Model Output Discussion - 23rd Jan - 12z onwards

[Ice Day]

More corking outputs on the 6z.  210hrs is looking interesting with cold moving in from the east.  Not staggeringly low uppers but should be conducive to some snowfall I would have thought.

 

 

 

I think it's going to get very busy in here!

Edited January 24, 2015 by Ice Day

[winterof79]

And all the while above all the action is this...Vortex you took one hell of a beating

Edited January 24, 2015 by winterof79

[IDO]

We are focusing in on that spoiler low at D7. It warms out the cold uppers as it moves across the Atlantic:

 

  By D8: 

 

It is more progressive on the 06z run compared to the 0z. On this run after D8 the energy within the Canadian vortex does not spill into the Atlantic as strongly, though some energy moves SE, so it helps send more WAA into the Atlantic Ridge so the amplified flow should last a bit longer:

 

 

If only the phasing was better as around D9 we have another wedge of HP exiting the US, that could help sustain the ridge if we don't get too much energy sliding SE off the Canadian vortex:

 

 

A bit better on this run as that wedge builds, eking out a little more for the cold spell:

 

 

 

 

 

 

[nick sussex]

If we can actually get to this point then we need to see that upstream troughing eject a shortwave se this will cut off the high.

 

Upstream its crucial to maintain enough amplitude to sharpen the troughing to the west of the UK, the red triangle is crucial you need this ridge amplification, over in the USA the further south the cold gets into the USA you can correlate with the amplitude.

 

 

The GFS doesn't take enough energy se after this point, too much goes ne as it begins to flatten out the pattern over in the eastern USA.

 

Still too far out to worry about, still a few hurdles to get through before then.

Edited January 24, 2015 by nick sussex

[EmmaF]

Sorry but whilst its fairly quiet could I just ask what the difference is between the last cold spell that promised so much but got watered down to well one day compared to next weeks upcoming cold spell ? I read Steve murrs post last night saying that the uppers weren't very good at all with the spell or snap showing at the end of next week so I'm a little confused thankyou

[Ali1977]

That snowfall showing by next Wed is only 4 days away, not sure if the GFS is bringing the cold in a little early but warnings could be out in the next few days if true.

[bluearmy]

Sorry but whilst its fairly quiet could I just ask what the difference is between the last cold spell that promised so much but got watered down to well one day compared to next weeks upcoming cold spell ? I read Steve murrs post last night saying that the uppers weren't very good at all with the spell or snap showing at the end of next week so I'm a little confused thankyou

Steve is being realistic from a glass half empty view and I think he's probably also speaking from a southeast perspective.

Emma - I'm not far from you and I'm not expecting any lasting snow cover at the moment. However, I believe that the environment is conducive to it if we get lucky with embedded features or the track of a secondary low. Where we are, that always been the case.

For many past of the country, I expect far wider snowcover from this cold spell than the one just ended and that would reflect in official forecasts which were far more reserved re snowfall than some posts on here. Wednesday was fairly marginal for a decent snow event.

Anyway, a week is a long time on here.

Back to the models and the low res dismantling of the vortex split yet again evident.

[Day 10]

More corking outputs on the 6z.  210hrs is looking interesting with cold moving in from the east.  Not staggeringly low uppers but should be conducive to some snowfall I would have thought.

 

 

 

I think it's going to get very busy in here!

Yes the cold trend appears to be building, and cruicially edging ever closer. Fingers crossed!!

[nick sussex]

Sorry but whilst its fairly quiet could I just ask what the difference is between the last cold spell that promised so much but got watered down to well one day compared to next weeks upcoming cold spell ? I read Steve murrs post last night saying that the uppers weren't very good at all with the spell or snap showing at the end of next week so I'm a little confused thankyou

The last cold spell had a less favourable upstream pattern, that PV chunk was always too close which meant it was difficult to establish any high pressure for a decent length of time.

 

In this set up theres a strong signal to edge that PV chunk in ne Canada further west, I would agree with Steve though re the uppers but its still too far out to be sure of in terms of depth of cold.

