Winter Model Discussion - Cold Hunting - 20th Dec

[nick sussex]

Been away from the models today so im catching up.. In my eyes an improvement and it does look as though the overall pattern could be shifted slightly further S. The real talking point though is the potential for Scotland especially N Scotland who could potentially see heavy snowfalls and if this pattern of the LP tracking further S continues then Scotland may not even see less cold interludes.

At the moment little for the rest of us to be excited but im focussing more on the output for those in Scotland. I would love to spend the next 7 days in Shetland Isles.

A mean of -8C with some runs dropping to -14C.

http://cdn.nwstatic....850Shetland.png

It could go either way, these shortwaves developing and how they run into the UK is becoming very complicated.

One thing I've noticed is that we're seeing some brief amplication which allows the Azores high to retrogress a little ahead of the low which exits the eastern USA at 120hrs:

So if we can squeeze a touch more amplification theres a better chance of getting that colder air further se.

[Tim Bland]

Lucky number 13 could give a few flakes in the north :)

http://www.meteociel.fr/modeles/gefs_cartes.php?ech=168&code=13&mode=0&carte=0

[kumquat]

Worries about the northern extent of the Azores High seem to be draining away as we move into the festive season. The 1020mb isobar doesn't breach the Brittany coast until one slight blip at T+ 264 by which time (in crazy FI it's both helping a mid-Atlantic ridge and then goes on to help form a Scandi High). Reminding me of that zipped out High Pressure that somebody posted last night heralding a pattern change back in the cold archive.

[LomondSnowstorm]

Lucky number 13 could give a few flakes in the north

http://www.meteociel...&mode=0&carte=0

That's a crazy run, -12C uppers then a storm that would cause utter devastation to North Sea coasts and probably flood the low countries.

[Duane S.]

2 days ago I was beomoaning the fact that the models were yet to show any proper hint of pattern change. Two days later that's all changed, the models are definitely onto something. I'm convinced this is going to be an improving picture.

Thankfully the PNA looks like it will play ball by going neutral then mildly positive in about a week, net effect hopefully will be some favourable downstream of it amplification and kick start the flat jet a bit. MJO a little undecided looking at the forecasts but there are signs it may head back to the Western Hempisphere in 2-3 weeks, which would also be favourable.

It's going to be interesting forecast chart viewing for the next 10 days going into January.

[SnowObsessor90]

If nothing else hopefully the positive trends strat wise continue, at 30pa level it looks to be in deep dodo on the 18z.

[Rocheydub]

00z from GFS a borefest with low pressures nearly permanently stationed over us bringing cool zonality right out to day 10 when a ridge from the Atlantic starts to extend towards Greenland, but just gets bowled out of the way easily.

One thing is for sure, there will be a lot more rain if those charts verify!

Some topplers are our best hope for cold meantime, but certainly, no sustained cold showing at present. ECM starting to roll out now, wonder if it can develop that Atlantic ridge in FI any better to give us hope!

[IDO]

Little to add re the 0z from GFS. Zonal all the way with maybe two colder PM excursions that are north centric. GFS in FI have been hinting of possible height builds but the 0z says Atlantic is too strong and these get flattened out: http://cdn.nwstatic.co.uk/gfsimages/gfs.20121222/00/384/npsh500.png

One run so we see where that goes. The control has more amplification and we get some cold uppers from the NE:

Signs are better from the GEFS: http://modeles.meteociel.fr/modeles/gens/graphe_ens3.php?x=306&ext=1&y=141&run=0&ville=Londres&runpara=0

It shows a colder profile of 850s as we head into the New Year with the op being in the milder runs from then.

The GEFS mean has an Arctic High at T192:

This gets pushed to Russia by the smaller PV and we end up with a large Russian High again:

More amplification on the mean which is unusual so a pattern change remains in the picture.

The ECM has pushed the zonal flow North, closer to the GFS runs:

and

UKMO is similar:

Both still have that brief shot of colder uppers for the north after Christmas but it is very transient.

Locked in zonal for at least 10 days then hopefully GFS will firm up on some favourable changes in FI so not too much of January is wasted.

[Frosty.]

Shockingly poor 00z from gfs and ecm for cold hunters, mostly mild or average temps for the next few weeks with more spells of wet and very windy weather racing in off the atlantic, some very mild days, some average and a few cooler days. The cold incursion next week is delayed again and only next thursday has a semblance of wintryness before milder, wet and windy weather sweeps in again, so more flooding is likely and frosts will be few and far between according to the above op runs. Christmas day and Boxing day currently look average/cool cyclonic days with some sunshine and a few showers or longer spells of rain with fairly light wiinds.

[Gibby]

Good morning. Here is my report on the output of the big four, namely GFS, UKMO, GEM and ECM for today Saturday December 22nd 2012.

