Polar blast & NI low 11-14th July

Richard · Unread post by **Richard** » Fri 07/07/2017 19:52

The models now pretty much set on a significant polar outbreak due mid week, at this stage its looking to mostly effect areas above 200m, but timing will be crucial if snow levels are to reach the lower urban coastal SI centers. Interesting few days leading up i can see.

EDIT- Changed title of the thread to include the development of a North Island low pressure system and extended the duration period to include Friday 14th.

Bradley · Unread post by **Bradley** » Fri 07/07/2017 19:58

Yep 200m seems to be the magical number at the moment, places like Darfield could get around 5-10cm but Hanmer Springs could get around 30cm by the looks of it from Tuesday night to Wednesday night, thinking I may need some chains for the trip to Hanmer Springs on Wenesday afternoon Richard or should I be ok with that road? I've heard it's pretty well maintained is that correct?

Richard · Unread post by **Richard** » Fri 07/07/2017 20:04

All depends on how much falls and at what time of the day or night, 30cm would be dealt with rather quickly if it was during the day.

Bradley · Unread post by **Bradley** » Fri 07/07/2017 20:17

Thanks mate we aren't leaving until midday so should be ok you'd think, it's not a warm advective scenario so shouldn't be much over a foot hopefully!

NZstorm · Unread post by **NZstorm** » Fri 07/07/2017 21:11

There is a warm advection component to it in so far as some over running of airmasses. NW aloft being undercut by southerly.

The gfs currently giving a snowfall signal for central NI as well.

moylanr · Unread post by **moylanr** » Fri 07/07/2017 22:23

Around Waimakariri Gorge/Springfield, is this like the June 2015 event?

Bradley · Unread post by **Bradley** » Fri 07/07/2017 22:55

moylanr wrote:Around Waimakariri Gorge/Springfield, is this like the June 2015 event?

No - nowhere near the 40cm that area received back in 15' - maybe half that if they're lucky...

Razor · Unread post by **Razor** » Fri 07/07/2017 23:07

I am far from convinced. Models have flip flopped for days and its far too early to have even remote confidence in any of this based on year to date and the likelihood of the critical SW pushing everything to sea

Thunder081 · Unread post by **Thunder081** » Fri 07/07/2017 23:16

Razor wrote:I am far from convinced. Models have flip flopped for days and its far too early to have even remote confidence in any of this based on year to date and the likelihood of the critical SW pushing everything to sea

Agreed don't get too excited just yet.

Richard · Unread post by **Richard** » Sat 08/07/2017 07:03

Razor wrote:I am far from convinced. Models have flip flopped for days and its far too early to have even remote confidence in any of this based on year to date and the likelihood of the critical SW pushing everything to sea

I dont see this one having a likelihood of a critical SW pushing everything it out to sea, if anything slightly more SE than straight southerly. Doesn't look like a prolonged event so far which is great.

spwill · Unread post by **spwill** » Sat 08/07/2017 09:05

A bit early for the detail but is not looking like critical southwester, models have the flow going onshore in the east. Wintry showers and snow to low levels likely I would say. Could be heavy snow for the eastern North Island high country.

Bradley · Unread post by **Bradley** » Sat 08/07/2017 09:20

Latest EC now has snow to sea level in Canterbury on Wednesday and an epic dump over half a metre for places like Hanmer Springs and around 30cm for Sheffield and Springfield. I've actually been thinking this event has been quite consistent in the models...

Richard · Unread post by **Richard** » Sat 08/07/2017 10:22

20 -30 cm here

, i'll be putting my sheep+lambs in a sheltered paddock for sure. Means likely a loss of power too.

+

=

mikestormchaser · Unread post by **mikestormchaser** » Sat 08/07/2017 11:58

Richard wrote:20 -30 cm here , i'll be putting my sheep+lambs in a sheltered paddock for sure. Means likely a loss of power too. + =

Your area Richard definitely is one to keep watch on. I'm not convinced yet for snow to sea level for coastal fringes but the latest model run does seem colder and more moisture there. Give it another 24 hrs yet I think to have a firmer idea

snowchaser01 · Unread post by **snowchaser01** » Sat 08/07/2017 13:21

Certainly looking nasty.. potential to cause big problems for many people on the plains above 200m. 40cm possible for places such as methven, oxford, hanmer, springfield and annywhere close by. will be keeping an eye on this.

