Model Output Discussion 17th Dec.2013-12z onwards.

[gottolovethisweather]

Not a lot to say about the current state of affairs other than its projected to be a quite a stormy period within the reliable and then some hope of respite from a relaxation of the Jet as we head deeper into the end of the first week of January and beyond.

 

The shocked expression on this particular GFS 12z says it all for the UK, really.

 

 

 

A definite WTF moment right there.

 

I sincerely hope those effected by the endless onslaught of wind and rain finally get to see some light at the end of the tunnel into the New Year. The signs short-term are for the South of the UK to get their share of wind and rain once again over the coming days, so stay safe folk.

 

 

 

 

[Gibby]

Good evening folks. Here's my evening attempt to disect the 12 noon outputs from the NWP for today Friday December 27th 2013.

 

All models shape a broadly similar pattern between now and New Year with the deep depression close to Northern Scotland filling and moving away slowly North tonight and tomorrow. In it's wake lies a showery WSW flow with the most showers in the West and near the coasts with some lengthy dry spells in the East. Later on Sunday a new trough moves in from the West with another band of wind and outbreaks of rain for all areas over Sunday night returning to sunshine and showers on Monday. On Tuesday Low pressure close to the West sends a new spell of rain and strong winds NE across all areas with New Years Day seeing much more of the same mix of outbreaks of rain and showers in brisk SW winds and temperatures close to average.

 

GFS then shows the post New Year period with a sustained windy and unsettled picture as Low pressure continues to be shown crossing the UK or within the proximity with unrelenting spells of rain and showers in average temperatures. Late in the run pressure is shown to build down from the North or NE and allow troughs from the West to come up against a tongue of colder air over and to the NE of Britain meaning a much increased chance of a break in the Atlantic train to something which could see some places receiving some snow at times in much colder air as mild Atlantic troughs come up against this colder air.

 

UKMO tonight closes it's run next Thursday with Low pressure out to the NW with a cyclonic SW flow over Britain carrying troughs NE overall areas with rain, heavy at times in brisk SW winds.

 

GEM shows a trend towards something colder too later as pressure builds over the Arctic and forces Low pressure areas further South and sends them SE over Europe. On this run the UK is in the battleground area with rain coming up against cold air over North and East Britain and potentially giving rise to some snow for some.

 

NAVGEM unavailable tonight

 

ECM shows a mobile Atlantic flow as Low pressure continues to pass Eastwards over or to the North of he UK with rain and showers for all in sometimes very windy conditions and temperatures close to average.

 

The GFS Ensembles remain uninspiring for cold fans as the vast majority of members still maintain a very active Atlantic sending frequent bands of rain across Britain in average temperatures. The colder outcome of the operational member was not supported by hardly any of it's colleagues but shouldn't be discounted as it has some support from GEM later.

 

The Jet Stream shows a much more mobile pattern as it continues it's unrelenting path across the Atlantic towards Southern Britain and on to Europe. It does show strong signals of sinking further South over Europe through Week 2 and this may involve sinking the flow a little way South of the UK too.

 

In Summary there is still a lot of support for the mobile Atlantic and sometimes stormy weather type to continue with spells of rain and showers along with temperatures close to average. However, there are a few grains of comfort for cold fans as the GFS operational and GEM shows some build of pressure to the North and NE late in their runs but they look very much in isolation at this stage. Having said that from small acorns big oak trees grow so if these rogue signals increase in frequency between the output in the days to come and gain more cross model support then they might be taken more seriously.

[ANYWEATHER]

There is something astir in the Artic regions with the polar low disrupted and increased high pressure , but with this projected output at T+240 its of course taken with the big load of salt.. The last few days have given us some building pressure to the north of the Uk, Tentative signs yes ,but still a way to go and yes more stormy weather to enjoy/ endure in the near future but increasing optimisim  that January will hold the key for the coldies  to enjoy .......

[Grimsby Snow Lover]

Its a long time since I've seen the AO forecast to go this negative in a long time, we just need this to materialise and help weaken the PV significantly enough to allow blocking to develop to the north of us (I know this is no guarantee for cold snow for us though).

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.sprd2.gif

The NAO looks like staying neutral to slightly positive for a while longer, in which case we will struggle to get the Atlantic blocked.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.sprd2.gif

[Gaz1985]

To be fair as long as the Met Office say no to any deep cold then it probably won't happen somethings got to give with the models, also they have more models to view and other data not available to the general public - having said that the Met Office have been wrong in the past and suddenly changed their medium term outlook. They are not infallible.

[swfc]

To be fair as long as the Met Office say no to any deep cold then it probably won't happen somethings got to give with the models, also they have more models to view and other data not available to the general public - having said that the Met Office have been wrong in the past and suddenly changed their medium term outlook. They are not infallible.

yes they do have more at there disposal this is true.Tbh im not sure where deep cold is or has been forecast?Tentative signs of a change in the nh profile ete but nothing more.

