Model Output Discussion - 23rd Jan - 12z onwards

[Roy]

It's actually 6 hours, 6AM to 12PM 

Will the temperature plummet suddenly once the front clears or slowly over the six hour period?

[karlos1983]

JMA can't be the only data hinting at that scenario at day 8 per IF's tweets albeit many hours ago.

In fairness those Ian F tweets were almost 24 hours ago. A lot can change in 24 hours in the world of weather, even a MetO forecast. We should know that better than most in here!

[nick sussex]

In reply to Mucka of course the shortwave direction is the symptom and not the cause if that makes sense. However I like to pick out features that are bellwethers. Basically the shortwave direction indicates in a nutshell whether the upstream pattern is favourable or unfavourable.

[snowking]

In fairness those Ian F tweets were almost 24 hours ago. A lot can change in 24 hours in the world of weather, even a MetO forecast. We should know that better than most in here!

Indeed and equally Ian also tweeted a response to somebody pointing out the tendency for NWP to return to westerlies towards the day 10-15 period

Conclusion - at this range it's all speculation for now

SK

[blizzard81]

JMA flattens out by day 8. I'm sure Exeter have taken note!

Can't remember if it was right or wrong last time

The JMA was 24hrs behind the game last time and it looks like it is this time as well.

[Snowy L]

I already know I'm going to hate the term "displaced polar vortex" in the next few days.

 

Back to the models, I'm not too excited about day 8+. I think with the vortex having some respite it looks like it will move west back over the North Pole again, so I'm favouring the JMA, perhaps not that quickly though. Though I think it's much more likely we'll have high pressure over us rather than a raging Atlantic like JMA is expecting. After that GFS is going for a much more significant warming with the vortex displaced to Siberia again so we could be on for a repeat in 2-3 weeks.

[Paul_1978]

JMA is cannon fodder, don't see too much mention of it when its showing cold but the three big aren't, not sure why its even being brought up, it usually isn't.

Wrong, it's been said on here numerous times, and by IF himself, that the MetO hold this model in high regard. Cannon fodder it ain't. Edited January 26, 2015 by Paul_1978

[tinybill]

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=6

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=204

 

well to me  its looking good for possible snow any were after Wednesday  -  to at least Feb 5  at the  moment 

 

ps

it you want  to see a  good snow storm  new york  looking  very good at the  moment

http://www.earthcam.com/usa/newyork/timessquare/?cam=tsstreet

[Hammer]

Sure, just suggesting there must have been some solid data to suggest that even if 24 hours ago, so 4th February remains an interesting benchmark imo.

In fairness those Ian F tweets were almost 24 hours ago. A lot can change in 24 hours in the world of weather, even a MetO forecast. We should know that better than most in here!

[ANYWEATHER]

Evening folks! Well the winter rollercoaster is in full swing! Great Winter charts tonight. There is really no point in getting hung up on one set of charts ,because that is what happens with model watching whether looking for hot or cold. Detail will change with each run as regards the upcoming cold spell, But the trend is there for something decent to unfold across the nation as regards wintry weather in the days ahead....    

[Dibdabbers]

Met office are still showing light rain for me, is this what's reflecting in the models at present?

[ANYWEATHER]

Met office are still showing light rain for me, is this what's reflecting in the models at present?

Perhaps, go on the Regional thread, Devil in the detail Im afraid...

[West is Best]

Encouraging 12z runs. Here are a couple of reasons to keep champagne on ice until this goes truly into reliable zone.

 

6z ensembles:

https://forum.netweather.tv/gallery/image/20766-/

 

12z ensembles:

https://forum.netweather.tv/gallery/image/20767-/

 

The point from those being that toppler territory and return to milder conditions from a transient northerly remain possible options, even probable ones. Let's hope the ensembles tighten up on the colder side to firm things up. Otherwise it continues to be a perilous path here.

[The Enforcer]

Dewpointwatch update (number of GFS frames above freezing for South Midlands area between Wednesday 3pm and Sunday 9pm:

 

25/1/6z - 10

25/1/12z - 1

25/1/18z - 2

26/1/00z - 7

26/1/06z - 12

26/1/12z - 9

 

The unfavourable dew points appear to be centering on Friday PM and daylight hours Saturday, so could do with precipitation falling outside those periods.

Of course, my concerns may be unfounded, as the UKMO and ECM have been consistently showing colder conditions than GFS, if only I had access to the dewpoint data from those models too.

[carinthian]

What a great run from the latest ECM. Super old school cold run this one. That high over the UK at day 10 has regression written all over it. I would like to bet a NE/Ely flow over Europe by 17th February to herald the coldest spell of the winter.

C

[SE Blizzards]

Encouraging 12z runs. Here are a couple of reasons to keep champagne on ice until this goes truly into reliable zone.

 

6z ensembles:

 

 

12z ensembles:

 

 

The point from those being that toppler territory and return to milder conditions from a transient northerly remain possible options, even probable ones. Let's hope the ensembles tighten up on the colder side to firm things up. Otherwise it continues to be a perilous path here.

