Severe Cold Outbreak over NZ 18th-21st

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Severe Cold Outbreak over NZ 18th-21st

Unread post by Willoughby »

GFS has it's sights for sea-level snow/sleet to Canterbury on Monday. Hopefully it's finally your turn! :D
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Last edited by Willoughby on Thu 15/09/2005 22:51, edited 2 times in total.
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Re: Canterbury Snow Possible - 19th September

Unread post by Gary Roberts »

Foggy Hamilton wrote:GFS has it's sights for sea-level snow/sleet to Canterbury on Monday. Hopefully it's finally your turn! :D
HAHAHAHAHAHAHAHAHAHAHAHAAAAAAAAAAA...sigh...
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Unread post by tich »

MetService is now forecasting snow to 'very low levels' (their words) for the South Island on Sunday and Monday. The last time NZ had a cold southerly was about the 27th August, and that was a pretty tame one, with snow only on some high country areas. Some places have had unseasonably warm tempertaures for the last few weeks, so a very cold outbreak will come as a shock. Especially somewhere like Alexandra, which has been getting up to the low 20s in recent days - snow would be a big change. Skifields could see the prospect of a wintry outbreak as a lifesaver for thier fields this season.
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Unread post by 03Stormchaser »

Thickness levels need to be around 520 and 850mb temp needs to be -8 to have sea level snow in chch. (same for Dunedin)

ChCh
Sunday: 540 thickness levels, 850mb Temp 0 C
Monday: 525 thickness levels, 850mb Temp -4 C
Tuesday: 522 thickness levels, 850mb Temp -6 C

Snow down to 400m on Tuesday, Canterbury.
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Unread post by NZstorm »

Just looking at latest ECMRF looks like a critical southwester, hence Southland and South Otago are likely to take the full brunt of what could be the coldest outbreak for over a year. Snow falling to near sea level.
Banks Peninsula could also cop it as well.

Models have a habit of toning down closer to the event, so will have to see how they pan out. Early days.
Last edited by NZstorm on Wed 14/09/2005 20:39, edited 1 time in total.
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Unread post by Gary Roberts »

NZstorm wrote:Just looking at latest ECMRF looks like a critical southwester, hence Southland and South Otago are likely to take the full brunt of what could be the coldest outbreak for over a year. Snow falling to sea level.
Banks Peninsula could also cop it as well.

Models have a habit of toning down closer to the event, so will have to see how they pan out.
See me turn blue as I hold my breath... :twisted: :P
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Unread post by Andy »

No more snow here this winter.... 25 degrees today, soil temps now are up over 10 degrees C. :lol:

Snow level of around 700m looks more likely to me, and that won't last too long either.
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Unread post by spwill »

Andy said
Snow level of around 700m looks more likely to me, and that won't last too long either.
Yes, snow would come and go but if Polar air dose come up snow will fall to near sealevel and your dry ground would quickly take snow.
Snow down to 400m on Tuesday, Canterbury.
Active Cb in Wintry flows tend to bring snow levels down.
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Unread post by TonyT »

03 Stormchaser wrote:Thickness levels need to be around 520 and 850mb temp needs to be -8 to have sea level snow in chch. (same for Dunedin)
IMHO, not so. -7 will do it with 524 or lower, and -8 or lower will do it with 528. for Chch. 520 is actually pretty rare in Chch.

For Dunedin snow at 530 is certainly possible as long as the 850T is low enough, say -8 or lower, and THK of 525 or lower will do Dunedin city snow regardless of the 850T.
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Unread post by NZ Thunderstorm Soc »

TonyT wrote:
03 Stormchaser wrote:Thickness levels need to be around 520 and 850mb temp needs to be -8 to have sea level snow in chch. (same for Dunedin)
IMHO, not so. -7 will do it with 524 or lower, and -8 or lower will do it with 528. for Chch. 520 is actually pretty rare in Chch.

For Dunedin snow at 530 is certainly possible as long as the 850T is low enough, say -8 or lower, and THK of 525 or lower will do Dunedin city snow regardless of the 850T.
There could still be a possibility of that but as the time gets closer the opportunity of that event may not eventuate.

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Unread post by Willoughby »

brr it's gonna get cold up here too!

Freezing levels dropping to 700m over Central North Island Sunday night bringing snow to the Desert Road, Napier-Taupo road and the Rimutaka Ranges etc. Some big frosts on the way as it becomes fine.

GFS now hinting Dunedin and Invercargill could also get snow on Sunday night as well as Christchurch.
Freezing level dropping to 250m for a time over Dunedin, 350m for Invercargill and 450m for Christchurch on Sunday night.
Tmax for Christchurch on Monday: 6c
Southwesterlies rising to gale on Monday for South Island East Coast.

1100m for Auckland on Monday night

Cheers :)
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Unread post by Willoughby »

Latest updates show colder conditions, light snow for Christchurch Sunday night, Monday night through to morning. Max on these days: 5c (But without southwestery gales)

Freezing level down to 850m for Waikato Tuesday night, 600m over Central NI Tuesday morning.

This is set to be the coldest outbreak this year beating the outbreak in April. Yahooooooo! :P

Gary, snow IS on the way, stop being so pessimestic :mrgreen:
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Unread post by tgsnoopy »

Sweet, that's really good news. I think I know where I'll be going on Sunday :)
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Unread post by Gary Roberts »

Foggy Hamilton wrote:Gary, snow IS on the way, stop being so pessimestic :mrgreen:
Well I suspect that's true because I have plans to begin some long-delayed construction on the mountain around the time the snow is forecast for. Typical.

