I appreciate it is a wee way out still but both EC and GFS have been in agreement for atleast 3 days now of a winter storm for the start of Queens Birthday Weekend.
EC currently likes the idea of snow right downon the Canterbury Plains on Friday night and Saturday morning (above 300m), while GFS is hanging around the 500-600m mark. Certainly something to to watch and discuss as winter draws closer... dare I mention the 4th of June as well ... which GFS and EC have been consistent on for a few days now also. After a mild may, it looks like June will plunge us into the depths of winter.
I think this should go into the General June Weather topic, as the rest of this week seems to be mild and very wet on the West coast, rather than being very wintry as what the title of this topic suggests?
Good alignment on most models of a fractured Polar Jet interacting with the subtropical Jet over the Tasman on Friday. Jet wind speeds projected around 340 km/h. This is one of the key ingredients of rapid cyclogenesis around the surface and a possible sting jet.
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Sudden stratospheric warming from mid May is really propagating deep into the lower troposphere. Americans are upgrading to a more aggressive long wave attack into the NZ region. If they verify, MS might be pulling out the new code red during this thread for some areas.
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In regards to the name of the thread, i think we might as well leave it as it is now. being 3-4 days out with most models in agreement of a significant winter event taking place.
snowchaser01 wrote: ↑Mon 27/05/2019 13:40
In regards to the name of the thread, i think we might as well leave it as it is now. being 3-4 days out with most models in agreement of a significant winter event taking place.
2nd thoughts, might as well continue with this run/topic for this weather event.
Last edited by NZ Thunderstorm Soc on Wed 29/05/2019 17:12, edited 1 time in total.
Interesting pattern in the models currently. For the last 2-3 days, GFS has backed right off in the morning run, but then on the midday run, ramps it back up again... will await the METVUW update at 11am.
A number of potential low pressure systems hanging around our neck of the woods over the next 10 days according to EC, there is one potentially next Thursday that could become very interesting warm advective event for mid and northern Canterbury, at present it's forecast location is off the west coast but with another week to go things could easily change and it could position itself nicely off the east coast of the south island, dredging up some antarctic air with a bucketful of snow/rain and provide another 6th June 2012 event exactly seven years later (7 year cycles perhaps?)
Bradley wrote: ↑Tue 28/05/2019 11:17
A number of potential low pressure systems hanging around our neck of the woods over the next 10 days according to EC, there is one potentially next Thursday that could become very interesting warm advective event for mid and northern Canterbury, at present it's forecast location is off the west coast but with another week to go things could easily change and it could position itself nicely off the east coast of the south island, dredging up some antarctic air with a bucketful of snow/rain and provide another 6th June 2012 event exactly seven years later (7 year cycles perhaps?)
Yes there are about 3 different pulses of air during the next 10 days or so as you say. Maybe it's best to keep them all in this thread? Might need to rename it if that is the case...
Modelling is still pretty variable as you'd expect. Only certainty is that there is some vigorous weather across parts of the country for an extended period. Especially the West Coast of the South
There is a lot of variability in the modelling even 48 hours out, but it looks interesting for Chch both Friday and Saturday with a potential -32C cold pool over the top of some sub-zero 850mb air on Friday, then the coldest 850 air reaches us Saturday evening. I’m not talking about snow, or even thunder, but it just looks interesting in terms of being a potent couple of days, maybe some hail? I’ll have to bow to those who know more about convection than I do, but it’s interesting.
Next week also looks interesting from Tuesday, but that might be another thread.
GFS has been wobbling along for about 10 runs. Seems to be a couple of issues that concern me. The latest run has the low right off the pegasus bay with a central pressure dropping into the high 970hpa range. I feel with such a drop in pressure from the mid 980s to 970s as it crosses this will be far more potent than what is first thought. The other issue is i dont think the 500thk levels are quite correct. 525thk for sheffield yet the cold air should be colder than that given where its come from.
Boy o boy, the metservice 3 day maps show a huge amount of moisture over the Canterbury Plains on Friday 9pm until atleast midday Saturday. Snow levels will be around the 400m at that stage so could be very interesting if that holds true.
Not sure I'd say huge (my own description however) but certainly a decent amount of rain/sleet/snow depending on elevation. Looks like a rate of 10-15mm/3 hour window for most, with heavier patches inland. It does seem to go on from late Friday through Saturday evening though. Of course it might back right off, but it's interesting that the GFS has been going for a low over Banks Peninsula dragging warmer air in then undercutting it with cold, and also potentially strong coastal southerly gusts.
Yes the low pressure system is sitting of the coast of Kaikoura on Friday night/Saturday morning feeding plenty of moisture into mid Canterbury, pity the colder air doesn't arrive until Saturday night and the 850hpa temps are only in the -1C or -2C range or we could have had snow down to 100-200m if it was 2C colder and a warm advective scenario came into play...
Yes the models starting to fire up now for this after they had backed off for a time over the last couple of days.
Still need to see a bit of agreement between them for some relative confidence on proceedings. But yes I agree Chris.. popcorn time! I see that CWU have gone out on a limb and mentioning sleet in city. I wouldn't be going that low but it certainly seems as if snow could fall and settle to about 400m based on current modelling. EC throwing out some intriguing numbers for sure.
Just ran EC's latest 18Z run and it's wiggled the deepening low westward from the 12Z run to be dropping pressure around Cook strait at 8am Saturday morning. Access R 18Z is very similar. UK also similar in the 12Z run.
From a NI point of view, total totals on EC and Access R are showing 55 to 60 on Saturday morning with some reasonable moisture at 700 hPa. Current water temps around the Upper NI and BOP are in the range of 17 to 18c. This could produce an outbreak of waterspouts if it verifies.
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snowchaser01 wrote: ↑Wed 29/05/2019 10:29
MetService CANTERBURY HIGH COUNTRY forecast for Saturday mentions heavy rain turning to snow at all levels. I presume this means above 500m?
Thats the thing with what the MS zones, the 'CANTERBURY HIGH COUNTRY' takes in my area and extends out as far as Cheviot, its not what you would call high country
... which GFS and EC have been consistent on for a few days now also. After a mild may, it looks like June will plunge us into the depths of winter. 
