Model Output Discussion - 16th Jan 12z onwards - Smile While You Post!

[Paul]

A fresh new model discussion thread - it's really busy at the moment so please do keep the discussion to the model output and head over to the banter thread for moans, ramps and loosely model related bits and pieces:

https://forum.netweather.tv/topic/81281-model-banter-moans-and-ramps-autumnwinter-2014/

 

With a cold spell upon us, the regional threads are great places to drop into for local weather chat:

https://forum.netweather.tv/forum/142-regional-discussions/

 

And, we also have a general cold spell thread open too:

https://forum.netweather.tv/topic/82292-upcoming-cold-spell-discussion/
 
For those who maybe don't know where to find the various model outputs, many of them are available right here on Netweather:
 
NetWx-SR
http://www.netweather.tv/index.cgi?action=netwx-sr;sess=
 
NetWx-MR
http://www.netweather.tv/index.cgi?action=netwx-mr;sess=
 
GFS
http://www.netweather.tv/index.cgi?action=nwdc;sess=
 
Ensembles
http://www.netweather.tv/index.cgi?action=ensviewer;sess=
 
ECMWF
http://www.netweather.tv/index.cgi?action=ecm;sess=
 
ECMWF EPS
http://www.netweather.tv/index.cgi?action=ecmens;sess=
 
Met Office Global
http://www.netweather.tv/index.cgi?action=meto;sess=
 
Met Office Fax
http://www.netweather.tv/index.cgi?action=charts;type=fax;sess=
 
GEM
http://www.netweather.tv/index.cgi?action=gem;sess=
 
Model Comparison
http://www.netweather.tv/index.cgi?action=modelcomp;sess=

[Paul]

Update re snow prospects in south/Midlands next 24-48 hrs...

Firstly, the situation tonight-tomorrow AM sees WBFL approx 400m with the showery occlusion moving in from the SW. Radiative cooling will enable snow to penetrate to fairly low levels by Sat AM, albeit patchy 2-4cm accumulations generally above 200m across W Country uplands/moors, probably then extending eastward to give light settling in other areas across to E Anglia.

The developments for Sunday are tricky re the SE. As it stands, threat of disruptive snow here is only 25%. This is because 00z EC, plus 06z UKMO-GM & E4 all backed-off on potency of cold undercut; moreover they allow most PPN to clear south before sufficient evaporative cooling could also happen... about 30% MOGREPS support a disruptive snow potential, thus current SE warning is predominantly for rain BUT with caveat of ongoing uncertainty re scope of snow potential.

Finally, I subscribe to Tamara's earlier post. With all forecast emphasis now switching towards colder weather and wintry hazards for at least a few days, it was bemusing to witness such a degree of online wrist-slashing. Equally, I echo her remarks re risk of over-analysing output into medium range in current situation. We have enough issues and operational forecast headaches at T+12 to scope-out, let alone T+120.

 

As requested - copying this over..

[warrenb]

Out to 6h and no change

[southbank]

IF post in the previous thread shows just how difficult it is to make a forecast specially in marginal situations using NWP.The SE rain forecast for Sunday can potentially be a disruptive snow event ,we are relying on computer model to factor in different scenarios that can flip very quickly. We've already seen them back off a bit on colder temps who's to say these don't flip back.You can only have admiration for the meto in these type of events . The SE being s highly populated area . From imby the fact that MOGEPS was higher prob at 30% against the rest of today morning suites gives us hope yet.

[Snowy L]

Another run, another shift to the east as early as 24 hours out.

 

Edit: Though hopefully we're seeing a split in the Greenland and Atlantic high, which may give a route for the Atlantic low to slde down rather than just push the high pressure East.

 

http://www.wetterzentrale.de/pics/Rtavn421.gif

Edited January 16, 2015 by Snowy L

[bluearmy]

Another run, another shift to the east as early as 24 hours out.[/quote

NURSE !

On topic and the gme reminds me of the failed easterly from a few years back which went at day 4.

Fortunately, it's the GME

Edited January 16, 2015 by bluearmy

[shaky]

Yup eastward shift already but that could just be the 12z bias!!! Lets see how the rest of the run goes!!

[CreweCold]

GME has us in a westerly flow now by 132. Not a particularly auspicious start to the 12z output.

[MR EXTREMES]

Out to 6h and no change

I don't expect there is any change in 6hrs but there most certainly will be changes to come.

From how quickly this cold spell has taken hold to how quickly it's going to disappear just don't seem right that's because there is so much to take into account that the models are most like struggling with short term effects !

so then how can mid and long term be counted as correct.....

