Model Output Discussion - 14th Jan 12z Onwards

[The Enforcer]

I see the usual party pooper is lurking on some of the charts:

 

[marksiwnc]

I see the usual party pooper is lurking on some of the charts:

 

Pesky Mild Sector Alert.png

Yes I see the warm sector drama has begun.. I am expecting it to be a smaller area than that as it looks to.be overcooked the low.. We shall see

[karlos1983]

That's a good thing, the temp difference between the sea and the cold air causes the convection that drops the snow showers.

Yes I'm well aware of that, which is why I said it, it was in reply to someone saying the further into winter the harder it is to get convection off the North Sea, I was merely saying that it shouldn't be hard as the sea temps are high.

[Timmytour]

Do people on these forums learn nothing over the years?

 

The cold spell hasn't really started yet and you're already talking about a return to Westerlies in over 10 days time? Lets take 2010 for an example, the models were continuously forecasting a return to milder weather at around the 10 day mark and with every run it was being pushed back, and back.

 

Why you're putting so much confidence in the return to milder weather at a distance of 10-15 days when we haven't even got detailed for this weekend/early next week pinned down yet is beyond me.

 

00z ECM, GFS and the 6z GFS are incredible runs. Details on snow remain uncertain but synoptically, they're a million miles away from anything we saw last year.

2010 saw stubborn heights over Greenland......we can't yet be sure that we have the same thing here. The hope is high, but the certainty is far from it 

 

Edited January 15, 2015 by Timmytour

[matty40s]

Do people on these forums learn nothing over the years?

 

The cold spell hasn't really started yet and you're already talking about a return to Westerlies in over 10 days time? Lets take 2010 for an example, the models were continuously forecasting a return to milder weather at around the 10 day mark and with every run it was being pushed back, and back.

 

 

 

Every single model has a base history of SW winds dominating the British Isles set ups.

Therefore the models will always have this pushing at the back of every other output from a few days on.

Yes, there is historical Easterly, Northerly and blocking set-ups etc, but the data is not as strong as the mean data of the SW flow. 

[Kentish Snowman in Yorks]

Well I for one am ecstatic with the 0z suite of runs this morning and the 6z GFS just seems to be a variation of two themes.

1) It is going to get colder

2) It is highly unlikely to be dry

Equals snow...some cold rain for certain areas granted but I will be amazed if the vast majority of the UK population doesn't see at least one snow event over the next 7 days!

Just remember last year and look where we are now...would you swap? No!

And to those that are worried about a return of mild Westerlies in the 7-10 day time frame...don't!

It was a mild fest January according to many only a week ago so who knows how the next 7 days will pan out.

Enjoy the ride!

[glenh]

Every single model has a base history of SW winds dominating the British Isles set ups.

Therefore the models will always have this pushing at the back of every other output from a few days on.

Yes, there is historical Easterly, Northerly and blocking set-ups etc, but the data is not as strong as the mean data of the SW flow. 

 

I think this is a misunderstanding of how deterministic numerical weather models work. They don't produce output based on historical data.

[Met4Cast]

2010 saw stubborn heights over Greenland......we can't yet be sure that we have the same thing here. The hope is high, but the certainty is far from it 

 

 

The fact that there is no certainty means writing off this cold spell before it's even begun is ridiculous.

[mushymanrob]

Do people on these forums learn nothing over the years?

 

The cold spell hasn't really started yet and you're already talking about a return to Westerlies in over 10 days time? Lets take 2010 for an example, the models were continuously forecasting a return to milder weather at around the 10 day mark and with every run it was being pushed back, and back.

 

Why you're putting so much confidence in the return to milder weather at a distance of 10-15 days when we haven't even got detailed for this weekend/early next week pinned down yet is beyond me.

 

00z ECM, GFS and the 6z GFS are incredible runs. Details on snow remain uncertain but synoptically, they're a million miles away from anything we saw last year.

 

sorry old chap but i disagree with this (bib) assuming you are referring to the deep cold of december 2010. the gfs picked up on the breakdown long before the ecm and ukmo, this was a classic case of the gfs being right over the europeans.

 

[nick sussex]

Not a bad GFS 06hrs run, I hope people can just remain patient and not get too hung up on the actual 850's if the easterly verifies.

 

It's very difficult at this range for NWP to be accurate,  deeper cold pools can form nearer the time. Although I think we're unlikely to see some 5 star cold  theres a decent chance of something close to -10 850.

