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Posted: Tue 20/06/2006 00:01
by Andrew Massie
NZ Thunderstorm Soc wrote:Interesting discussion on this:
I'm still going with my earlier prediction on this, despite the slow moving low off the Gisbourne coast.

I'm going with this from Ben's thread, at the moment:
think that there is NOT going to be anymore severe weather as surface barometer pressures are on the rise.
...but in saying that, stationary anticyclone pressures will rise to the west of us which will enhance cold, below temperatures for the time of year, for the rest of the coming week and possibly into next week as well
It will be more finer than wet outbreaks.



JohnGaul
NZTS
Ok JG, your cards are down... let's see how good your game is... ! :D :D :D

Posted: Tue 20/06/2006 04:31
by surtees
Well a big hello to everyone down under!

Allow me to introduce myself, my name is kris surtees, and i live in the SE of the UK, and am a very avid amature forecaster. I have a contact over in NZ who is a meteorolgical broadcaster on various radio stations around christchurch, and he has informed me of the impending situation that the Met Service have been forecasting for you guys, so i thought id take a look

The First thing that struck me was that apparently the met service rely upon the GFS MRF model, understandably more than the ECMWF output, but less understandable than the Australian/NZ model (of which i do not know where to find, if any of you could provide a link it would be brilliant!). In my experience in forecasting for europe the GFS is the most reliable model for a number of reasons, not least its superb accuracy, its fantastic resolution (some sites can use it to provide 0.25 degree GFS technology) and its 14 members, which thanks to recent updates by the NOAA (american met service) are now available to view, compared the the previous number of 10 only available, however what you guys have coming is a very borderline situation indeed.

When we have these in the UK, 9/10 times the best advice i can give is to look to the TV forecasts (the BBC are the best over here) because they have access to many more charts than i have freely available on the net. The Other problem is the GFS just cannot handle 2 things

1) Large scale blocking patterns, notoriously here in europe the GFS is useless at winter HP blocks because it is a very transitional model, meaning it always looks to bring back cyclogenesis at the earliest opportunity.

2) Borderline situations - The zoom on the maps is just not enough to tell with borderline situations

The main reason your upcoming situation is borderline is due to the 850 hPa temps. Ideally for snow you need them to be below -6c, but even with that there are exceptions because that is just at 1 particular reigion of the atmosphere. What the GFS is currently showing are temps between -5c and -6c at 850 hPa, so very borderline. What you guys are basically relying on below around 200m is a phenomenem called evaporative cooling, also known as downdrafts, where the sheer amount od precipitation falling cools the atmosphere as energy is used up, this is usually what occurs when we see rain falling at the same time as snow. This effect is likely to be a key factor for you guys on the south island. It could well be that you see 15-20 cms of snow in one area, yet 5 miles down the road it could just be sleet.

I can certainly see why the met service are being very cautious about this setup, i too would be, but certainly todays GFS runs so far have been a large downgrade for the situation, bringing friday out of the equation on the south island. But just as easily as it downgrades it could upgrade again still.

One thing is for sure, many mountaineous and hilly areas, largely above 200m will be hit very badly by this storm, particularly down the eastern seaboard as the LP deepens during thursday.

Perhaps still too early to suggest snowfall totals, but without a doubt you have to be looking at double figures, some probably into the 20's and upland areas possibly the 30's and 40's cms.

Take Care Everyone

Surtees

Posted: Tue 20/06/2006 06:59
by Manukau heads obs
the met service also use the UK Bracknel model alot
what they tend to do is look at all the models, and use their own collective experience.....
sometimes these things just dont happen at all that models predict (more ofen if its only 1 or 2 models predicting it...but if they all predict a similar thing, then its a sure bet)
they also dont want to get into a cry wolf situation too many times.....

just my 2 cents worth, inflation adjusted

Posted: Tue 20/06/2006 11:12
by gllitz
MS have release this for tomorrow afternoon/evening:

SEVERE WEATHER WATCH FOR CANTERBURY AND THE KAIKOURAS
ISSUED BY METSERVICE AT 1058hrs 20-Jun-2006

SNOWFALLS EXPECTED ON THE CANTERBURY PLAINS AND THE KAIKOURA RANGES
AGAIN ON WEDNESDAY COULD BE HEAVY FOR A TIME INLAND

Another cold southerly outbreak is on the way, and snow is expected
over much of the Canterbury Plains again on Wednesday.

The southerly should arrive Wednesday morning, then temperatures
should fall, with snow lowering to 100 to 200 metres during the
afternoon or evening. Some places above 300 metres could receive
10-15cm in a six hour period from mid afternoon.

In the Kaikouras, similar amounts could develop above 300 metres
Wednesday evening.

People in these areas should remain up to date with the latest
forecasts, and look out for any upgrade of this watch to a full
warning.

This Watch will be reviewed by 9pm Tuesday 20th June
Forecast prepared by: Mark Pascoe


....interesting...wait and SEE :-)

Posted: Tue 20/06/2006 14:11
by colin manson
I think that we get snow on the the ground in chch in from 5-7 pm wed looking at gfs .well i hope so!!

