General Model Output Discussion

[sandstorm2]

http://www.meteociel.fr/modeles/ukmo2.php?carte=1594&ech=6

Cheers

iceberg, in your post you seem to think there is a Scandi high building at 144, think tou must be looking at the wrong chart.

SS2

[cooling climate]

Just been looking at the GFS dew point charts and if the GFS model is correct then once they

go negative in the early hours tomorrow they will stay that way (-8 at times in some areas of England

and Wales) till post t180.

IF the model is correct then any precipitation is more than likely (very likely) to fall as snow.

[Tim Bland]

Just been looking at the GFS dew point charts and if the GFS model is correct then once they

go negative in the early hours tomorrow they will stay that way (-8 at times in some areas of England

and Wales) till post t180.

IF the model is correct then any precipitation is more than likely (very likely) to fall as snow.

Looking at the current radar there seems to be more precip around than forecast. Do experts on here think that as the dew temps drop that there will be back edge snow? Do we need under cutting for this to occour?

[patrickshere]

I'm not sure what all the excitement concerning snow is about with this run, there's very little snow around for most the country in the reliable time frame. Any sign of snow gets pushed back further and further as the runs progress. Originally the snow was forecasted to begin ~tonight (it's currently raining here). It'd be very cold, frosty, low mins and maxes but not much snowfall away from the coasts. I keep hearing comparisons with 62/63 in posts etc, but there's nothing on the charts to suggest something like that at the moment. Just a long period of very cold, largely dry weather. The only places that are likely to see significant snow are the usual suspects (East Anglia, far SE, NE and Scotland.)

[Frosty.]

The ukmo 12z is relatively disappointing regarding the longevity of the cold spell, as others have mentioned and puts a major doubt over the cold weather lasting until christmas (in the south at least) but a good gfs 12z which prolongs the cold until at least boxing day and even longer in scotland. Now it's over to the ecm

[Bristawl Si]

I'm not sure what all the excitement concerning snow is about with this run, there's very little snow around for most the country in the reliable time frame. Any sign of snow gets pushed back further and further as the runs progress. Originally the snow was forecasted to begin ~tonight (it's currently raining here). It'd be very cold, frosty, low mins and maxes but not much snowfall away from the coasts. I keep hearing comparisons with 62/63 in posts etc, but there's nothing on the charts to suggest something like that at the moment. Just a long period of very cold, largely dry weather. The only places that are likely to see significant snow are the usual suspects (East Anglia, far SE, NE and Scotland.)

Totally agree with this post.

A few days ago the models were predicting much better snow, cold prospects for whole swathes of the UK (granted the best scenarios were North and East), but the bitter cold will not reach west based on these runs. And snow prospects here look v.marginal indeed.

Some people werre comparing to Dec 81 - not a chance, nowhere near.

I think there has been a gradual downgrade for quite a few runs now (bar the 18z last night). Even tomorrow's predicted snow for the east is nowhere near as severe as predicted yesterday. Yes, temps are cold, but not that cold IMO.

[The PIT]

Just been looking at the GFS dew point charts and if the GFS model is correct then once they

go negative in the early hours tomorrow they will stay that way (-8 at times in some areas of England

and Wales) till post t180.

IF the model is correct then any precipitation is more than likely (very likely) to fall as snow.

If thye're right yes looks good for snow. The snow risk map is very interesting as well. In the GFS 12 oz we also stay well north the jet stream as well.

[aspire27]

I'm not sure what all the excitement concerning snow is about with this run, there's very little snow around for most the country in the reliable time frame. Any sign of snow gets pushed back further and further as the runs progress. Originally the snow was forecasted to begin ~tonight (it's currently raining here). It'd be very cold, frosty, low mins and maxes but not much snowfall away from the coasts. I keep hearing comparisons with 62/63 in posts etc, but there's nothing on the charts to suggest something like that at the moment. Just a long period of very cold, largely dry weather. The only places that are likely to see significant snow are the usual suspects (East Anglia, far SE, NE and Scotland.)

