Model Output Discussion 29th December - Into mid-Winter.

[SMU]

UKMO 168-

identical to ECM - an area of snow over the North & NW of england

Plus good wave amplitude in the atlantic-

ECM day 5 PPN flow

S

 

[Methuselah]

1 minute ago, bluearmy said:

Generally a hills thing steve 

the ecm snowcover charts on weatherbell are pretty unclear as they don't really take into account settling and are more snowfall rather than snowcover

Day 7 is a borders event and on,y about an inch

 

From my 'once bitten, twice shy' perspective and my rather jaundiced reading of the models, I fear you might mean the Scottish Borders?

[January Snowstorm]

3 minutes ago, Steve Murr said:

UKMO 168-

identical to ECM - an area of snow over the North & NW of england

Plus good wave amplitude in the atlantic-

ECM day 5 PPN flow

S

 

The azores high is a couple of 100 miles south west of Ireland. Also no Northern blocking. Am I missing something or has this Winter been so poor that even the resemblance of a toppler leads to rejoicing...

[chris55]

ECM day 10 looking looking great on wetter!

No massively cold 850s, but if you look at Dec 2010 850s were never really that cold, a cold continental flow is enough.

ECM 240 

 

 

[SMU]

15 minutes ago, January Snowstorm said:

The azores high is a couple of 100 miles south west of Ireland. Also no Northern blocking. Am I missing something or has this Winter been so poor that even the resemblance of a toppler leads to rejoicing...

Based on UKMO & ECM its not a toppler-

In terms of blocking to the west- its not that great to start with however the low pressure brings enough instability !

I would say its pretty good to be fair in terms of potential just because in the normal toppler scenario the cold is on its way out after 36 hours where as tonight its just getting going-

we do however need to extract the max amplification out of it - any flatter & the snow will be shunted east of the UK

S

Edited January 7, 2017 by Steve Murr

[Frosty.]

37 minutes ago, PersianPaladin said:

The simple fact that such low thicknesses are making their way to the British Isles in the reliable time-frame is good enough news for me. It makes things more interesting from a synoptic point of view, as I'm sure many here have gotten tired of the current dominant regime. Snow or no snow, I shall be pleased to see more energy and vigour from such cold cyclogenesis.

Me too, can't wait for the action packed wintry weather being shown for later next week..it's an exciting prospect...for the first time this winter!.

Edited January 7, 2017 by Frosty.

[The Enforcer]

44 minutes ago, Frosty. said:

 

The one disappointing thing about this ECM run is that it chucks in a mild sector seemingly out of nowhere to produce a rain day right in the middle of the cold spell . As this is at T+168 hopefully there is plenty of time for it to disappear before Saturday becomes T+0.

[Frosty.]

1 minute ago, The Enforcer said:

The one disappointing thing about this ECM run is that it chucks in a mild sector seemingly out of nowhere to produce a rain day right in the middle of the cold spell . As this is at T+168 hopefully there is plenty of time for it to disappear before Saturday becomes T+0.

It's the general trend I'm liking, the mood was very low as recently as yesterday morning but I think it's fair to say things have improved from a cold and snow perspective in a short space of time..for the first time this winter, there is a really good shot at seeing snow, even in the south / southeast late next week and potentially into week 2.

[The Enforcer]

1 hour ago, knocker said:

Fair enough the low does form east of Newfoundland and run around the HP and phases with the low near Iceland as it develops near the UK but I think we are at slightly cross purposes. I wasn't really concerned about the warm sector but the potential snowfall on the leading edge of the front. if the low was sliding SE the warm sector could well miss northern areas. Anyway has this all been lost in more recent salivation's.?

Mild sector even popping up on the latest ECM. You're right - in contrast, I welcome potential snowfall and am looking for these mild sectors to disappear from future runs.

Edited January 7, 2017 by The Enforcer

[radiohead]

4 minutes ago, The Enforcer said:

The one disappointing thing about this ECM run is that it chucks in a mild sector seemingly out of nowhere to produce a rain day right in the middle of the cold spell . As this is at T+168 hopefully there is plenty of time for it to disappear before Saturday becomes T+0.

GFS also has a low and the associated milder air giving rain to the south at the same time-frame.

Could produce quite a bit of snow for hills and Northern parts though. That's if it even appears on the next run!

[damianslaw]

As I said, in unstable NW airstreams, expect sudden developments, secondary low features, troughs, shortwaves, even polar lows - especially when the signal is for sustained amplification, so its perhaps not surprising to see the models showing secondary low/shortwave features embedded in the cold polar flow - a sign there are supporting sustained amplification, and not a quick toppler event. 

Many are speculating on depth of cold, snowfall potential, as ever predicting temps and precipitation is always a nowcasting event. One thing the models cannot pick out is the degree of evaporative cooling, at this time of year in deep rooted polar outbreaks, you don't need very cold uppers to pull down temps conducive to snow, get a bit precipitation and its cooling effect on the air temps does the job on its own. Dewpoints become important. I've seen many a deep snowfall with uppers around 0--2 degrees only, and thicknesses above 528 dam, in such set ups. Spring snowfalls often come courtesy of evaporative cooling, despite the powering effect of the sun.

Word on ECM it must be seeing something to keep showing an easterly outbreak, I'll be surprised if this verified, but as I said in my last post, the battle between the PV and the pacific low coming up against a mighty north russian/east asian high will be decider I feel on whether we see the ridge building over the top of the sinking european trough or not. 

