Model Output Discussion - 23rd Jan - 12z onwards

[Banbury]

The control finishes with a cold Easterly

[knocker]

But the anomalies after D10 tend to get rid of the  Scandinavian trough although the EPS is not quite so drastic.

Chart weatherbell

Edited January 25, 2015 by knocker

[Kentish Snowman in Yorks]

Are you serious? I detect an IMBY.

 

These northerly type of events rarely produce anything worthwhile away from coastal areas and high ground.

 

GFS chart for Thursday below shows this is a marginal event for North Wales and the North East.

 

I did say could.

In any event, I am talking about the overall evolution and setup for the UK over the coming week or more, and not the possible snow event on Wednesday, which incidentally is unlikely to affect where I live.

Far from being IMBY, I just cannot see that this upcoming spell will be a short lived one and I do believe that the majority of the UK population has a shot at seeing a snow event before the dust (snow) has settled.

The ECM in particular, and even the less favourable GFS run that you posted look good for cold for the UK as a whole and snow events can and do pop once the cold is in place.

I may be wrong but I am expecting some decent upgrades of the overall pattern on the 12z runs.

[Frosty.]

Ecm 0z ensemble mean shows the cold spell extending into early February, the scandi trough looks robust and nicely aligned for the UK to have a very good spell of arctic weather. There are already yellow warnings which will be followed by Amber warnings etc, I'm not into the negative mood from some again this morning, this will be the best wintry spell for a few years no matter what the prophets of doom and gloom say.

Edited January 25, 2015 by Frosty.

[Welsh_Weather]

This is nothing like last week, we have a completely disrupted PV, wth lobes going everywhere, the main one to note diving over or just to our East and itno Central Europe. This isn't far away from a December 2010 setup, yes we don't have the deep cold uppers that we had then and the pressure isn't, at the moment building as much towards Greenland.

If we get a mix of all the charts, everywhere will get a shot at snow, even South East Coast. The GFS is a little more marginal than ECM and UKMO but it also brings much more precipitation with very unstable air over the whole of the UK. I believe we will have something between GFS and ECM/UKMO, which would bring cold enough uppers for the whole country even at low levels. Polar lows can come from nowhere with as little as 6 hours notice and have the potential to bring quite a lot of snow in a short period to anywhere.

Very interesting model watching but this our best shot at a nationwide event for quite a few years, let's just enjoy the ride.

Edited January 25, 2015 by Welsh_Weather

[Cloud 10]

ECM 10 day totals clearly show the favoured areas with east and south coasts trace amounts and the SE small amounts. High snow amounts on hills and mountains with a NW and W bias:

 

  MarkVogan

ECMWF Europe SNOW COVER by day 10. Worst on winter coming up... http://t.co/hXZPryze5U

25/01/2015 11:05

 

Obviously with snow these are very rough but it does help with hot spots and therefore where the most likely heavy falls will be.

 

 

10 inches for Carlisle....

[Mark Parsons]

Ok - cold yes that's on its way - exceptional cold NO

A potent PM airmass brings snow for the favoured areas late Weds/Thursday

Then we rely on some Mid Atlantic ridging for the weekend and first few days of Feb - not expecting much from this - but some will do ok

Far from a Nationwide Event

Not being purposely negative - just realistic

That can be said, however this time there is the chance of troughs moving across the country which increases the risk of snow even to inland areas albeit maybe not to huge quantities, I would not discount even the less favoured areas missing out on at least some snow given the current output.

[bluearmy]

But the anomalies after D10 tend to get rid of the  Scandinavian trough although the EPS is not quite so drastic.

Chart weatherbell

 

a lot of mixed messages in the extended ens knocks. which ones will become the new way forward on the modelling ?  could be anything really. 

[ptow]

Aah. I remember a northerly in early Jan 2010. I remember this board being very downbeat with the predicted temps of 1 or 2 degs and it being "bone dry". Fast forward to Jan 5th in Reading and there is an even 34cm on the ground.The next few days were clear crisp ice days.All went a bit slushy thereafter.

I am not saying this will happen. Just that a longer northerly often comes up with something.

[Daniel*]

A very relaistic post, have we learned nothing from the recent disappointment we suffered last week? This will favour hills and some western parts of the UK but the heavily populated south and east of the UK will get nothing from this 'spell', Im just trying to temper expectations and stop toys getting thrown out of prams when nowt arrives for the majority. To have a nationwide snow event we need sustained Northern blocking and that isn't on show im afraid.

