Model output discussion 25th Jan - The final third of winter beckons..

[Frosty.]

I don't think we have taken a backward step this morning, it's still going to become colder from the east so the general trend is good and it's still evolving so the finer detail will have to wait but cold air is coming!

[Weathizard]

1 minute ago, Steve Murr said:

Yes - in Easterlies allignment can move right down to T48... but not a 'huge' amount

what we are really looking for as intimated above is the iberian low to be more pebble shaped not circular & deeper development of any lows over the balkans so the net flow is straighter -

That gives a chance for the deeper cold to migrate west

S

Being realistic though Steve, given the winter so far would you bet against the ECM evolution? I know it's progressive but it's been a high pressure/MLB dominated winter and when the models have shown this its generally come to fruition

i know you are positive but honestly I think we need a ridiculous amount of luck to get a snowy easterly now, it's just not realistically likely in my personal opinion, especially given the ensembles show little to no interest

[SMU]

& 1 more post to show the GFS 8 DAM bias on euro heights

3 charts - yesterdays 06z T60 ( first ) then the 00z today T42 & the 06z T36

Notice the blues grow & now a core of deeper blues - 8 DAM drop

& the wind allignment become less SE & more E...

so the expanse of cold gets bigger & further SW... -- look at the 06z 48 V the 00z 54--

Edited February 5, 2017 by Steve Murr

[Man With Beard]

On the D10-D15 again - something to look out for - notice how on the GEFS ensembles, the mean rises slightly around D9/D10 before dropping again afterwards, with quite a few members going cold again. Representative of a temporary injection of Mediterranean air before either more air from western Russia gets into the flow again or the air simply cools over the continental air mass. 

We're still just about in the period where the continent can make its own cold. Just need to keep the flow SE or E.

[Ali1977]

Another noticeable move west of the high at T54 and slightly better oriented to give us colder easterlies - just not sure it'll be much better further on yet.

Hard to tell here but the toggle shows it better

Edited February 5, 2017 by Ali1977

[Singularity]

So the EC ens trend the wrong way a bit while the background forcing trends the right way i.e. in favour of HLB over MLB.

So either EC ens are being brilliant and spotting a contrary forcing somewhere that derails the amplification signal, or they are being rubbish at handling the propagation of that amplification signal from the Pacific to the Atlantic and/or how that weighs up against - and also influences - the polar vortex behaviour.

Quite possibly the tipping point is toward the weekend as the model tends toward particularly vigorous lows powering NE and drawing cold air down behind which enables a further deep low or two to follow on behind. I've often wondered if ECM gets carried away when intense temperature gradients crop up  and this explains why it sometimes chucks out a sequence of hyper-progressive runs. Food for thought.

Anyway - something I just noticed about the ECM 00z is that a feed of sub -5*C uppers hits the Alps from the ESE at +192 and remains held up through to +240. With the surface flow more to the E and so likely getting held up less, it's possible the lower flow becomes even more disconnected from the upper flow than usual.

Also, not an organised vortex here - let alone to the NW - and could draw the Scandi block west days 11-12, though that vigorous low by Canada would probably keep the combined ridges as more of a mid-lat feature with the cold feed more across southern UK... for a time anyway.

[sebastiaan1973]

At day6 UKMO0h performs the best of several models including EC. Altough the differences are not big.

Edited February 5, 2017 by sebastiaan1973

[snowray]

Everthing further west again on the 06z at T66!

[Ali1977]

A much better cold pool to the east at T72

Edited February 5, 2017 by Ali1977

[JamesL]

And also better alignment of flow too at t72 

[northwestsnow]

6z shows the scandy high a hundred or so miles further west as early as 54 so chopping and changing still happening early in the runs..fi very early!

Edited February 5, 2017 by northwestsnow

[SMU]

So this is the end result @ T78 of forecasting a change in the GFS parameters

* bias of + 8 DAM is being removed to show correct heights

* allignment better

= deeper cold pool & edging closer...

 

[northwestsnow]

More energy going south on 6z than 0z at t90!

[Ice Day]

If ever a run demonstrated volatility with easterly weather patterns, this is it.  Significant differences shown from only 30hrs.  Cold pool better aligned and around 100 miles further west at 78hrs.  Looking good so far.

[Hammer50]

Why is it for the past three to four days we have had negative models about a colder output in the mornings models but then I the afternoon and evening it has reverted back to cold again .

[northwestsnow]

Huge difference in temps as early as wed night 00z had temps widely above freezing 06z has -2 -3 widely!!

[Singularity]

  

Comparing 00z on left with 06z on right, the Atlantic trough is just a little bit sharper such that the jet exit is over Iceland instead of just S - and this leaves a little more room for the Scandi high to edge across the North Sea toward the UK.

This brings GFS more or less in line with ECM except that a tad more cold air has been brought west due to slight differences out east. Fine margins indeed!

[TEITS]

Before getting too excited the 06Z often trends W only for the 12Z to move back E. Seen this many times with regards to progged E,lys. If the 12Z backs the cold even further W then I shall become more interested.

[Nick F]

Have to factor in that the weather is always evolving, so inevitably sometimes new data fed into each new model run may improve/expand the depth of cold advecting west that may make last run obsolete for same sector, good to see the deeper cold expanded further south on the 06z GFS. Small steps at such an early stage suggests that detail is FI at and early timeframe!

[Ice Day]

1 minute ago, Nick F said:

Have to factor in that the weather is always evolving, so inevitably sometimes new data fed into each new model run may improve/expand the depth of cold advecting west that may make last run obsolete for same sector, good to see the deeper cold expanded further south on the 06z GFS. Small steps at such an early stage suggests that detail is FI at and early timeframe!

Quite so, FI on the GFS appears to be around 24hrs at the moment!

[snowray]

Good old NE Scotland, never seems to miss out on a bit of snow. Place to be by the looks of it again.

[northwestsnow]

Looks to be going a bit pete tong at 120 though, temps above freezing across the south at night  as the scandy high gets shunted north..

[TEITS]

1 minute ago, northwestsnow said:

Looks to be going a bit pete tong at 120 though, temps above freezing across the south at night  as the scandy high gets shunted north..

I see the opposite. Note the massive shift NW of the high towards Svalbard compared with the 0Z. This could make a big difference further into the run.

[Ali1977]

3 minutes ago, TEITS said:

I see the opposite. Note the massive shift NW of the high towards Svalbard compared with the 0Z. This could make a big difference further into the run.

Yes was just about to mention that, and it's a better shape so me be able to feed some cold back in.

A much better picture at 144

Edited February 5, 2017 by Ali1977

[That ECM]

3 minutes ago, northwestsnow said:

Looks to be going a bit pete tong at 120 though, temps above freezing across the south at night  as the scandy high gets shunted north..

Rather than Pete tong more for Pete's sake  let it evolve. T 120 is good!