[Ali1977]

Looking forward to the updates.

[The Enforcer]

15 minutes ago, radiohead said:

GFS also has a low and the associated milder air giving rain to the south at the same time-frame.

Could produce quite a bit of snow for hills and Northern parts though. That's if it even appears on the next run!

One would expect such a small detail to be different between them at that range.

Mind, for 00z on Sunday 15th, GFS is a mild outlier on the ensembles and my guess would be that ECM is also a mild outlier at that point.

Edited January 7, 2017 by The Enforcer
Checked 12z GFS ensembles.

[Man With Beard]

On the ECM, a mixed bag with regards to the snow.

Thursday/Friday precip band not so heavy this time so unsure if anything white from this (maybe on high ground) - showers for N/W coasts probably of snow

Saturday - a mix of rain and snow as it sinks south, probably less likely to be snow the further S and E one is (why do these cold fronts always move down in marginal air??!)

  

But if the bingo easterly comes off, first snow since 2010 for N Kent (well that's what one poster said earlier!)

I suspect there'll be a lot of short range precip models posted on here by Wednesday night and lamppost watching on Thursday and Friday!

[Methuselah]

5 minutes ago, damianslaw said:

As I said, in unstable NW airstreams, expect sudden developments, secondary low features, troughs, shortwaves, even polar lows - especially when the signal is for sustained amplification, so its perhaps not surprising to see the models showing secondary low/shortwave features embedded in the cold polar flow - a sign there are supporting sustained amplification, and not a quick toppler event. 

Many are speculating on depth of cold, snowfall potential, as ever predicting temps and precipitation is always a nowcasting event. One thing the models cannot pick out is the degree of evaporative cooling, at this time of year in deep rooted polar outbreaks, you don't need very cold uppers to pull down temps conducive to snow, get a bit precipitation and its cooling effect on the air temps does the job on its own. Dewpoints become important. I've seen many a deep snowfall with uppers around 0--2 degrees only, and thicknesses above 528 dam, in such set ups. Spring snowfalls often come courtesy of evaporative cooling, despite the powering effect of the sun.

Word on ECM it must be seeing something to keep showing an easterly outbreak, I'll be surprised if this verified, but as I said in my last post, the battle between the PV and the pacific low coming up against a mighty north russian/east asian high will be decider I feel on whether we see the ridge building over the top of the sinking european trough or not. 

Indeed, being an old codger, I can recall a few NW'erlies like what you suggest, DL...In December 1967, we had an outbreak in which the air originated from Greenland, the result was snowfall just about everywhere with night-time minima around -8C. A very similar flow occurred at the back-end of November 1973, though, on that occasion the NW-SE'ward moving LP had more of a warm sector, ergo much of the snow turned to rain, though it all froze over again later.

My guess? The upcoming cold snap/spell will be marginal in many areas, and until details firm up, and the model-predictions start to converge, we are all still seeking answers...I just hope we all see some of the white-stuff, is all!

[feb1991blizzard]

ECM op not supported by ens mean unfortunately.

[SMU]

Best EPS mean of the season @ 192 for ridge development - obviously the 120-192 mean is great as well-

[Ali1977]

Just now, feb1991blizzard said:

ECM op not supported by ens mean unfortunately.

There's a shock - guess you mean the Easterly later on?

[shotski]

2 minutes ago, feb1991blizzard said:

ECM op not supported by ens mean unfortunately.

Have you got the supporting chart please, Thanks. 

[ANYWEATHER]

3 minutes ago, Ed Stone said:

Indeed, being an old codger, I can recall a few NW'erlies like what you suggest, DL...In December 1967, we had an outbreak in which the air originated from Greenland, the result was snowfall just about everywhere with night-time minima around -8C. A very similar flow occurred at the back-end of November 1973, though, on that occasion the NW-SE'ward moving LP had more of a warm sector, ergo much of the snow turned to rain, though it all froze over again later.

My guess? The upcoming cold snap/spell will be marginal in many areas, and until details firm up, and the model-predictions start to converge, we are all still seeking answers...I just hope we all see some of the white-stuff, is all!

It happened again in late 2000

[Summer Sun]

No great surprise to see the ens not supporting the Op's easterly

 

[Captain Shortwave]

2 minutes ago, feb1991blizzard said:

ECM op not supported by ens mean unfortunately.

It's not that bad

      

Of course by day 10 a lot of westerly solutions will flatten out the mean but low heights towards Italy and higher heights building north east through the UK towards Scandinavia isn't too bad. So the ECM and ens continue to suggest that the Atlantic ridge will collapse towards the UK, can it get far enough north for an easterly? Not sure but the evolution is there and is possible, so a cold north westerly or northerly followed by a possible continental flow or anticyclonic conditions, both will probably be cold, of course the former is the snowy solution.

[northwestsnow]

Ecm mean out to sunday is cold.

That will do for me.

Shout out to the NI CREW, your laughing, esp those with a bit of altitude..

Edited January 7, 2017 by northwestsnow

[feb1991blizzard]

4 minutes ago, shotski said:

Have you got the supporting chart please, Thanks. 

compare that to the stonking Easterly on the op.

[shotski]

Just now, feb1991blizzard said:

compare that to the stonking Easterly on the op.

Mmmmm, it all looks pretty low resolution to me so I probably wouldn't bother.