I thoroughly disagree you're not even being realistic

We do not need northern blocking to achieve snow, yes for something sustained, but it'll do what is currently being shown really bitter unstable airflow - all you do is downplay all potential it is comical...no snow blitz indeed bar up north, but it is the best chance of winter 14/15 so far. This is a different ball game to the last.

Ian: W COUNTRY Summary of latest f'cast thoughts: WEDS PM-FRI AM: Cold, windy. Through this period, any snow falling to all levels away frm coast

I know who I'm going with ^

Take the ECM 0z

Nothing marginal displayed there - air is sourced from coldest parts of the Northern Hemisphere. It is a breeding ground for troughs, perhaps merging showers into longer spells of snow for many. I do not think it'll be dry evident by London ensembles PPN is likely to fall as snow, as ever N/W is favoured. However initial indications from ECM & UKMO in particular suggest it will not just be an northern affair. In terms of â„ï¸.

Edited January 25, 2015 by Daniel*

[phil nw.]

Speculation already regarding what happens after the up and coming cold period it seems.

There is some indication from the later Naefs that we lose the Scandi/Euro troughing in the later frames and keep the low anomaly to our north west so maybe a sign of a more westerly flow after the cold spell.

 

 

quite a common evolution after a Scandi trough warms out,pressure rises and the Azores high eases back this way.

 

Still let's get through the next week or so first,things may change depending on the flow upstream.

 

The cold really kicks in around midweek as we can see from the cold front moving se  on the fax followed by polar air behind shown on the ECM chart.

 

 

and then it looks like at least a week of  much colder weather for all.

The ens graphs for Aberdeen and Warks plus the combined one for London all showing the cold extending into the first week of February.

 

probably our best chance this Winter of snow for many locations in the coming spell i would think but no good in trying to pin down any details at this stage.

A case of watching the day to day developments.

Edited January 25, 2015 by phil nw.

[TSNWK]

A very relaistic post, have we learned nothing from the recent disappointment we suffered last week? This will favour hills and some western parts of the UK but the heavily populated south and east of the UK will get nothing from this 'spell', Im just trying to temper expectations and stop toys getting thrown out of prams when nowt arrives for the majority. To have a nationwide snow event we need sustained Northern blocking and that isn't on show im afraid. 

CC you made a post 3 days ago posting a 144 chart with some strong words starting there was only one to go from there and it is mild.... 3 days later do you still feel the same? Clearly the models have picked up a new signal and we are looking at a decent cold period of weather with plenty of time for even more improvements.what is also encouraging is that some of the tweets from our met office contacts are dropping increasing less subtle hints that we are in for a noteworthy snap.. Reckon we might see "since 2010 "bounded around soon..

[A.J]

with the moderator hat firmly off, I have to say it does get very frustrating trying to decipher the 'bigger picture' of future events when members are squabbling over what constitutes the parameters of 'marginal uppers' (god, how I hate that phrase!)

 

first of all, they are not 'uppers', they are temperatures at the 850 hpa or millibar boundary which is normally around 1.5km in the atmosphere, and in terms of the vertical extent of our atmosphere, is hardly 'upper'

 

secondly, why are members getting so hung up on T850 temperatures relating to snowfall possibilities anyway?.....It's just one of several parameters that the weather afficienado looks at, and IMHO, it certainly isn't the most important.

 

IMO for surface snowfall, the key parameters are surface dewpoint, wet bulb temperatures (and the accompanying wet bulb freezing level) and the thicknesses between the 500hpa and 1000hpa boundaries and especially the 850-1000hpa thickness values........In theory you can have snowfall with T850's hovering around 0c providing a cold pool is in place, and their are low thickness values and low humidity (wet bulb/dewpoints) even if surface tmeperatures are above freezing.....flipping the coin, it is quite feasible to have T850's of lower than -5c, but with high thickness values (thickness represents the amount of atmosphere between to fixed pressure boundaries expressed in dameters) ppn will fall as rain/sleet as the ppn has more atmosphere to fall through and is therefore subject to to increasing temperatures for an increased time before reaching the surface....

 

Sorry to waffle on, but the gist is, don't get too sucked in to T850 charts on the output, or rather, look at the other parameters (heights, WBFL, dew points) in conjuction......

 

 

...and lastly, if in doubt, have a look at John Holmes excellent snowfall guide in the learning area of the forum, and I'm going to shut up now, and get back to lurking......lol

[The Beast From The East]

Weather for the Week Ahead -

25/01/2015

Each update seems to be upgrading the cold snap/spell.

http://www.bbc.co.uk/iplayer/episode/b04y8w9x/weather-for-the-week-ahead-25012015

I'm guessing they are going with there own model on this one.. ?!

