Model Output Discussion - The final stretch to Christmas

[snowangel32]

Dont know why we hunting for the next cold chance when we currently have freezing conditions over all of the uk. And models and beep forecast snow tomoz for the spine of the country wich is getting upgraded with more areas in with a chance. And as i haven't seen snow for almost 2 years i would take it and as the models also demonstrated the past week nothing is set in stone and will change. Enjoy the snow tomoz and enjoy it while its here.

[Mapantz]

ECMWF has very similar track to this below, posted on Twitter from the hi-res NMM output:

image.jpg

This maintains the general trend from today of advertising a generally Wales-Midlands-East Anglia track of the snow threat - once again to stress this does not mean this is the final track, but at present this seems the most likely scenario on the basis of forecast models.

This met office visual firms up on this idea too:

image.jpg

I wouldn't be paying too much attention to projected totals just yet as these situations tend to become pretty dynamic.

I'm off to enjoy the rest of the day - hopefully an exciting day of watching to come tomorrow

SK

Can I ask where you got that info-graphic from SK?

I haven't seen the MO put one out?! There's another one floating about, very similar to that one too. While it may not be far out, I cannot find any legit sources for it.

A late merry xmas to you, keep up the good posts.

[East_England_Stormchaser91]

All eyes to be kept on how this deep cold pool a stones throw away is handled over the next couple of days. Any slight movement North of that high pressure system could result into the SE tapping into some of that real cold air. 

Anything past 150 hours I'm going to pretty much ignore tbh. We've seen how much things have changed over this last week, its unbelievable!

 

P.S Wouldn't this be pretty funny if the parallel's predecessor picks out a scenario like this mornings run and proves to be correct...!!

Edited December 26, 2014 by East_England_Stormchaser91

[Mucka]

GFS (p) not up to much this morning quickly flattening the high but GFS Op is quite interesting through hi res keeping things cold at the surface and just about bringing in some colder air from the continent toward the end for the far SE - well what is left of it.

 

 

Out into FI and day 10 manages some undercut.

 

 

And from there it is battleground UK between airmasses. (Note the PV is pretty much split)

 

 

Parallel very different though as stated but the Op run does show there is till fight in the high yet and is actually pretty cold right the way through.

 

 

UKMO not stunning by any means but certainly not bad. A lot would depend on the track of the Atlantic low and how much it developed.

 

 

GEM is flat at the same point so still a long way to go before we can consider the output as moving back in our favour but I'm pleased with the small steps made this morning so far as it only needs incremental steps and small adjustments to get us back to keeping the Atlantic at bay.

 

Edited December 26, 2014 by Mucka

[Timmytour]

Can't help wondering if this winter is going a little bit 1954-55 wise where repeated attempts to push heights up into the North Atlantic were continually rebuffed until persistence began ro win the day resulting in this.....

We've only had two periods of Jan - March which have been colder since.....1963 and 1979....so that would certainly do me. Of course we only see what actaully did happen then, not how the models would have projected it to. But I have a feeling that in the same circumstances now, it was a pattern GFS would look to keep flattening in its later reaches....just as it seems wont to do now (as indeed as did keep happening in the early part of that winter)

[Mucka]

Euro4 doesn't have the ppn getting into Northern England, looking good for the Midlands though.

 

Edited December 26, 2014 by Mucka

[IDO]

I think the ECM sums up the hi-re for the next 10 days. A sinking high till d6-7 keeping us dry with surface cold. Then a flatter more Atlantic driven spell, similar to early December, with short wave ridge/trough combo. NH perspective we maintain a Pacific/Alaskan ridge so this may do damage in the long run strat wise and by D10 the PV is still mobile so the pattern of this winter of it not setting up shop continues:

 

  

 

Looking at the GEFS in FI and at D13 the mean is reflective of the clusters: 

 

It is continuing on from the D10 ECM chart with a zonal flow, though not as strong as it could be. With all the blocking potential out of our realm (Pacific) we are stuck with the recycling PV. D16 takes us up to Jan 11 and the pattern is maintained. No sign of any strat effects, just  a continuation of the PV coming and going to NE Canada, blocked from going anywhere else by the Pacific ridging. That set up is good for reloads of PM air running off the 850's PV lobe over Canada as it cycles around Arctic Canada/Canada. But is very unhelpful for any block to set up in our sector as it will power up the jet from the NW.