Posted: Tue 20/06/2006 14:14
by Gary Roberts
gllitz wrote:MS have release this for tomorrow afternoon/evening:

SEVERE WEATHER WATCH FOR CANTERBURY AND THE KAIKOURAS
ISSUED BY METSERVICE AT 1058hrs 20-Jun-2006

SNOWFALLS EXPECTED ON THE CANTERBURY PLAINS AND THE KAIKOURA RANGES
AGAIN ON WEDNESDAY COULD BE HEAVY FOR A TIME INLAND

Another cold southerly outbreak is on the way, and snow is expected
over much of the Canterbury Plains again on Wednesday.

The southerly should arrive Wednesday morning, then temperatures
should fall, with snow lowering to 100 to 200 metres during the
afternoon or evening. Some places above 300 metres could receive
10-15cm in a six hour period from mid afternoon.

In the Kaikouras, similar amounts could develop above 300 metres
Wednesday evening.

People in these areas should remain up to date with the latest
forecasts, and look out for any upgrade of this watch to a full
warning.

This Watch will be reviewed by 9pm Tuesday 20th June
Forecast prepared by: Mark Pascoe


....interesting...wait and SEE :-)
MetConnect is forecasting snow to low levels for Otago as well over the same period, but there are no warnings in force. Interesting to see what happens.

Posted: Tue 20/06/2006 14:32
by Willoughby
surtees wrote:Well a big hello to everyone down under!

The First thing that struck me was that apparently the met service rely upon the GFS MRF model, understandably more than the ECMWF output, but less understandable than the Australian/NZ model (of which i do not know where to find, if any of you could provide a link it would be brilliant!). In my experience in forecasting for europe the GFS is the most reliable model for a number of reasons, not least its superb accuracy, its fantastic resolution (some sites can use it to provide 0.25 degree GFS technology) and its 14 members, which thanks to recent updates by the NOAA (american met service) are now available to view, compared the the previous number of 10 only available, however what you guys have coming is a very borderline situation indeed.

Surtees
Hi there! MetService use UKMO primarily, coupled with their own LAM called CHAMPS.. then they'd be using LAPS/GASP/GFS ECMWF and what not.. quote me if im wrong MetService.. an explanation would be great! :)
Over NZ/Aus, GFS IMO does have that problem as you say, which tends to cyclogenesis too quickly.. has marked rapid displacement within runs with it's forecast of sub-tropical lows coming down onto us.. EC can be a bit slow off the mark when forecasting those situations, but is probably the least erratic of all models. GFS can often be useless here thanks to it's low resoloution, as we do have very sharp regional zones which GFS doesn't pick up.

Does look interesting for the Wellington region tomorrow, Northerlies easing with heavy rain developing.. overnight gale southerly/SSE change.. persisting into Monday with easing southerlies and rain. I think it's a bit too warm for snow at this stage.. we may just have to see!

ECMWF and GASP develop a broad warmer low in the Central N'n Tasman Sea by Monday :)

(sticking my neck out on this one...)

Posted: Tue 20/06/2006 16:56
by gllitz
Well, here it goes...sticking my neck out! :D 8)

For Christchurch, rain will turn to sleet and then over to all snow overnight after 6 pm WED. 21 June. The snow will continue throughout the night and into Thursday, with some breaks, but probably not clearing until Friday.

Snowfall amounts: I'm gonna say 8-12 cm in total here in CHCH, but all melting away by SAT, as is normally the case. :-P ....

(DISCLAIMER: I am NOT a professional meteorologist and anything I post on this website/forum are my personal opinions only and should NOT be used for making emergency planning, etc. Go to the MetService homepage for that stuff...)

Posted: Tue 20/06/2006 17:04
by Janos
Hi Glitz now do the same for Dunedin.....

Posted: Tue 20/06/2006 17:12
by Razor
And Auckland hahahahaha 8)

Posted: Tue 20/06/2006 17:15
by Gary Roberts
Razor wrote:And Auckland hahahahaha 8)
Auckland will receive some rain, some wind, and some fine periods every single day for the rest of eternity.

Phew, that was a tough one!

Auckland: World's most consistent and reliable weather!

Posted: Tue 20/06/2006 17:19
by gllitz
Janos wrote:Hi Glitz now do the same for Dunedin.....
I'll try, but remember, I do this for fun, ya know...there ARE people who are paid professionals who do this for a living and are probably WAAAAY more accurate than me....(many of whom are perhaps sniggling at me, but I don't mind...it's all a learning process....)

For Dunners...I think rain will turn to sleet then over to all snow as well, but I suspect it will actually happen earlier in the day for you guys, say early afternoon-ish :-P

Have no idea about accumulations...I imagine the people in the hills around Dunedin are gonna get a descent dumping, though...

Posted: Tue 20/06/2006 17:20
by gllitz
Razor wrote:And Auckland hahahahaha 8)
Bah! Any snow up there would absolutely CRIPPLE the city...people wouldn't know what to do! They might slip and spill their lattes!!