Bradley · Unread post by **Bradley** » Sat 08/07/2017 14:58

Latest Metservice severe weather outlook being very strong on the fact that heavy snow will only affect areas ABOVE 400m, obviously they must believe the air just won't be as cold as what other forecasters believe it will be...

snowchaser01 · Unread post by **snowchaser01** » Sat 08/07/2017 15:20

Bradley wrote:Latest Metservice severe weather outlook being very strong on the fact that heavy snow will only affect areas ABOVE 400m, obviously they must believe the air just won't be as cold as what other forecasters believe it will be...

I think they are about 200m to high.
Edit: Weatherwatch believes 200m for Canterbury.

Bradley · Unread post by **Bradley** » Sat 08/07/2017 15:37

Who to believe, Weatherwatch or Metservice...

snowchaser01 · Unread post by **snowchaser01** » Sat 08/07/2017 15:40

Bradley wrote:Who to believe, Weatherwatch or Metservice...

From past events you would have to say WeatherWatch

Bradley · Unread post by **Bradley** » Sat 08/07/2017 16:11

snowchaser01 wrote:
Bradley wrote:Who to believe, Weatherwatch or Metservice...
From past events you would have to say WeatherWatch

I'm sure Metservice would be aghast at hearing a member of the public saying that haha

snowchaser01 · Unread post by **snowchaser01** » Sat 08/07/2017 17:22

Unfortunately it's the truth. Its happened a couple of times this season already.

Richard · Unread post by **Richard** » Sat 08/07/2017 17:23

Ive been following the BOM's Southern hemisphere charts over the last few days where ive not seen the same level of deep fetch off Antarctica that ive seen in previous years major snowfalls, today's chart for Monday still doesn't have much of that direct pool of cold air needed for sand dune skiing http://www.bom.gov.au/australia/charts/ ... SH&model=G

I'm picking it wont be a to-sea level event, or very little.

Bradley · Unread post by **Bradley** » Sat 08/07/2017 17:38

Richard wrote:Ive been following the BOM's Southern hemisphere charts over the last few days where ive not seen the same level of deep fetch off Antarctica that ive seen in previous years major snowfalls, today's chart for Monday still doesn't have much of that direct pool of cold air needed for sand dune skiing http://www.bom.gov.au/australia/charts/ ... SH&model=G

I'm picking it wont be a to-sea level event, or very little.

I remember the event in June 2013 was straight off the Ross Ice Shelf with 850hpa temps of -8C over Canterbury and a very intense low pressure system off the coast which dumped 100mm in Canterbury over the course of 3 days - still no sea level snow and only 10cm of snow for the entire event where I was living at the time at 300m asl - sometimes the weather is just so unpredictable it wouldn't surprise me if this system ended up delivering more snow at low levels then that system - for no apparent reason!

snowchaser01 · Unread post by **snowchaser01** » Sat 08/07/2017 17:41

Bradley wrote:
Richard wrote:Ive been following the BOM's Southern hemisphere charts over the last few days where ive not seen the same level of deep fetch off Antarctica that ive seen in previous years major snowfalls, today's chart for Monday still doesn't have much of that direct pool of cold air needed for sand dune skiing http://www.bom.gov.au/australia/charts/ ... SH&model=G

I'm picking it wont be a to-sea level event, or very little.
I remember the event in June 2013 was straight off the Ross Ice Shelf with 850hpa temps of -8C over Canterbury and a very intense low pressure system off the coast which dumped 100mm in Canterbury over the course of 3 days - still no sea level snow and only 10cm of snow for the entire event where I was living at the time at 300m asl - sometimes the weather is just so unpredictable it wouldn't surprise me if this system ended up delivering more snow at low levels then that system - for no apparent reason!

I have said the whole time it looks above 200m with sleety falls below that, and that seems ot be holding true at the moment. Porters pass could be closed off for atleast a day or 2 with this. Which could cause problems for travelers. Lewis might not be much better.

jamie · Unread post by **jamie** » Sun 09/07/2017 05:04

GFS is looking quite similar to last year in August when the Taihape Napier and Taupo Napier roads got dumped on with snow

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