Winter Model Discussion 18Z 16/1/13 onwards.

[Liam J]

This isn't the thread for Met Office forecasts/discussing regional snow.

[IDO]

Yes FI from GFS is all rather puzzling. Despite the SSW the T384 chart mirrors the pattern in the UK's part of the NH we have had all winter. Raging PV piece west of Greenland allowing the Azores High to migrate over the UK for around seven days +. Cold/cool but snow chances for the north v low, and variable further south dependant on its situ.

ECM also similar, not in details but synoptically (MLB rather than HLB):

Too early to say whats going on, as the supposed full effects of the SSW will just start hitting the latter parts of the GFS soon. But maybe after the snow potential of the next 5/7 days, the weather will trend towards a relative cool calm HP pattern before another reset, early Feb, and who knows from there?

The GEFS have been trending towards normal 850s for a few runs and the mean is now back to 0c:

2m temps just below average at the end of FI, but still cold-cool up till then, at best:

With the model chopping and changing even at T36 its all rather academic but that looks like a possible trend (medium term), as of the 0z runs.

The next 5/7 days should see snow to many places and mostly very cold.

[Severe Siberian icy blast]

Yes FI from GFS is all rather puzzling. Despite the SSW the T384 chart mirrors the pattern in the UK's part of the NH we have had all winter. Raging PV piece west of Greenland allowing the Azores High to migrate over the UK for around seven days +. Cold/cool but snow chances for the north v low, and variable further south dependant on its situ.

ECM also similar, not in details but synoptically (MLB rather than HLB):

Too early to say whats going on, as the supposed full effects of the SSW will just start hitting the latter parts of the GFS soon. But maybe after the snow potential of the next 5/7 days, the weather will trend towards a relative cool calm HP pattern before another reset, early Feb, and who knows from there?

The GEFS have been trending towards normal 850s for a few runs and the mean is now back to 0c:

2m temps just below average at the end of FI, but still cold-cool up till then, at best:

With the model chopping and changing even at T36 its all rather academic but that looks like a possible trend (medium term), as of the 0z runs.

The next 5/7 days should see snow to many places and mostly very cold

Good post there, I would say the gfs run generally shows what we want to see , the high pressure is in a perfect position, just on this particular run it keeps cold uppers away from us and Europe !? Which lets be honest couldnt be more wrong. That chart will be absolutely bitter with cold east winds.

What we Will see over the next 5 days of model watching is the charts get to grips with a synoptic change, where northern blocking will take controle , Gp has been excellent so far and after yesterday's post just confirmed my suspicions , we are on the cusp if a big artic outbreak , and the models Are beginning to hint at this .

As for the next wk, I agreed, lets deal with the severe snowy spell about to embrace the uk these next 5 days.

[Joker]

The ECM is still excellent and signals a reload albeit in FI.

[nick sussex]

In the medium term theres still a big difference in the handling of the upstream energy .

The ECM isn't quite as good as yesterday in the medium term especially as it doesn't separate energy upstream which allows too much phasing and this results in the low tracking farther north , this is something I alluded to a few days back, if you're going to have the ECM/UKMO version you need a clean break with energy upstream to allow low pressure to track further se this then allows you to avoid a thaw for the majority.

Its very hard to make a call here because even the ECM and UKMO handle that upstream energy differently at 144hrs, I think given the orientation of the troughing upstream on the UKMO that has probably the best chance of delivering a stronger high to the north and the coldest longer term picture.

The GFS disagrees with both the ECM and UKMO and resolutely sticks to its previous runs, the differences start quite early so it looks like another case of one model or models looking rather silly once we see the true picture.

Edited January 17, 2013 by nick sussex

[Frosty.]

BIG improvement from GFS compared to yesterday, the 00z is far less progressive and the atlantic is pushed back, much better cold block alignment and shows the freeze lasting all through next week, another feature will be the increasing snow showers for the north and east as winds strengthen and pressure continues to fall (then rising during next week), it won't just be the frontal zone (s) that get all the snow. The models show the very cold spell is set to continue with severe frosts, snow showers and more persistent snow.