[kev238]

On the face of it, the gfs operational suggests limited snow opportunities for inland areas of England. However, , when you look at the ensembles it suggests there is hope of features cropping up

I think the initial blast will probably deliver to the usual suspects in these scenarios- other areas will have to be patient for their chances if the cold persists into February.

[Day 10]

On the face of it, the gfs operational suggests limited snow opportunities for inland areas of England. However, , when you look at the ensembles it suggests there is hope of features cropping up

I think the initial blast will probably deliver to the usual suspects in these scenarios- other areas will have to be patient for their chances if the cold persists into February.

Yes I think your right here, would be surprised if something more organised didn't crop up in this setup as we move forward.

[The Weather Dragon]

Weather for the Week Ahead -

25/01/2015

Each update seems to be upgrading the cold snap/spell.

http://www.bbc.co.

uk/iplayer/episode/b04y8w9x/weather-for-the-week-ahead-25012015

I'm guessing they are going with there own model on this one.. ?!

Didn't indicate anything severe though - just getting colder - element of doubt regarding longevity of cold - Met office yellow warning for Scotland & Northwest in keeping with current model output

[Biggin]

 the heavily populated south and east of the UK will get nothing from this 'spell',

Bold and brave statement CC

Edited January 25, 2015 by Biggin

[bluearmy]

Weather for the Week Ahead -

25/01/2015

Each update seems to be upgrading the cold snap/spell.

http://www.bbc.co.uk/iplayer/episode/b04y8w9x/weather-for-the-week-ahead-25012015

I'm guessing they are going with there own model on this one.. ?!

Nowhere in that forecast did TS mention CC's back garden! I mean, what do we pay our license fee for! Will it bloody snow there!!!

i mentioned before that there were mixed extended ens signals. One of these is another build of mid Atlantic high anomoly. However, it is also linked to a clear s European one. Now a high anomoly in s Europe is going to be a pretty decent high so if we do begin to see the end week 2 ops showing another mid Atlantic ridge rather than a s European high, that would be a significant nudge as to where we may be headed.

some of the other trends are very interesting but no point in going into them too deeply as they haven't occurred yet this season and I'm more interested in repeating patterns.

[Catacol]

Didn't indicate anything severe though - just getting colder - element of doubt regarding longevity of cold - Met office yellow warning for Scotland & Northwest in keeping with current model output

 

You are underplaying this. It will indeed get colder, but in fact it is set to get very much colder with a gradual decrease in surface temps through to Mon/Tues and maybe beyond. That turns it into a spell of perhaps a week or so - and maybe longer, and low dewpoints forecast along with gradually lowering 850s. The combination of these predictions makes it an unusually snow condusive setup - and whether it warrants the word "severe" or not - it does at least warrant emphasis.

 

IF's tweets are almost semi-frenzied this morning... I knew he was a closet coldie... ;-)

[bobbydog]

with the moderator hat firmly off, I have to say it does get very frustrating trying to decipher the 'bigger picture' of future events when members are squabbling over what constitutes the parameters of 'marginal uppers' (god, how I hate that phrase!)

 

first of all, they are not 'uppers', they are temperatures at the 850 hpa or millibar boundary which is normally around 1.5km in the atmosphere, and in terms of the vertical extent of our atmosphere, is hardly 'upper'

 

secondly, why are members getting so hung up on T850 temperatures relating to snowfall possibilities anyway?.....It's just one of several parameters that the weather afficienado looks at, and IMHO, it certainly isn't the most important.

 

IMO for surface snowfall, the key parameters are surface dewpoint, wet bulb temperatures (and the accompanying wet bulb freezing level) and the thicknesses between the 500hpa and 1000hpa boundaries and especially the 850-1000hpa thickness values........In theory you can have snowfall with T850's hovering around 0c providing a cold pool is in place, and their are low thickness values and low humidity (wet bulb/dewpoints) even if surface tmeperatures are above freezing.....flipping the coin, it is quite feasible to have T850's of lower than -5c, but with high thickness values (thickness represents the amount of atmosphere between to fixed pressure boundaries expressed in dameters) ppn will fall as rain/sleet as the ppn has more atmosphere to fall through and is therefore subject to to increasing temperatures for an increased time before reaching the surface....

