Model Output Discussion - 05/01/2016 18z onwards

[weather eater]

Yes out to 120hrs just looks like pretty standard inter run variation to me, the sort of stuff you see every day all year round. If the GFS is going to sift towards the UKMO, then it's going to have to make somewhat bigger leaps I feel.

Edited January 12, 2016 by weather eater

[East_England_Stormchaser91]

You may ask yourself how do they do this?  You may ask yourself where did that shortwave go to? You may ask yourself is this right or is it wrong, then you may say to yourself my god, what has it done?! 

Sums up what model watching has been like this past week! 

Anyway, what I'm now seeing if anything is backtracking from the GFS more towards a UKMO solution! With the heights raising and the Atlantic being pushed ever further back! 

Good thing is, the cold has began to filter in across northern parts, so we are getting there! 

[SMU]

So the first pidgeon steps again to the UKMO

the signs are there all the way to 144

- increase amplitude in the high

- more energy going SE at 132 

remember post that the GFS will try to blow the atlantic through - but through the mid term we are looking for x2 things

* more energy moving SE ( not NE )

* continental air dragged into the UK from the east to be the undercut

the best chart to view this is the Theta E one-

150v156 before & after

so 00z ^^ no continental flow & shallow low over the borders

06z

The system is now to the SE of the Uk & the continental air ( ideally sub 10c for snow ) is now filtering into the low...

a better run.....

S

 

[winterof79]

So as i thought,a slight build oh heights to our N/E sufficient to send the advancing atlantic front packing.

I would bet as we get nearer to that event that the front never reaches the UK.

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=156&mode=0&carte=1

Edited January 12, 2016 by winterof79

[Nick F]

11 minutes ago, northwestsnow said:

gfs6z showing a snow event on monday as the atlantic disrupts

Indeed, dew points 0C and below ahead of the frontal band though snow to rain event, just for fun:

Further corrections to a more negatively tilted trough/frontal alignment approaching UK late Sun/early next week from GFS on the 12z?

Really shouldn't be concentrating in such detail at that range given the uncertainty past t+120, but not a great deal of snow looking likely from this cold snap before then away from Scotland and higher ground.

 

Edited January 12, 2016 by Nick F

[Singularity]

Chionio's very helpful post yesterday regarding the effect of the incoming SSW on the vortex - to effectively focus the cyclonic circulation for a time ahead of the major displacement and (hopeful) reversal of the circulation around the pole by month's end - has but a lot of weight behind one of the explanations I was pondering over with respect to the dramatic switch from -ve to +ve AO by recent ECM det. runs. Indeed I can't see any reason to dispute that reasoning.

This also gives me cause to believe that the signs of a strong Euro High and mid-Atlantic trough combination are a result of the +ve AO combining with the effects of the North Atlantic 'Cold Pool' (a -ve AMO variant) much as we saw last month, though there is less support from the MJO this time, so seeing a high as strong as in Dec would say a lot about the relative contributions of each of the forcing mechanisms mentioned.

So yes, the overall direction of travel over the coming 10-14 days all makes a lot of sense to me... BUT there are big issues with assuming that the models have the timing of proceedings correct. Key things I noticed about the ECM 00z det. run compared to the previous two det. runs are that the development of low heights to the N and NW is less vigorous, and that - perhaps consequentially - the tipping point at which we see no way to sustain the cold has remained at +144 (i.e. not come nearer in time), maybe even been pushed back to +168 depending on how you look at it - that shortwave low west of the UK at +144 is so close to sliding SE and only the strength of the jet coming out of the U.S. prevents that.

 

Not only that, but the behaviour of the ex-subtropical low that moves to the Azores remains questionable, with UKMO choosing to split the low heights between the trough off the U.S. and the southern arm of the jet which carries it toward Iberia. This is a key difference to ECM and GFS at the range of just +96 hours, as these models allow little or no low heights to escape along the southern jet arm. These features tend to have a fair bit of spread in model solutions when it comes to their track even at just a few days range, plus these split-jet scenarios tend to prove particularly tricky to resolve in terms of the balance between the northern and southern arms, so either outcome is equally possible IMO. If we go the way of UKMO, then the initial response to the increasing AO is effectively undermined, and this allows the block in the vicinity of the UK to bolster its defenses ahead of the next push from the west, aided by that 'residual' low moving toward Iberia. 

Worth noting that UKMO was keeping more energy going SE yesterday than it is this morning so it hasn't held rock steady in that regard - but it's shouting for the 'sliding remnant' pretty hard.