 

Not a promising setup for the UK for the long term assuming the above is reflective of the outlook and it is very feasible. It seems clear now that trop wise we will struggle to get a HLB with any legs and we need to strike lucky with an SSW. The strat in GFS FI is underwhelming. At 10hpa warming fades after D7 and by D16:

 

p:  op: 

 

A recent tweet: 

 

  RyanMaue
Polar vortex hasn't completely split by 7-days ... big changes underway regardless way up there. Before & After http://t.co/mjIob6RZ0V
26/12/2014 06:53

 

So very interesting up there and looks like it could go either way re SSW for early Jan.

[Polar Maritime]

Some heavy snow for parts of the Midlands/Wales/N England later this afternoon, A very Wintry 48hrs with disruption possible..

 

Edited December 26, 2014 by Polar Maritime

[SMU]

Morning All

IDO - todays cold & snow highlights the point that using means past 10 days is about as useful as a chocolate teapot-

Rewinding 10 days I seem to recall you presenting pretty much the same post as today - highlighting no real poential in the charts, infact apart from the images its almost a copy & paste. I think many said you would overlook a cold spell with snow & today is a clear example of why living in days 10-16 bears minimal relevence to reality -

It would surprise many that the GFS 00z op is probably the best run for snow since March 2013, when you look at the run quickly it may not appear that great but in FI ( which is of course unreliable ) its snow event after snow event for the UK.

It is infact close to a cobra run- sadly all the action is past 168 though.

Theres is a distinct model diversity today around 144 with the unusal pairing of the GFS & UKMO presenting an undercutting scenario, where as the ECM is flatter ( like IDO indicates above ).

Its all about fine margins of energy distribution & whether that gets under the block

If it does its a snowfest , if not ECM is very quick to reamplify......

S

[bluearmy]

early thing to take from the 00z is that the forecast strat vortex split in week 2 could well be replicated in the trop which presents plenty of wintry opportunities for the mid lats. No reason to be downbeat on winter for the time being as in this scenario, even zonal becomes worth watching! (Though it could easily be the med pinching most of the snow again!)

The ECM day 10, whilst not worth analysis in itself, is a decent illustration what NH profile could verify when the split opens up from the other side. Plenty of others on view in the GEFS.

I Suspect that statistically, the westerlies will retain the upper hand for the time being on the NWP. (Thogh they look to be of the chilly variety)

And Steve, I couldn't bring myself to reference the gfs op as an illustration that the block could hold on at a higher latitude and force an undercut. especially as it does most of the work in low res.

One thing that those hoping the block can hang on should note that the upper ridge is sitting at a higher latitude than the surface ridge. That better than having it the other way around.

Most modelling sinks it but the fat lady hasn't quite been wheeled out onto the stage on this one as yet.

Edited December 26, 2014 by bluearmy

[nick sussex]

Todays outputs are a mixed bag but certainly no horror show. Even if the high gets flattened theres no sign of a flat jet from here to the Pacific and the pattern is likely to amplify again.

 

If we can avoid the possible flatter bit in the middle then the cold might remain, the GFS is the star of the show today with some battle ground scenarios, the ECM is keen to flatten the high but then goes onto displace the Azores high, I see nothing at all to get disheartened about today.

 

This isn't the normal flatten high, limpet PV blob for weeks scenario.

[MR EXTREMES]

I don't think the models beyond 144hrs have any idea to be honest if we look at the models at face value they never really know the reality of a trop or vortex split and when they don't know they tend to drop back to default zonal.

But even the ecm shows that even with out a split there will still be many opportunities of polar maritime air as the dominant air source of coarse still brief higher upper air temps but very brief.

I still fancy a Scandinavia heights a very possible out come.

But still better than last year and you lucky sods North of the m4 enjoy sometimes I hate living on the south coast.