 

Much depends on how the Euro trough sets up, as the initial slider slowly fills  you don't want the UKMO view of the low centre off the sw because this is more likely to draw up some less cold air into eastern Europe, after this you want the troughing aligning ene from France and as far east as possible to cut off any less cold air from getting drawn into the circulation.

 

The high near Scandi will try and escape se so you need this blocked off by troughing underneath.

 

In terms of the slider low still some room for changes but at this point its going to be hard going to avoid some less cold air from being drawn into the circulation, this is temporary as soon as this drifts sufficiently se then colder air will return.

[Frosty.]

GEFS 06z mean shows an increasingly much colder outlook with a risk of snow, the cold spell looks prolonged, certainly all next week and into the following week, especially further east / south east. I have a feeling there will be disruptive snow both this weekend and more especially next week for some of us but the devil will be in the detail.

Edited January 15, 2015 by Frosty.

[mushymanrob]

The fact that there is no certainty means writing off this cold spell before it's even begun is ridiculous.

 

whos doing that?... (ive not read all the pages).

the cold spell in nailed, its starting now, gradually. the only thing in doubt is the severity of the spell, currently its looking to me like the real cold wont arrive until later next week when we are due to pick up an easterly/northeasterly. the current runs suggest the -5c upper isotherm being displaced tues/weds. it will be cold... but perhaps not as cold as some sources might suggest?

 

anyway, imho its pointless trying to pin down detail several days ahead in this messy synoptical pattern. theres alot of borderline issues to resolve before the expected northeasterly delivers some real cold.

[TEITS]

Impressive mean with this not rising above -5C until the 27th.

 

http://max.nwstatic.co.uk/ensimages/ens.20150115/06/t850Cambridgeshire.png

 

Just a quick word if my comments this morning appear to be negative. Whilst I agree this cold spell could yet be upgraded, I am also trying to be cautious. What you sometimes find on this thread is the same people over ramping the potential cold spell are often the same people who moan when it doesn't meet their expectations. The E,ly shown on the 06Z would bring some snow showers to eastern areas especially NE but it isn't what I would call a classic E,ly bringing widespread heavy snow falls even into inland areas.

[legritter]

Not a bad GFS 06hrs run, I hope people can just remain patient and not get too hung up on the actual 850's if the easterly verifies.

 

It's very difficult at this range for NWP to be accurate,  deeper cold pools can form nearer the time. Although I think we're unlikely to see some 5 star cold  theres a decent chance of something close to -10 850.

 

Much depends on how the Euro trough sets up, as the initial slider slowly fills  you don't want the UKMO view of the low centre off the sw because this is more likely to draw up some less cold air into eastern Europe, after this you want the troughing aligning ene from France and as far east as possible to cut off any less cold air from getting drawn into the circulation.

 

The high near Scandi will try and escape se so you need this blocked off by troughing underneath.

 

In terms of the slider low still some room for changes but at this point its going to be hard going to avoid some less cold air from being drawn into the circulation, this is temporary as soon as this drifts sufficiently se then colder air will return.

yes very difficult to put any finer detail concerning precipitation for next week .with just possibly 1c temp making a Very big difference in any one location ,regards sleet snow .if i could hope for one change it would be for any possible pressure rise over scandy currently modelled to kick in a little earlier ,but certainly very good charts and possibilitys ,i,m pretty sure that each Fax chart will show some surprises .If low pressure does get set up to our south there could be a chance of fronts pushing back north ,tonights runs eagerly awaited and plenty of debate to increase our knowledge on the best weather forum around ,Stellas all round gang   

[Man With Beard]

Do people on these forums learn nothing over the years?

 

The cold spell hasn't really started yet and you're already talking about a return to Westerlies in over 10 days time? Lets take 2010 for an example, the models were continuously forecasting a return to milder weather at around the 10 day mark and with every run it was being pushed back, and back.

I was also going to add something about the lessons of the past ; can anyone south of Birmingham remember a recent major snowfall that was predicted more than 5 days in advance? Feb 2009 was about 5 days. Jan 2010 was 48 hours for most places (yes cold was in place but iirc people on here were saying it would be dry inland). My best snowfall of Dec 2010 was forecast a few days before, then it was off, then two days before it was on again. Jan 2013 - remember the turnaround by UKMO at T120, I remember IF coming on here saying rated 20% chance by the MET?

So historically with snow its been pretty useless to say it will/won't snow until very near the event, at least in southern areas. Just saying that because of the number of 'no snow in the south' posts recently.

