Model Output Discussions 18z 31/01/2016

[Tim Bland]

Several opportunities for marginal snow events this week. 

Tommorow night there is the chance for a small feature to slip SE bringing light snow from the NW to SE.

Friday has a chance for snow in central areas as per below image.

Then we have the deep low for the weekend which will give snow on its northern edge. Let's hope at least everyone sees snow from 1 of there opportunities ! 

 

[cheshire snow]

A Cold night Saturday Temperatures according to 06z Ranging from -10 to -3 North to South

Maybe lower over any Snow fields(if there is any snow)

C.S

[Spah1]

their opportunities 

[chris55]

GFS sticks to its guns! Slide baby lol

 

[Ali1977]

If this GFS is correct Sunday could be very interesting down South, with some significant accumulations and possible ice day.

Edited February 8, 2016 by Ali1977

[Polar Maritime]

Yes no real change from the GFS into next weekend, With cold air established over the UK from the North with plenty of moisture available..

Edited February 8, 2016 by Polar Maritime

[Singularity]

In the end, a cheeky run for the far south in terms of bringing the snow line very close on Fri, then all the way on Sat but only as the precip. clears, before finally delivering big-time on Sunday evening following heavy rain in the morning.

The idea of having several chances is both nice in terms of upping the odds of at least one success and concerning in terms of successive will it/wont it periods which can be quite exhausting if one is not careful.

Confidence is still rather shaky given that ECM run though. Also it seems today is not as clear-cut as the models would like; winds remarkably variable with time. Such details are the Achilles heel of even high-res models.

[Purga]

Friday could certainly be 'interesting for Midlands and higher ground in the south / Wales

Reasonable frosty nights on offer

Low temps over the southern snowfields!

IF there could be a shift a bit further south with the track of the depressions and IF the embedded air / uppers were just that bit colder, then there could be a decent wintry week coming up. Still time for adjustments either way of course.

Edited February 8, 2016 by Purga

[Man With Beard]

The snow charts on the GFS 06Z are startling for south of the Peak District. But to keep feet on the ground, large differences between almost all ECM ensembles and GFS op at just T96. The ECM postage stamps do not have many sliders, and would largely result in a northerly snow event, if that.

Support for the GFS op, however, is forthcoming from its own ensemble suite - here's the mean, much more slidey:

Of the others, the UKMO slides (of course it would!), so does the NAVGEM and the GEM is maybe halfway between ECM and the sliders.

But if the weekend doesn't work out for snow, no worries - ALL models seem to agree on Monday having a north/north-easterly under low heights, quite uncanny really:

Edited February 8, 2016 by Man With Beard

[Chris K]

I am still waiting for a dry, sunny spell lasting more than a couple of days to be honest.

But...there is certainly some interest for the snow hunters towards the closing end of this week & weekend. GFS is currently the main choice to follow with a possible pivoting band across large parts of Wales and Southern England, along with additional opportunities. However I am wary of these precipitation and snow accumulation charts at this range. It would also be great to see further conisistency and agreement across the other various model suites. 

If it were to verify, I think many here would take it after what winter 15/16 has offered us so far, even if it ends up a short-lived affair.

[nick sussex]

Just seen the GFS 06hrs run, thank heavens it didn't follow the ECM!

The shortwave issue south of Greenland is really the crucial factor here and you'd think with 6 hours of newer data the GFS 06hrs run within T72hrs would be on the right lines.

We'll have to wait for this evenings outputs though. Hopefully the ECM will backtrack and the GFS will stick to its output.

[NorthYorksWeather]

Hi res model NMM following its theme on the 6z from the 0z with a nice slider and lots of food air to the east waiting to flood in. 

[Purga]

18 minutes ago, nick sussex said:

Just seen the GFS 06hrs run, thank heavens it didn't follow the ECM!

The shortwave issue south of Greenland is really the crucial factor here and you'd think with 6 hours of newer data the GFS 06hrs run within T72hrs would be on the right lines.

We'll have to wait for this evenings outputs though. Hopefully the ECM will backtrack and the GFS will stick to its output.

Aren't the Yanks favouring ECM though at the moment Nick?

[warmintim]

4 minutes ago, vizzy2004 said:

Hi res model NMM following its theme on the 6z from the 0z with a nice slider and lots of food air to the east waiting to flood in. 

I know its a typo/autocorrect - but I love the idea of food air!

[Dunstable Snow]

Well,

I threw in the towel at the beginning of last week but I forgot to put my bins out for collection !. If we get to Wednesday's 12z and the GFS story is replaced across all of the main models with no downgrading of the snow potential I will start to get very interested. For the time being, I am not going to get carried away with excitement as the chances are it will only lead to a big disappointment. Here's hoping winter 2015-16 finally deliverers, the margins for adjustment however on these set ups, particularly with the lack of decent home grown cold pooling or cold immediately to our east Is small...

[NorthYorksWeather]

114hr chart is pretty epic with lows tracking across the South Coast and a cold and likely convective easterly flow setting in. 

[nick sussex]

22 minutes ago, Purga said:

Aren't the Yanks favouring ECM though at the moment Nick?

In the shorter term discussion for that low which exits the ne USA and phases with shortwave energy near Greenland they had an GFS/ECM combination however they did note that the ECM was the weakest and furthest south compared to the GFS/UKMO.

I've looked across all the 06hrs runs from normal to high resolution and theres no agreement on the detail however I haven't found any support for the ECM solution in terms of how far east it is with shortwave energy.

What we want is the low exiting from the USA to phase quickly with this shortwave circled red:

Once this phases the direction of that low pulls the shortwave west and absorbs this rather than throwing shortwave energy east/se.