If by feb the pattern is the same then I throw the towel in.

And put it down to the spike in solar activity.

Hoping this year we see a complete decline in solar activity interested to see if next cycle will be lower than cycle24.

Anyway the strat thread still holding onto a event let's hope it delivers the goods.

Fed up with have heating on for cold wet although nice to see Jack Frost at least it feels like winter.

[IDO]

Morning All

IDO - todays cold & snow highlights the point that using means past 10 days is about as useful as a chocolate teapot-

Rewinding 10 days I seem to recall you presenting pretty much the same post as today - highlighting no real poential in the charts, infact apart from the images its almost a copy & paste. I think many said you would overlook a cold spell with snow & today is a clear example of why living in days 10-16 bears minimal relevence to reality -

 

S

 

It is late December so a brief period of snow as a low slides through for the lucky few can never be ruled out. Nothing out of the ordinary for an average late December. The following cold high is also seasonal but just normal at this time of year. Of course compared to last year...but that was a one off and to keep comparing to that would be like comparing each winter to 1963.

 

ECM mean at D10 reflective of the op!  

 

Mostly when that happens there is good certainty. The GFS op in FI has little support for its cold outlook (coldest member most of FI):

 

 

So the most likely scenario is a flatter pattern after D7, and with a strong jet any undercut looks a low chance.

[bluearmy]

 

ECM mean at D10 reflective of the op!  EDH1-240.gif

 

Mostly when that happens there is good certainty. The GFS op in FI has little support for its cold outlook (coldest member most of FI):

 

graphe6_1000_306_141___Londres (5).gif

 

So the most likely scenario is a flatter pattern after D7, and with a strong jet any undercut looks a low chance.

That gefs diagram for London looks rather chilly IDO, even for London. I suspect northern England might be even more of a wintry look about it. even if flatter does verify, I think it will be a cold zonal which, with some upstream amplification will provide for further surprises.

[Frosty.]

When I mentioned snow the other day I got a load of abuse for ramping, misleading and confusing and yet here we are, some areas are in for heavy snow followed by sharp frosts and freezing fog for the next five days at least. High pressure and cold surface conditions with minima well below freezing.

[phil nw.]

Morning All,i hope everyone enjoyed the big day.

 

Yes looking at the 2mt temperature graphs based on the 00z GFS run the mean looks quite chilly or even cold at times right through and really little different to the Op on many days.

A glance at Warks and Aberdeen shows this.

 

The runs do show the high coming under pressure around month end but with the vortex being pushed this way by the Pacific ridging the resident polar air  eases closer just to our north.

 

I think the temperature graphs indicate a lot of polar air in the mix from any westerlies that come this way as minimum amplification will do the trick.

 

Meanwhile maybe some snow for me and other central  areas today/tonight then a few cold and frosty days before any change.

The start of January doesn't look like we will evolve in to any mild pattern as the high eases away, based on the 00z outputs.

Edited December 26, 2014 by phil nw.

[Thunder Snow]

Wouldn't get yo excited about snow, just had a heavy rain shower after a fairly harsh frost early on temp 2 dew 2c

Higher routes may do well out of this, bit I think there may just be a wintry mix to lower ground

Edited December 26, 2014 by Thunder Snow

[Polar Maritime]

Wouldn't get yo excited about snow, just had a heavy rain shower after a fairly harsh frost early on temp 2 dew 2c

 

The Meto seem to be, Some parts of the Midlands could see up to 15cm later tonight..

[PompeyFC]

this is a good site to track the weather conditions as they are developing - I know some of you use this model/website

 

http://meteocentre.com/analyses/map.php?lang=en&map=eur_full&area=eur&size=large

[johnholmes]

my thoughts initially in this link

https://forum.netweather.tv/topic/82113-boxing-day-snow-event-thoughts-and-reports/#entry3097491

a good day, for those in the ppn predicted area to try the Net Wx 'will it snow' post I did some years ago. If you use it properly and try to keep any understandable bias out it does work.

link following when I find it!