But these much-anticipated events have a monotonous way of fizzling out completely. If I was the Met Service, I too would tend to always overstate things, just to cover my a*s.
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Unread post by TonyT »

Foggy Hamilton wrote: Max on these days: 5c
Not possible at this time of year. Dont get too caught up on what the models say, they dont know what its going to do, even if they like to give the impression they do. They are but one of many factors to consider in a forecast.
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Unread post by Storm Struck »

This would certainly be a wake up call for south islanders :o from being in mild temps latly to going into cold bittery winds and snow iam sure ski feilds will benefit from it but lambs and other young may find it hard.
Looking forward to this Blast to watever it shall give us :D .
Nice family picture in the Northern Outlook last wekend Tony Nice to see smiles in there instead of stuff on crimes and the darn Herbal Heaven in Kaiapoi.
Cheers
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Unread post by NZstorm »

latest ECWMF still likes the idea of an very cold outbreak over the South Island. Looks like its on! The cold outbreak will move through quickly though which will soften its impact. Snow, sleet, hail, thunder, severe gales, all on the cards for much of NZ this weekend.
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Unread post by tich »

Max on these days: 5c


Not possible at this time of year.
I believe Chch has recorded such a low maximum in September (and a 6C max at least once in October), but only under conditions of persistent thick cloud and rain in a cold airflow, not in a showery outbreak where the higher sun raises the temps during breaks in the wintry showers.
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Unread post by Willoughby »

tich wrote:
Max on these days: 5c


Not possible at this time of year.
I believe Chch has recorded such a low maximum in September (and a 6C max at least once in October), but only under conditions of persistent thick cloud and rain in a cold airflow, not in a showery outbreak where the higher sun raises the temps during breaks in the wintry showers.
Agreed, don't underestimate this TonyT! :D
GFS now going with actual gales (60km/h+) on Monday night for the SI East Coast
Christchurch 4-6 Day Weather Summary A light covering of new snow mostly falling on Mon night will be washed away by heavy rain (total 41mm) on Mon night , Mild temperatures (max 6°C on Thu morning, min 2°C on Mon night), Winds decreasing (gales from the SSW on Mon night, calm by Wed afternoon)
Quoted GFS minimum temps are always much higher than they should be.

Temperatues set to be below average by over 10c :shock:, especially inland regions.

A maximum of 9c is not out of the question for Hamilton on Mon & Tues
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Unread post by TonyT »

I'm not underestimating it at all, the warnings we are sending out to clients are, if anything, predicting worse conditions than you are. However, as Ben points out, a 5deg max would equal the record for September which makes it a very unlikely occurance. 5deg max is uncommon in winter (maybe one winter in two would see that in Chch), so for September its pretty much out of the ball park.

I just checked, and the only maximums under 7 deg in September in the Chch record are:

22 09 1994 6.1
25 09 1983 6.0
01 09 1969 6.9
10 09 1961 6.9
11 09 1947 6.6
09 09 1934 6.9
07 09 1930 6.0
08 09 1930 6.3
08 09 1925 6.4
19 09 1911 6.7
12 09 1907 6.9
1878
1872

So, it looks like 6.0 is the lowest September maximum, and a max under 7 is about a 1 in 10-15 year event.
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Unread post by GraemeWi »

I like the look of the SnowForecast.com map for the next couple of days:

http://www.snow-forecast.com/maps/nznor ... days.shtml

The Kaimai Ranges look to be in, Pirongia, there is even a tiny spot near Port Waikato ;) I'm going to make sure all my cameras and video are charged.

Cheers,

G
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Unread post by tich »

I like the look of the SnowForecast.com map for the next couple of days:

http://www.snow-forecast.com/maps/nznor ... days.shtml

The Kaimai Ranges look to be in, Pirongia, there is even a tiny spot near Port Waikato I'm going to make sure all my cameras and video are charged.
That looks like a level of about 400m for the central North Island - definitely a seriously icy outbreak, probably the coldest of the year. The late June southerly would've been the coldest previously, but not much snow resulted from it.
BTW, snow falling in Chch in September isn't very common; settling snow even rarer. In the last 10 years (since I've been here) I recall September flurries in 1997 (unusual event - temps were around 5C during the flurries), and a few flakes in 2002. In late September 1995, snow fell in low lying areas southwest of the city (eg Lincoln), but only a little sleet reached the city.
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Unread post by 03Stormchaser »

tich wrote: That looks like a level of about 400m for the central North Island - definitely a seriously icy outbreak, probably the coldest of the year. The late June southerly would've been the coldest previously, but not much snow resulted from it.
BTW, snow falling in Chch in September isn't very common; settling snow even rarer. In the last 10 years (since I've been here) I recall September flurries in 1997 (unusual event - temps were around 5C during the flurries), and a few flakes in 2002. In late September 1995, snow fell in low lying areas southwest of the city (eg Lincoln), but only a little sleet reached the city.
Snow definitly wont fall to all that low levels in canterbury, above 500m as models have the southerly weaker than they did yesterday. Storms still on cards for canterbury.
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Unread post by TonyT »

03 Stormchaser wrote:Snow definitly wont fall to all that low levels in canterbury, above 500m as models have the southerly weaker than they did yesterday. Storms still on cards for canterbury.
The current run of the GFS has 12-18 hours of 523-524THK and -7 850T for Chch, both of which are certainly cold enough for snow to sea level. :)
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Unread post by 03Stormchaser »

lets wait and see, also small chance of something tomoro as southerly comes thru.
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