Posted: Tue 20/06/2006 17:47
by GraemeWi
gllitz wrote:
Razor wrote:And Auckland hahahahaha 8)
Bah! Any snow up there would absolutely CRIPPLE the city...people wouldn't know what to do! They might slip and spill their lattes!!
No - we would stay at home. I've never driven in snow conditions (just where it has been cleared off the roads), and I don't intend to wreck my car learning to drive on snow / ice.

Image

And we drink flat whites, not lattes' - they are mainly drunk by people visiting from Christchurch. :P

Posted: Tue 20/06/2006 17:58
by Gary Roberts
GraemeWi wrote:
gllitz wrote:Bah! Any snow up there would absolutely CRIPPLE the city...people wouldn't know what to do! They might slip and spill their lattes!!
No - we would stay at home. I've never driven in snow conditions (just where it has been cleared off the roads), and I don't intend to wreck my car learning to drive on snow / ice.
Very sensible. I wouldn't drive in snow and ice if I could avoid it. Bloody hair-raising.
And we drink flat whites, not lattes' - they are mainly drunk by people visiting from Christchurch. :P
Pffft...Christchurchians...they think they're so great...!

BTW, nice pics there, Graeme.

Posted: Tue 20/06/2006 19:11
by tgsnoopy
Gary Roberts wrote:Very sensible. I wouldn't drive in snow and ice if I could avoid it. Bloody hair-raising.
I prefer it to black ice! At least you can see the snow. Amazingly I did 720° on black ice at about 90km in a slight corner and managed to straighten up and get back on my side of the road without crashing (luckily it was very early and there was no oncoming traffic). Impressed the heck out of my passengers and scared the heck out of me. The remainer of the trip was of course rather sedate.

Posted: Tue 20/06/2006 19:28
by mikestormchaser
yay in for more snow tomorrow night looking farwd to it id say possible up to 10 cm in snow for christchurch at this stage but its early days really.still looking fawred to it ;)

Posted: Tue 20/06/2006 19:42
by Weathermad
Well Mike lets hope you have it right...certainly cold enough at the moment!

So many seem to be unsure of just how far the snow will fall and I had a few people asking me today how bad is it going to get!....oh the $64,000 question!

Posted: Tue 20/06/2006 19:46
by mikestormchaser
yeah tru the $640000 is reguraly asked but yeah i guess thats the point really isnt it ae? i dont think anyone knws how bad its going to get.

Posted: Tue 20/06/2006 19:49
by Gary Roberts
tgsnoopy wrote:
Gary Roberts wrote:Very sensible. I wouldn't drive in snow and ice if I could avoid it. Bloody hair-raising.
I prefer it to black ice! At least you can see the snow. Amazingly I did 720° on black ice at about 90km in a slight corner and managed to straighten up and get back on my side of the road without crashing (luckily it was very early and there was no oncoming traffic). Impressed the heck out of my passengers and scared the heck out of me. The remainer of the trip was of course rather sedate.
Crikey! A 720°! All I ever do is slide off into metre-deep snowdrifts at the roadside and have to listen to locals taking the piss out of me about it for the rest of forever.

Posted: Tue 20/06/2006 19:52
by Janos
Tks Gllitz I promise I read in the vane it was written.
But it is fun to guess.
Winter is great.

Posted: Tue 20/06/2006 20:20
by 03Stormchaser
SEVERE WEATHER WATCH FOR CANTERBURY AND THE KAIKOURAS
ISSUED BY METSERVICE AT 1953hrs 20-Jun-2006

SNOWFALLS EXPECTED ON THE CANTERBURY PLAINS AND THE KAIKOURA RANGES
ON WEDNESDAY COULD BE HEAVY FOR A TIME INLAND

A cold southerly outbreak is spreading north over the South Island,
and snow is expected over much of the Canterbury Plains on Wednesday.

The southerly should reach Canterbury Wednesday morning, then
temperatures should fall, with snow lowering to 100 to 200 metres
during the afternoon or evening. Some places above 300 metres could
receive 10-15cm in a six hour period from mid afternoon.

In the Kaikouras, similar amounts could develop above 300 metres
Wednesday evening.

People in these areas should remain up to date with the latest
forecasts, and look out for any upgrade of this watch to a full
warning.

This Watch will be reviewed by 9am Wednesday 21st June
Forecast prepared by: Erick Brenstrum

For further information after 9pm contact Duty Forecaster Chris
Noble
Latest from Metservice

Posted: Tue 20/06/2006 20:25
by Janos
On the theme of vehicles sliding heres an 2004 photo I took ..
Spot the car.

Posted: Tue 20/06/2006 20:32
by Gary Roberts
Janos wrote:Spot the car.
Spot the Ball was easier! Where is it Janos. Gettin' old ya know, so you'll have to point it out for me. :lol:

Posted: Tue 20/06/2006 20:36
by gllitz
Gary Roberts wrote:
Janos wrote:Spot the car.
Spot the Ball was easier! Where is it Janos. Gettin' old ya know, so you'll have to point it out for me. :lol:
Amen for that...I was beginning to think I need to go see my eye doctor! :D