Model Output Discussion - cold spell to end Autumn

[ukpaul]

4 minutes ago, shaky said:

Steve have you seen the latest hirlam!!looks tasty for london northwards to north wales!!

But then look at the Icon, also for 6z, which shifts things in comparison.

People are setting themselves up for disappointments by discarding charts they don't like. If you are in the snow zone on most models then you will more likely than not get lying snow. If you are in and out then there is a fair chance that you won't. The models, as a whole, tell a clearer picture.

 

[captaincroc]

I love this thread and this isn't a personal dig at anyone but the personalisation of the slider position is starting to become a bit frustrating in here, yes discuss it's projected movement but not just an emotional response. Personally I don't want it to slide any further south as I personally will miss out but I save my frustrations for the regional thread.  I am totally up for the excitement of where it will end up, as for me the positioning has been interesting to say the least, but the "Yey, it's moving south" is getting tiresome...as I'm sure the "Yey, it's moving north" would be the same too if that were the case.  This forum is fantastic for learning and have learned so much since I joined but I think I might have to give the thread a miss for 24 hours just for my own sanity. 

[Mark Bayley]

Marginal for Monday, however those on the northern edge of that low will get an absolute pasting if the 6z comes off! 

Some agreement from the ECM too, although further south

https://weather.us/model-charts/euro/2017120800/england/snow-depth-in/20171211-1800z.html 

 

Edited December 8, 2017 by Mark Bayley

[swfc]

Anyways 6z gfs looks a bit better ridging nne and lower heights to Europe around  the 200hr mark

 

[Singularity]

Making a call on Sunday is going to cause headaches today I'm sure... the question is, to trend or not to trend?

As in, extrapolate the overall multi-model trend southward. 

 

As for Monday, it can be seen on the GFS 06z how crucial it is that the LP to the S develops enough of an independent circulation from the one to the N to draw the cold air in from the east. It helps if the decaying form of Sunday's low positions itself more or less east of the one to the S as well.

 

Should the low turn out to be weaker than this run shows, that'll also be important as there will be less of a wrap-in of the cold air, with the snow line not tucking in so far south behind the low.

The ECM charts on the US site show mostly mixed rain/snow from the 00z version of events, which reflects on just how marginal the event is looking although that is with not quite as much cold.low DP air drawn into the circulation as the GFS 06z goes with. 

[Deep Snow please]

I'm going to post a more direct post in the ramping thread as last time used this forum that was the done thing but politely can we please discuss trajectory not emotional wah wah it's coming away from me; woop woop it's going to hit me responses. This thread is model discussion; and it's better to see that discussion on the infrequent occassion I visit here for information. Information that is not opinion.

[Tamara]

14 minutes ago, TEITS said:

The Low on Monday is becoming concerning!

Beyond all this excitement and the milder, flatter more mobile pattern is gaining momentum in the output as I mentioned a few days ago. I know this contradicts the posts by GP, Tamara but its consistently being shown.

Hi

Several posts since early-mid November have anticipated possible developments and detailed thoroughly in each post both the upside and the downside of the way ahead. My own initial doubts are well documented that weighted a milder trend, but increasingly plenty of evidence posted to show why "usual service" this season may not be so straightforward

Also just yesterday I suggested that too much face value paid to intra day operational and ensemble suites could lead to quick and not necessarily correct reaction in terms of the implications of any milder phase mid month.

It might be worth reading yesterdays post carefully  Its clear, I believe, from there where the boundaries lie, and why there is reason to believe that any milder phase could be a bridge towards a pattern that changes emphasis towards looking across the North Sea

Finally, as stressed fairly recently, my interest is very much driven by enthusiasm and curiosity of how patterns might pan out, not just based on weather preference and ideals. On that basis, creating a skewed basis for fitting evidence around either a cold or mild outcome would be futile, self defeating and a waste of my own spare time putting together some thoughts purely intended to help discussion on the thread

[bluearmy]

The gfs 06z and ec 00z agree on the slider low being Home Counties latitude - the ecm extends the trough towards Holland whereas gfs doesn’t have the extension and turns the system ne through Norfolk into the North Sea 

this will not be the end of the story and I await the 12z faxes to see if the warm front  is still shown ahead of the occlusion. Makes the difference to snow becoming rain or staying as snow 

latest met Office comp forecasts seem to have reacted to this bringing slightly higher temps to the Home Counties around midday than previous 

[Snowman.]