Well put. Im no expert but it seems people have been reading the models the wrong. Looking too much into FI. People here keep saying to watch the model output for the reliable, and everytime its a little disappointing. I was assured by many posters here that this was going to be the best cold spell for years, in FI yes. But never in the reliable.

[Mark Bayley]

GFS ensembles keep the cold going till around the 25th (many of the ensemble members still have the 850hpa around -5c). Most agree on the milder air reaching Derbyshire around the 27th. Seems this breakdown is being pushed slowly further back as they were not showing this a few days ago! There will be chops and changes though. The UKMO isn't great in the long term, however its just showing one of the many possible outcomes. Will be interesting to see what the ECM comes out with

Short term and its not looking bad to my eyes, just keep watching the radar as that's the best you can do in these situations

Edited December 16, 2009 by mark bayley

[grab my graupel]

May I remind everyone that this is the 'Model discussion thread

The team is having to delete/move way too many posts this-evening

There are plenty of threads available for general chat etc. - so there

is no need for all these off topic posts.

Thank you

Brian

[aspire27]

This is the model thread not the, I am going to throught the toys out of the pram thread isn't it.

Look back at the models we normaly view at this time of year compare them to now. Then collect all the toys up put them back and start enjoying models we rarely see at this time of year.

Thats my problem with what the models are throwing out. If we compare them to this time last year the current models are amazing.....but not producing and coming to fruition in the reliable timeframe. I think they are just teasing us..

[Snowyowl9]

This is going to be the coldest SW-ly for many many years

if this happens winds will be from the SW as a surface flow on sunday with snow showers.

http://91.121.93.17/pics/Rtavn1021.png

http://91.121.93.17/pics/Rtavn10217.png

[nick sussex]

Well put. Im no expert but it seems people have been reading the models the wrong. Looking too much into FI. People here keep saying to watch the model output for the reliable, and everytime its a little disappointing. I was assured by many posters here that this was going to be the best cold spell for years, in FI yes. But never in the reliable.

Aspire can you please cheer up a little? everything you've posted today seems to be how everyone's got the models wrong! unfortunately there are no guarantees with modelling, things do change and the current pattern is very complex, perhaps if you could put your location in your avatar then i might be able to give you an idea of your snow chances. It's nearly Xmas so come on try to not look at everything from a glass half empty perspective.

Edited December 16, 2009 by nick sussex

[bluearmy]

GEM T144 is going the same way as GME and UKMO in bringing the less cold air north by T144, if not a bit sooner. slack flow though so if we have snowcover, could still be v cold at surface. the runs that end T144 arent convincing in bringing the shortwave ne and i get the feeling that we're not far from them pushing e into the continent as per some of the ecm runs. the low coming into the north at the weekend is pushing too far west and makes the interaction with the trough to our sw which is no good for us as it drags up the s flow shown by these models. i dont believe the interaction is anything like certain by a long way. we could easily end up with the trough headed straight into france. it isnt sypnotically very far away from what UKMO et all are showing. anyway, ecm due out and given its not shown the s flow for 3 runs, i wouldn't be surprised to see it shown again now.

[nick sussex]

GEM T144 is going the same way as GME and UKMO in bringing the less cold air north by T144, if not a bit sooner. slack flow though so if we have snowcover, could still be v cold at surface. the runs that end T144 arent convincing in bringing the shortwave ne and i get the feeling that we're not far from them pushing e into the continent as per some of the ecm runs. the low coming into the north at the weekend is pushing too far west and makes the interaction with the trough to our sw which is no good for us as it drags up the s flow shown by these models. i dont believe the interaction is anything like certain by a long way. we could easily end up with the trough headed straight into france. it isnt sypnotically very far away from what UKMO et all are showing. anyway, ecm due out and given its not shown the s flow for 3 runs, i wouldn't be surprised to see it shown again now.

I think we're seeing here the complications caused by the Greenie block edging towards Canada, the interaction between the two lows has been a concern i had a few days back but it's just too early to say what will happen, ordinarily you look at a southerly and think game over but we need to take into account the very cold conditions across France if this does happen, i can tell you here in sw France at 1,250 feet above sea level its been below freezing all day and much of the country away from the Cote D'Azur is below freezing. This then effects any flow off France in the outlook period. I think we'll have to wait for the ecm to see whether this follows the ukmo.

