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#1424204 - 25/05/2017 07:52 Re: 2017 Australian Snow Season [Re: Snowy Hibbo]
Donzah Offline
Weather Freak

Registered: 11/02/2017
Posts: 469
Loc: Woonona NSW and JIndabyne NSW
Originally Posted By: Snowy Hibbo

That's certainly a good idea for most people. I like using the EC charts, so more than happy to share them here...

I get my EC totals from the snow accum charts, but yr.no is okay.

However yr.no contradicts the snow accumulation charts on pro-accue
there is going to be a bit more than as indicated on those charts above.
I like pro-accue for its intervals on EC being smaller, plus it renders EC better, has great resolution ... however I find pro-accu wildly inaccurate for snow accumulation modelling , I've had it for last three seasons or so. In fact I find most models very poor for accumulation . The tiling they use doesn't account for local factors ... if AXS-R had a snow model it would be quite cool (and yup I know meteye has it, of sorts)

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#1424205 - 25/05/2017 07:56 Re: 2017 Australian Snow Season [Re: HumphreyBear]
Donzah Offline
Weather Freak

Registered: 11/02/2017
Posts: 469
Loc: Woonona NSW and JIndabyne NSW
Running off yr.no this morning , taking into account and temperature . I'd expect 50cm (at Perisher) out of this 2 banger system.
The duration is the key.
Midnight (ish) Saturday to Midnight wednesday is close to 96 hours of potential snow. Even at an average of .05mm per hr (conservative)
Looking at the wind , orographic lifting will occur on the windward sides of NW ridges. The western faces of the MR will get smoked with snow.

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#1424206 - 25/05/2017 08:01 Re: 2017 Australian Snow Season [Re: HumphreyBear]
Donzah Offline
Weather Freak

Registered: 11/02/2017
Posts: 469
Loc: Woonona NSW and JIndabyne NSW
Wednesday is going as a cutoff on the spag.
If its cold enough, that will promote moisture,,, its actually quite a good think, considering the residual cold air from the proceeding change.

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#1424219 - 25/05/2017 10:33 Re: 2017 Australian Snow Season [Re: HumphreyBear]
DaveM Offline
Meteorological Motor Mouth

Registered: 21/05/2001
Posts: 9578
Loc: Bathurst NSW about 700 m asl
Keep it going lads, love it smile

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#1424223 - 25/05/2017 11:33 Re: 2017 Australian Snow Season [Re: HumphreyBear]
WarrenTheSnowMan Offline
Weather Freak

Registered: 18/04/2016
Posts: 317
Loc: Frosty, Kemp's Creek
Where are you getting 15-30cm from? I'm only seeing 6cm total for the 3 days.

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#1424228 - 25/05/2017 12:12 Re: 2017 Australian Snow Season [Re: WarrenTheSnowMan]
Donzah Offline
Weather Freak

Registered: 11/02/2017
Posts: 469
Loc: Woonona NSW and JIndabyne NSW
Originally Posted By: WarrenTheSnowMan
Where are you getting 15-30cm from? I'm only seeing 6cm total for the 3 days.


https://www.yr.no/place/Australia/New_South_Wales/Mount_Perisher/long.html

EC via Yr.no is a conservative model for precip.

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#1424232 - 25/05/2017 12:35 Re: 2017 Australian Snow Season [Re: HumphreyBear]
Blair Trewin Offline
Weatherzone Addict

Registered: 13/07/2001
Posts: 3676
Loc: Melbourne, Australia
yr.no uses ECMWF output but does some post-processing for temperature - for example, they now have an explicit elevation correction for temperature when equating temperature at the nearest gridpoint to temperature at a specific location. This seems to have improved performance a fair bit in areas of complex topography - for example, Canberra used to have a strong cold bias (presumably because the 'Canberra' gridpoint used a mean gridbox elevation which took in some of the Brindabellas), but this has been reduced (but not eliminated) more recently.

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#1424233 - 25/05/2017 12:47 Re: 2017 Australian Snow Season [Re: Blair Trewin]
Donzah Offline
Weather Freak

Registered: 11/02/2017
Posts: 469
Loc: Woonona NSW and JIndabyne NSW
Originally Posted By: Blair Trewin
yr.no uses ECMWF output but does some post-processing for temperature - for example, they now have an explicit elevation correction for temperature when equating temperature at the nearest gridpoint to temperature at a specific location. This seems to have improved performance a fair bit in areas of complex topography - for example, Canberra used to have a strong cold bias (presumably because the 'Canberra' gridpoint used a mean gridbox elevation which took in some of the Brindabellas), but this has been reduced (but not eliminated) more recently.


Yeah i've noticed this (as have others , eg Professional mountain guides) that it has improved on its algorithums for altitude temperature correction within its "tiles" (my understanding of the gridbox) .
Mind you its absolutely hopeless with wind.
I also think the precip modelling has improved along with that.

Re snow. The best moisture model is AXS-R. It models orographic effects most accurately in the mountains. Obviously its resolution helps.

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#1424235 - 25/05/2017 12:52 Re: 2017 Australian Snow Season [Re: HumphreyBear]
DaveM Offline
Meteorological Motor Mouth

Registered: 21/05/2001
Posts: 9578
Loc: Bathurst NSW about 700 m asl
Good information Blair smile

Shame "R" is so short term in outlook.

