Winter Model Discussion - The Hunt For Cold -18z 17/12/12

[chionomaniac]

I have just wasted 5 minutes of my life deleting off topic posts. Please keep on topic and relevent. If you want to discuss last Christmas then please do so elsewhere and moan in the moaning thread.

Thank You

[offerman]

CreweCold

Excellent question, although yes in 2010 we did but the majority of the time we always miss these for some odd reason as you say. It`s as if there is an invisible wall just off the coast of Ireland that goes right up to the stratosphere directing cold out to the Atlantic. The other key point as you mentioned. Why don`t we get the serious cold that the mid Atlantic gets, i thought cold air travelles better over land than sea yet deep cold only reaches Northern scotland and warms the further south it comes. Can`t be Gulf Stream as mid Atlantic also hugely affected by the G.S.?? ANy Experts enlighten us to why? Many Thanks.

P.S, the same happens to when North sea gets blast and often misses us and goes direct to Germany yet over there the cold air does sink all the way down there land.

Edited December 19, 2012 by offerman

[snowblues]

GFS and the UKMO at T144 are very alike

[bluearmy]

note the shortwave that appears south of iceland which prevents the troughing being able to clear east and allow the cold uppers to hit us from the north. this is a very common feature in this scenario and i assume has to do with the very cold uppers meeting the west to east atlantic flow. without a build of heights to our west/northwest, it will be tough to advect those low uppers directly from the north is a quick plainless fashion.

[Cheshire Freeze]

The vortex looks to be on the ropes by this point

The question is how do we shift those heights over Spain/Italy/N Africa? They can be very hard to shift once they're evident. Can anyone with better knowledge than me explain how we could feasibly get out of that predicament in quickish fashion were it to occur?

Edited December 19, 2012 by CreweCold

[Severe Siberian icy blast]

Over all a better gfs , that is until it get to 192z and then as per usual it goes into default mode which is really annoying because you can litterely watch as soon as it goes into low res it bumps up the jet and brings in the Azores and once again gives us southwesterlies , absoulute joke, but over all it's a nice step in the right direction.

[offerman]

The vortex looks to be on the ropes by this point

The question is how do we shift those heights over Spain/Italy/N Africa? They can be very hard to shift once they're evident.

Excellent Q, most of the time its the Azores high or Euro high that are such awkward ones to shift.

[Chess01]

People who are Writing off christmas eve + is really stupid . Nothing is set in stone yet and the models are having a tough time dealing with the sitution . The next few days look wet but. There after who knows

[Ian Brown]

so now we have dispensed with the 'tease from the east', attention will turn to the arctic to see what trajectory those low heights come in on and what block builds near greenland. i doubt it will be much clearer !!

Unfortunately, heights from the Canadian area can't build East into Greenland, it's simply doesn't happen synoptically so the only way it can go is what the GFS goes onto show in the low-res with a SW-NE tilted jet and subsequent pressure rise from the South.

[Cheshire Freeze]

Unfortunately, heights from the Canadian area can't build East into Greenland, it's simply doesn't happen synoptically so the only way it can go is what the GFS goes onto show in the low-res with a SW-NE tilted jet and subsequent pressure rise from the South.

Exactly what I'm thinking Ian. (see my previous post). More time wasted IF it comes off like that.

What I will say is that even though the picture is changing between runs, the high to the south is consistently modelled and very often is being modelled throughout the duration of FI. We'll struggle to get any meaningful cold with this feature in place. It needs to do one from the output!

Edited December 19, 2012 by CreweCold

[bluearmy]

Unfortunately, heights from the Canadian area can't build East into Greenland, it's simply doesn't happen synoptically so the only way it can go is what the GFS goes onto show in the low-res with a SW-NE tilted jet and subsequent pressure rise from the South.

depends what else come out of the arctic ian. re the GEM 00z run.

[bradymk]

Unfortunately, heights from the Canadian area can't build East into Greenland, it's simply doesn't happen synoptically so the only way it can go is what the GFS goes onto show in the low-res with a SW-NE tilted jet and subsequent pressure rise from the South.

A valid point Ian however if we can shift the high to the east quickly the pattern should move east but we want this high to clear off now!

[492]

12Z GFS run ismore progressive than the 06Z run especially in later frames. Slightly more consistency in nearer time frames but very cold air has become entrenched over western Russia and is starting to extend into Poland and is likely to extend further west before stalling. Consequently the high to the east may be more difficult to shift than models are currently predicting.

[Methuselah]

But then, by the time we're past Christmas the models' outputs will, no doubt, bear little resemblance to those of today?

[492]

But then, by the time we're past Christmas the models' outputs will, no doubt, bear little resemblance to those of today?

