Model Output Discussion - Sunday 20:35--->

[snowmadchrisuk]

Newbie question: Are we finally seeing these cold models entering the reliable timeframe and becoming more and more consistant?

Thanks.

High pressure building over the Uk is Certain and by Friday should cover the whole country , The fact that it will cool down is also nailed on . Cold and Snow isn't nailed on and won't be till a couple of days before. The high could go North enough to allow real real cold and heavy snow or it could stay put over us which at this time of year would cause alot of Fog and Frost which would also see temps struggle.

[Matt12345]

High pressure building over the Uk is Certain and by Friday should cover the whole country , The fact that it will cool down is also nailed on . Cold and Snow isn't nailed on and won't be till a couple of days before. The high could go North enough to allow real real cold and heavy snow or it could stay put over us which at this time of year would cause alot of Fog and Frost which would also see temps struggle.

Thanks for the reply.

[glasgow-guy]

High pressure building over the Uk is Certain and by Friday should cover the whole country , The fact that it will cool down is also nailed on . Cold and Snow isn't nailed on and won't be till a couple of days before. The high could go North enough to allow real real cold and heavy snow or it could stay put over us which at this time of year would cause alot of Fog and Frost which would also see temps struggle.

either way it will still be nice to get rid of the Atlantic for a while whatever set up comes through of course snow would be a early bonus but if not

there will still be plenty of time for models to fall into place for what we really want so thumbs up all around its going in the right direction.

[Pennine Ten Foot Drifts]

We are getting quite close to crunch time - probably not today, maybe tomorrow, but no later than Wednesday, we will be left with pinning down the detail or a huge model output hangover with another failed cold spell.

I'm not sure we're that close just yet Stu, (at least with regards to serious cold and/or snow), I would suggest that we will only have a really good idea in which direction this high is going to move towards the back end of this week, so I would put later Wednesday model runs and more firmly Thursday's output as being when we can really start to be confident about any evolution.

[SMU]

either way it will still be nice to get rid of the Atlantic for a while whatever set up comes through of course snow would be a early bonus but if not

there will still be plenty of time for models to fall into place for what we really want so thumbs up all around its going in the right direction.

http://91.121.94.83/modeles/gfs/run/gfsnh-0-138.png?6

hope for this-

NO SHORTWAVE--- I was thinking after my post regarding most recent let downs- if all else fails hope fo NO shortwave at all- at least then you know theres no jet cutting across iceland generating lift-

An absolute picture perfect GFS 06z run, but lets not put our eggs in one model basket- we must get to a reliable timeframe with no shortwave in the cruch area around iceland / eastern greenland

Even though the 06z has a weaker pressure area to the north- its what I call the sausage special- a sausage shape area of higher pressure running from NW scotland out to greenland-

It causes enough trough disruption in the atlabtic to get the track of the shortwaves towards france, at the same time allowing the cold air from the NE-

See Feb 79 for the sausage special......

its a bit like this from the parallel-

http://91.121.94.83/modeles/gfsp/run/gfs-0-204.png?6

S

Edited December 7, 2009 by Steve Murr

[Guest North Sea Snow Convection]

The main atlantic trough continues to fill and retrogress through the t120 to t144 period. That factor, in my mind, makes the hang over shortwave that the ECM suggests rather more questionable than it might otherwise be - as it is an 'energy reduction' process period in that part of the NE atlantic.

I think that the ECM has overreacted at t144 to t168 - however that is not to say that the high will still get far north enough with the right trigger to the NE to advect the coldest air to us. That trigger period is still too far away to have enough confidence in.

Either the ECM will bactrack this evening, at least to some degree, or the 12z GFS and UKMO will compromise - again, at least to some degree. I can't see the stand-off going beyond today - but as ever time will tell.

[TEITS]

Personally I am backing the ECM as I've seen this kind of thing happen all too often- February 2005, January 2006 for instance. A cold easterly or north-easterly is IMHO about 30% likely.

Im not sure I agree because using past examples means nothing to me as every synoptic pattern should be judged on its own merits. What happened in Feb 05, Jan 06 has no bearing on what may happen as each synoptic pattern is like a snowflake i.e never identical.

Also without wanting to blow my own trumpet I said 10days ago there was potential for an E,ly and yet many said they couldn't see an end to the unsettled weather. Im not sure if it was you who said this or Nick F?

Lets just wait and see what the 12Zs have in store and not base our predictions on past disappointmens.

[kold weather]

The ECM 0z is just aboutthe worst case from what we can expect so knowing the UK's weather, thats what we will get!

We'd end up with a few days of cold followed by anticyclonic gloom and the average temps that tends to give, whilst somewhere far to our east will eventually get the rewards...saying that the evolution wouldn't be bad IF the high could stay a little further east over the UK instead.

[glasgow-guy]

The ECM 0z is just aboutthe worst case from what we can expect so knowing the UK's weather, thats what we will get!

