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

[johnholmes]

610day.03.gif

 

thas a pretty astonishing chart. look at those mean heights !!  i dont recall seeing anything like that before.  of course the thicknesses are tempered by the low heights but i still think we will see a lot more wintry stuff beyond xmas than some on here envisage.

 

the 6-10 has over the last 2-3 days been slowly lowering the heights, I check each day for the Channel area, this evening is the largest 24 hour predicted drop for sure.

 

the thickness is derived, for those who are not aware of this, from the msl and 500mb heights-we used to call it gridding in my days as a junior forecaster.

Edited December 18, 2013 by johnholmes

[Severe Siberian icy blast]

610day.03.gif

 

thas a pretty astonishing chart. look at those mean heights !!  i dont recall seeing anything like that before.  of course the thicknesses are tempered by the low heights but i still think we will see a lot more wintry stuff beyond xmas than some on here envisage.

That really is astonishing , a lot of negativity because of the polar profile but I'm looking forward to cold zonality , it's bought surprises before and im sure it will this time. Johns post as always was top. With a real possibility of something wintry next week

[Ali1977]

I feel a pub run classic FI is on the way...

[bluearmy]

i just edited my post - not tempered by heights (that makes no sense) but slp.   doh!

 

to add that the extended ecm ens and moreso naefs bring the mean jet back across us as we head into the first weekend of 2014 and heights recover somewhat to our south in tandem. no sign of any euro troughing though the strength of the mobility certainly looks to ease off. (couldnt really keep up the intensity of the previous week)

[TSNWK]

Where is the uk on Boxing Day morning on the 18z GFS.

[forecaster]

UKMO 144 kind of reminds me of Xmas 2004. Some potential there for a flurry in places!

 

Not convinced. Xmas 04 had mid Atlantic ridge and scandi low with relatively deep n to nw flow. Current modelling has no substantial ridge in mid Atlantic. What was interesting in 2004...not super cold airmass. 850hpa temps above -6 everywhere I think. Dewpoints in s Wales sub zero....not sure we can get that with what you are showing.

[Purga]

610day.03.gif

 

thas a pretty astonishing chart. look at those mean heights !!  i dont recall seeing anything like that before.  of course the thicknesses are tempered by the very low surface level pressure levels but i still think we will see a lot more wintry stuff beyond xmas than some on here envisage.

Not in south we won't BA.

[Ali1977]

This looks a better run, 216 lining up a Northerly, and big high over arctic showing up

Edited December 18, 2013 by Ali1977

[Nick F]

Still a signal for some snow from the higher res models across Wales, The Mids and parts of N England tomorrow PM. 18z NAE has marginal rain to snow signal for Wales and NW England, to Mids and Lincs 18z to 00z. 12z E4 model faster with trough eastward, with its higher res showing snow for Cotswolds, North Mids, Peaks and Pennines by 18z. Very marginal situation, with elevation and intensity of precip probably the rain or snow decider.

[J10]

Still a signal for some snow from the higher res models across Wales, The Mids and parts of N England tomorrow PM. 18z NAE has marginal rain to snow signal for Wales and NW England, to Mids and Lincs 18z to 00z. 12z E4 model faster with trough eastward, with its higher res showing snow for Cotswolds, North Mids, Peaks and Pennines by 18z. Very marginal situation, with elevation and intensity of precip probably the rain or snow decider.

 

Is EA is more advanced version of NAE.

[Barry12]

Interesting GFS 18z from Boxing day onwards, with most of the PV moving East

 

Edited December 18, 2013 by Barry95

[nick sussex]

I wonder if the Aleutian Ridge is set to make a comeback? Theres quite a difference between the GFS and ECM in terms of the PV in their later outputs so the lower resolution GFS is still not one to really have much faith in.

 

To get anything wintry that's not a slushfest we're going to need to see the main trough further east, and need more amplification across the eastern USA. If this happens and the lobe of high pressure can nose south into the Arctic then perhaps things might look a bit better coldwise.

 

Overall my new underwhelmed rating stands at 7/10!

[Nick F]

Is EA is more advanced version of NAE.

I believe the EURO4 model has a res of 4km grid length, whilst NAE has a 12km grid length, so, yes, E4 higher res.

[J10]

I believe the EURO4 model has a res of 4km grid length, whilst NAE has a 12km grid length, so, yes, E4 higher res.

 

Thank you for that.

[bluearmy]

I believe the EURO4 model has a res of 4km grid length, whilst NAE has a 12km grid length, so, yes, E4 higher res.

