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Beginners guide to forecasting, GFS models?

 Poster: A snowHead
Poster: A snowHead
thanks matt.

that's kind of what i thought from looking at stuff, but wondered if any of the experts - you know the "qualified" ones - could say for sure. Very Happy
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 Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
More gems from Brian.....


So the currently available state of NWP (numerical weather prediction, 1st acronym in already ).

The clear leader in the verification stats and therefore the current leader of the pack is (drum roll .....):

- ECMWF, European Centre for Medium-range Weather Forecasts, it's a collaborative venture between numerous european countries.

They run twice a day (midnight and noon) and the freely available output goes out to 240 hours in 24 hour steps and consists of surface level pressure and 850 hPa temperature and wind charts. They run an ensemble of 50 members but we can't see it (except for one location in Holland, not much use).


Fighting it out for 2nd place, the other 2 members of the so called "big 3":

- GFS, Global Forecast System, the model of NOAA, National Oceanic and Atmospheric Administration, a US govt agency.

They run 4 times a day (every 6 hours) and the entire dataset is published for free by a variety of sites out to 384 hours in 6 hour steps (the first 180 hours at 3 hour steps). You get everything with this one, pressure, precip, temp/wind at various heights etc. etc. They run an ensemble of 20 members.

- UKMO, our own UK Met Office.

They run twice a day (midnight and noon) and publish pressure charts out to 144 hours in 12 hour steps to T+96 then 24 hour steps. They also publish temp and precip charts out to 72 hours. No free ensemble data, don't know what they do.


So that's the 3 it's worth looking at. Then we have the "lesser models". Actually that tag is a little unfair on ...

- GEM, the Canadian model, which isn't far off GFS and UKMO these days.

... but these aren't much cop:

- JMA, Japan
- NOGAPS, the US Navy
- DWD, the Germans


On top of that little lot, we have the FAX charts. These are produced by actual human forecasters using the model output and they draw on the fronts, troughs etc. This requires a pretty high degree of skill. It can be quite illuminating to look at the met office's ones though, as they have full access to their own model (obviously) but also the ECM and GFS, so you can sometimes get an idea of which model the real experts have confidence in.

So where can I look at all this stuff, brian, I (don't) hear you cry ?

Why at http://www.wetterzentrale.de/topkarten

and http://meteociel.fr/modeles/

of course !

Happy weather watching
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 Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
Afternoon all. This chart looks really useful - lots of info on one page. However, I am not 100% sure what everything means. Can someone help?

http://85.214.49.20/wz/pics/MS_070460_g05.png

OK, I think that the first chart shows cloud cover in 3 sections, high cloud, mid layer cloud and low cloud. If the white bit is fat, it means it is pretty cloudy. If the white bit is thin, it means it is less cloudy. Does the size of the white bit equate to % (ie a full bar = 100% cloud cover)?

The 2nd chart I take to be pressure at sea level.

The third chart is wind I think, and the higher the green line the stronger the wind is. Anyone know what this is measured in? Also, do the black lines give direction, and if so how do you read that?

The third line is temp. Is this given at the 850 hpa level?

Don't really know what the forth chart is...

The final chart is precipitation. What do the red lines mean?

Thanks in advance...

Ed
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...and on the subject of precipitation, on the Wetterzentrale graph, if I am correct thinking that the precipitation forecast is for mm rain, then do you multiply that number by 10 to get forecast snow depth? Or summat else? I've got 3 weeks before I hit Les Gets but it's never too early to start planning... Madeye-Smiley

Andy
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Anyway, snowHeads is much more fun if you do.
andyph, as far as I know, it is mm for rain and cm for snow....
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Snowmonkey,

- correct on cloud and surface pressure (bodendruck).

- windspeed is in knots (1 knot = 1.15 mph), direction is shown by the black lines as if they were the needle on a compass.

- Temp is given for 2m above the surface at whatever altitude the surface happens to be at (the one you've linked is 1862m, given at the top right). Red and blue lines are temp max/min, black is the dew point.

- next graph is relative humidity

- bottom is precip in 3 hour periods, red lines mean convective precip

andyph, yes, as a (very) rough rule of thumb, 1mm of rain = 1cm of level snow ... and welcome to snowHead s
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Then you can post your own questions or snow reports...
brian, welcome back!!!
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 After all it is free Go on u know u want to!
After all it is free Go on u know u want to!
Sorry Brian, a couple more questions

Quote:

- windspeed is in knots (1 knot = 1.15 mph), direction is shown by the black lines as if they were the needle on a compass.


What about the fact that the main lines have little lines coming off them? And which end of the line is the direction?

Quote:

Red and blue lines are temp max/min, black is the dew point.


Where does the dew point have to be in relation to temp in order for precipitation to occur? Or can it vary?

Quote:

red lines mean convective precip


What does that mean?