By all means speculate about what where and when but winter spring and autumn do tend to show more model headaches than summer.

And at 6hrs I didn't really expect massive changes but tomorrow at 6hrs things could be very different especially when there's troughs and occluded fronts floating around.

[Met4Cast]

GME says a complete no to prolonged cold and has us back in a mild Westerly flow very quickly.

 

12z GFS already further East too, though not by a whole lot. Could still end up being okay but the entire thing does seem to be going wrong as the clock strikes 12. (as far as prolonged cold, goes)

Edited January 16, 2015 by Daniel Smith

[Eskimo]

An eastward shift of the northerly, but that should allow the low to undercut better. We'll see. 

[Barry12]

Lets wait until the models get to at least day 4, before saying it's a bad run !

 

And at 6hrs I didn't really expect massive changes but tomorrow at 6hrs things could be very different especially when there's troughs and occluded fronts floating around.

 

I'm pretty sure it was a joke, there is never ever going to massive changes at 6 hours...

 

Edited January 16, 2015 by Barry95

[Snowy L]

Another run, another shift to the east as early as 24 hours out.[/quote

NURSE !

On topic and the gme reminds me of the failed easterly from a few years back which went at day 4.

Fortunately, it's the GME

 

Reminds me of the begining of the January 2013 cold spell, we got the slider that time

 

http://www.wetterzentrale.de/pics/archive/2013/avn/Rtavn00120130114.png

 

I remember GFS was having none of it until the last 2 days too...

[mulzy]

GME has us in a westerly flow now by 132. Not a particularly auspicious start to the 12z output.

 

Yesterday it was showing a lovely easterly.

 

Cannon fodder model...

Edited January 16, 2015 by mulzy

[Polar Maritime]

The Low over Iceland looks a little stronger on this evenings run, -10 850's covering most of Scotland with a slack Northerly by Monday.

 

Edited January 16, 2015 by Polar Maritime

[swfc]

Very strong atlantic ridge on the 12z.not sure where this low is going tho!!!know where app??

Edited January 16, 2015 by swfc

[Met4Cast]

No idea what the GFS is doing now

 

Stronger ridging in the Atlantic but a deeper low staying North around Iceland rather than sliding Southwards.

[TSNWK]

No idea what the GFS is doing now

 

Stronger ridging in the Atlantic but a deeper low staying North around Iceland rather than sliding Southwards.

My first stab at a guess would be.. The low would pump up the high a little and then it will topple over the uk as the jet rides over the top..

[pdiddy]

Completely different profile NE USA this run shows that it's all still up for grabs at t96.

[Barry12]

12z looks better to me in prolonging the cold spell

 

[Eskimo]

Knew that easterly bias would prevail. Hopefully GFS sticks with this sort of pattern...or better! 


 

[mulzy]

Am I the only one who thinks the GFS 12z is actually better in the medium term (days 4,5,6)?

 

Scandi high holding firm and toughing through the UK is keeping the AZH at bay.

Edited January 16, 2015 by mulzy

[shaky]

12z reverts back to what it was showing 24 hours ago!! Upgrades again!!

[MR EXTREMES]

GME says a complete no to prolonged cold and has us back in a mild Westerly flow very quickly.

 

12z GFS already further East too, though not by a whole lot. Could still end up being okay but the entire thing does seem to be going wrong as the clock strikes 12. (as far as prolonged cold, goes)

Yeah and it's also not a model to be trusted but the overall pattern may well be a return to the recent pattern which I might add is by no means winter over!.

Why you might ask well we had polar air with snowfall across the country now if you look at the upper air temps and polar profile it's dam cold in fact the air to our direct North and North west is as cold if not colder than anything to our East and northeast so any air from the north west although modified by the sea temps it's still proof as we seen this week that snowfall is a cert for the north northwest even the western side of the uk !.

Ok us in the south would need something exceptional but hey in the world of weather never say never.

Expecting massive swings in model outputs from now until there's a model that's 100% accurate and this is unlikely for sometime lol

But jokes aside upgrades down grades snow ice fog cold rain frost all feature but nothing remotely above average temp wise unless u live on lands end.

[Met4Cast]

Potential at 132..

 

 

But given how different the 12z is to the 06z by just 92hrs on a hemispherical level, you may as well be hanging teabags outside to predict the weather. Never known a year for the models to be such utter tripe at any type of predicting.

 

GFS Upgrade can go in the bin as far as I'm concerned, models are useless.