Polar Outbreak Jan 17th-21st

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Polar Outbreak Jan 17th-21st

Unread post by Chris W »

Looking locked in for a very cold polar outbreak (courtesy of that very resilient polar vortex from the winter) to approach and interact with the La Nina-derived humid air that's also being sent our way at the moment. Specifics to be revealed into the weekend and event itself, but looking like severe gales, heavy rain, thunderstorms of which some could be severe (GFS bringing upper air down to -32C in places Sunday 17th) and also snow for the higher passes.
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Re: Polar Outbreak Jan 17th-21st

Unread post by NZ Thunderstorm Soc »

What a shame. I'll be working at Barkers from next week so will miss all the action. :(
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Re: Polar Outbreak Jan 17th-21st

Unread post by Razor »

Sitting in Athol after 30 plus degree days competing in the Revenant race. So hot. Looks like serious changes on the way!
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Re: Polar Outbreak Jan 17th-21st

Unread post by NZstorm »

A lot going on today. Highlights are the possibility of a tornado in Taranaki early afternoon if a thunderstorm can become surface-based.
And an early evening lightning show over East Otago/coastal South Canterbury with that late day southerly change.
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Re: Polar Outbreak Jan 17th-21st

Unread post by Nev »

MS Outlook for today certainly looks interesting...
MetService Thunderstorm Outlook

Issued at 8:42am Sunday 17 Jan 2021
Valid to Midnight Sunday 17 Jan 2021

A cold front in the Tasman sea will move over the South Island this morning, and the North Island in the afternoon and evening. This front is expected to bring a period of rain and thunderstorms to many areas, especially in the west. Behind the front, an unstable northwest flow spreads onto the South Island with another embedded front bringing thunderstorms this afternoon and evening.

In the North Island, and also Marlborough and Nelson, there is a moderate risk of thunderstorms associated with this front spreading into Nelson and Taranaki late morning, then across many other areas from southern Northland to Kapiti, Wairarapa and Marlborough this afternoon or evening. A low risk covers all other North Island areas except Gisborne and northern Hawkes Bay. These thunderstorms will bring localised heavy rain and possibly small hail. There is also a low risk of a small tornado about North Taranaki this afternoon.

For Buller, there is a moderate risk of thunderstorms this morning, and then again in the late afternoon and evening. Localised heavy rain and hail can be expected with the thunderstorms. This evening, some the thunderstorms could also be squally with strong wind gusts and possibly a small tornado.

For Westland, Fiordland, and the Canterbury High Country (especially near the main divide), there is a moderate to high risk of thunderstorms starting in Fiordland late morning, then elsewhere in the afternoon and evening. These thunderstorms will be accompanied by localised heavy rain and hail. Some of the thunderstorms could also be quite squally in Westland for a time late afternoon and evening, with strong wind gusts and possibly one or two small tornadoes. If any tornadoes do occur, they will be small and localised.

In Southland and Otago, there is a moderate risk of thunderstorms this afternoon and evening, which then spread up into South Canterbury from evening on a southerly wind change. Localised heavy rain and hail can be expected with these thunderstorms.

A low risk of thunderstorms covers other parts of Marlborough and Canterbury as indicated on the chart (mainly in the afternoon and evening).

MetService T-storm map for Jan 17.png
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Re: Polar Outbreak Jan 17th-21st

Unread post by wembley »

Might be a bit of T and L then.
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Re: Polar Outbreak Jan 17th-21st

Unread post by Chris W »

Rain over Chch now, with some red patches in the radar towards Oxford way.
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Re: Polar Outbreak Jan 17th-21st

Unread post by Storm Struck »

Nice heavy band that from the west easily 5+mm, I almost wonder if that frontal band hit the moist air we've had the past week and ramped it up.
As the models didn't really pick it.
An active week ahead mostly out west, but watch that cross over tonight through south to mid canterbury might see some thunderstorms and again for eastern areas perhaps Thursday.
Canterbury, home of good rugby and severe storms
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Re: Polar Outbreak Jan 17th-21st

Unread post by Cyclone Tracy »

Latest water vapour image showing the upper level mothership injecting 2 polar streamers as they head equatorward over the Southern Ocean. 2nd streamer will cut off in the next 24 hours and head towards the SI as a rogue synoptic scale upper vortex.
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Re: Polar Outbreak Jan 17th-21st

Unread post by Awhituobs »

View from Te Papa Wellington
20210117_164050.jpg
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Re: Polar Outbreak Jan 17th-21st

Unread post by darcyplumb »

Looks to be a decent storm down near Timaru on radar. Any reports from there? I can see the tops from Ashburton.
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Re: Polar Outbreak Jan 17th-21st

