storm isn't though completely outta the question

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mikestormchaser · Unread post by **mikestormchaser** » Sun 02/10/2016 10:32

Surface moisture levels look ok for Canterbury today. Instability looks fine for me, currently light winds and should remain so most of the day! Low-moderate risk for mid to South Canterbury for me

David · Unread post by **David** » Sun 02/10/2016 11:04

Interesting morning here. Plenty of thunder/lightning 9.30-10am, mostly to the E/NE. A few rumbles sounded quite close though. Then had a big downpour just after 10am.

So that's an extra 23mm on top of already saturated ground. There was a lot of surface water/runoff during that downpour.

Richard · Unread post by **Richard** » Sun 02/10/2016 11:50

Tomorrow is looking the better day for my area with a low risk of severe

Valid to: Midnight Monday 3 Oct 2016

Issued at: 11:40am Sunday 2 Oct 2016

Atmospheric conditions remain unstable over New Zealand during Monday afternoon bringing showers to many parts. However with daytime heating and wind convergencs developing in eastern parts of both island, there is the potential for thunderstorms to develop.

In the east of the North Island from the eastern Bay of Plenty and Gisborne to Hawkes Bay, and then across to inland areas of Wanganui and Manawatu, there is a moderate risk of thunderstorms during the afternoon producing localised heavy rain with intensities of 10 to 25mm/hr and hail 10 to 20mm in diameter.

For the South Island, there is also a moderate risk of thunderstorms developing about eastern inland Nelson, Marlborough and inland areas of Canterbury and Otago, which could also produce heavy rain with intensities of 10 to 25mm/hr and hail 10 to 20mm in diameter. However about Marlborough and inland areas of mid to north Canterbury there is a low risk of SEVERE THUNDERSTORMS producing hail which could be larger than 20mm in diameter.

Additionally a lower risk of thunderstorms covers much of the North Island and remaining areas in the east of the South Island.

No thunderstorms or significant convection expected elsewhere.

mikestormchaser · Unread post by **mikestormchaser** » Sun 02/10/2016 12:01

Tomorrow does look better. Southwest change looks always a big trigger for Canterbury

NZstorm · Unread post by **NZstorm** » Sun 02/10/2016 12:02

The storms over North Auckland this morning looked more like elevated thundery rain. It was great to see some lightning so worth the drive. The rain was very heavy as well.

Tomorrow does look better. Southwest change looks always a big trigger for Canterbury

Today could be the better day as the convergence is very close to Christchurch.

Tomorrow looks like being over the ranges.

Richard · Unread post by **Richard** » Sun 02/10/2016 12:08

mikestormchaser wrote:Tomorrow does look better. Southwest change looks always a big trigger for Canterbury

Yes more so for the plains, Fridays storms due to land heating for areas north of Waipara

Nev · Unread post by **Nev** » Sun 02/10/2016 12:27

David wrote:Interesting morning here. Plenty of thunder/lightning 9.30-10am, mostly to the E/NE. A few rumbles sounded quite close though. Then had a big downpour just after 10am.

So that's an extra 23mm on top of already saturated ground. There was a lot of surface water/runoff during that downpour.

Yeah, similar to here with 24.5mm. Here's Blitzortung's CG's for the 8 hrs to midday today…

Blitzortung NZ - Oct 2, 4am-12pm.png

03Stormchaser · Unread post by **03Stormchaser** » Sun 02/10/2016 15:29

Cu along the foothills at present but struggling to get any higher

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spwill · Unread post by **spwill** » Sun 02/10/2016 15:33

An afternoon thundery shower over Northland shows up well in the Russell web cam.
http://www.takeabreak.co.nz/webcams/55/russell_webcam

NZ Thunderstorm Soc · Sun 02/10/2016 15:40

Some uplifts /instability westward from here. Light southerly here will a stratus cloud bank out towards the coast behind BP.

jamie · Unread post by **jamie** » Sun 02/10/2016 16:12

Nice line developing right above me. I might hear thunder soon

jamie · Unread post by **jamie** » Sun 02/10/2016 16:34

yep thunder here now!

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