We'd end up with a few days of cold followed by anticyclonic gloom and the average temps that tends to give, whilst somewhere far to our east will eventually get the rewards...saying that the evolution wouldn't be bad IF the high could stay a little further east over the UK instead.

stay positive

[Anti-Mild]

Im not sure I agree because using past examples means nothing to me as every synoptic pattern should be judged on its own merits. What happened in Feb 05, Jan 06 has no bearing on what may happen as each synoptic pattern is like a snowflake i.e never identical.

Also without wanting to blow my own trumpet I said 10days ago there was potential for an E,ly and yet many said they couldn't see an end to the unsettled weather. Im not sure if it was you who said this or Nick F?

Lets just wait and see what the 12Zs have in store and not base our predictions on past disappointmens.

Just seen the 6z ensembles and the operational run, whilst not an outlier, is definitely towards the colder side of the runs. However, the resolution of the op is greater so I always place more faith in that anyway

I'm trying so hard to keep my feet on the ground but it's very difficult given the 6z run. It's only a multitude of previous disappointments that is keeping me from going ramp-crazy!!

[Thundery wintry showers]

I'm tending more towards a 50-50 probability having seen the UKMO, which at T+120 and T+144 follows an almost identical evolution to yesterday's UKMO, and by implication, the 06Z GFS.

[kold weather]

Just seen the extended 0z ECM ensembles and they show that the 0z op run was pretty much at the top of the warm end of the scale:

http://www.knmi.nl/exp/pluim/vijftiendaagse/Data/15DAAGSE_06260_NWT.png

This doesn't mean that the rest atre suggesting a cold easterly per say but it does mean that the chances of the high getting as far west as the ECM has progged looked rather unlikely, which is a good thing because a cold high will still be better then anticyclonic gloom!

As for the 06z run, its a very good run but looks very shaky trying to transfer us to the colder easterly flow, that could quite easily bust IMO.

[Iceberg]

I said earlier that I felt the ECM handling of SW's between 120 and 168Z where incorrect as well as the general direction of the retrogression.

The further towards the arctic that a SW forms during this timeframe the less likely it is to form at all, obs are very poor for general initialisation purposes added in the abruptly changing surface conditions anyway. I also think this is one of the areas where the higher res of ECM and more atmospheric layers probably doesn't help.

I fully expect the 12Z ECM to play ball.

Also alot more ENS support from GFS on the 06Z, which is my biggest concern. Mean temps have fallen by 3C or so at 850.

The PV positioning is IMO nailed by the models at 144Z what is not is the movement of the PV cells after formation, up until now there has been considerable fluidity in N. Hemisphere patterns, but as GP has been saying this is probably due to carm down and fixate, (probably IMO until the full onset of the next pacific wave around the 20th of December.).

[Paul]

Just seen the 6z ensembles and the operational run, whilst not an outlier, is definitely towards the colder side of the runs. However, the resolution of the op is greater so I always place more faith in that anyway

That's not strictly true - the GFS operational is 0.5 degrees to 180 hours then 2.5 degrees after that, whereas the GEFS ensembles are 1 degree throughout, so are higher res than the operational after 180 hours, as marked on here:

There's a real mix of runs within the ensembles this morning with a huge range of possibilities in there...

http://www.netweather.tv/index.cgi?action=ensviewer;type=panel;

[Shunter]

is it just me or does somebody seem to be smiling on us !!!

http://www.wzkarten.de/pics/Rtavn2281.png

[Paul]

Quick reminder folks - this is the model discussion thread, not the met forecast/i hope it's cold/will it snow in [enter place name here] thread...

Off topic posts are being removed regularly, which is waste of your time if you're making them and the team's time too - so please ensure your post is being made into the relevant thread before hitting submit!

[Altostratus]

Im not sure I agree because using past examples means nothing to me as every synoptic pattern should be judged on its own merits. What happened in Feb 05, Jan 06 has no bearing on what may happen as each synoptic pattern is like a snowflake i.e never identical.

Also without wanting to blow my own trumpet I said 10days ago there was potential for an E,ly and yet many said they couldn't see an end to the unsettled weather. Im not sure if it was you who said this or Nick F?

Lets just wait and see what the 12Zs have in store and not base our predictions on past disappointmens.

TEITS, I fully understand your point but I’m sure TWS was referring to the fact that short waves are difficult to model due to them being such small features – hence why they are often under-modeled in the latter stages of the run and only get correctly modeled in the nearer time frame; examples being Jan 2006 etc. This is a well known modeling issue - nothing to do with synoptic patterns and uniqueness.

The really unfortunate thing for us is that these seemingly insignificant short waves running through Iceland have a significant impact on the fate of potential cold spells. This has caused many disappoints over the years and it surprises me that so many are getting excited already. My advice is to ignore anything beyond T+120 and focus on events within T+96. It is right to be cautious - we have been here too many times before. Every evolution being shown is possible, but as usual, the devil is in the detail.

