Tasman Low 3 Thursday 5th-Saturday 7th July, Snow watch!!!

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Storm Struck
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Tasman Low 3 Thursday 5th-Saturday 7th July, Snow watch!!!

Unread post by Storm Struck »

Was hard to pick a topic name for this one as we have had so many lows latly.
Looking interesting towards the end of the week perhaps Friday could see heavy snow to relativly low levels at this stage and that is good being so far out, hence the models don't change out of favour ( touch wood ) 8) .
I must admit with these mild Temperatures in the last few days of 17-19C which is unusual for July, It makes you feel as though something is on it's way.
But at this stage it is a watch being so far out and all we can do is hope something interesting comes of this.
Thoughts people :? .
Edit.. I have added a 3 next to the topic name as it's our third Tasman Low in the last few weeks, also makes it easier to seperate from the old Low topic.
Cheers
Jason.
Last edited by Storm Struck on Tue 03/07/2007 22:45, edited 3 times in total.
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Re: Tasman Low Friday 6th-Saturday 7th July, watch!!!

Unread post by Gary Roberts »

Jasestrm wrote:Was hard to pick a topic name for this one...
Ha, I thought this was a different thread!

Anyway, I'm sitting here waiting for next weekend.

:D
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Re: Tasman Low Friday 6th-Saturday 7th July, watch!!!

Unread post by gopolks »

Jasestrm wrote:Was hard to pick a topic name for this one as we have had so many lows latly.
Looking interesting towards the end of the week perhaps Friday could see heavy snow to relativly low levels at this stage and that is good being so far out, hence the models don't change out of favour ( touch wood ) 8) .
I must admit with these mild Temperatures in the last few days of 17-19C which is unusual for July, It makes you feel as though something is on it's way.
But at this stage it is a watch being so far out and all we can do is hope something interesting comes of this.
Thoughts people :? .
Cheers
Jason.
Well we are due for something, I dont think something major will happen, maybe some cold sleety showers on friday, with the white stuff on the hills, who knows? hopefully the models dont change overnight to bright sunny weather for friday/sat.
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Re: Tasman Low Friday 6th-Saturday 7th July, watch!!!

Unread post by Gary Roberts »

gopolks wrote:Well we are due for something...
Or not. The weather seems to do what ever the weather does and with complete disregard for us. :? :cry:
...hopefully the models dont change overnight to bright sunny weather for friday/sat.
About the only thing I would consider betting on is that the models will definitely change, because they always do!

:o
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Unread post by TonyT »

It will be interesting to check out the next few model runs and see if there is any consistency there. Certainly the way things are shaping up has the potential to give some warm advective snow to the South Island (which is always the heaviest type of snow fall) and to lower levels than the previous system, due to the much colder air advecting over the South Island from the anticyclone in the Southern Ocean due about Wednesday/Thursday. But, potential and actuality are two different things, as we all know when thunderstorms threaten.
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Unread post by Gary Roberts »

TonyT wrote:It will be interesting to check out the next few model runs and see if there is any consistency there. Certainly the way things are shaping up has the potential to give some warm advective snow to the South Island (which is always the heaviest type of snow fall) and to lower levels than the previous system, due to the much colder air advecting over the South Island from the anticyclone in the Southern Ocean due about Wednesday/Thursday. But, potential and actuality are two different things, as we all know when thunderstorms threaten.
Tony can you give me/us a clear explanation of the term "advective snow".

I understand the basic concept (cold air mass passing over warm moist airmass, freezing at intersecting plane, falling snow causing lower levesl to cool, etc...) and I'm familiar with the term "advection" as it's applied in physics and other sciences, but I'm still a mite unclear of how the twain meet.

Cheers you weatherologist, you.
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Unread post by TonyT »

The terms you need to know about are "warm advective" and "cold advective" rather than "advective snow" :)

Now I have put it that way, you probably have an inkling of what the differences are.

Warm advection is what happens with a warm front - warm air advancing, riding up on and eventuallly replacing colder air below. Produces broad sheets of rain (or snow) and often results in heavy falls if orographic enhancement plays a part (ie if the warm air meets an obstacle such as a range of hills or mountains).

Cold advection is what happens at a cold front - the cold air replaces warmer surface air, usually from the ground upwards. This typically enhances convection, which is why cold fronts often have thunderstorms embedded in them, and why the precipitation on cold fronts is often more showery, less widespread. Ranges of hills and mountains can interact here too, but often result in "steering" of the showers, rather than enhancing uplift (not always though).

If you look at a satellite picture, a broad generalisation is that the areas of sheet cloud are areas where there is warm advection happening in the atmosphere, whereas the areas with spotty and speckled cloud are areas of cold adevection.

Most snow in NZ comes with cold airflows from the south, and is cold advective. Hence its showery and while often reaches to low levels it not always heavy. Warm advective snow is rarer (perhaps a few times a winter) but usually produces big dumps over wide areas (last June an extreme example). Just how heavy depends on how much moisture there is (which in turn is influenced by where the warmer air is arriving from). The level it falls to depends on how cold the lowest layers of the atmosphere are beforehand. If a southerly flow turns northeast, thats often a good situation for warm advective snow in the east of the South Island.
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Unread post by Gary Roberts »

Uhuh. So what I had been told about "advective snow" (and thought I knew) was in fact wrong. Great. I hate being clueless. It gives me Gauss.
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Unread post by TonyT »

0Z modelling wants to build a ridge into the cold air on Friday and Saturday over the SI, keeping the warm advective precip over the NI on those days. Cold enough for some cold advective snow to low levels perhaps in Canty on Thursday night/Friday morning, but not a lot.