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#1424238 - 25/05/2017 12:55 Re: 2017 Australian Snow Season [Re: DaveM]
Donzah Offline
Weather Freak

Registered: 11/02/2017
Posts: 469
Loc: Woonona NSW and JIndabyne NSW
Originally Posted By: DaveM
Good information Blair smile

Shame "R" is so short term in outlook.


I had explained to me that R would need a bloody expensive main frame to continue its resolution at the same level beyond 72 hrs..

But it may happen.

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#1424240 - 25/05/2017 12:58 Re: 2017 Australian Snow Season [Re: HumphreyBear]
Blair Trewin Offline
Weatherzone Addict

Registered: 13/07/2001
Posts: 3676
Loc: Melbourne, Australia
That's right - to go, say, from 25km to 5km resolution means a 25x increase in the number of gridpoints (even if you don't change the number of vertical levels), which means using 25x the amount of computer time.

The ability to run higher-resolution models for longer is one of the things you get as computing infrastructure improves.

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#1424241 - 25/05/2017 13:01 Re: 2017 Australian Snow Season [Re: HumphreyBear]
WarrenTheSnowMan Offline
Weather Freak

Registered: 18/04/2016
Posts: 317
Loc: Frosty, Kemp's Creek
You do realise that is in mm right...? The CM of snow will be much different.

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#1424242 - 25/05/2017 13:07 Re: 2017 Australian Snow Season [Re: WarrenTheSnowMan]
Donzah Offline
Weather Freak

Registered: 11/02/2017
Posts: 469
Loc: Woonona NSW and JIndabyne NSW
Originally Posted By: WarrenTheSnowMan
You do realise that is in mm right...? The CM of snow will be much different.


Yr.no.... roughly at -1 a mm of precip translates to a cm of snow. At say 95% humidity ... if you drop the humidity down and the temperature down...the formula is more favourable

at minus 3 that formula is 1.33 times
at minus 6 that formula is 1.5 times

And so on as the air gets colder its ability to form high volume snowflakes decreases.

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#1424245 - 25/05/2017 13:13 Re: 2017 Australian Snow Season [Re: HumphreyBear]
WarrenTheSnowMan Offline
Weather Freak

Registered: 18/04/2016
Posts: 317
Loc: Frosty, Kemp's Creek
The size of a snowflake can't alter how much moisture is available in a system.

Eventually as more snow falls the more the snow underneath the top layer melts. The value will be far less than 50~60cm.

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#1424246 - 25/05/2017 13:19 Re: 2017 Australian Snow Season [Re: WarrenTheSnowMan]
Donzah Offline
Weather Freak

Registered: 11/02/2017
Posts: 469
Loc: Woonona NSW and JIndabyne NSW
Originally Posted By: WarrenTheSnowMan
The size of a snowflake can't alter how much moisture is available in a system.

Eventually as more snow falls the more the snow underneath the top layer melts. The value will be far less than 50~60cm.


No the moisture in the snowflake determines how much falls... ie a stellar dendrite at -1 won't accumulate as much depth as a stellar dendrite at say minus 5..
The composition of the snowflake is determined by the moisture and the temperature of its creation all the way to its arrival . That composition or structure then determines how it bonds with other snowflakes to create a snowpack.
Obviously surface temperature is one of the biggest factors.

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#1424247 - 25/05/2017 13:22 Re: 2017 Australian Snow Season [Re: HumphreyBear]
Donzah Offline
Weather Freak

Registered: 11/02/2017
Posts: 469
Loc: Woonona NSW and JIndabyne NSW
So the amount of snow that falls is a formula of precip/vs temperature (simply)

I'm also a big Believer in duration of events.

In my experience a prolonged flow with embedded troughs accumulates more snow that a "wonder" system that looks fantastic then gets ridged out to the tasman.

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#1424249 - 25/05/2017 13:33 Re: 2017 Australian Snow Season [Re: HumphreyBear]
Donzah Offline
Weather Freak

Registered: 11/02/2017
Posts: 469
Loc: Woonona NSW and JIndabyne NSW
I added up the precip on yr.no

Between sunday and wed midnight... 59.3 mm is progged

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#1424253 - 25/05/2017 14:05 Re: 2017 Australian Snow Season [Re: HumphreyBear]
slotmachine Offline
Weather Freak

Registered: 02/11/2007
Posts: 198
Loc: Newcastle
That yr.no forecast is for 1900m yeah? Marginal temps on Sunday?

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#1424254 - 25/05/2017 14:09 Re: 2017 Australian Snow Season [Re: slotmachine]
Donzah Offline
Weather Freak

Registered: 11/02/2017
Posts: 469
Loc: Woonona NSW and JIndabyne NSW
Originally Posted By: slotmachine
That yr.no forecast is for 1900m yeah? Marginal temps on Sunday?

Nah
Altitude: 1719 m.

Yeah the temps are so so ish..I think the freezing level will be around 1700 until after noon Sunday .Though the uppers aren't that warm.

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#1424268 - 25/05/2017 15:13 Re: 2017 Australian Snow Season [Re: HumphreyBear]
WarrenTheSnowMan Offline
Weather Freak

Registered: 18/04/2016
Posts: 317
Loc: Frosty, Kemp's Creek
That is still 5.9cm... I'm extremely doubtful of this 60cm everyone is talking about, even 30cm is pushing it.

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