[Paul]

Quick reminder folks - this is the model discussion thread, not the met forecast/i hope it's cold/will it snow in [enter place name here] thread...

Off topic posts are being removed regularly, which is waste of your time if you're making them and the team's time too - so please ensure your post is being made into the relevant thread before hitting submit!

Hello, anyone listening!!!!!!!!!!!!!!!!

3 posts removed for being off topic, since the above was posted.

[Eugene]

Excellent GFS 06Z ensemble mean here, consensus is on HP to our northeast with the cold pool tantalisingly close

http://www.wetterzentrale.de/pics/Rz500m7.gif

http://www.wetterzentrale.de/pics/Rz500m8.gif

http://www.wetterzentrale.de/pics/Rz500m10.gif

http://www.wetterzentrale.de/pics/Rz500m9.gif

[TEITS]

TEITS, I fully understand your point but I’m sure TWS was referring to the fact that short waves are difficult to model due to them being such small features – hence why they are often under-modeled in the latter stages of the run and only get correctly modeled in the nearer time frame; examples being Jan 2006 etc. This is a well known modeling issue - nothing to do with synoptic patterns and uniqueness.

I certainly understand that which is why even im remaining cautious. However in saying that I always believe that there is a possibility that some of these awesome charts will come off. If I had the attitude that all cold spells will go pearshaped based on past disappointments then I would choose a different hobby and stick with the countryfile forecast.

The big difference for me compared to previous disappointments is the UKMO. This model has really been a pain in the backside in the past but thankfully the UKMO is very similiar to the GFS. If it was the UKMO/ECM Vs GFS then I would side with the UKMO/ECM but at the moment im thinking the ECM is wrong. Hopefully tonight we shall get some consistency between all 3 models at +144.

[Snow Queen one]

I hope you are right TEITS But isn't it a fact that the ECM tends to pick up on trends before the other models? What if we see the GFS and UKMO start backing the ECM? Is it possible?

Maybe someone who knows the charts better than me can ans with an idea of how possible it is for the other two to go the way of the ECM?

Thanks

[NorthNorfolkWeather]

The really unfortunate thing for us is that these seemingly insignificant short waves running through Iceland have a significant impact on the fate of potential cold spells. This has caused many disappoints over the years and it surprises me that so many are getting excited already. My advice is to ignore anything beyond T+120 and focus on events within T+96. It is right to be cautious - we have been here too many times before. Every evolution being shown is possible, but as usual, the devil is in the detail.

Before I say something about the models, can someone point me to some info on 'Short Waves'?

Looking at the panel maps put up earlier, there are a few cold ensemble members in there, but there are also quite a lot that are pretty average. From that run of ensembles, I'd say that it's only 30-40% chance of really cold weather getting further than the south east within a reliable timeframe

[Altostratus]

I certainly understand that which is why even im remaining cautious. However in saying that I always believe that there is a possibility that some of these awesome charts will come off. If I had the attitude that all cold spells will go pearshaped based on past disappointments then I would choose a different hobby and stick with the countryfile forecast.

The big difference for me compared to previous disappointments is the UKMO. This model has really been a pain in the backside in the past but thankfully the UKMO is very similiar to the GFS. If it was the UKMO/ECM Vs GFS then I would side with the UKMO/ECM but at the moment im thinking the ECM is wrong. Hopefully tonight we shall get some consistency between all 3 models at +144.

I agree with you - there is always a possibility - who's to say these charts won't come to fruition. There is certainly nothing wrong with being optimistic. I had a look at the UKMO. I remain unconvinced atm. There is evidence of a shortwave around Iceland and a potential sinker could have been displayed had there been a T+168 chart. The ECM is also a major concern. A few more days and hopefully we'll be in a better position to tell.

[TEITS]

I hope you are right TEITS But isn't it a fact that the ECM tends to pick up on trends before the other models? What if we see the GFS and UKMO start backing the ECM? Is it possible?

Thanks

Still remains possible that the GFS/UKMO could trend similiar to the ECM. However looking at the ECM ensembles and the Met O outlook I would say the UKMO is correct at the moment. If the 12Z UKMO/ECM are similiar to the 06Z GFS at +144 the next hurdle will be getting this within +72.

This is why at the moment I shall be happy with frosty, settled weather and if a bitter E/NE,ly does arrive then its a bonus. I just hope it doesn't prevent my family travelling to see me at xmas. I don't fancy sitting on my own with my cat as company at xmas!!

Paul and mods, apologies, but this cannot go without comment

Classic.

Edited December 7, 2009 by THE EYE IN THE SKY

[kold weather]

Another big difference I'm seeing is both the GFS and the UKMO have a strong Arctic high that isn't that far from the main ridging high, whilst the ECM shows no evidence of it at all even at 120hrs, which is a huge difference at such a short range. Given it was also at the top end of the ensembles I think its idea of having the high get out to our west by 192hrs is very wide of the mark...as I said earlier that doesn't mean we will get what the GFS shows, but I think that is a synoptic outlier there.