I dont think this is the definitive forecast yet - we need to keep an eye on the models for a few more days, I suspect there are some more twists and turns coming.
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Unread post by mikestormchaser »

Wicked! Now i havnt recently checked the models And i proberbly cant work it out :lol: but sure sounds great!
Maybe this time, just maybe!
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Unread post by NZ Thunderstorm Soc »

Edit.. I have added a 3 next to the topic name as it's our third Tasman Low in the last few weeks, also makes it easier to seperate from the old Low topic.

i think it is the 4th one although not coming from the same source as the other 3???

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Unread post by Razor »

Well if the last two weekends are anything to go by I look forward to mountain biking in the Canterbury region in 16-18 degree temps again next Sunday for the 3rd weekend in a row!

Latest metvuw prognosis makes that next low look like a real fizzer.

Its a warm winter folks....my call is no snow in Canterbury to sea level this year. Not even once, its a La Nina year- bad enough for skifield snow let alone in town
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Unread post by gopolks »

Razor wrote:Well if the last two weekends are anything to go by I look forward to mountain biking in the Canterbury region in 16-18 degree temps again next Sunday for the 3rd weekend in a row!

Latest metvuw prognosis makes that next low look like a real fizzer.

Its a warm winter folks....my call is no snow in Canterbury to sea level this year. Not even once, its a La Nina year- bad enough for skifield snow let alone in town
I didnt want to hear that. :(

From the way I read the models, I dont even see rain for chch over the weekend, Friday may be cold, and we may get soem sleety showers. I see some people are predicting snow on friday for Timaru.

I guess five days out is still a long way.
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Unread post by mikestormchaser »

AAHHH thats just Razors opinion.
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Unread post by Andrew Massie »

Hmmm... my Jury's out until later on.. Ever optimistic for bad weather!
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Unread post by evltre »

I see the met-service rural forecast for Canterbury now has pretty little snow icons for Thurs/Fri/Sat (was just Saturday before)! Wooohooo might be in luck!
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Unread post by gllitz »

evltre wrote:I see the met-service rural forecast for Canterbury now has pretty little snow icons for Thurs/Fri/Sat (was just Saturday before)! Wooohooo might be in luck!
Yeah, for today's SWO they have said basically the same thing they did yesterday...which tells me they aren't too sure about what is going to happen...fair enough, I guess ? :?

...will be interesting to watch the next few model runs, as Tony T has mentioned...I have noticed, however, for the GFS, at least, they have been consistent with having 850 mb temps right around -8C for an extended period of time...but thickness levels are around 530 mark...based on previous discussions on this, the 850 temps are good for snow to sea level in Canty, but the thickness levels are too high... :(

Thoughts from others?
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Unread post by Storm Struck »

I wasn't expecting any rain to fall today.
It clouded over about early afternoon and the temperature dropped as well. Then it went from light rain to heavy rain by 5pm, now back to moderate as I arrive home.
Hmm yes moisture lacking abit perhaps but lets jst wait and see as the models can and will change hopefully for our good sakes 8) .
Cheers
Jason.
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Unread post by gllitz »

Jasestrm wrote:I wasn't expecting any rain to fall today.
It clouded over about early afternoon and the temperature dropped as well. Then it went from light rain to heavy rain by 5pm, now back to moderate as I arrive home.
Hmm yes moisture lacking abit perhaps but lets jst wait and see as the models can and will change hopefully for our good sakes 8) .
Cheers
Jason.
00 Z GFS run shows more precip than b4...and with somewhat colder temps than my previous post 8) ...but it looks not to last too long (typical CHCH snow, if it does eventuate) and we are still 72-84 hours away from the "fun" anyway...won't hold my breath for now until about THUR morning or so ;) :D
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Unread post by Andy »

Drizzel here since breakfast, a little bit heavier now. :D
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Unread post by mikestormchaser »

So how likely is this event going too take place? it could be a fizzer or the big snow fall for the winter. :?
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Unread post by Gary Roberts »

tornadoman18 wrote:it could be a fizzer or the big snow fall for the winter. :?
Or it could be somewhere in between...maybe a day or two of snow, totalling perhaps 5-6", but not really amounting to much. A bit like we had a couple of weeks ago, really.
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Unread post by TonyT »

tornadoman18 wrote:it could be a fizzer or the big snow fall for the winter. :?
I couldn't have put it better myself! :)
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Unread post by gopolks »

TonyT wrote:
tornadoman18 wrote:it could be a fizzer or the big snow fall for the winter. :?
I couldn't have put it better myself! :)
We will know more tomorrow, as time grows nearer.

I think we might get something out of it, but it wont be massive.
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Unread post by mikestormchaser »

who knows! it might be massive! just never know what it might decide too pull off lol
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