Unread post by NZ Thunderstorm Soc »

darcyplumb wrote: Sun 17/01/2021 17:56 Looks to be a decent storm down near Timaru on radar. Any reports from there? I can see the tops from Ashburton.
Yes. Lots of sferics coming out of it. I've been out once but not going back for another look. Waimate might be getting it again.
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Re: Polar Outbreak Jan 17th-21st

Unread post by NZstorm »

darcyplumb wrote: Sun 17/01/2021 17:56 Looks to be a decent storm down near Timaru on radar. Any reports from there? I can see the tops from Ashburton.
Radar indicated hail on the coast south of Timaru last hour.

Front was almost a non-event for Auckland apart from disrupting the America's Cup!

No measurable rain here.
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Re: Polar Outbreak Jan 17th-21st

Unread post by Chris W »

Looking south west from Spreydon just now
20210117_203311.jpg
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Re: Polar Outbreak Jan 17th-21st

Unread post by mikestormchaser »

=D>
NZstorm wrote: Sun 17/01/2021 07:52 A lot going on today. Highlights are the possibility of a tornado in Taranaki early afternoon if a thunderstorm can become surface-based.
And an early evening lightning show over East Otago/coastal South Canterbury with that late day southerly change.
You were spot on about the storms in north otago/ Canterbury today

I didnt look at models in great depth today but looking back i i probably should have and taken a drive down south of timaru this afternoon like we did a couple weekends ago.
Looks like today was our best set up going forward into next week unless models flip around for the good.
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Re: Polar Outbreak Jan 17th-21st

Unread post by Chris W »

Looks like the polar jet must have really fired up those storms yesterday, the clouds to the south looked epic last night. Coldest uppers tomorrow through Weds. Maybe a storm chance for Chch today/tomorrow if there's any NE convergence against the NW/W and MS going low risk here, maybe moderate Weds with the SW change if it's not offshore.

A lot of rain for the west coast, Southland and Otago the next couple of days, no doubt thundery with the upper temps. Also generally GFS has high shear going on today/tomorrow SI, Weds NI so maybe some decent storms up there when the southerly gets up that way.

One more, NW toting mod-high risk of severe gales for Southland, Otago and inland Canterbury Tues-Weds. Low for coastal Canterbury.
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Re: Polar Outbreak Jan 17th-21st

Unread post by Cyclone Tracy »

Cold core cyclonic gyre with the comma head now making an appearance.
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Re: Polar Outbreak Jan 17th-21st

Unread post by Chris W »

Wind was certainly up and about on SH1 yesterday evening and in the night in Lyttelton. More to come today.
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Re: Polar Outbreak Jan 17th-21st

Unread post by mikestormchaser »

I dont see this affecting us much at all. Strong NW today and a chance of some spill over rain from west.

Might have a chill to the wind over next day or two though.
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Re: Polar Outbreak Jan 17th-21st

Unread post by NZstorm »

500mb chart for midnight tonight. Very good cold pool for January! Pity it will be a weak event thunderwise although some spillover rumbles may occur near the lakes.

Wanaka's high yesterday was 8C below normal. Met Service have Wanaka's high 9C below normal today and 7C below normal tomorrow.
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Re: Polar Outbreak Jan 17th-21st

Unread post by Razor »

Wanaka was lovely last night. Pouring in Makarora this morning. Heading for Haast soon.
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Re: Polar Outbreak Jan 17th-21st

Unread post by NZstorm »

A lowish risk of thunder for the Auckland area overnight tonight with a front crossing but instability looks weak. But some decent upper level speed shear may encourage some lightning.
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Re: Polar Outbreak Jan 17th-21st

Unread post by Chris W »

mikestormchaser wrote: Tue 19/01/2021 06:38 I dont see this affecting us much at all. Strong NW today and a chance of some spill over rain from west.

Might have a chill to the wind over next day or two though.
Other than the strong NW in Canterbury today/tomorrow as you mention, and lowish thunder risk. Polar outbreak doesn't just mean cold weather, we're just on the warmer edge of the system and of course the lee of the NW :). Just couldn't think of a more appropriate thread title for a system that's coming right off the trop vortex.
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Re: Polar Outbreak Jan 17th-21st

Unread post by spwill »

Cardrona ski area webcam shows light snow.

Wanaka currently 10C with heavy rain.
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Re: Polar Outbreak Jan 17th-21st

Unread post by darcyplumb »

Getting smashed by the NW winds here in Ashburton. Power on and off, windows flexing on the house. Strongest I’ve witnessed for a couple of years now.
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