 

At this point I would be more worried about getting over a few hurdles as by no means is that a given, we are pretty sure of the initial Euro troughing, but theres still uncertainty as to what happens in the Atlantic afterwards.

[winterof79]

Sorry but whilst its fairly quiet could I just ask what the difference is between the last cold spell that promised so much but got watered down to well one day compared to next weeks upcoming cold spell ? I read Steve murrs post last night saying that the uppers weren't very good at all with the spell or snap showing at the end of next week so I'm a little confused thankyou

Hi i think we were relying on one sliding low from n/w to s/e last week and the output was showing it holding and deepening to our s/e thus pulling in easterly winds.In reality it slid but drifted away without drawing in the cold Easterlys.This time there is a large trough of low pressure that will sit to our east and is easier to model.Once this is established then we could well see various cold scenarios playing out.Also there is a chance that heights will be building to our west to halt the Atlantic.Long way to go but i have a feeling it could get busy in here.Hope that helps a little.The uppers are modelled cooler today but location will always play a large part too.

Edited January 24, 2015 by winterof79

[Day 10]

The last cold spell had a less favourable upstream pattern, that PV chunk was always too close which meant it was difficult to establish any high pressure for a decent length of time.

 

In this set up theres a strong signal to edge that PV chunk in ne Canada further west, I would agree with Steve though re the uppers but its still too far out to be sure of in terms of depth of cold.

 

At this point I would be more worried about getting over a few hurdles as by no means is that a given, we are pretty sure of the initial Euro troughing, but theres still uncertainty as to what happens in the Atlantic afterwards.

Hi Nick, new in here. Surely the cold enough uppers with follow though if the predicted pattern can set in long enough which hopefully it can this time. This looks our best shot of the winter I think.

[WINTRY WALES]

Steve is being realistic from a glass half empty view and I think he's probably also speaking from a southeast perspective.

Emma - I'm not far from you and I'm not expecting any lasting snow cover at the moment. However, I believe that the environment is conducive to it if we get lucky with embedded features or the track of a secondary low. Where we are, that always been the case.

For many past of the country, I expect far wider snowcover from this cold spell than the one just ended and that would reflect in official forecasts which were far more reserved re snowfall than some posts on here. Wednesday was fairly marginal for a decent snow event.

Anyway, a week is a long time on here.

Back to the models and the low res dismantling of the vortex split yet again evident.

Surely though BA Only fringes of the coasts, mainly North west and east and inland Scotland look like being affected with regards to any snow?? Can't see how this would be more country wide than the previous spell...unless I'm reading wrong from the latest charts?

[bluearmy]

Surely though BA Only fringes of the coasts, mainly North west and east and inland Scotland look like being affected with regards to any snow?? Can't see how this would be more country wide than the previous spell...unless I'm reading wrong from the latest charts?

WW - this is a trough led cold flow as opposed to a block led one. There will be plenty of disturbances in the flow. how much precip they bring (troughs) and whether there are any warm sectors left in them to prevent snowfall down to low levels (shortwaves) is much too far away to pin down. As we get closer, the models will begin to show these features more reliably though that's only as a rough guide as to whether they will exist. As we know only too well, pinning these down is a 24/48 hour job at best!

London ens trending colder clustered re the longevity of this period. Latest on the right.

.

[BLAST FROM THE PAST]

Sorry but whilst its fairly quiet could I just ask what the difference is between the last cold spell that promised so much but got watered down to well one day compared to next weeks upcoming cold spell ? I read Steve murrs post last night saying that the uppers weren't very good at all with the spell or snap showing at the end of next week so I'm a little confused thankyou

Steve may be focussing on SE but also unless a northerly is sustained and brings air sourced from the arctic they are disappointingly shortlived and not too effective for all UK.

For me no doubt N Wales/N England and especially Scotland and N Ireland will benefit but the pattern developing to me IF continued would be a countrywide coldspell with snow chances for all.

06Z enhanced again....excellent run

 

My new chart of the winter so far

 

 

BFTP

Edited January 24, 2015 by BLAST FROM THE PAST

[chionomaniac]

It's great to see some distorted vortex shapes coming into play in the output. Today we are seeing a 3 wave attack - it could almost be sponsored by the Isle of Man!

