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

[Chris Raine]

Small hail showers have started

[Richard]

Just swung from a light/mod NNE to a strong NW

Picked up 7mm from showers this morning

[Chris W]

Strong NW in New Brighton, increasingly gusty through the morning. Report, we have a wheelie bin down outside in the mall! It's really picking up though. Blue skies after an early shower.

GFS and UKMO output still pretty consistent at least for low positioning and isobar orientation, EC seems like the outlier so far but let's see how it goes. Still looks like we have the potential for snow on Tuesday. Wondering about the thunder risk tomorrow for an Otago/Canterbury? I know it's strong NW but those uppers are frigid at about -36C.

[Cyclone Tracy]

The air mass at sea level has consistently been recording 2c below what global models have been projecting on Macquarie Island over the last 12 hours. EC at 1pm NZT projected the island at -1c, actual is -3c. The coldest of the air is still to come. The BoM observation which has operated since 1948, is likely to break it's record tomorrow for the coldest September day its recorded. This is a very rare post equinox cold shot heading towards NZ.

BoM observation http://www.bom.gov.au/products/IDT60801 ... 4998.shtml
Webcam https://www.antarctica.gov.au/antarctic ... ie-island/

[Bradley]

The air mass at sea level has consistently been recording 2c below what global models have been projecting on Macquarie Island over the last 12 hours. EC at 1pm NZT projected the island at -1c, actual is -3c. The coldest of the air is still to come. The BoM observation which has operated since 1948, is likely to break it's record tomorrow for the coldest September day its recorded. This is a very rare post equinox cold shot heading towards NZ.

BoM observation http://www.bom.gov.au/products/IDT60801 ... 4998.shtml
Webcam https://www.antarctica.gov.au/antarctic ... ie-island/

Well EC forecasting 2C warmer then GFS over the coming days now makes sense based on that observation, GFS has not wavered at all on its -9C 850’s over Chch on Tuesday/Wed - still sounds too
low to be real though. I know they are talking about this event being linked the SSW event on certain Facebook pages around the grand solar minimum...

[Willoughby]

Sure is CT, sounding is out now as well from Macquarie Island:

image.png

[Avalanche]

Thank you CT for your inspiration and knowledge of the weather, with all these current weather dynamics in place do you think Wellington could see some snow to near sea level on Tuesday. 522 thickness keeps coming and going here, i notice the winds seem to be SSW on Tuesday. which exposes Wellington to these cold temps. Your thoughts on this id be interested to know. Thank you appreciate it.

[Chris W]

Some impressive cb development over the peninsula right now

20200927_142027.jpg

[NZ Thunderstorm Soc]

Just swung from a light/mod NNE to a strong NW

Like that here, Richard.
Been a nice sunny day until about 2pm, then the NW picked up with some wind gusts, strongest since yesterday afternoon.

[mikestormchaser]

Nice cumulus congestus clouds rolling towards banks peninsula atm. Going offshore. Checked the radar and a small cell has popped up near ashburton

[Richard]

Just swung from a light/mod NNE to a strong NW

Like that here, Richard.
Been a nice sunny day until about 2pm, then the NW picked up with some wind gusts, strongest since yesterday afternoon.

Swinging further west now. The mountains had no new snow an hour ago but now it looks like its snowing up there now

[Chris W]

Blowing fairly well north side of the hills, but just got home and there's not a breath. However, the yellow bin seems to have knocked the green bin over so it must have got up at some point!

[mikestormchaser]

Just a quick cell skirted past eastern Canterbury earlier.
Tomorrow will be another windy day.. perhaps a gust front with the SW change tomorrow.

[NZ Thunderstorm Soc]

Just a quick cell skirted past eastern Canterbury earlier.

It did have some lightning in it apparently.

[einzack]

The wind has dropped away completely here in the last hour or so (Rolleston). It had gotten quite gusty for a while before that, but virtually completely still out there now.
Wind was patchy all day with fits of strong gusts, but nothing unusual at all.
It was quite annoying on my run, but it was the heat that was causing me more problems.

[Tone Malone]

not too much happening here in Te Anau at the moment. Breezy W. Sun out most of the afternoon with snow showers hanging around the hills to the west to maybe 400m. Not really pushing into the Te Anau basin yet.

[mikestormchaser]

Just a quick cell skirted past eastern Canterbury earlier.

It did have some lightning in it apparently.

Definitely keep eye out tomorrow afternoon. Coastal heavy showers/ hail/ Gust front along the SW change

[NZ Thunderstorm Soc]

It did have some lightning in it apparently.

Definitely keep eye out tomorrow afternoon. Coastal heavy showers/ hail/ Gust front along the SW change

At the moment, I'm tending towards the gust front, here

[Razor]

Strong blustery NNW at the moment after some earlier spill over rain, tomorrow may see one or two coastal fringe cold CBs up the coast to maybe Ashburton river mouth.
As its very strong Westerly influence but briefly SW also, strong upper jet might be enough to get some forcing going and decent sized hail.

It tried, heres my view from my run across Mt Sinclair this arvo. Lovely day up there, not all that windy either. Was blowing hard through Lake Forsyth on way home tho as the dry change dusted its way through

[Chris W]

Nice work Razor. Really looking forward to the gust front, with that big a swing in temperature and the uppers it should be a good one!

[Storm Struck]

Was that surface SW in the models? It really snuck in under that strong NW flow and kept very coastal.
Back to the strong westerly again now, but was cool to see that line bubbling away none the less.
If it can do that today, tomorrow should be quite spectacular.
Any storms that do form could see hail 20+mm given such a strong upper jet and cold upper air, but like I said earlier very coastal fringe stuff.

[mikestormchaser]

Was that surface SW in the models? It really snuck in under that strong NW flow and kept very coastal.
Back to the strong westerly again now, but was cool to see that line bubbling away none the less.
If it can do that today, tomorrow should be quite spectacular.
Any storms that do form could see hail 20+mm given such a strong upper jet and cold upper air, but like I said earlier very coastal fringe stuff.

Id agree, any storms tomorrow could see hail 15-20mm hail. Given strong 500mb jet and any storms will be moving fast! Strong pre frontal NW which will keep it coastal but something to keep eye on tomorrow for sure. The SW change looks very SW so will have to see if the models can pull it more SSW. ill take camera gear incase i need to head out straight from work

[Chris Raine]

Had couple hours of fine weather CB's to west . Gusty westerly this arvo up to 32 knots >Temp steadily falling now 5.4C

[hozza95]

I see MS now have a high confidence of heavy snow above 200 metres here on Tuesday in today’s severe weather outlook, should be an interesting couple of days. Down to 4°C here now but pretty settled for the moment.

[Bradley]

Latest run of EC has downgraded the temps even further in Canterbury with the lowest 850hpa temps now only -6C - it has certainly been on a consistent downward trajectory the last 2 days!!