All models show a very unsettled period in the few days up to Christmas and the holiday period itself. There are numerous troughs and depressions swinging in from the West giving spells of rain and showers with just short drier interludes in between. It remains very mild in the South for a few more days before temperatures fall back to nearer normal values everywhere as winds turn more into the West over Christmas. There will be sufficient rain to give rise to further flooding issues almost anywhere as the ground remains saturated nationwide.

After Christmas GFS shows a very zonal pattern with Low pressure passing close by to Northern Scotland and bringing bands of rain followed by showers which in turn be followed by a drier 24 hours or so in an often strong Westerly wind. The heaviest of the rain will likely transfer to the North and West though all areas will see more than enough. Into the New Year and FI shows no real pattern change apart from a rather longer drier and colder spell in the South especially as a strong ridge moves East to the South following an equally brief cold NNW flow with wintry showers.

The GFS Ensembles show a slow decline in uppers over the two weeks after the next few days and more notably after a milder blip prior to New Year. There seems good agreement on rather colder conditions right at the end of the run with at long last a high pressure coming into play lowering temperatures and reducing rainfall. At this point the operational run became a mild outlier.

The Jet Stream shows an undulating West to east flow across the Atlantic towards the South of Britin over the coming week or so.

UKMO for midnight on Friday shows a ridge of High pressure moving away East ahead of a milder SW flow carrying rain bearing troughs NE over the UK in the day that follows.

GEM shows a very unsettled end to its run too with Low pressure well established to the North of Britain with a broad and unstable west or SW flow continuing to bring rain at times in normal temperatures in off the Atlantic.

ECM too shows this familiar pattern with the addition of strong and mild SW winds for a while with periods of rain in association with Low pressure to the North or Northwest.

In Summary there is little to say than what has been said already in that the UK is now set in a zonal train for some considerable time. Successive Low pressures will continue to feed bands of rain and showers East over the UK with some transient brighter, slightly colder and more showery spells mixed in too. Little in the way of frost, ice and snow is to be expected in the next 10 days or so with flooding continuing to be the most likely newsworthy event.

[TEITS]

Disappointing for those in Scotland this morning. The 18Z GFS suggested they could remain cold for a number of days but today it looks a very brief cold spell. This can clearly be seen on the GEFS ensembles.

http://cdn.nwstatic.co.uk/ensimages/ens.20121222/00/t850Aberdeenshire.png

The only positive I can find this morning is the number of cold ensemble members from the 3rd Jan onwards.

http://cdn.nwstatic.co.uk/ensimages/ens.20121222/00/t850Cambridgeshire.png

[Frosty.]

The only positive I can find this morning is the number of cold ensemble members from the 3rd Jan onwards.

http://cdn.nwstatic....bridgeshire.png

Yes and we all know what will happen to that as we get closer, failed easterly ring any bells?

[TEITS]

Yes and we all know what will happen to that as we get closer, failed easterly ring any bells?

Well if could downgrade but personally I never view the model output in that way. I always judge the model output on its own merits and forget about past disappointments.

Overall it has been a very disappointing Dec so far and despite all the promising signals throughout this month i.e (stratosphere/teleconnections posts) I still haven't seen a snowflake.

[Frosty.]

Well if could downgrade but personally I never view the model output in that way. I always judge the model output on its own merits and forget about past disappointments.

Overall it has been a very disappointing Dec so far and despite all the promising signals throughout this month i.e (stratosphere/teleconnections posts) I still haven't seen a snowflake.

I don't think the models have much merit so far this november and winter so far, they have downgraded every cold spell showing in FI and even those in the shorter range. Most worryingly we have widespread flooding and more to come probably.

Edited December 22, 2012 by Frosty039

[chris55]

This little southern runner on the ECM and GFS may be something to watch, small chance of some northern edge snow, especially on the hills?? Not really enough cold air in the mix on the 00zs and DPs a bit high but you never know. Some evaporative cooling could come into play.

Overall though a very unsettled picture , with plenty more rain to come.

[East_England_Stormchaser91]

My untrained eye will be scanning models for pattern change in early January,if only to see end of this rain,Think picked wrong time to learn models

Yes, it really has been a washout so far this winter. I thought the nail was hit on the head earlier in the month with the models showing all of that cold potential, but still the waiting game goes on. Mind you, December never really has been a good month for snow anyway tbh, January and Feb are much better for piercing cold and prolonged snaps.

[Chess01]

I think we are nearly past the worst for wet zonal conditions . December is the most zonal month of winter

[IDO]

I don't think the models have much merit so far this november and winter so far, they have downgraded every cold spell showing in FI and even those in the shorter range. Most worryingly we have widespread flooding and more to come probably.

Very concerning for the areas already under flood alerts. The next 7 odd days totals:

http://www.weatherweb.net/tvweather/gfsopuktotpcp192.gif

Look at S. Wales and the SW, 120mm+ in places. Plymouth have already had 243mm this month. Their average is 80mm a month over the year!!! If the winter continues with this zonal flow it will have major implications.

