Model Output Discussion

[TEITS]

Personally, the golden rule of not trusting anything much beyond 5 to 6 days in advance seems to be as valid during a cold block as it is during mobile patterns.

Certainly agree and you only have to compare yesterday with today. During some of the model runs yesterday it appeared only E Scotland would see cold ENE,lys due to the SW. Now only 24hrs later the SE is favoured, although worth adding that what we are seeing today is what the GFS Parallel run was showing yesterday.

I will also add that I know some think there is a SE bias on this forum. However the truth is the SE will always be favoured from an E,ly due to its proximity to the continent. The Jan 1987 event might of delivered snow to many regions but nobody was hit as hard as Kent during that spell.

[WhiteFox]

It is true that the general setup is something we haven't seen for years , HOWEVER how many times has a northerly come across the uk in one form or another through the years. Yep nearly every year ! , northerlies unless it was the thundersnow type event are generally boring for us down south. Now a blasting north east/ east with snow is much more rare , if it ends up with more of a northerly event i'll not be pleased and for me that's a downgrade. However if we do end up with a 24+ hr ne blast with snow then a northerly i'll take that.

Still awhile yet to go though

If you're talking about a Northerly toppler, then you are absolutely correct. However, a sustained Northerly flow is not so bad for the south; remember the northerly a few years ago (I think it may have been November; can't remember the year) which brought heavy snow to the South West and other areas? The fact that we have not seen such sustained northerly outbreaks over the past few years has changed expectations. Given an already cold airmass, a sustained norhterly can deliver something quite interesting for the whole country. Topplers tend to follow on from a mild period with a brief rise in pressure to the west which then breaks within 36 hours; an entirely different beast.

[Thundery wintry showers]

True but one could argue if you are a cold lover would you prefer to see those type of charts at this stage or ones where the block collapses quickly ie Jan 1972/Dec 1997 and no chance of sustained cold?

Aye, indeed- and if that northerly regime does arise it could even things up in the snow cover stakes (the same areas that will most likely be cold and dry from these easterlies stand a chance of getting something from a northerly). If it persists, a white Christmas even becomes a distinct possibility.

A Dec 1997 style breakdown would be a nightmare- I remember that in Tyneside we didn't see any sunshine for over a week afterwards. As others have suggested, the toning down of the southern arm of the jet makes that evolution unlikely this side of T+200!

Surprisingly looking back over the latest charts it does seem that the ECMWF output would be the most likely to deliver a widespread snow event via that second easterly outbreak (in contrast to recent days where ECM has tended to go for something less snowy than the other models). The easterly flow may only last 36 hours but it looks a pretty potent beast.

[kold weather]

The thing that should prevent atlantic lows from ruining the show is that big Scxandinavia vortex, it'll simply absorb any low that tries to come in until at least 240hrs and that'll mean it should swing any low safely round its southern side and prevent the milder air from getting to the UK, of course in turn you'll probably see the vortex get dragged away as well. A lot depends on where it sets up.

We don't want it to come down to our west, that would almost certainly eventuqally cause a big SW push...

Anyway models are indeed backing away from the intial easterly, now only the GFS does anything with it, so still some disgareements even at just 60hrs, though the GFS does seem to be falling inline.

The end of the week into next weekend could be very cold if we do see that shallow high sink southwards as suggested by the models.

Edited December 11, 2009 by kold weather

[Guest North Sea Snow Convection]

There is always a SE IMBY bias going on here when a bit of snow is possible, most on here don't live in the SE and there is some interesting weather being shown for everyone in the british isles at some point during the next 7-10 days according to the GFS & ECM.

I thing regarding this subject, my own comments relate to the UK as a whole. TWS post just now about the subtleties of the actual weather that an Omega block of this type can bring can mean quite different conditions from one region to another within the context of an overall cold theme is an illustration of that. Hence why the easterly/north easterly could be ideally positioned slightly further north for countrywide benefit - even if it does look pretty interesting down here atm.

One certainly hopes that the next ten days or more bring something that everyone can enjoy

Edited December 11, 2009 by North Sea Snow Convection

[snowfart]

Could you please tell me how accurate GFS is and

could this :

http://weather.unisys.com/gfsx/7d/gfsx_4panel_7d_eur.html

happen in 7 days o_0?