Edited January 17, 2013 by Frosty039

[Tim Bland]

UKMO has been very good over the last week and we have see the other models gradually playing catch up so hopefully it's on the money. If it is can one of the pros predict where the snow line would be early next week?

http://www.meteociel.fr/modeles/ukmo2.php?ech=6&carte=1021

[Gibby]

Good morning. Here is the report of the 00z outputs of GFS, UKMO, GEM and ECM for this morning Thursday January 17th 2013.

All models show a similar synopses between now and the start of next week. Through this time there are likely to be two attacks of milder air trying to move in from the SW both of which are unlikely to succeed in any major way. Today shows a freshening SE wind with an active trough approaching the UK from the West later today and tonight. Most areas will be dry today and very cold. For the most part it will be dry with a lot more cloud about than yesterday with a few light snow flurries here and there. Tomorrow will be cold and cloudy and an area of snow with rain near the coasts extends NE through the day to most areas. The snow will be heavy and disruptive for many especially in Wales and NW England. Through Saturday the trough will weaken as it slides away SE into Europe leaving a cold and raw East wind with cloudy and grey skies for most. Early next week sees a repeat performance as a new surge of mild, moist air attacks the cold block over the UK on Monday but pulls away SE again over Tuesday.

GFS then shows the midweek period as being quiet but very cold as pressure builds from the NE over the UK. Over the snowfields some very low night time temperatures are possible through the latter end of the week. The cold anticyclonic weather is then shown to last throughout the FI period today as High pressure remains over or to the North of the UK. With time the severest of the cold would slacken with a slow thaw of lying snow through the daytimes though still frosty at night.

The GFS Ensembles show a steady rise in uppers as we move through the forecast period today with the long term average being reached for many areas by the end of the run. There is some precipitation shown, particularly earlier in the run though no excessive quantities are shown once the current breakdown of the cold is shown.

The Jet Stream shows the flow strengthening from the West over the coming days and crossing Europe over France and Northern Spain. Little general change is shown thereafter through a slow retreat North later is possible.

GEM shows a slightly less cold interlude in the far South early next week behind a period of snow turning to rain. Later pressure is shown to build too with some fine and frosty conditions for several days before the pattern resets to some degree late in the run as further Low pressure disrupts again to the West in response to the cold air over the UK.

UKMO for midnight on Wednesday shows Low pressure over Brest with a cold Easterly breeze over the UK. Some rain, sleet or snow could still be expected with the rain most likely in the South.

ECM shows a cold spell continuing through the middle of next week with some snow possible here and there. It becomes drier towards the end of the week as a ridge of High pressure slips South with a sign of rather milder air moving gently in from the West late on as the High drifts away SE.

In Summary the cold spell continues on for the next week or so at least. there will be snow opportunities for tomorrow and the start of the weekend and again early next week though then the snow might affect more Northern areas while the South sees less cold weather briefly. Later on in the output a dry, very cold and quieter spell looks likely with some very cold nights before a relaxing of the cold shows it's hand later in the outputs.

[nick sussex]

UKMO has been very good over the last week and we have see the other models gradually playing catch up so hopefully it's on the money. If it is can one of the pros predict where the snow line would be early next week?

http://www.meteociel...ch=6&carte=1021

Unfortunately we don't get the smaller steps on the UKMO but looking at the 120hrs chart, that shows the snow line from central Wales through Birmingham to East Anglia north of say Cambridge.

After that the low slips se and the snow line sinks with it. As long as you don't get phasing upstream at 120hrs then the low should readily sink away.

The UKMO charts would bring some snow initially to most areas before a change over to rain below that snow line. Indeed could be some very large totals north of that boundary.

The boundary though is likely to change between outputs so this is just taking the UKMO at face value.

I should add if people are wondering why I'm so obsessed with this phasing upstream its because as the troughing edges east out of the USA if it phases with that low pressure near the UK you lose the se momentum.