 

https://forum.netweather.tv/topic/27989-how-to-try-and-forecast-snow/

Edited December 26, 2014 by johnholmes

[snowking]

Quick update with regards to today's snow potential

 

Still a very tricky cool with temperature profiles proving very marginal indeed. I would say above 200m, and indeed North of the M4, it looks a fairly dead cert. For the remaining 95% of the landmass affected by today's precipitation, a lot may come down to evaporative cooling, and hoping the precipitation stays intense enough all the way through in to this evening. 

 

GFS, and hence NMM, remains the furthest North solution:

 

 

As outlined by Mucka, Euro4 keeps the precipitation much further South:

 

 

And at present the best time for the widest cross section of England and Wales, at least according to the Euro4, is around 3am in terms of dew points:

 

 

Though as you can see, still marginal (though at that resolution it is tough to decipher just how much of an area might be above/below 0c).

 

Two things to note here. Firstly, no model is really able to accurately calculate the effects of evaporative cooling (quick FYI for those newer members - as precipitation falls from the clouds, it carries down parcels of air. These parcels of air, having come from much higher up in the atmosphere, are much cooler than the air temperature closer to the surface, and so there is a cooling effect. The heavier the precipitation, the more air parcels get carried down, and so the cooling effect is even greater. This can see rain turning to snow as the temperature profile from cloud to surface cools sufficiently enough to support snow), and so we should be wary of this. Secondly, I have also seen some suggestions that the Euro4 tends to underplay snowfall potential. I personally can find no scientific evidence of this, but something perhaps to consider.

 

The 0z ECMWF paints a halfway house between the two, and tends to follow the track of the updated Met Office yellow warnings - I would suggest that represents the best guess that I could make in terms of a potentially affected area at this juncture. That is not to say it will be the correct track, but based upon model consensus that is the best estimate.

 

We can do some quick checking on this right now. Euro4 projection for 9am:

 

 

Radar imagery from 9am:

 

 

Observations - The intensity projection of the precipitation is pretty accurate. The system itself looks a tad further North, but that may be down to the fact that it is simply more expansive than projected, covering a larger area from North to South. It has advanced further Eastwards more quickly than projected too so far, though may slow down a little later. 

 

So it looks to me as though in terms of track, the halfway house solution of the ECMWF may be the closest to the truth.

 

From here on in we can monitor the models as much as we like, but the more useful time will be spent looking at obs and radars.

 

Good luck to all.

 

SK

[Frosty.]

This really is classic stuff today with rain spreading from the southwest and bumping into the colder air which then turns the rain to sleet and then wet snow, some central areas could see 15-20 cm which is a good 6 to 8 inches, and the good news is it will then freeze and no thaw is expected for certainly the reliable timeframe. I can see there being some impressive overnight minima once things settle down. Looking further ahead, the met office are bullish about the Atlantic returning during the second half of next week but things could become very interesting with battle ground scenarios, undercuts and general disruption and certainly not a return to run of the mill, mild Atlantic mush. I think January could deliver the wintry goods this time around. :-)

[Downpour]

Morning All

IDO - todays cold & snow highlights the point that using means past 10 days is about as useful as a chocolate teapot-

Rewinding 10 days I seem to recall you presenting pretty much the same post as today - highlighting no real poential in the charts, infact apart from the images its almost a copy & paste. I think many said you would overlook a cold spell with snow & today is a clear example of why living in days 10-16 bears minimal relevence to reality -

It would surprise many that the GFS 00z op is probably the best run for snow since March 2013, when you look at the run quickly it may not appear that great but in FI ( which is of course unreliable ) its snow event after snow event for the UK.

It is infact close to a cobra run- sadly all the action is past 168 though.

Theres is a distinct model diversity today around 144 with the unusal pairing of the GFS & UKMO presenting an undercutting scenario, where as the ECM is flatter ( like IDO indicates above ).

Its all about fine margins of energy distribution & whether that gets under the block

If it does its a snowfest , if not ECM is very quick to reamplify......

S

It is late December so a brief period of snow as a low slides through for the lucky few can never be ruled out. Nothing out of the ordinary for an average late December. The following cold high is also seasonal but just normal at this time of year. Of course compared to last year...but that was a one off and to keep comparing to that would be like comparing each winter to 1963.