[Thundery wintry showers]

If you're talking about a Northerly toppler, then you are absolutely correct. However, a sustained Northerly flow is not so bad for the south; remember the northerly a few years ago (I think it may have been November; can't remember the year) which brought heavy snow to the South West and other areas? The fact that we have not seen such sustained northerly outbreaks over the past few years has changed expectations. Given an already cold airmass, a sustained norhterly can deliver something quite interesting for the whole country. Topplers tend to follow on from a mild period with a brief rise in pressure to the west which then breaks within 36 hours; an entirely different beast.

25th November 2005 is the date you're looking for.

In fact, while most snowy Januarys and Februarys tend to have predominantly easterly winds, most of our snowiest Decembers have traditionally resulted from northerly regimes (notably Decembers 1950 and 1981). I agree completely with you- while a 36 hour toppler usually only delivers to north-facing coasts and hills, if we get a northerly that lasts upwards of 2-3 days, we usually see some kind of trough activity or even a polar low, delivering more widespread snowfalls. Also, a succession of northerly outbreaks often results in frontal snow events in between outbreaks. The snowy winters of 1954/55, 1967/68, 1968/69 and 1969/70 were also caused mainly by repeated northerly outbreaks.

It's looking likely that the main source of cold air will be the north rather than east as we head beyond next week (a common "cold regime" pattern- easterlies followed by retrogression of high to NW allowing northerlies in) but it's too far out to be able to be sure of any detail- history teaches that sometimes high pressure ridges over to Britain preventing the northerly flow from taking hold, and in other cases, we end up with our snowiest phase of the cold spell from them. Despite my previous post (which Mr_Data replied to) a 36 hour toppler is not a common evolution from this particular setup.

[pyrotech]

Yep must be a huge wall around England and more so around the South East as if you listen on here the models only show that area.

Funny coz i see this set up effecting the whole UK at different periods.

[Duane S.]

This term 'nailed' has come up several times in the last few days.

Yesterday T36 and T48 was 'nailed' then the ECM took the nail out (but that ECM run was suspect).

The only thing 'nailed' is the fog today.

Its clear that the models cant agree T48/T72.

If we 'nail' things say to T72 or T96 we then just post FI charts (because all the rest is 'nailed') and then get surprised when FI doesn't come of.

That easterly has had more nails in and out of it then a coffin in the last week !

Totally disagree. The 'cold spell' is now 'nailed on' and I won't waver from that belief. You could of course accuse me of being ambiguous when I say 'cold spell' in inverted commas and maybe I am a bit, but - the fact remains that a cold spell IS going to happen in the UK from very early next week. I don't see what could scupper this now.

I didn't say it will be a SUSTAINED cold period (although personally I think it will be, relative to our usual cold snaps), I didn't say it will dump bucketloads of snow on every inch of the UK. Cold though it will be and unless all the models and all the signals are telling us porky pies I simply don't see any way in which this whole thing could implode to the point that we don't get a 'cold spell'. Unless you can tell me one of course...

[Shirelord]

Yep must be a huge wall around England and more so around the South East as if you listen on here the models only show that area.

Funny coz i see this set up effecting the whole UK at different periods.

Well rather than complaining and adding nothing why not step up to the plate and provide your opinion on SE wales?

[MR EXTREMES]

True, true, the northerly that the GFS is progging now looks very potent for many areas however this is still outwith the reliable timeframe so it is still squeeky bum time!

i would not even bother looking that far out lots will change by then.

cold is apon us and will deepen how cold how snowy is not set in stone,

as gp has said great start to winter with maybe things falling futher inplace for january,

ofcoarse milder air will be about but europe is looking good,

look back 2 weeks ago not much going on in europe except mush look now and mid nextweek it will be very cold.

and its true let the cold settle in and let the party begin expect to see the models flap about because thats what there going to do 100% cert on that.

but what will happen will happen.

[TEITS]

Yep must be a huge wall around England and more so around the South East as if you listen on here the models only show that area.

Funny coz i see this set up effecting the whole UK at different periods.

Could indeed affect all of the UK.

However upto +144 and the SE is most favoured. The progged E,ly looks short in duration(36hrs) until the flow returns to the N. So with this in mind the SE would experience the E,lys the longest and furthermore the coldest upper temps. This is due to promixity to the continent plus being exposed to the E,lys the longest.