In theory a victory for the westerlies is highly likely by late Jan given the climbing AO - but there is a chance that the models are assuming too straight forward a connection between the stratosphere and troposphere... and even if they aren't, UKMO keeps dropping hints that the blocking over Siberia might get friendly with our own area of high pressure should it stick around for long enough. A small but tantalising possibility - what a steal that would be 

[Frosty.]

The Gfs 6z is showing a wintry spell with the coldest weather at the end of this week and start of next week, rather than worrying about next week we (coldies) should be enjoying this week because some of us are going to get a covering of snow and we are in for some very cold frosty nights, especially where there is snow cover...it's just so nice to have wintry charts in the reliable timeframe as it's usually T+240 plus!!

[nick sussex]

Given the timeframes a welcome nudge towards the UKMO from the GFS 06hrs run. The GFS does exhibit a bias in terms of always wanting to throw more energy ne rather than se. So once you factor this in its more likely to correct slowly se rather than ne as the timeframes gets closer.

If you look at the GFS trends yesterday was a relentless push east, both the 00hrs and 06hrs runs have started edging the pattern west.

Maybe it over reacted to that increase in zonal winds, the irony of course is that the warming of the strat and the apparent last stand of the PV where it has one last big increase in westerlies couldn't have come at a worse time because its trying to now fire more ammunition at western Europe.

If this SSW precursor ends up shortening the longevity of the cold then it had better deliver after that!

 

 

Edited January 12, 2016 by nick sussex

[Man With Beard]

42 minutes ago, Steve Murr said:

So the first pidgeon steps again to the UKMO

the signs are there all the way to 144

- increase amplitude in the high

- more energy going SE at 132 

remember post that the GFS will try to blow the atlantic through - but through the mid term we are looking for x2 things

* more energy moving SE ( not NE )

* continental air dragged into the UK from the east to be the undercut

the best chart to view this is the Theta E one-

150v156 before & after

so 00z ^^ no continental flow & shallow low over the borders

06z

The system is now to the SE of the Uk & the continental air ( ideally sub 10c for snow ) is now filtering into the low...

a better run.....

S

 

Steve, your analysis of the UKMO has brought back memories of how it trumped all the other models in 2013, and yes, there are shades of it in its T144 chart. I can go even a bit further - looking back through the archives, I was surprised to see that UKMO was fairly consistent with the pattern from T144 on its 0Z chart (bit more wobbly on the 12Z chart) the ECM didn't really pick up the change in pattern properly until T96, and the GFS wasn't consistently right until about T66!!! I've never discounted the UKMO since this time, although of course it has had some fails recently.

This is of course very relevant because we have a very similar situation now, where today's UKMO seems destined to lock cold in for next week, whilst the GFS/ECM look to sweep it away.

 

 

 

 

Edited January 12, 2016 by Man With Beard
I realised Steve Murr had already posted these charts

[Singularity]

The sheer magnitude of the failiure by ECM on that occasion is astounding. That it could come down to +96 before ECM comes around (if it does)... well, we'll all need to put our best sensible hats on if we're to come out of this with our sanity intact.

Liking the hints of trough disruption from the GFS 06z. A backdown does often start with the subtlest of hints from that model.

[northwestsnow]

GFS6Z turns on the blowtorch in FI but doesn't look a long lasting blowtorch as the euro high retrogresses to the mid Atlantic pulling down colder air from the north west.

Hopefully a trend that will gather momentum in the days ahead.

[Newberryone]

Bitterly (forgive the pun) disappointing Fi pc model forecast compared to the "epic" cold spell predictions of quite recently. To my untrained eye, all I can foresee going by one of the big players, Ecm, is a return of the Euro slug, as some like to call it,l.

Met Eireann now predicting a return of the Atlantic influence with mild weather from Mon onwards 

Edited January 12, 2016 by Polar Maritime
To move discussion on.

[winterof79]

15 minutes ago, Newberryone said:

Bitterly (forgive the pun) disappointing Fi pc model forecast compared to the "epic" cold spell predictions of quite recently. To my untrained eye, all I can foresee going by one of the big players, Ecm, is a return of the Euro slug, as some like to call it.

I believe you have mistakenly awoken early from hibernation.It is still winter

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=108&mode=1&carte=1

http://www.meteociel.fr/modeles/ecmwf.php?ech=72&mode=0&map=3&type=0&archive=0

http://www.meteociel.fr/modeles/ukmo2.php?nh=0&ech=144&carte=1021

Sleep tight.

Edited January 12, 2016 by Polar Maritime
To move discussion on.

[johnholmes]

20 minutes ago, Newberryone said:

Bitterly (forgive the pun) disappointing Fi pc model forecast compared to the "epic" cold spell predictions of quite recently. To my untrained eye, all I can foresee going by one of the big players, Ecm, is a return of the Euro slug, as some like to call it.