I'm getting there, thanks in advance for your help!
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I am being silly or is anyone else having issues seeing the latest data. For example London, seems not to have updated since friday. The same with any others I look at Puzzled

http://85.214.49.20/wz/pics/MT8_London_ens.png
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norris, looks like Wetterzentrale have moved server, try:

http://www.wetterzentrale.de/pics/MT8_London_ens.png
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brian, I knew you would be the man in the know - thanks!
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 And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
If anyone could accurately forecast 10 days ahead, they would be very wealthy indeed.

Have a look at the synoptics for a few days on the trot for just 5 days forward and see how many of them are accurate. You will find its very few, unless we are talking about massive high pressure systems and stable jet streams. At the moment its hard enough to get accurate 3 days ahead.

I wouldn't throw away your fleeces just yet.
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So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
Quote:

What about the fact that the main lines have little lines coming off them? And which end of the line is the direction?


Just seen the query above, now rather old. The number of little lines coming off indicates speed - the more lines, the windier. The end without any lines points to where the wind is GOING.
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 You know it makes sense.
You know it makes sense.
brian,
Quote:
norris, looks like Wetterzentrale have moved server,

Looks like the server ip address has changed, so 85.214.49.20/wz/pics/MS_070460_g05.png has now become http://212.227.101.120/wz/pics/MS_070460_g05.png , which resolves to URL = http://www.wzkarten.de/pics/MS_070460_g05.png

Need to replace all 85.214.49.20 in any shortcuts with 212.227.101.120 or better, replace 85.214.49.20/wz with www.wzkarten.de so won't matter if the ip changes again

Hope that helps ...

I thought I'd lost me wigglies... Mad
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 Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
Hi Everybody

My 1st post although I've been reading this website for a couple of years!!

I have a quick question that I hope somebody can help with - I'm trying to figure out how to get the chart with the wigglies on it for Val D'Isere (or nearby). I think there used to be a link on this thread for Tignes but I can't find it anywhere now. Any help would be great - maybe if somebody has time they could post the link please? (I've tried going through the wetterzentrale website but I always get the wrong charts somehow).

Am off on Jan 18th and whilst I know its too early I can't help but start watching the forecasts!


Very Happy Puzzled
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 Poster: A snowHead
Poster: A snowHead
nickbuckers, welcome to S-Heads

Hi - you can find the lat / long of Val d'Isere, which is around 45.5N; 7E (type 45.5,7 into google maps & it'll show you that lat & long - longitude:East is positive & West is negative)

If you then put the longitude as 070 and latitude as 455 into this URL http://www.wzkarten.de/pics/MS_070455_g05.png you'll get the required meteogram

This shows the high;mid;low level cloud (blue is sky, grey is cloud): pressure: wind speed & direction: temperature: humidity (I think) & precipitation.

Change the values for different locations....
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 Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
or if it's the wigglies you're after


clicky clicky
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 Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
Geoffers, Rogg - many thanks & happy new year!

I'll be using this a lot in the next couple of weeks - hoping for a bit of a refresh to the pistes....


Little Angel
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Trouble is, trying to follow the arguments from the beginning, the fact that all the charts constantly update does make it rather tricky.... Sad
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 Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
Not sure if this is the right thread, but just wanted to give a quick heads up on some new forecast options on TWO. On the homepage you can now select 'Winter Sports' from the drop down menu. Once it has updated you can begin typing the name of the resort and the autosuggest will show you available options. Once your option is selected you can then either pick the 16 day or day forecast options for your forecast.

http://www.theweatheroutlook.com/default.aspx

If you want to use the old method for picking a resort and plotting graphs (as well as seeing the 16 day weather forecast, go to this page and select from the drop downs in the page body rather than header.

http://www.theweatheroutlook.com/twoforecasts/ski%20and%20snowboard%20weather.aspx

Time permitting I intend to add in more features to the winter sports forecasts before the start of the new season. Very Happy Let me know if you've got any questions or requests.

Thanks

Brian
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bwg, Looks great - easy to understand for GFS phobes like myself.
is there an altitude option to see the precipitation snowline on the way?
Ta
Martin
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Then you can post your own questions or snow reports...
"Looks great - easy to understand for GFS phobes like myself.
is there an altitude option to see the precipitation snowline on the way?"

There isn't at the moment. There are a number of different ways of calculating the snowline, but I'm not convinced any of them are entirely reliable. Does anyone here have nay thoughts on the best way to approach it? Data such as freezing level, 850hpa, thickness and lapse rates are availableto be used in the calculation. Rain turns to sleet and then to snow, and at first will be slushy and not accumulate etc. Is the snowline at the point where the transition begins or where the snow starts to accumulate?
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 After all it is free Go on u know u want to!
After all it is free Go on u know u want to!
This isn't nearly as detailed as some of the stuff you guys have been posting, but this ( http://www.worldreviewer.com/ski-conditions-map/?region=#50.2408:-48.7084:3 ) has some good, basic info (like snow depth) for a lot of different areas in one place. Pretty idiot-proof, I should think.
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If you want to find the GFS graph near your destination ski resort I have tried to capture them here:

http://www.ski-finder.co.uk/mapgfs.html

Note: This does not display all ski resorts in Europe but should help you find the nearest GFS graph - comments/suggestions appreciated
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As a webby geek rather than a weather geek I thought this might be useful:

GFS graph grabber

How does it work?