 

 

 

 

I have always thought that any vortex shape that we see that looks like a star wars spaceship is generally a good thing.....

 

The tie fighter vortex will do:

 

 

Happy with a b wing vortex too

 

 

The orl shuttle vortex is similar to todays projection:

 

 

But there is one star wars vortex we dont want - the death star vortex......

 

 

 

 

[stratty]

Steve may be focussing on SE but also unless a northerly is sustained and brings air sourced from the arctic they are disappointingly shortlived and not too effective for all UK.

For me no doubt N Wales/N England and especially Scotland and N Ireland will benefit but the pattern developing to me IF continued would be a countrywide coldspell with snow chances for all.

06Z enhanced again....excellent run

 

My new chart of the winter so far

 

 

BFTP

............if you think that is going to happen like that, with those LPs in ideal placement and in over a weeks time, can you please give me tonight's lottery numbers BFTP? (ironically, as a snow lover, if I won the lottery I think I would take the family on a nice hot and sunny holiday! )

[EmmaF]

Thankyou so much for your explanations

Emma

[IDO]

You can see from the D7 GEFS the chaos that Atlantic low causes within the members:

 

 

Certainly looking like a 2 stage cold spell with that low mixing out the cold for a day or two around D8-9, nothing major, but enough for the south to turn snow to rain as the rain band associated with that low slides east.

 

The op and control are not dissimilar at T204: 

 

 

[stratty]

That snowfall showing by next Wed is only 4 days away, not sure if the GFS is bringing the cold in a little early but warnings could be out in the next few days if true.

90% chance on the back edge for Wednesday!

Edited January 24, 2015 by stratty

[shaky]

Corking output over the past couple of days! ! Looks like winter is about to go out with a bang! ! All this happening whilst we have just finished with another cold spell!! Gfs 06z is a thing of beauty! !

[EML Network]

Sorry but whilst its fairly quiet could I just ask what the difference is between the last cold spell that promised so much but got watered down to well one day compared to next weeks upcoming cold spell ? I read Steve murrs post last night saying that the uppers weren't very good at all with the spell or snap showing at the end of next week so I'm a little confused thankyou

 

I think you're absolutely right to mention this and it could still end up like that.

 

If the cold spell is to be watered down to just a 2 or 3 day damp squib then you would expect that over the course of the weekend the tell tale sign would start to appear on some of the runs.

 

The control run looks great

 

 

But here's why you are right to be cautious as this could just as easily happen...

 

 

 

personally I have seen enough evidence to really not care either way as IMBY I won't see snowfall from anything other than an Easterly, if you live along the East Coast of England then I'd be getting excited about this, if you're in N.ireland I'd be getting my snow shovels ready

[IDO]

We have to hope the op and control are right as the 06z GEFS are poor as a whole with many flattening the pattern around D8-9 due to that spoiler low. The mean at D10:

 

  Control

 

 

[mulzy]

The 0z ECM ensembles for London

 

 

Not bad but the cold temperatures still 5-6 days away and even then it's unlikely to be the 'brutal cold' that we all want.  Northerlies look great on charts but deliver rarely away from coasts and high ground in the North.  Loved to be proved wrong though...

Edited January 24, 2015 by mulzy

[Summer Sun]

Take this with caution still but Wednesday could deliver some snow for some with temperatures likely to fall quite rapidly as the day progresses

 

7am

 

 

1pm

 

 

7pm

 

 

Precipitation would turn to snow as the colder air moves over the country especially for higher parts

 

 

Of course some lower levels could be marginal at times but with some elevation January could well be about to go out on a snowy note

 

Edited January 24, 2015 by Summer Sun

[terrier]

Think I'm going to remain cautious of the output at the moment. We have been here so many times this winter. Yes the ECM looks great this morning but I think it has performed poor this winter. As Steve Murr has said the temps don't look great for a big freeze. Think I will wait to see if gfs ECM ukmo are still showing intrest around tues/weds until then I will look at the output and take it with a huge pinch of salt.