Resource Weather Links / Maps / Terms Thread

Claude Cat

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Great idea.

Things I look for on weather charts

Images may update.

Thickness
Mean Sea Level Pressure, Thickness, Precipitation

As a generalisation, if the blue line marked 5400 rises above the latitude of the Alpine region and there is precipitation following - shown as blue, green, yellow, etc - (i.e. behind or below the 5400 line) then that precipitation will most likely fall as snow. Otherwise precipitation will fall as rain.
"Thickness" is simply a measure of the thickness of the air.
What does "Thickness" mean?


imageserver.jsp




850hPa Temp
This is the temprature of the air where at a pressure level = 850hPa
A rough figure of merit is that 850hPa = 1600m, but note pressures do change with weather, so when we have a strong low, then that altitude will be less than 1600m.
Ideally, 0deg C temp for snow
smile.gif




Freeze level
Similar to 850hPa, it shows the altitude where the temp is 0C. For obvious reasons.



Precipitation accumuation
How much is going to fall.

GFS will show you 3 hour totals as per
Or go to WeatherOnline for 3, 6 or 12 hour durations
Or here for whatever period you like/
Dial in the dates you you're looking at there it is.
http://forecasts.bsch.com.au/raincast.html


500 hPa Tempratures and Thicknesses
The so called temprature of "uppers".
The colder it is in the upper atmosphere the better.
 
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Donza

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I also look for something such as this.
The dotted line following the front is an "embedded trough" or area of unstable air.
Typically after a cold south west change the air will lose its moisture and therefore capability of producing snow. Ie it will dry out.
Embedded troughs will increase the amount of moisture. When embedded in cold SW stream they are epic.

IDX0102.201008251800.gif
 
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Donza

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Also re precipitation amounts that CC listed above.
They shouldn't be treated as gospel in relation to the amount of snow that will fall.
The the amount of snow that falls is also relative to temperature.
Ie 10mm of precipitation forecast at -2 at 1700 will probably produce 10cm of snow
Ie 10mm of precipitation forecast at -8 at 1700 will produce usually 2 to three times that amount.
I use the freeze level charts vs the precip charts to determine snowfall.

Its also prudent to take into account the duration a storm will be over the alps.
A prolonged storm will always produce more snow than anticipated.
 

Claude Cat

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Also in terms of precipitation, consider the effects of orographic lift. Models can be not that good at allowing for this, so you may well get more over the mountains than is shown on the model.
 

Donza

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Claude Cat said:
Also in terms of precipitation, consider the effects of orographic lift. Models can be not that good at allowing for this, so you may well get more over the mountains than is shown on the model.
You might need to explain the concept of orographic lift vs topography.
 
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Claude Cat

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Wiki can do it a lot better than I.

Orographic lift occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain. As the air mass gains altitude it quickly cools down adiabatically, which can raise the relative humidity to 100% and create clouds and, under the right conditions, precipitation.

http://en.wikipedia.org/wiki/Orographic_lift

135451-004-A6B6636B.jpg
 
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mick chopps

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I can decipher the info (or at least recognize what looks good and what doesn't) displayed on most of the charts you guys use and reference and I've managed to find some of them online for myself. My issue is understanding their progression and why you guys might or might not find the model charts to be somewhat fanciful. Accepting that certain models aren't all that reliable the further out they are, are there any indicators in particular that you guys look for to judge whether they're "on crack" as is sometimes suggested? Or is it just experience in watching the sort of weather we actually receive?
 
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Claude Cat

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That's probably something that can only be gained by experience I think.
Essentially, based on past experience you can usually know what a weather system is going to do.
If the model starts showing something unexpected, that's when you might consider you've got an outlier (perhaps due to a specific set of inputs the model has been provided).
 
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Donza

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Its also personifying models Mick. They get traits...personalities.
I know PG will disagree .
Yet you spot trends and behavioral aspects.
I mentally lay every model over each other, then expand them by each timestamp. Look at the progression and see if it looks logical. Using experience I guess of past outcomes.
Its good to compare history.
 