The ECM fails to absorb this shortwave and you'll see this heads east/se and then the net result is the weak high lobe to the north has less influence:

 

Ordinarily we wouldn't really be that bothered with this early divergence but the stakes are high for snow lovers because this divergence effects the subsequent track of low pressure into the UK and how much trough disruption occurs. And because there is likely to be enough cold to the ne to engage any low and readily turn any rain to snow then its really the most important divergence of the whole winter season.

 

 

 

Edited February 8, 2016 by nick sussex

[wishingforsnow]

1 hour ago, nick sussex said:

Just seen the GFS 06hrs run, thank heavens it didn't follow the ECM!

The shortwave issue south of Greenland is really the crucial factor here and you'd think with 6 hours of newer data the GFS 06hrs run within T72hrs would be on the right lines.

We'll have to wait for this evenings outputs though. Hopefully the ECM will backtrack and the GFS will stick to its output.

Wasn't there a shortwave on some of last month's run pre January cold spell that put doubt into whether it would happen or not? The devil is in the detail and model confusion at such a short range is making me think back to last month with forecasting of the cold spell and if it was to happen and then how long it would last for.

And its again one model that refuses to play ball like the GFS last month. Remains to be seen what ECM will do with that shortwave. There is still loads of uncertainty but looks like more support for colder and wintry conditions from the GFS and UKMO. There is a trend for El Nino winters to end with cold so I'm hopeful that will still somehow come off with this current output. 

[Mucka]

ECM was very much on the mild side of its ensembles so a less likely option than the colder scenario as with GFS perhaps but within GFS ensembles there is spread for that period with a significant number of milder options. (beginning 12th) though at least the Op and control are with the cold cluster.

As is often the case after much teeth gnashing from some of Southern contingent it looks as though the South is more likely to see frontal snow than North if we get the worthwhile disruption shown on GFS with the North of England staying mainly dry. I can't count how many times over the years some in the South post about how nothing of interest for them but good for the North in a N/NE flow and I end up seeing little or nothing while they get good snowfall, quite galling really.  

(Nah good luck and I'm trying the reverse jinx )

Anyway the alternative is only more rain for the NW if the low blows up or drier and colder for us if it disrupts with only a tiny margin where ppn can get this far and be snow while the South gets snow so I hope it comes off. Who knows where the sweet spot will be but the norm would be for West Midlands with the further SW you are the more likely you will get rain/sleet and the further N the more likely you will stay dry. Better some get snow than none at all so fingers crossed this evenings output goes that way.

 

 

 

 

[wishingforsnow]

1 minute ago, Mucka said:

ECM was very much on the mild side of its ensembles so a less likely option than the colder scenario as with GFS perhaps but within GFS ensembles there is spread for that period with a significant number of milder options. (beginning 12th) though at least the Op and control are with the cold cluster.

As is often the case after much teeth gnashing from some of Southern contingent it looks as though the South is more likely to see frontal snow than North if we get the worthwhile disruption shown on GFS with the North of England staying mainly dry. I can't count how many times over the years some in the South post about how nothing of interest for them but good for the North in a N/NE flow and I end up seeing little or nothing while they get good snowfall, quite galling really.  

(Nah good luck and I'm trying the reverse jinx )

Anyway the alternative is only more rain for the NW if the low blows up or drier and colder for us if it disrupts with only a tiny margin where ppn can get this far and be snow while the South gets snow so I hope it comes off. Who knows where the sweet spot will be but the norm would be for West Midlands with the further SW you are the more likely you will get rain/sleet and the further N the more likely you will stay dry. Better some get snow than none at all so fingers crossed this evenings output goes that way.

 

 

 

 

It would really be 'sod's law' if the outcome ends up being that the low blew up into another powerful and destructive storm after all of this support for another potential cold spell with more snow chances. For once, we need things to go our way this winter and if the ECM outcome did come off in the end I'd simply resign myself to the fact that this winter the atmosphere and El Nino in one way or another, through rogue shortwaves, hurricanes and the PV simply didn't allow for settled wintry conditions to develop.

[Alexis]

 

The high res ARPEGE also manages to absorb the shortwave.

[nick sussex]

The earliest of the 12hrs outputs is out. The NAM high resolution model backs the GFS 06hrs run at least with phasing the shortwave within T60hrs.

Unfortunately we don't get the east Atlantic with this model so don't know whats happening near the UK.

At T84hrs and comparing it to the other outputs its nothing like the ECM with the west Atlantic set-up. This isn't a global model so we need to bear this in mind and is really designed for the USA but anyway at least no backing from the first output, thankfully!

[weirpig]

for me im glad to see th 6z  following on from were the 0z left off  although the ecm was playing the part of the grinch  its good to see the gfs being quite consistant from run to run. the postion of the low will certainly change but i am slightly optimistic that the ecm will come in line with the gfs   as ever  the 12z will be awaited with interest. 

[wishingforsnow]

3 minutes ago, Alexis said:

 

The high res ARPEGE also manages to absorb the shortwave.

That's good to see  Hopefully the ECM will start following this path. 

[wishingforsnow]

1 minute ago, weirpig said:

for me im glad to see th 6z  following on from were the 0z left off  although the ecm was playing the part of the grinch  its good to see the gfs being quite consistant from run to run. the postion of the low will certainly change but i am slightly optimistic that the ecm will come in line with the gfs   as ever  the 12z will be awaited with interest. 

The main issue of confusion is the shortwave, I think ECM is just throwing around a different scenario which at the moment remains an outlier across the model output, and I hope it stays that way.