[Iceberg]

iceberg, in your post you seem to think there is a Scandi high building at 144, think tou must be looking at the wrong chart.

SS2

No here it is at 1035mb. Forming from a surface high. Debatable what happens next but it is there.

[nick sussex]

The ecm upto 120hrs looks better than the ukmo, we should hopefully see the low to the sw absorb the low heading south thats over Scotland at 144hrs.

[SMU]

significant ECM- I have tracked todays 12z's UKMO GFS & ECM together - 72, 96 & 120-

ECM still keen- just like the GFS to get the shortwave UNDER the block at day 5 with an initial Easterly vector-If this happens its almost odds on that the UK will stay on the Northern side of the PF until xmas eve, with some potentially heavy snow moving up into the South thereafter-

how far does it get North is the question-

Steve

[Cloud 10]

No here it is at 1035mb. Forming from a surface high. Debatable what happens next but it is there.

Easier to see in wetterzentrale format.

[Thundery wintry showers]

I'm not sure what all the excitement concerning snow is about with this run, there's very little snow around for most the country in the reliable time frame. Any sign of snow gets pushed back further and further as the runs progress. Originally the snow was forecasted to begin ~tonight (it's currently raining here). It'd be very cold, frosty, low mins and maxes but not much snowfall away from the coasts. I keep hearing comparisons with 62/63 in posts etc, but there's nothing on the charts to suggest something like that at the moment. Just a long period of very cold, largely dry weather. The only places that are likely to see significant snow are the usual suspects (East Anglia, far SE, NE and Scotland.)

Again when I see posts like this I wonder if I am looking at a different set of charts to some other members. The easterly for tomorrow and early Friday has actually upgraded in the last two days- there were some earlier runs that had limited snow potential away from the extreme SE as the shortwave currently over East Anglia was progged to move too far east. The snow from the easterly behind this shortwave was always forecast to begin at any time between today at the earliest, and Friday at the latest. The reality is late on Thursday, so the middle ground solution is set to come to fruition.

Regarding December 1981, I am one of the members who mentioned parallels with that month. True, some of the milder runs, like the UKMO, have low pressure sinking to the west and pulling up warmer southerlies. But this morning's ECM, and the GFS 18Z/00Z/06Z, all had a very December 1981-esque pattern with an initial northerly bringing widespread snowfalls, and then a low-index pattern with low pressure to the south, intense cold over the UK despite unexceptional 850hPa values, and chances of further snow events from fronts and troughs. Unless the other models start falling into line with the UKMO I will continue to suspect that this could end up like a less extreme version of the December 1981 setup.

I am also yet to see anyone suggest that this upcoming spell was likely to be similar to another 1963 or a February 1991. There were tentative suggestions from the more fanciful GFS runs that the easterly behind the shortwave could manage it but I think few people realistically thought it would be that extreme.

Edited December 16, 2009 by Thundery wintry showers

[Iceberg]

ECM presents another solution. slightly different but still very snowy.

There is very good agreement for sat/sun which might be why it's not being talked about, at least one band of snow moving down the country, frequent showers and lots of snow for Scotland. !

[Cloud 10]

Nothing wrong with discussing events at 120-140 hrs,this is the model discussion thread not the "incredibly short range model discussion thread"

[nick sussex]

Tota;;y agree 24hrs 48hrs not 120 140.

The reason that we are discussing the later output is if you haven't forgotten its Xmas next week, we are relatively sure of the pattern upto the weekend but next week is looking very complicated and many people are hoping for a white Xmas or at least one where theres snow on the ground so this is completely relevant seeing as its called model discussion.

If anyone has any questions regarding the next 48hrs i'm sure they can be answered in here so i don't see the problem.

[D KARLSON]

On the face of it this less cold air on the charts will play into our hands could well produce an awful lot of snow

[Snowyowl9]

What a chart.

Now thats when I`ll get my east wind.

http://91.121.93.17/pics/Recm1681.gif