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Donza

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Claude Cat said:
Wiki can do it a lot better than I.

Orographic lift occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain. As the air mass gains altitude it quickly cools down adiabatically, which can raise the relative humidity to 100% and create clouds and, under the right conditions, precipitation.

http://en.wikipedia.org/wiki/Orographic_lift

135451-004-A6B6636B.jpg
Yeah you have to consider also the rise in altitude offset by the distance the air travels .
If the rise is gradual the lifting is slow and ineffective.
 
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azzski

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I realise I'm just dumping a heap of topics of varying lengths together here, but this is some jargon/acronyms from the latest predictions thread that could stand further explanation for the layperson, along with their significance (if any):

The "Spaghetti" model
06Z GFS (00Z GFS) 00Z EC and the +84/96 etc that go along with it
AXS-G/R
ECL
EC
CMC
JMA
UKMET
Access
LWT

Some of these are obvious contractions/model names like BoM for Bureau of Meteorology but that doesn't mean that it necessarily means anything to someone who is trying to follow what is being said
smile.gif
 
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Donza

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azzski said:
I realise I'm just dumping a heap of topics of varying lengths together here, but this is some jargon/acronyms from the latest predictions thread that could stand further explanation for the layperson, along with their significance (if any):

The 'Spaghetti' model
06Z GFS (00Z GFS) 00Z EC and the +84/96 etc that go along with it
AXS-G/R
ECL
EC
CMC
JMA
UKMET
Access
LWT

Some of these are obvious contractions/model names like BoM for Bureau of Meteorology but that doesn't mean that it necessarily means anything to someone who is trying to follow what is being said
smile.gif

The 'Spaghetti' model - it's an ensemble model that graphs the height of the 500hpa (therefore the temp) using a "spaghetti" plot. In other words it creates a graphical "mean" or average of all the model runs. Its a trend model. rather than specific.

06Z GFS (00Z GFS) 00Z EC and the +84/96 etc that go along with it. Thats just the time stamp of the model run on zulu time.

AXS-G/R Australian model...G being a lower resolution (models forecast using grids so to speak, the smaller the grid the more calculations) R is a smaller grid yet shorter forecasts

ECL East coast low..a trough that deepens over the east coast of Australia. usually as a reaction to warm sea surface temps

EC European model..(ie its from)

CMC Canada

JMA Japan

UKMET UK

Access (see AXS)

LWT Long wave trough A measure of the polar vortex.. circles around the poles kinda like a cold lava lamp...spewing forth cold air towards lower latitudes. It has peaks and troughs...much like a swell on a ocean..the peaks are nodes.
The best is a defined 5 node pattern.
 
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Claude Cat

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ok.

EC = European Centre for Medium-Range Weather Forecasts
model runs at 00 UTC and 12 UTC (00Z, 12Z)

GFS = Global Forecast System - the US main model.
model runs 4 times per day 00UTC, 06Z, 12Z, 18Z

CMC = Canadian weather model

UKMet = United Kingdom met-office model

JMA = Japan Meteorological Agency model

Access = Australian BOM's model (various flavours AXS-R (regional) AXS-G (global)

AXS-R has smaller grid size, but is only 3 days ahead. AXS-G has a larger grid size, but is longer term model (10 days IIRC)

OCF = Operational Concensus Forecast. Combines the output from up to 8 computer weather prediction models, gives weighting to those that have recently performed best.
 

azzski

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So that helps with what those acronyms stand for. Of what use are the models from around the world for Australia's weather patterns? Which do the predictors (in their opinion) think most consistently predict the weather patterns?

For my own interest, what's the significance of the Z on the time periods?
smile.gif


This is all good stuff and will be great once we've got it all out and rolled up into a single page/post.
 