[TSNWK]

Shame about the ECM as there was a definite buzz around the place between 4:30 and 6:00 this evening after the 12z UKMO and GFS runs.

On the down side I was thinking to myself yep they look good, but what about the ecm32 and the updates on the bbc on Boxing Day, and then we had the rather underwelming ECM.. So back to square 1.....

But hey model watchers, in 45 mins we have the 18z to hopefully lighten the mood again.

[Ali1977]

Let's hope the 18z builds on the 12...maybe bringing the cold in earlier.

[Gaz1985]

yes they do have more at there disposal this is true.Tbh im not sure where deep cold is or has been forecast?Tentative signs of a change in the nh profile ete but nothing more.

 

Not been forecast but GFS hints at deep cold -10 uppers at the end of it's 12z run with a Scandi block setting up

 

Edited December 27, 2013 by Gaz1985

[swfc]

Not been forecast but GFS hints at deep cold -10 uppers at the end of it's 12z run with a Scandi block setting up

 

yes but its 14 days away!!granted its worth discussing and possible but certain synoptics and weather types are scupperd at 48 hours as last year showed

[nick sussex]

The Da Vinci Code part 2!

 

It seems that way with the earlier differences between the Euros and the GFS.

 

The ECM control run given the change in wind direction and temps does develop a snow boundary, so initially I think we see some trough disruption through the UK although even the control run brings the Atlantic back before temperatures drop again under a cyclonic set up.

 

So it would be a case of a delay with the same initial result, thereafter and given comments from NOAA re a retrogression of the pattern, high pressure anchored further to the west, high pressure to the ne still in evidence and a lobe of lower heights through the UK.

 

The ECM operational run looks similar to the UKMO although even here there are differences to the ne not like the GFS versus the Euros but in terms of the orientation of  this, indeed the ECM at T120hrs has almost the perfect alignment to help disrupt the troughing near the UK, sadly the PV moves se sends a missile east and puts paid to that, its quite frustrating to see the ECM120hrs chart.

 

Later the ECM goes a bit AWOL, high pressure nosing ne very unlikely so days 8 to 10 look like outlier solutions.

 

In terms of the GFS that eventually gets to some interest in its lower resolution, its a positive that we're talking about differences earlier that still have a chance to lead to cold rather than an Obi One type you're my only hope situation, thankfully Princess Leia has two options!

 

Overall it looks like the first half January at this stage will be more wintry than December, yes I know that wouldn't be difficult! The NH pattern is more favourable for that, perhaps not a smooth ride down the mountain, a few bumps along the way but generally I think more chance of seeing some snow and colder temperatures, as for a deep freeze and ice days which I know coldies would love to see , I think the juries still out there, I think we're moving in the right direction, which is better than marooned as we were for much of December.

Edited December 27, 2013 by nick sussex

[minus 9]

Off to alps on 11th jan. Cold will come 11th 18th of jan. Belive.

[mcweather]

GFS 12Z operational run. Wouldn't be the first time an outlier has proved to be a trendsetter........................................

[Cloud 10]

More sandbags at the ready by the looks of it over the next 10 days at least,with a trough

slap bang over the UK.

 

Longer range ensembles have the trough dropping into Europe,but its a slow old process.

 

   

[bluearmy]

to compare fi ens on gefs and ecm as per yesterday ?

 

ecm T264    today                                                                        gefs T264   today

 

                         

 

 

 

and same timescale with yesterday to see variation in modelling over 24 hours

 

ecm T288 yesterday                                                                  gefs T288 yesterday

 

                       

 

 

assessment:  not much difference between the models over the uk and to our east  (the ecm is more marked with our low anomoly). howevwer, to our west, there are differences, some quite subtle and some more marked. ecm has the canadian vortex further east and the atlantic ridge further west.   it seems pretty certain that we will sit under a trough in 11 days time.

 

regarding the day on day changes - both models have dropped (ie increased) the size of the anomoly over us. gefs has increased the high anomolys over n greenland. both models less keen to drop the trough so far and so strongly to our south. the chances of an easterly around the top of a secondary depression at this timescale reduced from yesterday the further south you head. 

 

heading on even further into the apparent mist:

 

ecm T336 today                                                                          gefs T336 today

 

                     

 

 

and again looking at yesterdays for same timescale

 

ecm T360 yesterday                                                                   gefs T360 yesterday

 

                     

 

given the timescale, there isn't much mist is there !  decent x model agreement. again, ecm is deeper with the low anomoly. infact, ecm has the 528 dam thickness across the centre of the uk from T216 onwards. with average slp around the high 990's, that should tell you where i'm coming from in saying it should be much colder than it is now.

 

compared to yesterday, thats excellent continuity. gefs, as per earlier in the run now showing higher anomolys around greenland than yesterday and clearly less deep than the ecm model in general with the depth of the thickness'.

 

so although there appears to be uncertainty, if we trust the nwp ens modelling, is there really ????

