Thunderstorms - 6th - 7th October

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Thunderstorms - 6th - 7th October

Unread post by Tornado Tim »

In for a good belt of Storms in the Upper central North Island it seems:

First of all a cold front swings by early morning, and then we have a rather significant upper cold trough move in early-mid afternoon.

The CVA (Convective Vorticity) from that front is significant, Wouldn't be surprised if an isolated Twister touched down along the coast.
The frontal system moves across the North Island during the morning, bringing a burst of heavy rain to central and western areas. There is a high risk of thunderstorms with this front from Taranaki to Northland, and across to eastern Bay of Plenty. These thunderstorms may produce localised rainfall rates of 10 to 20mm/hr, strong wind gusts of 100 km/h, and hail of 10 to 20mm diameter. A lower risk extends from the central North Island to Wellington, the Marlborough Sounds and Nelson. A trough moves over the west of the South Island early morning, bringing a moderate risk of thunderstorms from Westland to northwest Nelson. These thunderstorms may produce brief heavy rain and small hail.

Also of note, late morning wind convergences are likely to produce showers through inland North Otago and inland parts of the Canterbury Plains up to about Christchurch. There is a moderate risk of a few thunderstorms late morning,producing localised heavy rain and small hail.

No thunderstorms expected over the remainder of New Zealand.
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Re: Thunderstorms - 6th - 7th October

Unread post by NZ Thunderstorm Soc »

Yes. I'm looking forward to all the thunderstorm activity down here, as well. Probably get nothing :rolleyes:
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Re: Thunderstorms - 6th - 7th October

Unread post by Demchy »

The Auckland TAF only gives 40% chance of thunderstorms with SCT CB tomorrow morning for the airport. Usually that means none although I see that they are going for FEW CB as a fall back position.
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Re: Thunderstorms - 6th - 7th October

Unread post by NZstorm »

It's a strong 500mb polar trough for October. 500mb jet 90kts later tomorrow for upper North Island!

I think we stand to see some big squall gusts with tomorrow evenings front. Perhaps quite a bit of lightning with that front too.
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Re: Thunderstorms - 6th - 7th October

Unread post by tgsnoopy »

Irony in that image. Nice lil curl up & around Tauranga excluding us ;-) The Kaimai force field protects us yet again ;) Darn that Kaimai Force field :P
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Thunderstorms - 6th - 7th October

Unread post by jamie »

Time to get excited!
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Re: Thunderstorms - 6th - 7th October

Unread post by spwill »

Hopefully some good upper level cooling can occur ahead of tomorrow evenings front.
Looking very cold in the upper levels overnight tomorrow into Friday , hail and thunder in some of the showers overnight hrs into Friday.
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Re: Thunderstorms - 6th - 7th October

Unread post by NZstorm »

Timing of the front tomorrow evening over Auckland/Waikato about 8pm.
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Re: Thunderstorms - 6th - 7th October

Unread post by NZ Thunderstorm Soc »

...but nothing down here? >_<
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Re: Thunderstorms - 6th - 7th October

Unread post by Tornado Tim »

Yea this setup looks quite potent...
We have 2 jets at 200-300 hpa on both sides of upper trough but there is a quite powerfull mid-level jet forecast over the eastern Tasman with the exit region of jet flowing straight into Taranaki to southern Northland which is going to further favour divergence and enhance the trough as it comes through.
The amount of banking the trough is forecast to have is also quite impressive for NZ.

CVA's are coming around the same as the 00z cycle so the GFS seems quite fixed on how much brute the Storms will have, still seems favourable for an isolated tornado.
Squalls will be the main severe risk.

Looking like a healthy storm setup for sure tomorrow for sure :)
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Re: Thunderstorms - 6th - 7th October

Unread post by mikestormchaser »

NZ Thunderstorm Soc wrote:...but nothing down here? >_<
Since Monday iv eyed up tomorrow and Sunday being Canterburys chances. A trough comes up Over the south island in the afternoon. Given good daytime heating there should be some heavy showers/ thunderstorms around. Esp inland
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Re: Thunderstorms - 6th - 7th October

Unread post by NZstorm »

mikestormchaser wrote:
NZ Thunderstorm Soc wrote:...but nothing down here? >_<
Since Monday iv eyed up tomorrow and Sunday being Canterburys chances. A trough comes up Over the south island in the afternoon. Given good daytime heating there should be some heavy showers/ thunderstorms around. Esp inland
Yes, I agree Mike, should be thunder tomorrow in Canterbury. Timing for Christchurch middle of the day as the convergence is crossing.
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Re: Thunderstorms - 6th - 7th October

Unread post by NZ Thunderstorm Soc »

A lack of sunshine may hinder tho' :(

I thought the forecaster on TV One tonight wasn't all that good with his explaining of the forecasts for the weather coming up, especially the warning of overnight thunderstorms for west North Island areas, and around the Auckland area. :eek:
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Re: Thunderstorms - 6th - 7th October

Unread post by Manukau heads obs »

a good thunderstorm here already this morning :)
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Thunderstorms - 6th - 7th October

Unread post by jamie »

Already 10mm fallen here very quickly. Under an hour. Now have another downpour on our door coming from Brian's way.
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Re: Thunderstorms - 6th - 7th October

Unread post by Tornado Tim »

Next trough after the front looking good in the Tasman :)
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Re: Thunderstorms - 6th - 7th October

Unread post by spwill »

Some storms near the Northland west coast currently on the morning front
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Re: Thunderstorms - 6th - 7th October

Unread post by mikestormchaser »

Some nice weather this morning down here, good heating already with 17C feels rather muggy to..great prior to the change coming
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Re: Thunderstorms - 6th - 7th October

Unread post by NZstorm »

Lightning thunder just observed over Auckland now. Very heavy rain.
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Re: Thunderstorms - 6th - 7th October

Unread post by KiwiWeather »

Thunder in South Auckland :)
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Re: Thunderstorms - 6th - 7th October

Unread post by spwill »

A couple of heavy showers here last 30mins, one lightning flash, a couple of secs for the thunder.
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Re: Thunderstorms - 6th - 7th October

Unread post by NZstorm »

7mm here off that front. Instability is quite weak this morning.
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Re: Thunderstorms - 6th - 7th October

Unread post by mikestormchaser »

Showers just starting to pick up down here on radar. Forming off mt peel and heading into the Plains. I'm working outside today on a scaffold so got a good view if anything happens. Can see TCU on the plains going up
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Re: Thunderstorms - 6th - 7th October

Unread post by Orion »

Overcast here in Ashburton with a southerly freshening over the past hour or so.
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Re: Thunderstorms - 6th - 7th October

Unread post by Demchy »

The first PROB40 looks a little serious
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