NZ Weather Forum

Cyclone Tracy wrote: ↑Tue 05/06/2018 08:29 my 2 bobs worth.

Should see some sort of secondary circulation off the old Tasman low in around 6 hours. Looking at the current water vapour image, reasonable amount being detected near the -40c 500 hPa cold pool. Should get a clearer picture this afternoon on how the mid levels look as it approaches the SI.

Is that passing somewhere near Macquarie Island?
http://www.antarctica.gov.au/webcams/macquarie-island

katipo wrote: ↑Tue 05/06/2018 15:09

Cyclone Tracy wrote: ↑Tue 05/06/2018 08:29 my 2 bobs worth.

Should see some sort of secondary circulation off the old Tasman low in around 6 hours. Looking at the current water vapour image, reasonable amount being detected near the -40c 500 hPa cold pool. Should get a clearer picture this afternoon on how the mid levels look as it approaches the SI.

Is that passing somewhere near Macquarie Island?
http://www.antarctica.gov.au/webcams/macquarie-island

It's currently in the wake of the system. It would be a touch cold down there at the moment

Some brief low level snow inland South Island early Thursday ? before warmer air takes over.

Looks like Metservice hedging their bets with a "chance morning snow" in the forecast for Christchurch tomorrow morning...

spwill wrote: ↑Tue 05/06/2018 17:05 Some brief low level snow inland South Island early Thursday ? before warmer air takes over.

Yes, its a warm front so we could call it warm advective snow. There is plenty of moisture with this front, so snow will be heavy before turning to rain as the warm front crosses.

Raining in Rangiora

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NZstorm wrote: ↑Tue 05/06/2018 17:34

spwill wrote: ↑Tue 05/06/2018 17:05 Some brief low level snow inland South Island early Thursday ? before warmer air takes over.

Yes, its a warm front so we could call it warm advective snow. There is plenty of moisture with this front, so snow will be heavy before turning to rain as the warm front crosses.

So going by the current models any idea whereabouts in the inland South Island this warm front and moisture will meet up?

Snowing here now and pretty heavily. Wouldn't be surprised if it's snowing in Gore at the moment either, temp only 0.6 in gore which is roughly only 50 metres asl

hozza95 wrote: ↑Tue 05/06/2018 19:02 Snowing here now and pretty heavily. Wouldn't be surprised if it's snowing in Gore at the moment either, temp only 0.6 in gore which is roughly only 50 metres asl

Yep only 0.3C in Gore with plenty of snow coming through, I have to say I am very surprised by how low that temperature is, tells me the models might not have picked this cold front up as well as they could have and it may be 0.5-1C colder then forecast...

Bradley wrote: ↑Tue 05/06/2018 17:28 Looks like Metservice hedging their bets with a "chance morning snow" in the forecast for Christchurch tomorrow morning...

I'm so desperate for a Chch snow that this fills me with hope!

Interesting the temp difference between Gore -0deg and Invercargill and 6deg

Richard wrote: ↑Tue 05/06/2018 19:27 Interesting the temp difference between Gore -0deg and Invercargill and 6deg

Might be all the cold air from the last week trapped inland??

Snow on the deck at sister in laws in Gore

Tonight’s run of EC is interesting to say the least - they are saying too warm for snow for even places like Springfield at 400m asl, just completely bizarre the difference between the snow levels of the major models for this system...

Heavy rain in Dunedin, temperature is dropping very slowly 4.5C......ever the optimist

Bradley wrote: ↑Tue 05/06/2018 19:59 Tonight’s run of EC is interesting to say the least - they are saying too warm for snow for even places like Springfield at 400m asl, just completely bizarre the difference between the snow levels of the major models for this system...

Snow should fall to 200m tomorrow early hours and again at night but not sure if any will settle.
I love snow to but being more into the thunderstorms side of things is also be keeping eye on thunder/hail on the coast. Big wintry CBs should pack a punch to. 500mb -34 So very cold air aloft

Bradley wrote: ↑Tue 05/06/2018 19:59 Tonight’s run of EC is interesting to say the least - they are saying too warm for snow for even places like Springfield at 400m asl, just completely bizarre the difference between the snow levels of the major models for this system...

The EC accumulation map has been pretty consistent for the last 48 hours, and Springfield would definitely be in the zone. The EC accumulation map and the GFS accumulation map are now pretty similar, and have been for a few model runs.

I see Dunedin Airport is AT 1deg according to MS. Can anyone confirm if its snowing there? Has had a few mms of moisture in the last hour

TonyT wrote: ↑Tue 05/06/2018 20:23

Bradley wrote: ↑Tue 05/06/2018 19:59 Tonight’s run of EC is interesting to say the least - they are saying too warm for snow for even places like Springfield at 400m asl, just completely bizarre the difference between the snow levels of the major models for this system...

The EC accumulation map has been pretty consistent for the last 48 hours, and Springfield would definitely be in the zone. The EC accumulation map and the GFS accumulation map are now pretty similar, and have been for a few model runs.

Yes Springfield certainly sits in an area on that map where there will be some decent snow falling yet the latest run of EC for Springfield on the Yr website it shows no snow at all for Springfield?

https://www.yr.no/en/overview/daily/2-2 ... pringfield

Can’t confirm re Dunedin airport but can see it’s snowing on the Highate web Cams and on Stuart St.

Cheers Ice Maiden. What altitudes are they?

165m asl

Had confirmation it’s snowing in Mosgiel which lies between Dunedin city and the airport

Snowing on Porters Pass. Seems a lot earlier than expected. MS might be a bit light on the 5-10cm for the top of the pass. Given the bulk of the moisture isnt due for another 4 hours yet its hammering down now. temps seem to be dropping quicker than expected too around Canterbury and Dunedin

After that Gore photo, I had a very close look at multiple Gore PWS observations associated with temperatures and dew points during that period from 6pm to 8pm and compared to model runs from the 00z. It seems to me that snow has fallen around 400m below the freezing level at that time, hinting at very good energy from the evaporation and melting process.

Effectively the strong cooling process is dropping the freezing level further than expected and Gore’s temperature has maintained well below what models had projected during that period. Temperatures have gone back in the last 30 minutes but still around 1 to 2c with moisture. I'm not surprised at those levels in Dunedin. There is going to be a lot of low altitude white looking hills in the morning across the SI