NZ Weather Forum

I thought that I would start this topic early as there looks likely to be a significant weather event to start the month off, according to the models, and with lots of comments regarding this in the "General June Weather " topic, which the moderators might want to edit into this?

Im ony seeing thinkness of 530 at there lowest so not ging to be to significant for the low lands and hey its ment to snow in the mountains in winter so i hope its not going to be another over hyped run of the mill winter cold snap

Thickness readings can be misleading though when cold air undercuts a rain band. Seems to be potential for that scenario.

melja wrote:Im ony seeing thinkness of 530 at there lowest so not ging to be to significant for the low lands and hey its ment to snow in the mountains in winter so i hope its not going to be another over hyped run of the mill winter cold snap

Potential for it to be a warm advective event, where cold air coming out, collides or undercuts slightly warmer air... therefore snow can fall to near sea level even with a THK of 530... It is still a while out mind you, but models have been consistent thus far with it being more direct southerly than SW, so IF it comes off, might be interesting... will know more by Saturday me thinks.

far too far out to be making predictions that's for sure. That's how reputations are shredded.

Hmm yeah i see the potential there looking at the maps.. see how they go in next few days, 48 hours out from an event normally gives you a good idea with what is going to happen but if the models can keep it up consistantly its a good sign alright! also just keep an eye on the 850mb temp melja, even in a cold advective event " witch is what it normally is" the 500mb thickness can be rather high but given the 850mb temps are very cold, snow levels can drop to relitivley low levels. " excuse the spelling"

Razor wrote:far too far out to be making predictions that's for sure. That's how reputations are shredded.

Last June's event/non event comes to mind that's for sure, didn't help that The Press were reporting 'biggest snowstorm in 20 years'

Razor wrote:far too far out to be making predictions that's for sure. That's how reputations are shredded.

Hence I am not mentioning anything on Facebook until the weekend, if it still looks possible by then. I haven't made any predictions yet.

Bradley wrote:

Razor wrote:far too far out to be making predictions that's for sure. That's how reputations are shredded.

Last June's event/non event comes to mind that's for sure, didn't help that The Press were reporting 'biggest snowstorm in 20 years'

The media over hyped that massively... you never know 100% with snow until it is actually happening most of the time. It is a waiting game.

Dont think i have ever seen snow in chch with 530 THK and the 850mb are only showing -4C so hardly very cold and models have been like this for 24h now, just think people are making up what they want to happen

melja wrote:Dont think i have ever seen snow in chch with 530 THK and the 850mb are only showing -4C so hardly very cold and models have been like this for 24h now, just think people are making up what they want to happen

If my memory serves me correctly... in June 2012, it was a warm advection event, the THK was around 530, it was 4deg on the ground and chucking it down.

Time will tell i guess and as australia is gettting a megablizzard or Snowpocalypse as there media put it then it may well come here, but that would be from the west

We might get a bit of fluff up on arthurs then, melja.. saw your photos in the June topic, very very dry around places. Megablizzard or megaflop.. lets not have this thread as a mine is bigger than yours.. you know who you all are.

CWUweather wrote:

melja wrote:Dont think i have ever seen snow in chch with 530 THK and the 850mb are only showing -4C so hardly very cold and models have been like this for 24h now, just think people are making up what they want to happen

If my memory serves me correctly... in June 2012, it was a warm advection event, the THK was around 530, it was 4deg on the ground and chucking it down.

4deg on the ground? How is that possible when the maximum temperature for the day was 0.4C?

CWUweather wrote: If my memory serves me correctly... in June 2012, it was a warm advection event, the THK was around 530, it was 4deg on the ground and chucking it down.

4deg on the ground? How is that possible when the maximum temperature for the day was 0.4C?[/quote]

Yes thats right bradley. when it snows you can bet ur bottom dollar the temp is not 4C hence the fact freezing is 0C
There is another type of event that can happen that i have heard about, and thats evaporative cooling.. where the freezing level is at a certain height, but with such heavy precipitation can drag that freezing level down lower.
i guess its on the same lines as warm advective snow but slightly different.

It snowed very briefly in hamilton 2011 and it would have been 4 degrees. But that's different again as that was just bazaar.

I think Bradley was saying that the max temp recorded that day was 0.4C so i could not have been 4C and snowing as 4C was never recorded that day

Yep that's right Melja, it definately IS possible for it to snow at 4c, just didn't happen on June 6th 2012 that's all...

It wasn't June 2012 it was 2006 when the THK level was at lowest 534 and an 850mb temp at its lowest of -6C, with this in mind most of the snow fell more substantially inland from 200m elevation upwards for a much longer time period.
The snow started around 1am that morning for areas 300-400m high while heavy rain fell on the rest of the region below that, and by 5am the freezing level had reached 200m heavy enough to bring down the freezing layer to sea level.
Amounts were less at sea level around Christchurch only 5-8cm but were 20-35cm around Timaru and Ashburton, with close to 1 metre in Methvan.

But anyway I am seeing far too much inconsistency in the models the past few days, we have gone from 540thk this morning to 527thk again tonight with -6C on the 850mb.
But the surface maps are now starting to pick the event up which they were not initially doing, however it doesn't line up with the likes of the metrogram which shows the majority of the rain through Tuesday instead of Wednesday .

Its good to watch as we get closer but it really is sit on the fence wait and see, count the NW arch clouds until early next week .

Bradley wrote:

CWUweather wrote:If my memory serves me correctly... in June 2012, it was a warm advection event, the THK was around 530, it was 4deg on the ground and chucking it down.

4deg on the ground? How is that possible when the maximum temperature for the day was 0.4C?

Yes Bradley- you are correct, 0.4 was the record minimum maximum that day. Remember it well, had my 'engagement photo shoot' in a wonderfully snowy Hagley Park

Note that that record low max-temp of 0.4C recorded at Chch Aero for June 6, 2012 was taken during the 24 hrs from 9am on the 6th to 9am on the 7th. Temps there were up around 7C just after midnight on the 6th and still around 4C in the hour to 4am. It was also still 5C in Rolleston in the hour to 5am and at New Brighton Pier in the hour to 6am.

latest runs looking more like a major snow event next week in the S/East with a SE flow ,good fetch and plenty of moisture.Ruapehu looks good also with NW flow and loads of cold moist air/snow at higher levels [above 1000m]

THK of 537 in latest and 850mb temps of -2 for the Chch area so im not seeing much below about 4-500m at this stage.

ECMWF is consistent with the cold air over the SI
Hail and isolated thunder on the cards for the west of the North Island early to mid next week.

The surface maps suggest to me this could be a brief polar blast and the metrogram numbers will line up a bit lower from now onwards, but the only thing is the surface maps and ARL still dont line up the time frames.
I am seeing it coming in from late Wednesday morning and clearing Wednesday night.