1) Select the co-ordinates for the GFS graph you want (e.g. 45,7)
2) Click "Get GFS graph button"
3) A copy of that graph, for that moment in time is then stored on my server
4) You then just need to cut and paste the code from the box beneath the graph image

Any suggestions or comments as always appreciated.

e.g.



Note: To save space it will only allow one run per set of co-ordinates per hour (sorry!)


Last edited by Ski the Net with snowHeads on Mon 13-12-10 20:39; edited 1 time in total
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ski-finder, excellent! snowHead
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 And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
Not sure if this belongs here, but sounds interesting:

http://wattsupwiththat.com/2009/12/28/the-arctic-oscillation-index-goes-strongly-negative/
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 So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
Hello, to help me find the weather wiggles more easily I set up this map on Google over the weekend - just click on the snowflakes to see the plot for that latitute / longitude - initial version is small but click on it and the full version will appear in a new window.

Over the next few days I'll add a few points further east as well as more names of nearby resorts

Happy skiing!
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 You know it makes sense.
You know it makes sense.
Nice work thebongolian!
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 Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
Just seen this thebongolian, what a great map - well done! snowHead snowHead All my wiggly needs in one place Toofy Grin
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 Poster: A snowHead
Poster: A snowHead
thebongolian, did you not see mine 3 posts up? Puzzled
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 Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
ski-finder, thanks for the link, the graphs are very interesting, but it is a mystery (to me at least) why even 24 hours away the green GFS Hauptlauf can be so different (relatively anyway) to the apparent convergence of all the other so called "wiggles". The GFS graph for St Anton, etc (47/10) shows it now (03FEB 12Z) even better than the graph above. Anyone know what accounts for the difference and what we should have the greater confidence in? Puzzled
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 Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
what about it? snow from gfs!!!

http://theweatherland.com/


Last edited by Well, the person's real but it's just a made up name, see? on Thu 10-06-10 21:26; edited 1 time in total
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Next is looking very snowy and cold for the west - should be a great week for anyone heading out....
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Anyway, snowHeads is much more fun if you do.
Hi, does anyone know where i can find a GFS chart for Chamonix?
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Find the lat & long of the location your after (Cham), then type in the (nearest whole number) values into an existing "wigglies" link - may not be the exact location, but near enough.
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Then you can post your own questions or snow reports...
This link is great to find lat-long
http://www.whatsmygps.com/
So with chamonix at 45.9, 6.87 then reverse to get 07 and 46, nearest whole numbers
http://www.wzkarten.de/pics/MS_746_ens.png
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CAVEAT EMPTOR
NWP charts are based on rather coarse datasets. A 1 degree model only has datapoints every degree on the surface. About 60 nautical miles apart in latitude and a bit less on longitude depending on how near the equator you are. 60 degrees North = 1/2 mile. THe terrain is modelled at the same scale so mountains are severely flattened. Really accurate depiction in the mountains requires a totally different forecasting technique. A lot of this is based on local knowledge of empirical rules built up over many years. For example most of the Tarrentaise resorts would fall within one or two grid squares. And we all know how different the weather is from one part of the same mountain to another far less from one resort to another.

However NWP is a great way of getting a qick and dirty view of the general trend in temperature and precipitation.

I am an WMO accredited forecaster so I do have a little bit of knowledge here.

for anyone who is serious about learning this is great resource which I have used in the past.[url] http://www.meted.ucar.edu/topics_mountain.php[/url]

Its free to register and offers a variety of Meteorological Training Courses. It does assume some level of basic knowledge for most of the elements. You are never too old to learn. I should know. I'm 85 rolling eyes


edited to add after contemplation.
Hmm? I've just reread the topic title. Beginners guide.....
When I say basic knowledge. I say that as post graduate qualified Meteorologist.
I read the course descripition for mountain weather and might reappraise 'basic' as at least a gcse in met preferably an A Level. Embarassed

Bit like on day three at ski school after mastering standing up on the flat. "...and now for steeps and deeps children."

But seriously, GCSE MET courses are all over 'interweb. Maybe even at your local schools in evening classes.

There is a whole new world out there. The snow pack assessment module at MetEd is 'easy' to approach and is worth its weight in gold. Its a BIG picture module and goes far beyond off piste and back country but tune in and enjoy. Cool

listen to the back country skier on page 1.2.

The modules are american so prepare for inches and fahrenheit although cm are included. Also Sleet in US does not mean the same as UK. I think they mean Hail Stones, as in Gobstoppers of hard ice (uncommon in blighty). Decipher this if you will? http://wapedia.mobi/en/Talk:Sleet

Graupels are like soft hail, the sort you sqeeze and it squidges.

Bet you all wished you had never asked. Toofy Grin
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Thanks for the information all Smile Was looking for it Smile Laughing
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I am trying to find the GFS Charts for Nendaz, Switzerland and Les Gets, France without any luck (the old links I have saved have stopped working Confused ) - can someone assist?

Many thanks. snowHead
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