Spring Weather Bomb - Gales and Snow - 26th - 29th September

[JP.]

Very interesting storm.. Ive planned to cycle the port hills out to godley head tomorrow morning so hopefully avoid most of it. Looks like a nice day to stay at home and batten down the hatches on Sunday.

[Richard]

If only a little moisture for Chch, not too much of course. It's going to be a very interesting few days whatever eventuates.

I'm picking quite a bit of splil over rainfall here from this system once the cold airflow moves in.

[tornado]

metservices latest severe weather outlook is just wow. i think red warnings might be needed for this system.

[NZstorm]

Lightning looks to be increasing in western Tasman on the trough currently. Hopefully we can get a hit from it in Auckland overnight. And probably a better chance late Saturday as it may fire up again out there. Some heavy rain for my garden would be great.

[Chris W]

GFS tanking the cold numbers, brings -8C 850s and -38C 500s over Chch by midday Tuesday. Maybe no moisture, but brr!

Should be some spectacular thunderstorms somewhere during this event, surely. Deep layer shear alone is off the charts.

[NZ Thunderstorm Soc]

Should be some spectacular thunderstorms somewhere during this event, surely. Deep layer shear alone is off the charts.

Where?

[Bradley]

Interesting that Metservice just has a typical gale warning for Canterbury High Country of 120kmh gusts for Saturday/Sunday and only a Watch issued for the plains - they aren't thinking this is an extreme wind event at all? We typically get 2 or 3 of these warnings a year...

[snowchaser01]

Interesting that Metservice just has a typical gale warning for Canterbury High Country of 120kmh gusts for Saturday/Sunday and only a Watch issued for the plains - they aren't thinking this is an extreme wind event at all? We typically get 2 or 3 of these warnings a year...

Yet on their chch forecast they have severe gales on Saturday night and Sunday. Lets see what their warnings say tonight.

[Chris W]

Should be some spectacular thunderstorms somewhere during this event, surely. Deep layer shear alone is off the charts.

Where?

GFS op run, weather online. Have a look and decide for yourself Shear is super high in many locations at different times during the event.

[TonyT]

Interesting that Metservice just has a typical gale warning for Canterbury High Country of 120kmh gusts for Saturday/Sunday and only a Watch issued for the plains - they aren't thinking this is an extreme wind event at all? We typically get 2 or 3 of these warnings a year...

It doesn't look like a really extreme event for Canterbury. Not to say it won't be, just the guidance is not off the scale. Could be similar to the winds last Thursday when Richard lost trees in the Culverden area. Its always a lottery exactly where the strongest winds will be.

[tornado]

Lightning looks to be increasing in western Tasman on the trough currently. Hopefully we can get a hit from it in Auckland overnight. And probably a better chance late Saturday as it may fire up again out there. Some heavy rain for my garden would be great.

Yes we need some rain in Auckland. Thursday failed to bring much here. A interesting weekend . Won't be good for the bridge.

[Bradley]

Interesting that Metservice just has a typical gale warning for Canterbury High Country of 120kmh gusts for Saturday/Sunday and only a Watch issued for the plains - they aren't thinking this is an extreme wind event at all? We typically get 2 or 3 of these warnings a year...

It doesn't look like a really extreme event for Canterbury. Not to say it won't be, just the guidance is not off the scale. Could be similar to the winds last Thursday when Richard lost trees in the Culverden area. Its always a lottery exactly where the strongest winds will be.

Yeah latest EC run has max gusts of around 90kmh for most of the plains, a relatively mild ‘extreme’ system wind wise for Canterbury by the looks of it...

[snowchaser01]

The winds will be on par with the September wind storm or 2013.

[mikestormchaser]

The winds will be on par with the September wind storm or 2013.

I really dont think it will be that bad for Canterbury. Gale winds yes but not that extreme.
I hate to sound like a party pooper in this event but this will be a Southland and eastern otago event for sure.
Especially when it comes to the snow down there. Perfect set up down south but for us cantab folk more very strong cold winds with it straightening up on tuesday might bring low snow on the hills.

[tich]

This happened in late September 1949, but could easily be what's in store for the far south this coming Monday.

https://paperspast.natlib.govt.nz/newsp ... 90929.2.46

[Storm Struck]

Yes I'm picking simular to last Thursday just more widespread in terms of the winds, we should get maybe 1 or 2 pulses of gale to severe gale force winds out over the plains and coast.
Like Thursday these would be short lived around a few hours, say averaging 90 gusting 110kmh.
For the most period of the day I'd expect those winds to be around 40-50kmh, meanwhile in the high country and alps a different story.
Its the straight line parallel isobars that squeeze through the alps which have seen the worst of the winds in recent times,this low is deep but its also complex being able to spread the energy out with the strong jet stream.

[Willoughby]

The ECMWF 00Z run has a bit of an 'upgrade' with it's guidance.

Depicts 1000-500 hPa thickness down to just 5160m over virtually all of Southland and Otago. This is impressive even for a mid-winter outbreak.

image.png

850 temps as low as -10°C and 500 temps to -40°C (especially over Otago) this system sure looks to be a doozy.

This run of ECMWF has Invercargill and Dunedin struggling to get past 3°C with wintry precip on Tuesday. And yes as Chris says, there should be some good hailstorms about too.

[Chris W]

I know it’s one run, but GFS now has -10C 850mb temperatures and -40C 500mb up to Chch Tuesday evening, -11C and -36C for Dunedin. Trend is colder at this stage. Even if it’s just a model going a bit far it’s quite something to see that. Few cm of snow chain showers for Chch city through the night, if it eventuates.

44CF3F7C-D4C2-403D-8846-F70AB1FE9849.jpeg

For balance, EC is about 2C higher for the 850s and maybe more SW but at 24h resolution on that site it’s hard to see where it goes between Monday and Tuesday.

[spwill]

Certainly very impressive cold numbers modelled for next week, some rare snowfall for time of year on the way, will be interesting to follow it.

[Cyclone Tracy]

Latest water vapour image showing a dual polar injected streamer now coming together over the Southern Ocean, heading for the Tasman disturbance which is starting to aggressively spark on the occluded frontal boundary.

[Awhituobs]

we are heading to south island...driving down...crossing the straight on tuesday (looks SW so will be OK), and doing the Otago bike trail
should be lots of snow to see..first stop will be hanmer springs wednesday

[Bradley]

Some social media weather websites are saying Christchurch could see 150kmh gusts tomorrow, I don’t see gusts of 110kmh let alone 150kmh for Christchurch City, I wonder what data they are looking at...

[mikestormchaser]

Some social media weather websites are saying Christchurch could see 150kmh gusts tomorrow, I don’t see gusts of 110kmh let alone 150kmh for Christchurch City, I wonder what data they are looking at...

I am not one that follows those social media sites Bradley.
I would stick to your big guns and trusted outlets such as weatherwatch, blue skies and metservice for your most accurate forecasters

[Awhituobs]

the NWer in canterbury/CHCH is a fickle thing.. depends on where the down stream waves get setup.. ..i.e in between the waves you will get strong winds...but as the wind increases, the waves migrate and change frequency ..and so the wind can come and go in a particular spot...and be local too...
at least that is what is what last time I was in the area

[mikestormchaser]

Will definitely be strong gales though, going to be sleepless night for those who want silence in the night.
500mb jet 4am