[Cecil Hogmanay Melchett]

Well the meto update doesn't really agree with GFS!!!

Rain or sleet and perhaps hill snow is not my idea of a freeze,cold it will be according to the pro's,but hardly

freeze up.

I think we are going to get a spell of cold settled weather with wintry showers in the east at times.

GFS this evening will not be showing uppers of -10 i wouldn't have thought.

I awaut the 12z suite with dread

[MR EXTREMES]

ok so what model is the met office following because the outlook has changed alot since yesterday.

perhapes a slow progressive build of cold this could be good.

Edited December 11, 2009 by badboy657

[Frosty.]

I thing regarding this subject, my own comments relate to the UK as a whole. TWS post just now about the subtleties of the actual weather that an Omega block of this type can bring can mean quite different conditions from one region to another within the context of an overall cold theme is an illustration of that. Hence why the easterly/north easterly could be ideally positioned slightly further north for countrywide benefit - even if it does look pretty interesting down here atm.

One certainly hopes that the next ten days or more bring something that everyone can enjoy

Hi Tamara, hope you are well

It just grates a little with the SE bias but I realise that the models are showing the highest risk of snow showers or flurries in the SE quarter of England during the early to middle part of next week, good luck to those areas but we should all have a cold week coming up and some possibly interesting developments to the north which may introduce an Arctic blast later on or at least maintain the generally cold unsettled pattern.

Edited December 11, 2009 by Frosty039

[kold weather]

I'm not sure actually Eye, it all depends on the shortwave again, the ensembles seem pretty keen to take it across the SE of England which would mean we are in the warm sector whilst the easterly winds would orginally hit the east coast in general, its only when that clears southwards that we get our shot. Of course the ECM could be correcxt as it takes the shortwave to our south and allows a very flat easterly to hit the UK, in which case obviously the usual spots are favoured. I can see the east coast doing well, perhaps even better then the SE depending on the exacts.

I'm just happy that I'm still able to talk about this, I had a big fear about the famous downgrade, we've had a change, but its not really a downgrade which is good and there is much stronger agreement.

[pyrotech]

Well rather than complaining and adding nothing why not step up to the plate and provide your opinion on SE wales?

All my posts have been for whole of uk both in here and climate change forum!

Yes initially the South East and eastern UK have the best chance of wintery percipitation if you look at all the models. From mid week onwards this progresses Westwards.

I am a little worried about the Fax charts regarding the 528dam but everything else looks good.

As for snow, where etc it is way to far ahead to predict, but the building blocks are in place which is what we need.

For Wales i expect a dusting of snow at best early in the week, but later on has potential for more signifigant falls, along with just about anywhere in the UK.

Scotland looks to do well if the northerly comes off.

GFS has been very stubborn with this cold spell and its Fi charts have been very good in bringing this in. Not so sure its got the 240+ fi right now thou and think its being over progressive.

Not sure how well the parralel has performed but that looks awesome - anyone got any info on its performance?

Sorry for ranting about se posts but really got annoyed with the me me me kind of posts. Its better for everyone reading the forum if we include everyone in our convrsations

[kold weather]

Well the meto update doesn't really agree with GFS!!!

Rain or sleet and perhaps hill snow is not my idea of a freeze,cold it will be according to the pro's,but hardly

freeze up.

I think we are going to get a spell of cold settled weather with wintry showers in the east at times.

GFS this evening will not be showing uppers of -10 i wouldn't have thought.

I awaut the 12z suite with dread

That is certainly true for the first half of next week, I suspect the GFS will continue to shunt the intial easterly shot southwards to match up with the other big two but I think the second easterly shot looks far stronger on all of the big three, I'd have thought all would be cold enough by 144hrs for snow at low levels.

I think thats probably the MO hedging thier bets.

[MisfitDog3]

Remind me someone, when was that appalling occasion when the cold outlook collapsed across the models with very short notice? I was talking to someone a while ago about this yesterday and couldn't pin down the date! I do remember it traumatised practically everyone at the time and really put the skids under the trust in a couple of models for months afterwards....

BTW I'm not suggesting we are going to see a re-run before anyone starts twitching!

[Methuselah]

Come on all???

So what, if peeps have interests in their-own areas? It seems only natural to me...