 

Ah, but the most important thing about those ENS is that the Cold signal is in the more reliable 'ish' (High res) time frame, the uncertainty after that is in the unreliable (Low res) time frame. I don't disagree that a toppler is one of the options on the table at present, but something more sustained is most certainly on offer too imo.

[West is Best]

Ah, but the most important thing about those ENS is that the Cold signal is in the more reliable 'ish' (High res) time frame, the uncertainty after that is in the unreliable (Low res) time frame. I don't disagree that a toppler is one of the options on the table at present, but something more sustained is most certainly on offer too imo.

Kind of  but kind of not. My point all along has been that this risks being a 2-3 day wonder. The pressure out west from a powerful, non amplified and non bifurcated jet suggests to me from past experience considerable likelihood that the whole event will be shunted east nearer the time and we may then have a toppler. That's what the ensemble scatter seems at least to consider possible. Hopefully not and this digs in, and we see some proper upstream blocking in evidence.

[Hotspur62]

Another rollercoaster day with the Models. This morning stopped the positive trend of yesterday with Models going for a 5 day coldish spell and then likelihood of coolish Westerly regime. But with this afternoons runs things look more positive for 7-8 day cold spell with a number of snow chances for UK(Not possible to hazard a guess where until T12 as per normal)

Very interesting post by Tamara earlier this afternoon(don't begin to understand all of it but got the gist) and the background signals look promising. Whether this projected current spell materialises or not, the pattern in the NH is changing and although sustained Heights are not in the positions we would like to either NW or NE I think that they soon will be. TBH last weeks coolish spell(which was rightly forecasted by Met office) failed to deliver these heights,this current forecast spell I'm not convinced either as None of the models are showing HLB so I think it may be a case of 3rd time lucky in say 10-12 days time. That is not to say that there will not be snow in the next 7 days as I think there will be and will be more widespread than last week but I don't think it will be "the holy grail" that some are looking for.

 

Not being pessimistic here , i would love what I call a proper UK cold spell but am trying to use head over heart in saying that I don't think the next week will produce the goods(especially for the snow deprived South who have waited 22 months to see 1 flake!!) but the next round of cold is waiting in the wings and this will provide the Heights(along with the other factors that are already in place) which could result in 3rd time lucky. This is my take on it and to be fair to the models it seems to be there's as well in the absence of HLB that they are showing. 

 

Would settle for Boston type snow event here in a couple weeks time lol!!

[Great Plum]

Encouraging 12z runs. Here are a couple of reasons to keep champagne on ice until this goes truly into reliable zone.

 

6z ensembles:

 

12z ensembles:

 

The point from those being that toppler territory and return to milder conditions from a transient northerly remain possible options, even probable ones. Let's hope the ensembles tighten up on the colder side to firm things up. Otherwise it continues to be a perilous path here.

Richard,

I do wonder what relevance these ensembles have now as they are based on the old GFS - is it like comparing the GFS op with the NAVGEM ensembles?

Does anyone know if the control is new GFS or old?

[nick sussex]

Looking at the ECM ensemble mean and spreads the 12hrs run is an improvement on the 00hrs. The spread cluster to the nw however is still in relation to low pressure, the 850 spread does show some colder air advecting into the UK from the east.

 

Looking at the mean theres still likely a large split in solutions with some toppling the ridge more quickly, the control run supports the operational run, by day ten two more distinct clusters appear on the short De Bilt ensembles, one cluster likely flattening the ridge quickly and hence less cold, the other holding the high further north.

[bluearmy]

Richard,

I do wonder what relevance these ensembles have now as they are based on the old GFS - is it like comparing the GFS op with the NAVGEM ensembles?

Does anyone know if the control is new GFS or old?

The control run is part of the gefs suite. It will be running on the same model structure as the old gfs op but at a lower resolution. (Vertical and horizontal).

I'm not sure I totally buy into the apples and pears argument. The gefs is still the second highest resolution ens suite we get to see in detail. I guess if the gefs control is similar to the gfs op then even more notice should be taken of the joint solution than used to be the case.

[ANYWEATHER]

What a great run from the latest ECM. Super old school cold run this one. That high over the UK at day 10 has regression written all over it. I would like to bet a NE/Ely flow over Europe by 17th February to herald the coldest spell of the winter.

C

I think we all need to learn a lesson , Just be carefull of the every day run from the models . follow the trends and you will be happy...    

[polar vortex]

If the low exiting the eastern USA at T144hrs is more amplified and held further back then yes you'd probably get the ridge further north so your start point in terms of topple would be more favourable.

The amplification in the pattern will determine the way the low behaves. Less amplification = deeper low more eastward 

direction. 

[feno13]

Encouraging 12z runs. Here are a couple of reasons to keep champagne on ice until this goes truly into reliable zone.

 

6z ensembles:

 

 

12z ensembles:

 

 

The point from those being that toppler territory and return to milder conditions from a transient northerly remain possible options, even probable ones. Let's hope the ensembles tighten up on the colder side to firm things up. Otherwise it continues to be a perilous path here.

At what day does the scatter begin ??, as you have chopped the dates of them charts lol.  

[nick sussex]

The amplification in the pattern will determine the way the low behaves. Less amplification = deeper low more eastward 

direction. 

Lol!  I thought that was obvious, after ten years on here I sort of worked that out!