 

ECM mean at D10 reflective of the op!  EDH1-240.gif

 

Mostly when that happens there is good certainty. The GFS op in FI has little support for its cold outlook (coldest member most of FI):

 

graphe6_1000_306_141___Londres (5).gif

 

So the most likely scenario is a flatter pattern after D7, and with a strong jet any undercut looks a low chance.

Compare your posts of today with those 7-10 days ago. You are saying the same things.

[Nick F]

Morning all, looking at the more immediate future - a fairly widespread risk of seeing some snow over the next few days across the UK, some may get a covering - especially higher ground, some quite a good covering across parts of Wales, The Midlands, southern half of northern England in the next 12-24 hrs as we see a low scoot SE across Wales and southern England later today, bumping into cold air in place and also sucking in colder air with lower thicknesses and dew points behind it to bring snow to lower levels across England and Wales this evening/tonight - I have done a snow risk map below based on UKMet, NMM4 and GFS snow predictions.

 

 

Snow showers for Scotland and NW England too later today and through Saturday before easing in the evening

 

Once the low clears, risk of some wintry showers for eastern England tomorrow, turning increasingly to snow I should think, by Saturday night, these sleet and snow showers perhaps keeping going across Kent and Sussex on Sunday morning before easing. Otherwise, Sunday's looking fairly dry.

 

Looking further ahead, high pressure rules right through to New Year's Day, then the big three hint at the high getting pushed away to the E/SE with pressure falling from the NW by Friday, but some uncertainty over the flow beyond that. 00z GFS op wanted to have block over Baltic and eastern Europe with the Atlantic shortwave troughs disrupting into Europe, whilst ECMWF and GFS para seem keen to have a more zonal progressive flow from the far North Atlantic in across Nern UK and on into Scandi with the high supressed into central Europe. Though potential even from this more progressive regime of some cold zonality- particularly in the north.

 

Despite the flatter ECM, it and GFS op in the end of the 'medium' range t+216-240 has a strong ridge building north across Alaska toward the North Pole (below), so a signal of waves from the trop starting up a renewed atttack on the PV as we head into early Jan?

 

 

... also note above the trough disruption into Europe on GFS and flatter ECM.

Edited December 26, 2014 by Nick F

[mushymanrob]

When I mentioned snow the other day I got a load of abuse for ramping, misleading and confusing and yet here we are, some areas are in for heavy snow followed by sharp frosts and freezing fog for the next five days at least. High pressure and cold surface conditions with minima well below freezing.

 

no karl, you got pulled up for over estimating it... 'a week of cold guaranteed' and 'blizzards' , you never post charts to highlight the areas that might get cold/snow, even here youre saying 'some areas'... well where?... that IS misleading and confusing for those with little knowlege but view these pages for info.

even this post is overstating what we are likely to get.... the bbc / news have daily maxs above freezing, no mention of fog, and little in the way of 'heavy snow' for 95% of the country.

todays shortwave will produce some snow, but its mostly rain for the south of the uk, its largely sleet or wet snow thats unlikely to settle but produce a slush-fest for the % where it will snow. very few places will get much in the way of lying snow (higher ground most favoured), although clearing skies after late rain/sleet / snow could well freeze whatevers on the ground. but a winter wonderland is imho highly unlikely. im in line for a dumping, tomorrow morning im expecting a crispy frozen slight covering at best.

wintry showers are expected tomorrow and sunday, but with daytime max's comfortably above zero anthing lying will slowly melt.

by tuesday much higher uppers are expected to cross the uk, with the southeast hanging on to the cold frosty conditions longest. now these uppers wont lift the temps much, and is likely to ride over the embedded cold air - inversion, and that means dull, raw, overcast, dry days . but it would prevent overnight fog and frost.

so we have 3 colder wintry days before things return to more average (which is cold). theres nothing  particualy mild unless those warmer uppers dont invert... weds-fri might turn out milder especially in the northwest, the southeast hangs on to the coldest weather longest.