Model Output Discussion 19th January 2014-18z onwards.

[Cecil Hogmanay Melchett]

Wanting to see that Azores high pulled west now.

Thats one fierce Atlantic(in keeping with winter so far really)...

[A.J]

worth reporting posts as opposed to replying to posts which are best suited to other threads.....back on with the model output discussion please 

[conor123]

UKMO and GFS don't have Thursday's low undercutting and diving south like the 00z/06z runs to leading to a much flatter pattern thus making for a more complicated run.

Ideally we need that low to sink much sooner to help pull in those cold upper's from Scandinavia, 06z was almost there, still many changes to come but main thing is waiting for the ECM now to see if it's moved towards the others.

Edited January 20, 2014 by conor123

[gottolovethisweather]

Often in here when there aren't any charts to back up certain one-liners or those folk who may even reach a whole sentence or two or perhaps a paragraph, I would advise folk to follow the discussions which do have added details attached to them in such instances. This applies to seasoned model-watchers, newbies and/or the inexperienced. There is also the report or ignore function which can be used too. Back to MODEL OUTPUT DISCUSSION PLEASE especially if complimented with informative links and additional charts where at all possible please.

Edited January 20, 2014 by gottolovethisweather

[Mucka]

Azores high wants to play the part of spoiler on this run but don't take it at face value, the timing and strength of low pressure from the Atlantic and how far North the jet gets after day 5 will make big changes to the output we see thereafter for the UK.

 

Edited January 20, 2014 by Mucka

[Kentish Snowman in Yorks]

To my untrained eye the UKMO 12z looks much colder than the GFS 12z at an early stage in terms of the 850s...good news perhaps?

 

Maybe even a surprise snow event for some as early as Thursday?

[Bobby]

UKMO at 96, perhaps similar to GFS with some leading edge wintriness in the N/E corner

 

 

 

Atlantic in control after, significant rainfall in places likely as the airmasses mix and clash. 120, 144hrs

 

 

Edited January 20, 2014 by Bobby

[fergieweather]

 

The much quoted MetO sounds realistic TBF but I bet they would prefer to get Friday/Saturday out of the way beforehand, Shannon wotsaface anyone? Come the weekend, SW flow NW flow, NE flow, E dominated flow? Take your pick.

No, they're actually fairly happy with it all, as it stands. Aside from the snow already in existing forecast expectations Tues-Weds (for northern uplands, significant in some areas), plus some transient amounts late Fri (just a 10-15% chance of colder air lingering long enough in extreme east to make this any more noteworthy), it's the rain amounts later Fri overnight into Sat that catch the eye and forecast emphasis. Either way, good confidence now on the westerly 'breakthrough' post-Friday, albeit exact rapidity still unclear, but the end result well signalled across all operational centres.

[IDO]

I mentioned earlier that the T180 mean from the 06z did not support the op.

 

eg: 

 

So no surprise that the 12z op is closer to that chart: 

 

The mean has been trending towards modest trough disruption and a flatter flow. The block will hopefully move east and we can get the PV to do its business as quick as possible.

[Mucka]

GEM not great I'm afraid, much more back and forth before this gets resolved but the lack of amplification being modelled upstream is a worry. We should still get a period of cold zonal at worse though. Here is hoping further output strengthens the blocking and weakens the Atlantic

 

Edited January 20, 2014 by Mucka

[R.P. McMurphy]

 

Potential for some Snow surprises on that chart, especially for higher area's, Pennines, Scotland and parts of the East., Worth keeping an eye on.

[gottolovethisweather]

 No, they're actually fairly happy with it all, as it stands. Aside from the snow already in existing forecast expectations Tues-Weds (for northern uplands, significant in some areas), plus some transient amounts late Fri (just a 10-15% chance of colder air lingering long enough in extreme east to make this any more noteworthy), it's the rain amounts later Fri overnight into Sat that catch the eye and forecast emphasis. Either way, good confidence now on the westerly 'breakthrough' post-Friday, albeit exact rapidity still unclear, but the end result well signalled across all operational centres.

 

Oh well, fair enough. Quite a few variations at the shorter timeframe I would have thought, at least judging by what's available to us online. Can't wait to see the updated Fax Charts for later this week with one eye firmly trained on the 528DAM line, that's for sure. Further ahead, GFS is currently modelling a particular deep feature for SUNDAY which if it comes to fruition could be another potential snow event for some I imagine, what are your thoughts on this and into next week Ian? Thanks for your input once again.

Edited January 20, 2014 by gottolovethisweather

[MR EXTREMES]

ukmo at t144

gfs t144

almost identical

Edited January 20, 2014 by emotional rollercoaster

[IDO]

FI continuity from the 12z GFS with the PV on the move west to east, this has been the synoptics for a couple of days:

 

T324: 

 

The variety has been where the jet runs through, on this run it is further north so maybe a chance for the south to dry out if this run is nearer the mark.