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azzski

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Cheers
smile.gif


From the Weather links thread, a Spaghetti plot explanation:

Gerg said:
spagshanim.gif


The NCEP GFS ensemble 500z Spaghetti Plot listed in the OP draws a lot of queries. Here's a layman's attempt at an explanation:
<ol style="list-style-type: decimal"><li>Crudely put, this is a plot of atmospheric thickness. It shows two contours of the thickness of the bottom half of the atmosphere, starting from sea level - that is, contours of the height from sea level to 500mb pressure. (Atmospheric pressure is ~0mb at the edge of space and ~1000mb at sea level; but that varies across the planet, so &quot;thickness&quot; is a bit imprecise here. The so called &quot;thickness charts&quot; implement a more precise definition.)</li><li>The light blue lines are 5820m height contours and the red lines are 5940m height contours.</li><li>There are lots of each because this is a plot of an ensemble of runs. It shows the results from the GFS model run 42 separate times: 21 starting at 00z (midnight universal time) and another 21 starting at 12z (midday). The 21 runs comprise one using a best estimate starting condition (the &quot;control runs&quot;, plotted in brown for 00z and grey for 12z), plus another 20 starting from very slightly differing starting conditions.</li><li>This approach gives an indication of the chaotic nature of weather systems. Strongly divergent behavior over time would suggest highly chaotic conditions and therefore low predictability. It has been shown that appropriate consideration of ensemble behavior increases overall prediction skill.</li><li>Because our atmosphere is a free column of gas bound only by gravity, its thickness is proportional to its average absolute temperature. That is, PV=nRT (approximately, subject to the effects of atmospheric flow dynamics).</li><li>So contours of thickness are also approximate contours of average lower troposphere temperature. That's why the blue ones are mostly closer to the pole than the red - it's colder there, so the half-atmosphere thickness is less.</li><li>It turns out that a red contour extending to well north of our alps means it's usually cold enough to snow; a blue one means it definitely is. Of course, that doesn't mean there's moisture and appropriate instability to make that happen. But if there's a nice shape to the contours, there may well be.</li><li>The green lines are the average positions of the two contours for the time of year.</li></ol>
Feel free to correct...
 
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Claude Cat

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azzski said:
So that helps with what those acronyms stand for. Of what use are the models from around the world for Australia's weather patterns? Which do the predictors (in their opinion) most consistently predict the weather patterns?

IMO, the european model EC, is by far the most consistent medium range forecast model.
GFS (US) is very good, but has idiosyncrasies. The classic &quot;all-in&quot; at 144 hours where the model predicts deluges before rapidly backing away &quot;downgrading&quot;.
AXS-R tends to be very good within 3 days.

It's also worth noting that models behave differently in Summer and Winter. Eg GFS tends to predict thunderstorm activity and precipitation from very well in summer.
UKmet is very similar to EC - use as a cross-check
CMC is very similar to GFS - use as a cross-check
 
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7wombathead

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The Orographic lift effect is a little bit over simplified with respect to a prediction with respect to the main range.

In a windy storm the snow is dumped then blown off the western side and the peaks (2200m) back to eastern side. Perisher, Thredbo, and Charlotte Pass.

Often on these types of events the whole main range is stripped of any snow and the resorts are replenished each day with windblown snow.
 

nfip

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Thanks all this is excellent. Have been flicking around trying to put a lot of this together and a few times decided the good old BOM 4 day synoptic (Alan Wilke used to point at) is for me. But maybe there's now hope yet.
Appreciated your time for this. Cheers.
 

Tanuki

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7wombatheadhe Orographic lift effect is a little bit over simplified with respect to a prediction with respect to the main range. In a windy storm the snow is dumped then blown off the western side and the peaks (2200m) back to eastern side. Perisher said:
IMO what you have descried has nothing to do with O-lift,rather spatial distribution of frozen water following precipitation
 
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7wombathead

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Yep these days this is the best chart and AXS R.

That's because the regional synoptic forecast model that BOM has developed is pretty good compared to say 5 years ago, its just a bit short sighted thats all.

The GFS is the best to keep you thinking about the future ( two weeks) IMO.
 

7wombathead

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Well its just what happens based on observation of localized conditions.

Try going up to the main range sometime after a windy blizzard.