[nick sussex]

In terms of the type of Euro trough and how this could impact any cold advection into the UK:

 

Below are two examples, the first with the troughing more rounded and you can see the Scandi high sagging se on its eastern flank:

 

 

After any initial cold the troughing will start drawing less cold 850's into the circulation from the Med.

 

Now in this example you can see the troughing is aligned more ene and stretches much further east, this cuts off any milder air from the Med and you also can tap into colder air:

 

 

So what you want to look for in future outputs is the shape of the troughing and how far east it extends into eastern Europe.

 

 

 

 

 

 

 

 

[snowy weather]

I was also going to add something about the lessons of the past ; can anyone south of Birmingham remember a recent major snowfall that was predicted more than 5 days in advance? Feb 2009 was about 5 days. Jan 2010 was 48 hours for most places (yes cold was in place but iirc people on here were saying it would be dry inland). My best snowfall of Dec 2010 was forecast a few days before, then it was off, then two days before it was on again. Jan 2013 - remember the turnaround by UKMO at T120, I remember IF coming on here saying rated 20% chance by the MET?

So historically with snow its been pretty useless to say it will/won't snow until very near the event, at least in southern areas. Just saying that because of the number of 'no snow in the south' posts recently.

I had no idea about the snow in 2010 coming, it was so unexpected.

[Jason M]

Agree with Mushy here. A cold spell is nailed IMHO, but what isn't nailed is the extent and severity of the cold spell.

 

In the nearer term the slider scenario is unlikely to deliver in a big way in my view for many on here. I thought Steve Murr nailed it last night with his initial assessment of who gets snow and who gets rain. Of course the charts will keep throwing out different scenarios and nobody can be certain but I think based on common sense and experience a basic feel for what will probably occur can start to be established. Different members on here will have slightly different views (all of which should be respected). 

 

FWIW I think one of two scenarios will come to pass with the slider

 

1. Pretty much what is modelled now, where warm sector ensures rain for the south and especially southeast (favourite in my view)

2. The slider is further SW, meaning snow for midlands, wales, southwest England with only modest elevation with snow / sleet mix on lower ground. EA & SE to stay dry, cold and cloudy.

 

For option one, If I had to pick the least likely areas for snow I'd say Kent, East Sussex, Essex, Suffolk and Greater London area. Many other areas such as Central Southern England including west country etc. its a coin throw frankly, but you are in the game. SE England, forget it as will have warm sector to deal with and be too near to the warm core of the low pressure system!!

 

If the low clears to the south, then SE England and EA enter the game at that point (although it won't necessarily be quick).

 

What happens after the slider though is really up for grabs. Big freezing easterly, bog standard winter easterly (nothing wrong with that) or quick sinker with zonal returning. Right now, I'd say 'bog standard' is favourite, followed by big freeze and then a close third zonal.

 

Overall encouraging charts today so far. Nothing exceptional (IMHO) but still with room to add if luck is with us.

[IDO]

The fact that there is no certainty means writing off this cold spell before it's even begun is ridiculous.

 

Yes it has been a long wait for a genuine cold spell and confidence is growing that for the south we will be witnessing a 12 day plus of colder than average uppers:

 

 

Without that we would not even be talking snow down here. My take is that the Atlantic will be knocking on our door for about 5 days from Monday. These will bump into the block to the NE and they may stall somewhere over the UK. That will be the best chance for snow for the lucky ones. Of course they will weaken as they cross east so the SE/E may miss out (or not if the battleground is further east).

 

Then the question is how long will it take for the Atlantic ridge to link with the heights to the NE? It is looking like around D9 the Ridge cuts off the slider flow. Though by D6 28% of members have already toppled the ridge. Will there even be a link up or will the ridge topple?

 

Then how long can that easterly sustain before the lower heights to the north sinks it, assuming it does; at the moment that is the most likely solution. What will that easterly bring, snow, grey, drizzle, etc?

 

Then what happens next after that? Bearing in mind the JMA keeps us in a mean cold flow for the next 4 weeks further sliding reloads may be viable.

 

Lots of questions and not many answers at the moment. So we are really looking for some good runs to cement the snowy route as there is a good cluster that breaks these outcomes by this time next week. Though of course it is the GEFS so usual caveats with the Atlantic bias.

[glenh]

The above chart from 'I'm dreaming of' looks remarkably similar to this:

 

 

That was from further north, hence the colder temps, but a similar look relative to the 30 year mean 

Edited January 15, 2015 by glenh

[nick sussex]

I think theres somewhat of a misconception with the slider low.