[ITSY]

Is it just me or does the 12Z UKMO paint a snowy picture for Thursday afternoon across much of England and Wales? (And Scotland).

[Mucka]

 

No, they're actually fairly happy with it all, as it stands. Aside from the snow already in existing forecast expectations Tues-Weds (for northern uplands, significant in some areas), plus some transient amounts late Fri (just a 10-15% chance of colder air lingering long enough in extreme east to make this any more noteworthy), it's the rain amounts later Fri overnight into Sat that catch the eye and forecast emphasis. Either way, good confidence now on the westerly 'breakthrough' post-Friday, albeit exact rapidity still unclear, but the end result well signalled across all operational centres.

 

Hi Ian, thanks for the update, I wonder if you could elaborate on the "Westerly breakthrough"though.

We know It is how the Westerly breakthrough develops that is important to end of January prospects so do they expect low pressure to be forced into Europe with this Westerly breakthrough and if so how far West and how effectively do they expect this to happen or is the jury still out on this?

Both GFS 00z and 12z both show a Westerly breakthrough but they handle it quite differently.

 

 

 

I realise that these developments are outside any reliable range (day 5+) but do they give any hints as to which option they see as more likely? Thanks.

PS

No mention of possible snow on Thursday - is this discounted? Thanks again.

Edited January 20, 2014 by Mucka

[gottolovethisweather]

Indeed...one choice perhaps you missed? Go with the flow

 

 

What, in here? When would that ever happen.   Oops, my own one liner.

Edited January 20, 2014 by gottolovethisweather

[snowmadchrisuk]

You have to laugh , the whole Atlantic covered in -10's and the UK in +5's... GFS just seemed within 1 frame to return to default haha. Still plenty of improvements in the modeled NH profile out to +144

 

[winterof79]

Hi Ian, thanks for the update, I wonder if you could elaborate on the "Westerly breakthrough"though.

We know It is how the Westerly breakthrough develops that is important to end of January prospects so do they expect low pressure to be forced into Europe with this Westerly breakthrough and if so how far West and how effectively do they expect this to happen or is the jury still out on this?

Both GFS 00z and 12z both show a Westerly breakthrough but they handle it quite differently.

 

 

 

I realise that these developments are outside any reliable range (day 5+) but do they give any hints as to which option they see as more likely? Thanks.

PS

No mention of possible snow on Thursday - is this discounted? Thanks again.

There is also a theme of it being a cold westerly if the UKMO and GFS are to be believed.

[IDO]

Hi Ian, thanks for the update, I wonder if you could elaborate on the "Westerly breakthrough"though.

We know It is how the Westerly breakthrough develops that is important to end of January prospects so do they expect low pressure to be forced into Europe with this Westerly breakthrough and if so how far West and how effectively do they expect this to happen or is the jury still out on this?

Both GFS 00z and 12z both show a Westerly breakthrough but they handle it quite differently.

 

 

 

I realise that these developments are outside any reliable range (day 5+) but do they give any hints as to which option they see as more likely? Thanks.

PS

No mention of possible snow on Thursday - is this discounted? Thanks again.

 

The op run from the 0z was in a synoptic cluster of 20%: 

 

The 12z op is much closer to the main clusterings of the 0z.

[weirpig]

Just a quick question from a novice, If and when we get a period of westerlies could this still result in potential snow fall?  I understand that the uppers would have to be lower than if the air was sourced from europe   but is it possible or would the atlantic modify the temps to much?.

[karyo]

Just a quick question from a novice, If and when we get a period of westerlies could this still result in potential snow fall?  I understand that the uppers would have to be lower than if the air was sourced from europe   but is it possible or would the atlantic modify the temps to much?.

 

99% of the time the Atlantic modifies the temperatures too much for settling snow.

 

Karyo

[Mucka]

The op run from the 0z was in a synoptic cluster of 20%: Screenshot_20_01_2014_16_51.png

 

The 12z op is much closer to the main clusterings of the 0z.

 

Yes that is worth knowing but as I mentioned on the 00z output the ensembles had not caught up with modelling the increased blocking across the Arctic in the mid range and only around 30% were close to what the other models and the Op were suggesting. Since then we had more energy modelled into the jet with it taking a slightly more Northerly track so it is swings and roundabouts. One part of the output improves another deteriorates but I will look through the 12z ensemble set to see if they better model the Arctic high which should give a slightly different look to the mean not forgoing the fact that the Atlantic is likely to be modelled more active to counterbalance any gains.

Edited January 20, 2014 by Mucka

[Summer Sun]

8 day temperature anomaly from GFS 12z is another cold run for a lot of the UK however the far west and south west of England and wales sees temperatures slightly above normal

 

 

Below is the 00z and 06z anomaly's to see how things have changed over the past 12 hours or so

 

[swilliam]

The op run from the 0z was in a synoptic cluster of 20%: Screenshot_20_01_2014_16_51.png

 

The 12z op is much closer to the main clusterings of the 0z.

Doesn't mean that it is 'right' though - fortunately the weather does not run by averages