Paul posted earlier that euro4 is 12km. Seems odd to me. (EDIT: it was upgraded to 4km from 12km last year)And purga, the UK is far more than the south. You are right, the chances of seeing very wintry conditions approaching new year in the south of the UK are not high. Edited December 18, 2013 by bluearmy

[Nick L]

I believe the EURO4 model has a res of 4km grid length, whilst NAE has a 12km grid length, so, yes, E4 higher res.

 

I read someone else posting earlier that the EURO4 is also a 12km, and the 4 meant something else. Research needed...

[Nick L]

Ok, it WAS 12km, and now it's 4km (bottom of page 2 on this):

 

http://www.metoffice.gov.uk/media/pdf/d/h/13_0068_Accuracy_v09.pdf

[nick sussex]

I know people have been inundated with my ratings over recent weeks! We've had horror, sledge, cold ratings. In the New Year I will be unveiling the following:

 

Can I Take A Day Off Work Due To Snow Without Getting My P45 Rating

 

The PV Get Lost Rating

 

Will COBRA meet rating

 

Will London Buses Stop Running Rating

 

Will Boris Johnson Sort His Hair Out Rating

 

Apologies to those who are rated out !

 

Overall the output is neither a mild horror show or particularly wintry, hopefully we can see changes in the New Year and won't have to be obsessing over the marginality of any snow, SAY NO TO SLUSH! We want  HLB!

[fergieweather]

I believe the EURO4 model has a res of 4km grid length, whilst NAE has a 12km grid length, so, yes, E4 higher res.

E4 runs from UKMO-GM hence distinct from NAE. Indeed the E4 can be run embedded within GM anywhere globally (such for ongoing military theatres, I recall being told ).

[phil nw.]

Just a hint that the vortex may be under renewed pressure from warmings in the new year.

http://modeles.meteociel.fr/modeles/gfs/runs/2013121818/gfsnh-10-384.png?18

 

A sausage shaped pv at 10hPa.This stretched scenario has popped up in recent runs.It's in the later outputs but the first signs for a while of some change to it's current rounded core.

It may reform but this what we need and more of it to penetrate the core.

[fergieweather]

PS on topic E4, re tomorrow's trough in afternoon we are running with notion of E4 timing being circa 2-3hrs fast... hence slower progression eastwards preferred; e.g. across Cotswolds around 17-18z.

[Costa Del Fal]

PS on topic E4, re tomorrow's trough in afternoon we are running with notion of E4 timing being circa 2-3hrs fast... hence slower progression eastwards preferred; e.g. across Cotswolds around 17-18z.

Possibly better for increasing snow chances then as by then temperatures should be a little lower than the days peak, not that they will be very high anyway?

[Cloud 10]

Just looked through the first 10 of the 18z ensembles for christmas day/boxing day and its like an episode of Salem's lot.

 

http://modeles.meteociel.fr/modeles/gens/run/gens-1-1-168.png?18

 

http://modeles.meteociel.fr/modeles/gens/run/gens-2-1-180.png?18

 

http://modeles.meteociel.fr/modeles/gens/run/gens-5-1-180.png?18

 

http://modeles.meteociel.fr/modeles/gens/run/gens-7-1-180.png?18

 

http://modeles.meteociel.fr/modeles/gens/run/gens-8-1-180.png?18

 

 

[karyo]

Just a hint that the vortex may be under renewed pressure from warmings in the new year.

http://modeles.meteociel.fr/modeles/gfs/runs/2013121818/gfsnh-10-384.png?18

 

A sausage shaped pv at 10hPa.This stretched scenario has popped up in recent runs.It's in the later outputs but the first signs for a while of some change to it's current rounded core.

It may reform but this what we need and more of it to penetrate the core.

Yes, that's good to see. The vortex squeezed from both sides!

 

Karyo

[fergieweather]

Possibly better for increasing snow chances then as by then temperatures should be a little lower than the days peak, not that they will be very high anyway?

Diurnal temperature range will play critical role, yes. But especially track/development of the meso-low and associated evaporative cooling alongside the broader drop in WBFL's. Much uncertainty on latter matters still but more northerly bias of UKV & NAE have been preferred solution since early today. E4 has joined that notion.

Ok, it WAS 12km, and now it's 4km (bottom of page 2 on this): http://www.metoffice.gov.uk/media/pdf/d/h/13_0068_Accuracy_v09.pdf

And note from the verification graph just why UKMO rate JMA and ARPEGE... (an old story).