 

Let me explain,  if the low is as deep and is going to take time to fill as suggested by the outputs then you do not want to see this be modelled further west, if the low drops south and slowly fills to the sw you're more likely to end up with the first example in my previous post or indeed worse.

 

You have to take some pain shorter term so that this fills with the centre over eastern France. I've seen many people urging a westwards correction. But a westwards correction with the low as suggested by the outputs will not end well!

 

If we were dealing with a shallow elongated feature then it would be somewhat different but you'd still need the energy heading se not south.

 

Remember you need troughing developing to the se not just the south or sw.

Edited January 15, 2015 by nick sussex

[Downpour]

I was also going to add something about the lessons of the past ; can anyone south of Birmingham remember a recent major snowfall that was predicted more than 5 days in advance? Feb 2009 was about 5 days. Jan 2010 was 48 hours for most places (yes cold was in place but iirc people on here were saying it would be dry inland). My best snowfall of Dec 2010 was forecast a few days before, then it was off, then two days before it was on again. Jan 2013 - remember the turnaround by UKMO at T120, I remember IF coming on here saying rated 20% chance by the MET?

So historically with snow its been pretty useless to say it will/won't snow until very near the event, at least in southern areas. Just saying that because of the number of 'no snow in the south' posts recently.

Excellent point and post. Who can forget Feb 09 Thames Streamer – epic event for the capital that was modelled at about T12 if I remember correctly! 

[Hotspur62]

Just logged onto today and just gone through the last 8 pages. Nothing has really changed imo since last night.Its just a question of where these Sliders go,how far West and how quickly they sink Southwards.Once we know these answers we will know what the Medium Future Holds.There will be subtle changes which can make significant changes down the road but my analysis of models and past experience tells me:

 

1.Snow likely from Monday evening onwards from South Midlands Northwards to cover large part of England,Cen & North Wales and NI.I don't think NE England will be that affected by heavier precipitation and the SW,Southern England,SE England and EA will see rain/sleet(maybe wet snow with elevation) or be too far East(EA & SE maybe) and stay dry.

 

2.Once slider out of way and on proviso the above has happened I think we will be in an Easterly flow. Now as others have mentioned what is crucial to develop a cold and snowy set up for those that missed out on P1 is the alignment of troughing in Europe and how strong the Scandi High.It really is a heart ruling head thing for me but I think we will not get the ENE flow that we require as Heights aren't strong enough up in Scandi.Again this will lead to disappointment for SE and EA but in the NE and E Scotland temps will be cold enough to sustain snow.

 

I am maybe looking on the gloomy side of things(following Spurs does that!!) but I hope it is a bit or Reverse psycology going on and it wouldn't take much for things to turn out very good for the whole of the UK this time next week. I also happen to think we are going to have a colder than normal first half of Feb and I see the JMA have also highlighted this in their latest outlook of things for Feb. A number of LRFs also have stated they believe that winter will start from approx. this time so even if next week doesn't pan out as I and many on this forum hope(esp Southerners) we still have another 4-5 weeks of winter left    .

 

As ever big thank you to likes of SK,NS,SM and many others(you know who you are) who really explain things to help laypeople to continue to learn the finer parts of the Weather  

[phil nw.]

Looking at the latest ens temperature graphs we can see why the UK met have commented that the cold spell could be the coldest nationwide since 2 years ago.

 

and the combined

 

The cold really kicks in around day 4 onwards after the current low clears north east and a brief Arctic northerly to it's rear brings the -8c uppers further south with -10c to N.Scotland.

 

so the cold arrives just ahead of the the low sliding se with the frontal zone approaching from the west by day 5.

This of course is where the interest rises for many of us wrt snow fall.

 

Too early yet to know where this will be but unless there's is a sudden and dramatic change to the overall pattern then some parts will i am sure see some by mid-week.

There is the brief mild sector to look out for which does create a temporary problem but the cold returns behind.

All in all a cold week to come nationwide.

.

 

Edited January 15, 2015 by phil nw.

[Barry12]

If you live in the North a week of cold and snow is pretty much guaranteed, with -4 uppers at worst. For the south it's more uncertain in terms of snow, but I would bet a lot of money that you will get snow at some point in the next 7 days. On boxing day here we only had -4/5 uppers in a NW flow, and it rained for hours before that but we still got a good 5cm of snow with Sheffield getting 15cms. No reason to be negative even if you live in the south, unless your looking for severe cold with massive blizzards.