The diagram listed by wiki indicates that no moisture reaches the eastern side of the ranges

But the topography of the Main range is pretty flat and wider than high on the top.

So you have to imagine that Orographic lift does not limit snow falls to Perisher or Thredbo too much. Rather it limits precipitation to the Monaro Plains and coast down here in Merimbula.

That is the correct way to visualize the Orographic lift effect in the Snowy Mountains.

Thats why we are fortunate here in OZ.

Bom could and should update AXS R to include the topography better though.
woohoo.gif
 
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Rush

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7wombathead said:
Bom could and should update AXS R to include the topography better though.
woohoo.gif
Actually what is most likely to happen in the future is that Access G will be further refined (down to 20 km or so) and Access R will be ditched all together. Instead you'll have high resolution models in in the majors urban areas (resolution of &lt; 10 km).
 
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Rush

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Its also personifying models Mick. They get traits...personalities.
I know PG will disagree .
No I don't. Each model will tend to have its own biases due to parameterisations that work better/worse under certain initial condition. The range of data assimilated will also affect forecast performance. The EC assimilate the most which is arguably the main reason why the are the best.

This is different to what you said a few weeks ago, implying that models need time to 'bed in' during the early winter. This isn't true, the models have no automatic adaptive tuning or bias corrections over time. They aren't neural networks.

Of course, the development team may identify biases in the model and alter various settings to give better forecasts but this happens manually, not automatically.
 
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Rush

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In any case if you want to understand how the ECMWF forecast systems works, they have lots of documentation available here
 
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This certainly a very informative thread about what actually goes on in predicting the weather. Meteorologists have to look at so many different pieces of information and possible scenarios before they actually tell you whether or not it's going to rain or snow or whatever tomorrow. Fortunately for you guys down south the weather is fairly predictable with cold fronts coming through all the time. Northern Australia is pretty different though even in the wet season. The monsoon trough can be clearly drawn on the synoptic chart and not have drop of rain in it. A common weather forecast heard on local radio here over summer can read "mainly fine with the chance of an afternoon shower of thunderstorm". Wouldn't have a clue? You're dead right, called covering your arse. @Claude Cat I notice that you also run a thread for the cyclone season each year. Something useful to throw in there would be a video update done by a bunch of guys in Townsville called Oz Cyclone Chasers. I've been following their updates for the last 2 years and everything they've said that could possibly happen with a current cyclone event has been spot on using all the information mentioned above along with a couple of others like predicted humidity levels.
 

Jellybeans

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Time to start a updated Weather Links Thread!
Please post any weather links you may have (snow related)

I will get the ball rolling
@Gerg
http://gergs.net/
Snow depth predictions and general weather (human written blog)
@janesweather
http://www.janebunn.net/
Snow predictions and general (Melbourne) weather (human written blog)
More @janesweather
https://www.ruralbank.com.au/for-farmers/weather
General climate info with a rural focus

Other sites I use:
http://www.weatheronline.co.uk/cgi-...&MODELLTYP=1&VAR=prec&HH=3&BASE=-&WMO=&ZOOM=0
Extreme long range (up to 2040 hours) CFS + JMA, GEM, GFS, EC.

http://www.bom.gov.au/climate/model-summary/
BOM POAMA Climate Models (IOD and ENSO)

http://www.weatherzone.com.au/models
Weatherzone models EC GEM GFS

http://www.weatherzone.com.au/climate/indicator_sst.jsp?c=ssta
Weatherzone SST anomaly (Climate)

@nfip please post that links summary again and @jeffx hoping for more links from you please :D
Anyone else feel welcome to post any of your favourite weather sites. Cheers
 

nfip

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Here's a bunch of the relevant links I've bookmarked from these pages over the years.

Of course you'll need to customise them to suit your specific purpose.