Edited December 27, 2013 by bluearmy

[shaky]

to compare fi ens on gefs and ecm as per yesterday ?

 

ecm T264    today                                                                        gefs T264   today

 

eps_z500a_exatl_45.png                           gefs_z500a_exatl_45.png

 

 

 

and same timescale with yesterday to see variation in modelling over 24 hours

 

ecm T288 yesterday                                                                  gefs T288 yesterday

 

eps_z500a_exatl_49.png                        gefs_z500a_exatl_49.png

 

 

assessment:  not much difference between the models over the uk and to our east  (the ecm is more marked with our low anomoly). howevwer, to our west, there are differences, some quite subtle and some more marked. ecm has the canadian vortex further east and the atlantic ridge further west.   it seems pretty certain that we will sit under a trough in 11 days time.

 

regarding the day on day changes - both models have dropped (ie increased) the size of the anomoly over us. gefs has increased the high anomolys over n greenland. both models less keen to drop the trough so far and so strongly to our south. the chances of an easterly around the top of a secondary depression at this timescale reduced from yesterday the further south you head. 

 

heading on even further into the apparent mist:

 

ecm T336 today                                                                          gefs T336 today

 

eps_z500a_exatl_57.png                       gefs_z500a_exatl_57.png

 

 

and again looking at yesterdays for same timescale

 

ecm T360 yesterday                                                                   gefs T360 yesterday

 

eps_z500a_exatl_61.png                       gefs_z500a_exatl_61.png

 

given the timescale, there isn't much mist is there !  decent x model agreement. again, ecm is deeper with the low anomoly. infact, ecm has the 528 dam thickness across the centre of the uk from T216 onwards. with average slp around the high 990's, that should tell you where i'm coming from in saying it should be much colder than it is now.

 

compared to yesterday, thats excellent continuity. gefs, as per earlier in the run now showing higher anomolys around greenland than yesterday and clearly less deep than the ecm model in general with the depth of the thickness'.

 

so although there appears to be uncertainty, if we trust the nwp ens modelling, is there really ????

hopefully means slow moving bands of snow in a stagnant flow across the UK!!

[Mucka]

GFS so much flatter to the East at the mid term than UKMO, GEM and ECM that if it is proved correct it will be quite a coup. If it is wrong it will look pretty terrible.

Edited December 27, 2013 by Mucka

[nick sussex]

The GFS 18hrs run resolutely sticking to its previous trend shown on the 12hrs, the lobe of deeper low heights which runs west through Svalbard is pretty crucial going forward, the Euros clear this west quickly allowing ridging to build there, here the GFS is much slower and indeed never really removes these.

 

An interesting test here between the models as to which is better at modelling an area notoriously difficult, lack of observational data in that region part of the reason but we often see this with that region.

 

If you just look at the outputs at T120hrs in terms of the pattern near Svalbard its the ECM/UKMO/GEM/JMA against the GFS, if it pulls this one out of the bag it will be a real feather in its cap.

 

You'd have to favour the majority here but we'll see in the morning.

Edited December 27, 2013 by nick sussex

[Ali1977]

Some WAA heading up to the east of Greenland at 168..could be another good FI coming

[Captain Shortwave]

GFS in complete disagreement with the Euros, not just over surface conditions to our north east, but the overall polar profile. GFS not developing the Scandi high at all, at the same time is casually draining near enough all the energy from Canada across the Atlantic, which is also against the Euros which want to keep a strong vortex segment in the region.

[Mucka]

Some WAA heading up to the east of Greenland at 168..could be another good FI coming

 

Or to put it another way;

Looks like another random FI coming up. 

[Ali1977]

String Northerly about to set up at day 9 looking at the GFS. High over Greenland is higher than the 12Z too, not sure where this will go in FI though.....not that that really matters yet!!

[SMU]

I Hate to say it- the GFS is being more consistent than the ECM Op at the moment- however the UKMO is equally consistent!!!

 

 

I must say the AO looks tanked at 180 on the GFS- we are just missing the atlantic heights-

 

More updates soon -

 

S

[IDO]

I am more of the belief that the difference between the models is the phasing of the energy from the Canadian vortex at the crucial time (T120): 

 

GFS:  ECM:   UKMO: 

 

More pressure is being exerted on the Canadian vortex by HP on the GFS and there is a flow of energy feeding the UK daughter vortex. ECM and UKMO have a lull in activity allowing the downstream to become more amplified, whereas the GFS has to send the energy somewhere, and it is currently modelling some of that energy going over the developing ridge to the east.

 

Of course that means the GFS splits the vortex energy earlier than the other models so that latent amplification can build, but likely to be more an Atlantic/Greenland ridge as downstream has now been cut off for ridging. To me the model that has the vortex sussed will be correct and I leave that for the experts to resolve, more runs needed for me.

[Ali1977]

Another nice looking extreme FI....shame so far in FI

Atleast we are back to some days of interesting model watching again...

Edited December 27, 2013 by Ali1977