This then pulls the low more east than se and it can become slow moving so the key point is to get this low ejected cleanly se'wards, the build of pressure to the n/ne then does the rest by helping to sink it.

Edited January 17, 2013 by nick sussex

[pdiddy]

Just to help clear things up...

The 00Z FAX for midday on Friday shows why things have and will change;

http://www.wetterzen...ics/brack0a.gif

The occlusion, somewhat frustratingly to say the least, develops a low pressure along it now initially in the Irish Sea before moving into Ireland. This, without question, holds the front further west and keeps NW Eng and the Midlands out of the firing line, particularly compared with previous forecasts. Parts of the south may see an increase but I think the biggest change will be to Ireland, especially N Ireland which could see the bulk of the snow from this event now after clearly likely not having very much.

Granted I don't have access to the UKMO UKV and the likes, but I still have other, higher resolution models from work which aren't available for public use and combining all the high resolution models I have here, then the forecasts for NW Eng from the MO look odd now, without question. I would say at most NW Eng look like getting 2cm to 5cm and similar for the Midlands, perhaps locally 10cm at very most.

Matt.

Thanks Matt. How significant is the trough off the NE coast re ppn?

[TEITS]

Yet again some excellent output again. The ECM might not be as impressive as last nights especially towards the end of the run but at this stage im not worrying about +240.

Looking at the UKMO/ECM mean and another big snow event is going to occur during Monday and Tues. How far N the snow will push is uncertain as in the snow/rain line but as it stands N Wales, Midlands, N parts of E Anglia would see an all snow event before pushing S. Those to the S of these areas would see snow turning to rain.

As for tomorrow and an upgrade on the latest NAE run for those in the E.

http://expert-images.weatheronline.co.uk/daten/proficharts/en/nae/2013/01/17/basis06/ukuk/prty/13011818_1706.gif

Looks like Wales and parts of the SW (Bristol etc) are going to get nailed tomorrow. Very pleased for the members who live in these locations.

[Thundery wintry showers]

BIG improvement from GFS compared to yesterday, the 00z is far less progressive and the atlantic is pushed back, much better cold block alignment and shows the freeze lasting all through next week, another feature will be the increasing snow showers for the north and east as winds strengthen and pressure continues to fall (then rising during next week), it won't just be the frontal zone (s) that get all the snow. The models show the very cold spell is set to continue with severe frosts, snow showers and more persistent snow.

When I look closely at the GFS 00Z, it doesn't look like a particularly snowy run to me into next week. We get a shot at frontal snow over western and southern areas on Friday and then scattered snow showers into eastern areas over the weekend, but into next week we pick up modified continental air from the south-east- this results in frontal situations being quite marginal (e.g. temps of 0 to 2C predicted from the advancing fronts on Tuesday) and in between, the south-easterlies would bring mainly dry cloudy weather, rather than sunshine and snow showers.

I think next week will be rather more snowy if the UKMO/ECMWF verify as they have deeper lows to the south (indicating more potent fronts) and also more inputs of colder continental air from the NE which would promote snow showers in eastern areas to the north of the fronts.

[Cheese Rice]

As for tomorrow and an upgrade on the latest NAE run for those in the E.

http://expert-images...011818_1706.gif

Looks like Wales and parts of the SW (Bristol etc) are going to get nailed tomorrow. Very pleased for the members who live in these locations.

Potentially a fair bit of snow for many areas if the NAE PPN accumulation charts are anything to go by.

Using 1mm = 1cm there's widespread 5-10cm across Yorkshire, Lincolnshire, Midlands, Southern England etc.

Edited January 17, 2013 by Cheese Rice

[ChartViewer]

CMA Keeps us in the colder mix short term and then starts again to show us this (I wish!)......... ...Keeping with the upbeat mood and potential continuation of cold theme

CMA T120

CMA T144

CMA T168

Edited January 17, 2013 by ChartViewer

[Frosty.]