32 minutes ago, TEITS said:

Must of missed some of the posts because last I read was a continuation of what we currently have. Easy to miss posts on this thread.

I believe it was along the lines of a flatter regime up to the holiday season then at the turn of the new year pressure rises to the NE. GEFS is a bit fast with its transition.

Edited December 8, 2017 by SN0WM4N

[TheIceManCometh]

I've a question for those familiar with this kind of low. I've heard a few saying it gets over cooked by GFS and tends to swing South compared to what the models show at this stage.

I'm hosting an event on Monday in Coventry. Disruptive snow on Sunday/Monday would cost a five figure sum (by disruptive read 'closed schools'). Should I be worried or are we confident it'll be a fairly minor event?

This is the first time I've prayed to be out the way of these systems and I feel dirty!

[carinthian]

7 minutes ago, Tamara said:

Hi

Several posts since early-mid November have anticipated possible developments and detailed thoroughly in each post both the upside and the downside of the way ahead. My own initial doubts are well documented that weighted a milder trend, but increasingly plenty of evidence posted to show why "usual service" this season may not be so straightforward

Also just yesterday I suggested that too much face value paid to intra day operational and ensemble suites could lead to quick and not necessarily correct reaction in terms of the implications of any milder phase mid month.

It might be worth reading yesterdays post carefully  Its clear, I believe, from there where the boundaries lie, and why there is reason to believe that any milder phase could be a bridge towards a pattern that changes emphasis towards looking across the North Sea

Finally, as stressed fairly recently, my interest is very much driven by enthusiasm and curiosity of how patterns might pan out, not just based on weather preference and ideals. On that basis, creating a skewed basis for fitting evidence around either a cold or mild outcome would be futile, self defeating and a waste of my own spare time putting together some thoughts purely intended to help discussion on the thread

Well spoken Gal. Love to read your input and thoughts going forward. Your views are a great asset to this forum, even though its way above me !

 C

[swfc]

Mean while 6z builds the pressure across to the east be it"fi"and looks ok if not deep cold.big swings in the nhp look to be coming up hopefully

 

[bluearmy]

MWB will no doubt post the clusters but the eps post day 10 have two clusters - one which is Scandi upper ridge and the other which looks cool zonal. 50/50

the Scandi cluster looks quite settled for us but way too far out to know how far west it could influence 

[Alexis]

ARPEGE 6z now out http://www.meteociel.fr/modeles/arpege.php

Much more representative of the precipitation amounts as the band fragments. The low res GFS precipitation charts never show how the radar image will look on the day.

[carinthian]

1 hour ago, carinthian said:

Certainly not without support . Many milder clusters for Christmas week , about 60/40 in favour of milder westerly flow. However,no prolonged zonality is being shown to break through the Russian High block to allow a deeper penetration of the westerlies. Indeed, its this stubborn block that continues to support the Scandinavian trough. This trough cannot go anywhere in the medium term, so much of Western Europe to be cold for next 7 days or so at least. I have a inkling that this Russian block is not going to retreat/collapse and may even start to flex its might on proceedings as we move towards New Year.

 RE : The above post .OK , its another run and another outcome but shows there is no easy way back to zonality.

C

[Deep Snow please]

Looking beyond; Wednesday looks interesting on the latest run

 

[Paul_1978]

1 hour ago, TEITS said:

The Low on Monday is becoming concerning!

Beyond all this excitement and the milder, flatter more mobile pattern is gaining momentum in the output as I mentioned a few days ago. I know this contradicts the posts by GP, Tamara but its consistently being shown.