 

Sorry to waffle on, but the gist is, don't get too sucked in to T850 charts on the output, or rather, look at the other parameters (heights, WBFL, dew points) in conjuction......

 

 

...and lastly, if in doubt, have a look at John Holmes excellent snowfall guide in the learning area of the forum, and I'm going to shut up now, and get back to lurking......lol

great post. just to add, on the high res GFS 0.25°, apart from a brief few hours on saturday in the south, dewpoints are below zero for the whole country for at least 7 days from wednesday. a very important factor where snowfall is concerned

[EML Network]

with the moderator hat firmly off, I have to say it does get very frustrating trying to decipher the 'bigger picture' of future events when members are squabbling over what constitutes the parameters of 'marginal uppers' (god, how I hate that phrase!)

 

first of all, they are not 'uppers', they are temperatures at the 850 hpa or millibar boundary which is normally around 1.5km in the atmosphere, and in terms of the vertical extent of our atmosphere, is hardly 'upper'

 

secondly, why are members getting so hung up on T850 temperatures relating to snowfall possibilities anyway?.....It's just one of several parameters that the weather afficienado looks at, and IMHO, it certainly isn't the most important.

 

IMO for surface snowfall, the key parameters are surface dewpoint, wet bulb temperatures (and the accompanying wet bulb freezing level) and the thicknesses between the 500hpa and 1000hpa boundaries and especially the 850-1000hpa thickness values........In theory you can have snowfall with T850's hovering around 0c providing a cold pool is in place, and their are low thickness values and low humidity (wet bulb/dewpoints) even if surface tmeperatures are above freezing.....flipping the coin, it is quite feasible to have T850's of lower than -5c, but with high thickness values (thickness represents the amount of atmosphere between to fixed pressure boundaries expressed in dameters) ppn will fall as rain/sleet as the ppn has more atmosphere to fall through and is therefore subject to to increasing temperatures for an increased time before reaching the surface....

 

Sorry to waffle on, but the gist is, don't get too sucked in to T850 charts on the output, or rather, look at the other parameters (heights, WBFL, dew points) in conjuction......

 

 

...and lastly, if in doubt, have a look at John Holmes excellent snowfall guide in the learning area of the forum, and I'm going to shut up now, and get back to lurking......lol

 

 

And on that note netweather have two of those nice and snugly fitted into one ''drop down menu'' on the charts. 

select ''UK Surface Overview" and you'll see the dew points and humidity.

 

Wednesday Night | Thursday morning and the whole of the UK on the 06 z run has dew points supportive of snow fall. 

 

Wed night 9pm and then Thursday morning, going through these periods the Dew point does increase overnight in the South presumably as the warmer moister air is mixed in from the West and then on the back edge of this the dew point drops again giving the possibility of back edge snow fall. 

 

Problem is that unless the temperature drops to below freezing and if you get snowfall on the back edge of rainfall, and if the wet bulb isn't sufficiently low enough the snowfall would simply melt into the rain the has preceded it. 

 

 

You can always click on ''previous run'' to swap between what the chart was showing at the same time frame in the previous run to see any consistency. 

 

The Dew point on the past few runs has at least been supportive of snowfall right through from Thursday and into the weekend for most , exception being the extreme South West and at times the south coast . 

 

It would be nice to have a wet bulb chart to view , I tend to go to a different site for that, so the wet bulb level shown foe Wed evening (this is showing the elevation needed in meters above sea level for the wet bulb level to be at freezing point)

 

 

and then at 6am on Thursday 

 

So IMO as things stand the best chances many of are are going to get to see something white falling from the sky is overnight Wednesday and into Thursday morning. 

 

I'm doubtful of seeing anything here, and if I was living along the coast in the south and south west I'd not be getting my hopes up, but then again we had a surprise snowfall here last week which wasn't modeled, wasn't forecast and just seemed to appear out of nowhere, so who knows. 

 

[bluearmy]

That last sentence is such a tease Ba ...

Give you a clue on one of the more interesting ones for coldies - begins with 'retro' and ends with 'gression' !

[blizzard81]

Bad update on the AO. Going firmly high positive territory as we head towards second week of Feb. The state of the AO will have a huge bearing on whether this upcoming cold will be a cold snap or a cold spell. We need tomorrows update to bring the forecasted AO down into negative territory as we head towards week 2 of Feb.

Edited January 25, 2015 by blizzard81

[Spurry]

The set up from Wednesday (according to the Meto) of cold N/NW winds tend to deliver some good events for low lying parts of NW England