Sooner than that.

[Snowmad79]

Can anyone with better knowledge than me explain how we could feasibly get out of that predicament in quickish fashion were it to occur?

A plane to Scandinavia ?

And so not to leave my post as an off topic one liner I will give you my summary of the model output so far today...

Summary:

SAND BAGS AT THE READY PEOPLE!

[Harsh Climate]

People who are Writing off christmas eve + is really stupid . Nothing is set in stone yet and the models are having a tough time dealing with the sitution . The next few days look wet but. There after who knows

I wouldn't say their stupid but If I was to have a cheeky bet I would probably choose some where in north west scotland or northern ireland as our next cold snap looks like coming from the north west.

[phil nw.]

The upper trough around or just to the west of the UK through Christmas week. has been well trailed in mean outputs over the last few days so these 12z GFS/UKMO runs are no real surprise i guess.

A wet period now ahead over the next few days as the Atlantic fronts only slowly move north east across the UK.

The weakness in the vortex can be seen over the Canadian side but the Siberian energy unfortunately is modelled to spread across towards Greenland keeping us in the westerly pattern for a while

It looks like a period of typical UK Atlantic weather for the next week at least while we continue to look for some upstream developments to move the pattern east.

[Ian Brown]

depends what else come out of the arctic ian. re the GEM 00z run.

Again historically we don't want to be having to relying on pressure coming out of the Arctic because invariably it will not be able to extend or influence far enough South for long enough before the jet comes back into play.

We don't want to be in the position shown at day 9/10 on the GFS, that would be a long road back to anythng decent because we would have sluggish high pressure over Europe with no forcing to get rid of it.

[Chess01]

I wouldn't say their stupid but If I was to have a cheeky bet I would probably choose some where in north west scotland or northern ireland as our next cold snap looks like coming from the north west.

i dont mean stupid as nasty but rather foolish . Yes maybe most of england are odds agaisnt the cold but it would only take a few shifts to get the cold over . Now im not straw clutching just saying that the way the models have being swaying about dont take things to heart when you see them until the consictency is there . The past few 12z runs have upgraded the cold yet on the other runs they have downgraded it or got rid of it . That tells me that the models are having trouble

[snowmadchrisuk]

At +120 If them heights were a little stronger , and delayed the low to it's West for 48 hours you could end up with a Northerly for Christmas .... I wonder if the models have a surprise up there sleeve ....

[Harsh Climate]

Let's just say that if the ECM 240H was to come to fruition, I would say that this chart is a serious step in the right direction.

With a high pressure like that building over greenland, it would only be a matter of time before we got locked into cold. Because it would avert our usual atlantic tracking low pressure systems up the western side and over the blocking high. That pressure on the high would probably have it squeeze south and possibly leave us in a north easterly/easterly air flow!

A long way away but will be nice to see if the 12z ECM can follow this route.

[Harsh Climate]

i dont mean stupid as nasty but rather foolish . Yes maybe most of england are odds agaisnt the cold but it would only take a few shifts to get the cold over . Now im not straw clutching just saying that the way the models have being swaying about dont take things to heart when you see them until the consictency is there . The past few 12z runs have upgraded the cold yet on the other runs they have downgraded it or got rid of it . That tells me that the models are having trouble

To me I can't see any sudden change to proper cold weather before or during the christmas period but at this stage there is certainly the possibility that we could end up with a sudden northwesterly flow around christmas in it's early stages, which could bring the chance of a little wintry precipitation or a single flake of snow to the more favored areas.. ; ) Still odds are still against this and I will not be having a bet at this stage.

Edited December 19, 2012 by Harsh Climate

[Cheshire Freeze]

Again historically we don't want to be having to relying on pressure coming out of the Arctic because invariably it will not be able to extend or influence far enough South for long enough before the jet comes back into play.

We don't want to be in the position shown at day 9/10 on the GFS, that would be a long road back to anythng decent because we would have sluggish high pressure over Europe with no forcing to get rid of it.

Really can't fault your reasoning here Ian. It's always ominous to see HP build in that position. As you say, potentially little forcing to remove those heights which is why I asked that question in my earlier post (600).

Let's hope we begin to see those heights modelled a little bit less ferociously in future output

[Chess01]

To me I can't see any sudden change to proper cold weather before or during the christmas period but at this stage there is certainly the possibility that we could end up with a sudden northwesterly flow around christmas in it's early stages, which could bring the chance of a little wintry precipitation or a single flake of snow to the more favored areas.. ; ) Still odds are still against this and I will not be having a bet at this stage.

i would be very happy if the came of for my location . The only white christmas i have seen was 2004 when a sudden north westerly dumped some snow on us and that was unexpected