Very cold southerly blast NZ wide Sept 7-9th

[melja]

Yeah i hope there not lumping Rangiora into Christchurch now

[NZ Thunderstorm Soc]

Wouldn't BP/Port Hills be a blocking effect for a dusting of snow, ChCh and northern suburbs|?

[Richard]

Wouldn't BP/Port Hills be a blocking effect for a dusting of snow, ChCh and northern suburbs|?

Straight southerlies dont seem to effected by any BP blocking, its more from the SSE & SE direction

[Chris W]

Metservice wind barbs are SSW quite consistently, no shelter from the peninsula for many of us. Office in Middleton will get quite a thump when the gust front arrives and be bitter outside after!

[snowchaser01]

This has popped up out of no where... yesterday data was suggesting 400m maybe 300m for Canterbury. Now there is talk of sea level... hmm

[Bradley]

This has popped up out of no where... yesterday data was suggesting 400m maybe 300m for Canterbury. Now there is talk of sea level... hmm

EC which has been far and away the best performing model this year only has snow to 400m for mid-Canterbury tomorrow night and Thursday morning whereas Metservice is going for snow to 100m for a time, someone is going to have egg on their faces come Thursday afternoon!

[Razor]

This has popped up out of no where... yesterday data was suggesting 400m maybe 300m for Canterbury. Now there is talk of sea level... hmm

EC which has been far and away the best performing model this year only has snow to 400m for mid-Canterbury tomorrow night and Thursday morning whereas Metservice is going for snow to 100m for a time, someone is going to have egg on their faces come Thursday afternoon!

As long as people don't get personal...lets jsut wait and see

[snowchaser01]

CWU are mentioning a 40% chance of snow in Christchurch city... not sure I agree with that. Personally my money is on about 300m. Worth a note also that Metservice have sleety showers for ChCh on Thursday

[Razor]

Metservice has significantly upped the moisture in their forecast for today. Some action weather ahead it seems, a rare thing this year for our part of the world

[NZstorm]

Nice upper cold pool over the North Island tomorrow. With the spring sunshine perhaps some afternoon convection over land Auckland? We had a similar set up on August the 10th last year and got afternoon convergence with winter precip and thunder. But the wind pattern was weaker SE and air slightly more moist then.

Anyway, I expect hail and isolated thunder over north Auckland/Northland where the flow will be onshore SSW.

500mb situation for midday Thursday.

[NZstorm]

Metservice has significantly upped the moisture in their forecast for today. Some action weather ahead it seems, a rare thing this year for our part of the world

The southerly change today could come in as a severe squall particularly if there has been plenty of heating.

[Richard]

Blowing a nasty gale at times at the moment - 50kmph @ 2 metres

[Nev]

Here's this morn's MS T-storm Outlook update for today...

MetService - Thunderstorm Outlook

Valid to: Midnight Wednesday 7 Sep 2016
Issued at: 9:21am Wednesday 7 Sep 2016

Very cold unstable air spreads north across southern and central New Zealand today, bringing squally showers to many places, and snow to low levels over the South Island.

There is a moderate risk of a few thunderstorms about Fiordland, Southland and Clutha this morning, which spreads to Buller, western Nelson and also eastern areas of Canterbury this afternoon. Then this evening the strong southerly change brings a moderate risk of a few thunderstorms to eastern and northern Marlborough, Wellington, Wairarapa, Horowhenua, Kapiti Coast, Wanganui and Taranaki.

These thunderstorms if they occur have the potential to bring heavy rain with intensities of 10 to 20mm/hr, hail mostly less than 10 mm in diameter, but possibly 10 to 15mm in diameter over the lower North Island, and strong winds gusting 90 to 110 km/h hour, especially about eastern areas of the South Island and the lower North Island.

A lower risk of thunderstorms covers remainaing areas of central and southern New Zealand.

No thunderstorms expected over the remainder of New Zealand.

MetService T-storm Outlook Map Is 9.21am for Sep 07.gif

[mikestormchaser]

Metservice has significantly upped the moisture in their forecast for today. Some action weather ahead it seems, a rare thing this year for our part of the world

The southerly change today could come in as a severe squall particularly if there has been plenty of heating.

Yes southerly buster thunderstorm on the cards today. Only thing could trouble it is a very strong NW but plenty of heating/sun so far.

[dogmelon]

Yes southerly buster thunderstorm on the cards today. Only thing could trouble it is a very strong NW but plenty of heating/sun so far.

We had a similar situation in chc some years ago where it had been NW ahead of a squally change but it still managed to produce thunderstorms on the change anyway. Its not ideal to have a NW but its not a disaster either.

Edit: Metservice have contracted the moderate risk envelope to the coast.

[Tornado Tim]

Southerly has now passed Invercergill and most of Southland now, Cantab next.... hopefully temps can peak before it comes ripping through. Key will be temp differentiation, the larger the difference, the more likely things will kick off. Wellington I think will do well out of this setup, should see a wicked guster as it comes through.....

[Tornado Tim]

GFS got the Southerly change bang on time! Nice!

[Bradley]

Multiple models still going for thickness levels down to 520 in the wee hours of the morning for Canterbury which would certainly mean snow to sea level combined with 850hpa temps of -7C but there is something else at play here which means it is marginal at best and why EC is still only going for snow down to 400m for Canterbury...places like Sheffield at 300m isn't forecast to received even 1 cm according to EC! The models are really struggling with this one

[mikestormchaser]

Looking good for chch, lightish west to northwest winds, 17C, dew point isn't high though, only 4C but u expect that with NW

[Dean.]

Multiple models still going for thickness levels down to 520 in the wee hours of the morning for Canterbury which would certainly mean snow to sea level combined with 850hpa temps of -7C but there is something else at play here which means it is marginal at best and why EC is still only going for snow down to 400m for Canterbury...places like Sheffield at 300m isn't forecast to received even 1 cm according to EC! The models are really struggling with this one

Could clear inland behind the main front tonight in the southwest airflow before it tilts more southerly north of the Rakaia in the morning.

[Richard]

Could clear inland behind the main front tonight in the southwest airflow before it tilts more southerly north of the Rakaia in the morning.

Looks more southerly than SW as you can already see it clearing of the Fiordland coast

[petem8nz]

First very heavy shower overhead in bromley, east christchurch

[Karliosis]

Hail and a loud clap of thunder observed in Riccarton!

[Razor]

Brief light hail and a few spots of rain thru Merivale area. One clap of thunder. Quick clearance behind. No wind.

[Bradley]

Interesting to see that Metservice has now changed their forecast from 'snow to 100m' to 'snow to low levels' in its Canterbury plains forecast for tomorrow morning...