[bluearmy]

Good x model agreement on an atlantic ridge early jan. the gfs op rather less enthusiastic than most ens members. given the clustering of cold ecm london temps for the same time period, i am fairly confident of at least a two day toppler (remember there are low heights to our north) and given the turmoil in the upper strat at the same timescale, something rather more sustained may well transpire.

[swfc]

Very poor output this morning ie rain and more rain for folk already suffering with flooding.The "change" shown on the 18z is gone and ecm is pretty pony to be honest.I did say yesterday that any change towards a colder outlook"app10-14 jan"lol was based on background signals and should be taken with a pinch of salt!Hopefully a big change will occur in Jan but esp for the new members i woudnt take some posts as gospel to be fair.Altho as i said ive no idea what will happen in the next two weeks this applies to everyone even the meto.The perfect scenario would be a dry cool spell of weather then moving to a much colder spell ete.The dry spell is so needed for our flooded members.merry xmas guys

[Kentish Snowman in Yorks]

*Straw Clutching Mode Activated*

I know it was mentioned a while back over on TWO that the Saturday 00z model suite is quite regularly the mildest set of models of the weekend if not the week, with a gradually colder / cooler picture returning as the subsequent model runs roll out.

Now I have no idea why this should be the case, or whether it will happen on this occasion, but it does seem strange that the models (the operationals anyway) appear to have 'flipped' overnight, which seems to go against alot of the favourable teleconnections being referred to yesterday.

I am quite sceptical of this myself, as I cannot see why a milder bias should appear on a Saturday morning, although I would say that on at least two or three occasions, this trend was apparent.

*Straw Clutching Mode De-activated*

Of course that could all be alot of 'hot air' (pardon the pun) and on this occasion the models could have picked up on a genuine new trend regarding a flatter more northerly tracking jet etc.

Watch this space....

[Duane S.]

Very poor output this morning ie rain and more rain for folk already suffering with flooding.The "change" shown on the 18z is gone and ecm is pretty pony to be honest.I did say yesterday that any change towards a colder outlook"app10-14 jan"lol was based on background signals and should be taken with a pinch of salt!Hopefully a big change will occur in Jan but esp for the new members i woudnt take some posts as gospel to be fair.Altho as i said ive no idea what will happen in the next two weeks this applies to everyone even the meto.The perfect scenario would be a dry cool spell of weather then moving to a much colder spell ete.The dry spell is so needed for our flooded members.merry xmas guys

"The change" will not be smooth and progressive on the forecast charts, with every day an improving picture on the last, there will be many more poor charts / runs to get through before we start to firm up on what potential there is for us early-mid Jan. The 00z GFS operational is poor but the trend is still there as there are a lot of colder GEFS members again as we come into that period.

[swfc]

"The change" will not be smooth and progressive on the forecast charts, with every day an improving picture on the last, there will be many more poor charts / runs to get through before we start to firm up on what potential there is for us early-mid Jan. The 00z GFS operational is poor but the trend is still there as there are a lot of colder GEFS members again as we come into that period.

I stand corrected and await the change with much anticipation!!merry xmas

[nick sussex]

*Straw Clutching Mode Activated*

I know it was mentioned a while back over on TWO that the Saturday 00z model suite is quite regularly the mildest set of models of the weekend if not the week, with a gradually colder / cooler picture returning as the subsequent model runs roll out.

Now I have no idea why this should be the case, or whether it will happen on this occasion, but it does seem strange that the models (the operationals anyway) appear to have 'flipped' overnight, which seems to go against alot of the favourable teleconnections being referred to yesterday.

I am quite sceptical of this myself, as I cannot see why a milder bias should appear on a Saturday morning, although I would say that on at least two or three occasions, this trend was apparent.

*Straw Clutching Mode De-activated*

Of course that could all be alot of 'hot air' (pardon the pun) and on this occasion the models could have picked up on a genuine new trend regarding a flatter more northerly tracking jet etc.

Watch this space....

Lol! good post!

The overall pattern really hasn't changed and with the PV located to the north you're always likely to find pressure to take the jet further north, yesterday mornings runs also had the jet further north before taking it south later in the day.

Later on the ECM and GFS both agree on that deep low in the ne USA, so its now down to the amplification that will determine whether we get to see a northerly.

Generally the GFS isn't too volatile with that type of set up and in terms of the overall pattern it does fit in with the discussions over at NOAA yesterday evening.

If its a northerly toppler the GFS does well at that although it does tend to overblow the cold, in terms of the actual northerly verifying its much easier than God forbid another easterly!

Edited December 22, 2012 by nick sussex

[bluearmy]

There was nothing 'tangible' re cold in the reliable or semi releiable timeframe. Gfs low res - perhaps but then you may as well post any ens member at that range. If you are going to trawl through fi op runs for inspiration, you must start with at least two and better three models pointing at the same solution. for once we have that upstream at day 10. Had the gfs control been the op this morning, there would be a different mindset. (Although its good to see a lot of disbelief with fi patterns as that will help lower expectations).

btw, the fi gfs strat forecast gets ever more incredible.