Met Eireann now predicting a return of the Atlantic influence with mild weather from Mon onwards 

The penalty of believing the synoptic models when they 'appear' to promise deep cold and snow everywhere. One does need to treat these predictions with great care. At long term say beyond 168h and sometimes less always check one model run against the same time the day previous and keep doing this. IF it shows a particular scenario then it may well keep this and gives some confidence. If it keeps switching from one idea to another be very very wary of it showing the one you want.

Edited January 12, 2016 by Polar Maritime
To move discussion on.

[grca]

I was just taking a look through the GFS ensembles at 120hrs and I am amazed at the differences shown within that timeframe. Does that suggest anything after 96hrs (or before even) is far from decided on the GFS that is?

Some examples below

Control -

No 2 (there are many more variations of this theme like this as well)

[Waterspout]

As Steve and others have pointed out, comparing the GFS 06z to 24 hrs ago highlights the massive changes in pressure distribution to our NE and NW:

As an Overlay:

As an Error Signal:

Circa 30-40 mb in 24 hours - starkly changing between T+120 and T+168 on this mornings run.

[bluearmy]

The spread on uppers on the ECM ens days 8/9 reveal a cluster that bring in a nor Easterly flow which almost makes it as far as the UK. That has to tie in with a block further north. The updated London ens keep a colder surface temp cluster longer bug no idea if this might just be under a stagnant block centred over s England .  Whilst the ops and ens means look quite convincing at the moment post day 7, I would be cautious for a few more runs yet. 

[chionomaniac]

49 minutes ago, Singularity said:

Chionio's very helpful post yesterday regarding the effect of the incoming SSW on the vortex - to effectively focus the cyclonic circulation for a time ahead of the major displacement and (hopeful) reversal of the circulation around the pole by month's end - has but a lot of weight behind one of the explanations I was pondering over with respect to the dramatic switch from -ve to +ve AO by recent ECM det. runs. Indeed I can't see any reason to dispute that reasoning.

 

Another good post S. Worth pointing out that so far no SSW has been forecast. The 'crush' on the vortex will also occur prior to a major warming that does not produce a SSW. So you can have the +ve AO pain but not the end game tropospheric disturbances.....Though the strat vortex will be a lot weaker as a result anyway.

[snowray]

Anyone notice that little LP just North East of Scotland, every run shows it motionless for about 5 days! Seems to me it can be little features like this that can scupper everything, should have moved away South East to allow pressure to build further north but it won't budge.

Edited January 12, 2016 by snowray

[Mark Neal.]

Euro 4 for the next 48hrs from the 6Z run that has just trundled out.

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=euro4&MODELLTYP=1&BASE=-&VAR=prty&HH=24&ZOOM=1&ARCHIV=0&RES=0&WMO=&PERIOD=

 

[NO LONGER POSTING]

1 minute ago, Mark N said:

Euro 4 for the next 48hrs from the 6Z run that has just trundled out.

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=euro4&MODELLTYP=1&BASE=-&VAR=prty&HH=24&ZOOM=1&ARCHIV=0&RES=0&WMO=&PERIOD=

 

I have always said and I think many will mirror me, the rule of thumb with snow is get the cold in first worry about snow later.

The problem with the cold spell we are now on the cusp of is that the cold never really gets a chance to dig in more flirt with us

[warrenb]

OK so we are looking at a possible breakdown at 120, so do we have comparative charts for 120 hours ago from the big 3 from the 0Z runs, to compare to where we are right now ?

[Mark Neal.]

Just now, Surrey said:

I have always said and I think many will mirror me, the rule of thumb with snow is get the cold in first worry about snow later.

The problem with the cold spell we are now on the cusp of is that the cold never really gets a chance to dig in more flirt with us

Your first comment is very true, and your second goes on to answer that theory, the cold just isn't as extremely cold to guarantee us a wintry mix, those favoured are Hills and elevation further North but a wintry mix further south can't be ruled out and back edge snow falling likely for many as cold air digs in behind and conditions become more favourable for a time.

[Frosty.]

11 minutes ago, Surrey said:

the cold never really gets a chance to dig in more flirt with us

I don't agree, we are not just going to flirt with cold, it's a proper cold snap with plenty of frosts and increasingly wintry ppn with accumulating snow for some of us.

Edited January 12, 2016 by Frosty.

[Gazza H]

2 minutes ago, Surrey said:

You speak for the North of the UK we must remember that us snow starved southerns are gagging for snow that just doesn't look to materialize in the current cold snap! 

 

Looks good for down south out on Monday, i'l take this all day long, props won't materialise those 850's have been changeable over the the last few days