When I look closely at the GFS 00Z, it doesn't look like a particularly snowy run to me into next week. We get a shot at frontal snow over western and southern areas on Friday and then scattered snow showers into eastern areas over the weekend, but into next week we pick up modified continental air from the south-east- this results in frontal situations being quite marginal (e.g. temps of 0 to 2C predicted from the advancing fronts on Tuesday) and in between, the south-easterlies would bring mainly dry cloudy weather, rather than sunshine and snow showers.

I think next week will be rather more snowy if the UKMO/ECMWF verify as they have deeper lows to the south (indicating more potent fronts) and also more inputs of colder continental air from the NE which would promote snow showers in eastern areas to the north of the fronts.

I was thinking more of this weekend and early next week before pressure rises more strongly, strengthening SEly winds and falling pressure, it's going to be bitterly cold anyway with ice days and severe frosts, the T850's look very cold. I'm very happy with the latest output, winter is finally here BIG TIME.

Hopefully we will all get snow either in the form of snow showers or persistent frontal heavy snow (blizzards). My main point about the gfs was the big upgrade for next week when yesterday the op runs on 00z/06z/12z were showing a flat zonal pattern coming in by midweek but now it's very cold and blocked.

[Ian Brown]

The GFS still looks nothing like the Euro models though it has at least strengthening the block to the East to maintain a colder flow for longer.

In the shortterm, the snow risk over coming days covers many areas with the exception of the NW England and the N Midlands, as is often the case with what could be a fairly lengthy cold spell.

[Cumulonimbus Tower]

Whilst the development of a low pressure system over the Irish Sea, holding up the Eastwards advancement of the front tomorrow does undoubtedly mean some areas won't see as much of the white stuff as previously hoped, looking at the NAE in more detail I do wonder if the development of this system will actually mean that the precipitation lasts longer across some areas, particularly the North East, where as it was going to die out fairly readily previously, the Easterly wind looks to pick up and I can see tomorrow night turning into quite a raw, blowy and snowy picture across large swathes of the BI. And lets be fair, it is possible that wider areas of the Irish Republic will get a bit of snow too, which seems only fair!

Edited January 17, 2013 by Cumulonimbus Tower

[Methuselah]

Any chance of you enlarging your font there, CT? I know I get free eye-tests and all, but...

[Great Plum]

Whilst I commend the gfs for its enthusiasm, isn't that low just little excessive?

http://www.wetterzentrale.de/pics/Rtavn841.png

[Lynxus]

Whilst I commend the gfs for its enthusiasm, isn't that low just little excessive?

http://www.wetterzen...cs/Rtavn841.png

It is indeed..

Did that read 940?

GFS is a little on the progressive side with Lows though.. So thats probably a little over hyped ( Probably not by much though ) So worth noting.

[Thunder Snow]

Well im still not impressed with the 06z this morning, it seems they are downgrading the event bit by bit.However further upgrades for NI and Wales i think, with Northern/NW England out of the main area of concern. Then as it moves east it turn light and patchy in nature. So close to a major snow event, but yet so far.

[TEITS]

Whilst I commend the gfs for its enthusiasm, isn't that low just little excessive?

http://www.wetterzen...cs/Rtavn841.png

Im sure yesterday the GFS had this LP at 930mb!

Some differences in the modelling in this LP between the GFS/UKMO/ECM. The GFS has this deeper and further N at +72 compared to the ECM/UKMO.

The GFS does tend to be OTT with the depth of these LPs but in my opinion the UKMO is the opposite.

[swfc]

very nice chart at 120 hrs.suspect plenty of snow showers pushing in land there

[Coast]

Well im still not impressed with the 06z this morning, it seems they are downgrading the event bit by bit

The caveat being I guess; depending on your location??????

[blizzardwizzard]

My very first post but been watchng for a couple of years. Wales is defo in the firing line for fridays event as the models slowly backing the trough further west. Been watching this low in the atlantic for a few days thinking its to far east against the block. Ukmo has been very crediable during this cold. Gfs is a classic default long term as its a happy go mild