This is Yr.No , a Norwegian forecast based on the ECMWF modelling .
It is a simple go-to and pretty accurate if you're after a quick click.

http://www.yr.no/place/Australia/New_South_Wales/Perisher_Village/

Here another easy read from BOM . AXS-R & AXS-G models .
User friendly , just hit play and you get a fair idea of what is likely.
http://www.bom.gov.au/australia/cha...EDT&area=Au&model=CG&chartSubmit=Refresh+View

@Claude Cat fave go to here.
I has GFS , CMA , ECMWF, Gem and JMA so all the best of in one. (Pick and choose to compare).
http://www.tropicaltidbits.com/anal..._frzn&runtime=2015042118&fh=6&xpos=0&ypos=581

Similiar one from the UK.
http://www.weatheronline.co.uk/cgi-...&VAR=t85p&HH=168&ARCHIV=0&ZOOM=0&PERIOD=&WMO=

Again another from the US
http://www.pivotalweather.com/model.php?m=gfs&p=sfcwind_mslp&rh=2016091400&fh=0&r=au&dpdt=

Stormcast is really handy as it has few other features , for you guessed it ...., which are easier to access than may be on the other models above.
http://forecasts.bsch.com.au/stormcast.html

The "famous Spaghetti plot".
An animated prediction of the state of the Southern Polar circulation

http://www.esrl.noaa.gov/psd/map/images/ens/spag_f000_sh.html

A great explantion from @Gerg of the Spag plot.
http://gergs.net/2014/06/reading-spaghetti-plot/

This one is part of @Vermillion quiver he shared a while back , a good companion to Spag.
Bit easier to read at times.
http://www.atmos.washington.edu/~hakim/tropo_sh/trop_theta_sh.html

Here's the latest good thing that @jeffx shared last week.
A really great user friendly one stop shop for myself and I'm sure a few of us here.
Plenty of bells and whistles when you spend some time to play.
https://www.ventusky.com/?p=-30.2;127.7;3&l=gust&t=20161011/18&w=0QEQYp_5B

This another of mine fave quick go-to for , arguably , accurate live info from the hill.
Add this and Thredbo together , divide by 2 and you'll be a bit closer onto it than the daily reports from the Resorts.IMO.
http://www.bom.gov.au/products/IDN60903/IDN60903.94915.shtml

I have a bunch of others that I look up at times to learn what is being talked about here.
Bom Glossary is a starting point.
http://www.bom.gov.au/lam/glossary/?ref=ftr
or the US National Weather Service
http://w1.weather.gov/glossary/

If you really want to confuse your-self this will get you scratching your head but has a lot of actual / "live " - ish info.
Aerological diagrams
http://www.bom.gov.au/aviation/observations/aerological-diagrams/

I've tried quote those that have shown me / us the links they have shared over the last 10 years or so.
Many thanks to all who contribute here.
Hope this helps others as it has helped me.
 
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nfip

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Couple more I look at every day , not just for snow but general weather watching.

Based upon the UK Met Office Unified Model system.

Has been pretty reliable this year Access-R , as it is only 3-days out.
http://www.weatherzone.com.au/models/?mt=accessr&mc=mslp&mh=36&mso=0&lt=wzcountry&lc=aus

Longer term / less reliable Access-G models to 240hrs
http://www.weatherzone.com.au/models/?lt=wzcountry&lc=aus&mt=accessg.

Look up wind , precip 850 , 500 levels in drop down box.
Same for time.
Can also zoom in on State view.
 
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POW Hungry

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Observational
NASA Worldwide HD Satellite Swath:
https://worldview.earthdata.nasa.gov/

Determininstic
German Model Runs (With ICON Model & Regional Europe)
http://www.wetterzentrale.de/de/default.aspx

Climate
BOM ENSO Wrap-Up
http://www.bom.gov.au/climate/enso/

Elders SOI
http://www.eldersweather.com.au/climimage.jsp?i=soi

NOAA SST Anomaly Charts ('96-current)
http://www.ospo.noaa.gov/Products/ocean/sst/anomaly/

Aus Specific Elder's SST Anomaly
http://www.eldersweather.com.au/climimage.jsp?i=sstaa
 

Jellybeans

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These are for North America, but they are Weather Links!
I guess most people know and often use the big global models GFS, EC, GEM, UKMO, etc for predicting snow for North America. But lots of people don't use mesoscale models. IMHO within a 5 day range, these are the charts to check. Mesoscale charts are charts that use a higher resolution than the big global models. This allows a chance to see more localised falls and smaller systems, where global models are good at looking at the bigger picture. Here's my guide to make sure you don't use the wrong one.