Cut each-other some slack, eh??? And, enjoy the rollercoaster! :blush: :blush:

[Neilsouth]

Come on all???

So what, if peeps have interests in their-own areas? It seems only natural to me...

Cut each-other some slack, eh??? And, enjoy the rollercoaster! :blush: :blush:

Well said that man!

I still hope that this cold shot delivers for all , even if i do favour my own area who wouldn't?

[nick sussex]

Come on all???

So what, if peeps have interests in their-own areas? It seems only natural to me...

Cut each-other some slack, eh??? And, enjoy the rollercoaster! :blush: :blush:

Totally agree pete

It's obvious people will be more interested in their own area, at the end of the day people want to see snow falling in their back garden and if they highlight their own area thats still related to the models and so no harm done. The longer the cold spell can last the more likely more people will see some snow but of course the current pattern is more favourable for the east and se, generally if the cold can hang on for a while surprises often pop up elsewhere.

In terms of the ecm ensembles for the Netherlands the ecm operational run well supported until next Thursday this then is one of the colder solutions then becomes one of the mildest solutions for days 8-10.

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

Sill uncertainty upstream as highlighted by NOAA this morning.

THE MEDIUM RANGE PERIOD IS EXPECTED TO FEATURE A MEAN TROUGH OVER

ERN NORTH AMERICA...WITH RISING HEIGHTS ACROSS THE WEST. THE

DEGREE OF AMPLIFICATION REMAINS UNCERTAIN WITH THE 00Z SUITE OF

GUIDANCE.

THE GFS CONTINUES TO BE STRONGEST/DEEPEST WITH THE SYSTEM REACHING

FROM THE MIDWEST TO NORTHEAST AND ERN CANADA DURING DAYS

3-5....WHILE THE ECMWF IS ON THE FAST AND WEAK SIDE OF THE 00Z

GUIDANCE. FOLLOWED A SOLUTION IN BETWEEN THESE EXTREMES WHICH

MAINTAINS CONTINUITY AND IS REASONABLY SIMILAR TO THE UKMET AND

CMC FCSTS.

Edited December 11, 2009 by nick sussex

[Yeti]

Remind me someone, when was that appalling occasion when the cold outlook collapsed across the models with very short notice? I was talking to someone a while ago about this yesterday and couldn't pin down the date! I do remember it traumatised practically everyone at the time and really put the skids under the trust in a couple of models for months afterwards....

BTW I'm not suggesting we are going to see a re-run before anyone starts twitching!

I believe that was January 2006, with the mother of all Easterlies (-15 isotherm reaching UK) out at about 144 only for it to collapse dramatically into a total non-event!

[Thundery wintry showers]

I'm just happy that I'm still able to talk about this, I had a big fear about the famous downgrade, we've had a change, but its not really a downgrade which is good and there is much stronger agreement.

Yes. I have to say that I was pretty concerned by yesterday's 12Z ECM which went the way most attempts at cold spells have tended to go during the last couple of decades (albeit usually with far less impressive northern blocking beforehand). At least we still have two easterly outbreaks to focus on- one mainly for the SE and one potentially rather more widespread for eastern areas afterwards.

I still think it's too early to claim victory for one model or another- the pattern could still change, given how uncertain the models have been until recently, and bearing in mind how poorly the models traditionally handle easterly incursions. My hunch is that they might actually be toned up slightly, rather than down, as we get nearer the time- my mind goes back to late December 2005 for example when the models were too keen to send high pressure south too quickly.

I think there has been a downgrade relative to earlier GFS outputs (not so sure about the UKMO- perhaps its earlier high-potential outputs would've led to the scenario the models are now showing? It's certainly been the most consistent of the three models out to T+144). But certainly not the downgrade that many of us were fearing - at least not yet, anyway.

[robert]

Absolutely agree, I think even T120 at the moment is going to change quite a bit. None of the models are handling it that well, a difference of 300 miles further North with the high pressure and we could be seeing snow showers for the majority of the UK, 300 miles further South and it's cold and dry conditions. It's little changes like that that will make a massive difference come next week.

Hey Andy Good to see your about mate :blush: on it's way! Winter is calling me back to my favorite weather site netweather Back on topic now! how the models have been the last few days and the swing in mainly one direction means only one thing, upgrades to come later today!

Edited December 11, 2009 by robert