Respectfully disagree TEITS . I think everyone expects a less cold spell is on the cards (and still over a week away), and GP and Tamara expect this too. Longer term signals suggest a return to a colder pattern, and of course not forgetting the Met Office output which has been consistently stating a cold theme for the rest of the month "with brief milder periods".

For me, this is exactly what we are seeing in the output so not unexpected, and we could say everything is going to plan.

As regards the GFS 06z, it looks a like it's going to be a cold week! We have a northerly influence all the way out to T+186 (8 days away!) and even after that the Atlantic doesn't really make any inroads. (Appreciate it's one run).

Going back to Sunday's "slider", I think it's interesting how a secondary low pressure centre actually starts moving back up the country again on Monday, with cold air well and truly entrenched. Surely Monday has got just as much, if not more potential than Sunday.

Model watching at its best!

Edited December 8, 2017 by Paul_1978
Typo

[West is Best]

Fax charts really starting to show the more southerly route. The problem here is that with 48 hours to go, if this trend continues it could end up in France

 

Let's keep a sense of humour here. It's ever thus with these boundary snow events and there's no point getting irritated. My sense is that the Fax charts are on the money: maybe another 100 miles further south.

[karlos1983]

Aperge brings the snow threat down to the central southern coast temporarily and generally the snow band is slightly further south.

On London's doorstep

[TEITS]

Thanks for your post Tamara. Your comment "Looking across the N Sea" gets me excited.

Speaking of excitement I will take this run from the NMM

http://modeles.meteociel.fr/modeles/wrfnmm/runs/2017120806/nmm-1-49-0.png?08-11

[TEITS]

2 minutes ago, West is Best said:

Fax charts really starting to show the more southerly route. The problem here is that with 48 hours to go, if this trend continues it could end up in France

 

Tend to agree. Based on experience the trend towards being further S is something I have witnessed many times. My location always seems to miss out on these situations with the snow band being much further S and W.  My early punt is somewhere along the M4 being the N edge.

[Alexis]

6 minutes ago, karlos1983 said:

Aperge brings the snow threat down to the central southern coast temporarily and generally the snow band is slightly further south.

On London's doorstep

Low res for precipiation - have a look at the 0.1 degree output

[pinball wizard]

13 minutes ago, West is Best said:

Fax charts really starting to show the more southerly route. The problem here is that with 48 hours to go, if this trend continues it could end up in France

 

Let's keep a sense of humour here. It's ever thus with these boundary snow events and there's no point getting irritated. My sense is that the Fax charts are on the money: maybe another 100 miles further south.

Are the thicknesses shown there conducive to snow though? Still need more hours before we can make a call for areas in the East and South East. 

[bluearmy]

The latest meto warningd state that there is increasing confidence in the areas likely to be affected on sunday

looking at the map they seem to have taken account of the warm front further east and seem happy with their faxes issued earlier re track. 

I wouldn’t expect much more southward adjustment on Sunday - we have already gone up and down thirty miles over the past 24 hours so settling on a line top of the Severn estuary across to Luton and then up toward Peterborough and the wash - east of that line could be too warm for lying snow. Of course snowfall is likely south of there, especially to begin with but settling is more of an issue away from elevation 

Euro 4 06z should be soon out

[tight isobar]

1 minute ago, bluearmy said:

The latest meto warningd state that there is increasing confidence in the areas likely to be affected on sunday

looking at the map they seem to have taken account of the warm front further east and seem happy with their faxes issued earlier re track. 

I wouldn’t expect much more southward adjustment on Sunday - we have already gone up and down thirty miles over the past 24 hours so settling on a line top of the Severn estuary across to Luton and then up toward Peterborough and the wash - east of that line could be too warm for lying snow. Of course snowfall is likely south of there, especially to begin with but settling is more of an issue away from elevation 

Euro 4 06z should be soon out

Yes..

Models and met getting a grip now.

Even the 'much talked about m4 corridor' (my location!)..

Looks out of the equasion!..main banding of precip in snow form.. likely to be 'well north' of london.

With to much mild sector mixing keeping things wet and cold at the surface.

Midlands to the borders are in for a news making event!!!!