US Models
http://www.pivotalweather.com/model.php?m=nam&p=sfcwind_mslp&rh=2016120100&fh=0&r=conus&dpdt=
NAM North American Mesoscale Model
This is the standard mesoscale chart used by many news weather meterologists and parts of the General public. It is good within 3 days, terrible beyond that. Some meterologists say this chart has poor accuracy, despite its higher resolution. Use caution with this one!

http://graphical.weather.gov/
NDFD National Digital Forecast Database
This has got heaps of graphical forecasts and is used for NWS forecasts. The benefit of this is it uses internal NOAA data and data from the big global models. So this is the model using the data from all the other models.

http://www.spc.noaa.gov/
SPC Storm Prediction Center
This model uses NOAA data to predict severe weather. Good if you want to know when a blizzard is due.

http://wrf.nssl.noaa.gov/
WRF Weather Research Forecast Model
This is another general mesoscale model using a variety of NOAA data. This is often considered to be better than NAM and is my personal choice for forecasting snow.

https://rapidrefresh.noaa.gov/
RAP Rapid Refresh
This is a very short scale model, only going back 6 hours. It predicts the rain radar and is good for knowing when it is going to snow during that day.

http://rapidrefresh.noaa.gov/HRRR/
HRRR High Resolution Rapid Refresh
A Higher Resolution version of RAP

http://www.spc.noaa.gov/exper/sref/
SREF Short Range Forecast Ensemble
Says it in the name, it's an ensemble of forecasts similar to both SPC and NAM forecasts.

http://meteocentre.com/models/model...n&mode=latest&yyyy=latest&mm=latest&dd=latest
HIRESW (also known as HRW-ARW) High Resolution Window Forecast System
This is the mesoscale model from the NCEP using NOAA data and the WRF Model.

Canadian Models (I know less about these)
http://meteocentre.com/models/models.php?lang=en&mod=gemreg
RDPS Regional Deterministic Prediction System
This is the main mesoscale model from the CMC.
http://meteocentre.com/models/models.php?lang=en&mod=cmc_hrdps
HRDPS High Resolution Deterministic Prediction System
This is a higher resolution version of the RDPS.

All these have maximum ranges of 6 hours to 7 days. They are best considered within 5 days of the event, and are most accurate within 3 days of the event. These are great tools if used with global models. As I said at the start, things like the polar vortex, massive cold fronts, arctic nodes, etc should be observed from a global model, but mesoscale models are great for looking at smaller sections of land, smaller storms, localised falls of snow, etc. Some of you might use these tools, but this is just a handy list of most of the NA mesoscale models.

Correct me if I am wrong. Spelling mistake or fact error guaranteed somewhere ;)
 

Jellybeans

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Explanation and links to Verifcation of NWP models...

Here is a verification of all the models. 1 is the best and 0.3 is the worst for the top chart. Bottom chart is differences with GFS which just makes things more confusing. Should Update...
acz_wave120_NH500mb_day5.png

GFS is black, US model up to 16 days
ECMWF is Red, European model up to 10 days
UKMO is Green, UK model (also ACCESS) up to 6 days I think
GEM is Blue, Canadian model up to 10 days
NAVGEM is Yellow, US Navy model up to 10 days

CDAS is essentially a model from the US that uses tech and knowledge from pre1996, often called Legacy GFS.

To group them
EC and UKMO are probably the best
GEM and GFS are in the second accuracy bracket
JMA and NAVGEM are the worst of the models

Simples.

Source: http://www.emc.ncep.noaa.gov/gmb/STATS/html/new_aczhist.html
Add in this for 31 day verifications.
http://www.emc.ncep.noaa.gov/gmb/STATS/html/acz6.html
And this for acronyms
http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/www/main_body0.html
 
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