The hunt for cold - Model discussion (late November)

[Ali1977]

20 minutes ago, CreweCold said:

This is the toastiest we've seen the strat forecast so far this season...

That’s getting close to SSW territory - as predicted by some 

[CanadaAl]

35 minutes ago, Ali1977 said:

That’s getting close to SSW territory - as predicted by some 

I'm fairly sure that is SSW territory. I was told -8 or above to classify as SSW. shame its 384 hours out! 

[ArHu3]

10 minutes ago, CanadaAl said:

I'm fairly sure that is SSW territory. I was told -8 or above to classify as SSW. shame its 384 hours out! 

No for a ssw you have to have zonal wind reversal at 60N 10hPa

[Coopsy]

1 hour ago, ArHu3 said:

No for a ssw you have to have zonal wind reversal at 60N 10hPa

Technically that’d be for a major SSW. For a minor one to occur you don’t need full reversal just a slowdown and if there shows to be a temp increase of 25oC or more over the week then the minor SSW is on (I haven’t checked that on the charts)

That said we all want that major SSW for the vortex to be affected and winds to become easterly increasing our chance of winter proper hitting 

The next day or two is going to be a roller coaster I feel. Short term still 50/50 for me on getting it all in place. Long term looking good for cold and snow if all comes together. 

Edited December 4, 2018 by c00ps

[Seasonality]

Cold creeping closer on 00z ECM and not being held at days 9 and 10

[bluearmy]

getting really close to squeaky bum time now 

we are lost gem and icon has never really wanted to play on this easterly  .......make a note on that if it fails 

Gfs phases the low heights too far north (as it has more than once )

gfsp and ecm consistent

Ukmo could go the way of the binary 25% cluster from yesterday’s 12z eps in the 6/7 day period with poorer amplification but whilst there were two extra ones appear at day 8, the poor coldie cluster remained at 20% so we would need to be really unlucky to avoid the scandi ridge ...... uncertain if it plays out with the very cold uppers reaching us and sustaining for more than a snap. 

[Met4Cast]

Have I woken up in a different universe?

GFS looks great to me!

UKMO looking okay

ECM fantastic

[Wilxy]

14 minutes ago, Daniel Smith said:

Have I woken up in a different universe?

GFS looks great to me!

UKMO looking okay

ECM fantastic

I fell asleep before the 18z so I have seen a massive improvement overnight

[Duane S.]

19 minutes ago, Daniel Smith said:

Have I woken up in a different universe?

GFS looks great to me!

UKMO looking okay

ECM fantastic

Watching through the GFS Op on the 500mb frames, around D6 / D7 I must admit to thinking it wouldn't make it. However by D8 energy split and a strong dive south of the jet saved the day.

Clearly FI thereafter as lo res kicks in.

All in all, a fairly decent 00z suite. Certainly in terms of no particular downgrade trend has emerged.

[markw2680]

Although the main models all look pretty decent this morning there will probably be the usual upgrade as the day goes on, quite often the 0z seem to be the worst imo but this morning they certainly ent bad.

this chart is something I’m liking

[ArHu3]

1 hour ago, c00ps said:

Technically that’d be for a major SSW. For a minor one to occur you don’t need full reversal just a slowdown and if there shows to be a temp increase of 25oC or more over the week then the minor SSW is on (I haven’t checked that on the charts)

That said we all want that major SSW for the vortex to be affected and winds to become easterly increasing our chance of winter proper hitting 

The next day or two is going to be a roller coaster I feel. Short term still 50/50 for me on getting it all in place. Long term looking good for cold and snow if all comes together. 

You're right, I was in a hurry. Anyway, not that discussing this changes anything but I think that displacements are more often than not unfavorable for us and we need an actual split. In the stratosphere thread catacol explains why displacements often can be unfavorable 

 

 

Edited December 4, 2018 by ArHu3

[snowray]

ECM still looking very good this morning, we actually get some colder air moving in, -8c uppers, and the undercut at D9, could be a fair bit of snow around if it were to verify. Still a long way off of course, I'm hoping that the Scandi high can hang on in there or ideally move towards Iceland for a reload from our NE.

Edited December 4, 2018 by snowray

[Summer Sun]

Looking at the ECM mean and op on the 850's and the mean still isn't following the Op yet with this potential really cold air

More runs needed to see which way this will go after the 10th

[Bristawl Si]

8 hours ago, snowray said:

First week or two of February are ok, but it's all downhill after that, the sun gets too strong. Although if a cold spell starts in early Feb and we get a big freeze, that alters everything, this is when February can be memorable.

Erm....March 2018?! 6-8ins of Snow and below zero temps at 14.00 here in Bristol, SW England? Short memories and all that!

Edited December 4, 2018 by Bristle boy

[snowking]

17 minutes ago, ArHu3 said:

You're right, I was in a hurry. Anyway, not that discussing this changes anything but I think that displacements are more often than not unfavorable for us and we need an actual split. In the stratosphere thread catacol explains why displacements often can be unfavorable 

 

 

It depends entirely upon where the displacement pushes the vortex to - and often the ‘angle’ of the displacement too.

What we see with the current/forecast Wave 1 action is the core of the vortex pushed from over the arctic/Greenland/Canada across to Siberia and Asia.

There’s a lot of ifs, buts and maybes, but if you are eventually looking for a draining of the low heights to our NW (and assuming that the tropospheric response is near identical to the stratospheric one) then this is good news in the longer term - and especially in association with the later (I suspect East Asian Mountain Torque led, but I have not checked this yet) more significant warming in the Asian sector, which in recent stratospheric history has been one of the more exciting warming locations in terms of cold tropospheric consequences

But what we should bear in mind is that with this westerly push of the vortex (and again assuming the tropospheric pattern follows the stratospheric one quite closely) is that it is likely to mean we get some more momentum in the Atlantic at some point in December. That is not to necessarily say a return to raging zonality is on the cards, but I suspect the forecast potential height rises to our north-east may be somewhat short lived (unless we get very lucky) for now - but a) the continued tendency towards Scandinavian/Siberian blocking in the short term will continue to damage the already wobbly vortex, and b) I really do think this would be short lived whilst we see the vortex shift above our heads take place. And what happens the other side of this could be something quite welcome for most members on here

In summary - it’s all very complicated, but there’s no magic formula to say that Wave 1 = this and Wave 2 = that - but observations of this season so far look really rather positive to me

[SLEETY]

interesting that if this verifies this will be the 2nd easterly outbreak in a matter of weeks,to follow on from the easterly outbreaks in March and  lots of blocking over the summer.

That SSW has really changed things this year ,could be one mega cold blocked winter if it continues.

[SLEETY]

9 hours ago, snowray said:

First week or two of February are ok, but it's all downhill after that, the sun gets too strong. Although if a cold spell starts in early Feb and we get a big freeze, that alters everything, this is when February can be memorable.

Most of us had  lying snow and temps below freezing all day in March this year ,you have forgotten that ? and mid March 2013 3f snow drifts at sea level and about 4inches of lying  snow here,so don’t know how from mid FEBUARY you think we can’t get a decent cold spell.FEB 86 was colder 2nd half of month.lots of examples of deep cold in late Febuary.

Edited December 4, 2018 by SLEETY

[northwestsnow]

It does look like the Azores ridge it going to make it into Scandy, after that, who knows.

EC det is lovely but there must be a helluva lot of members that push the block back before it gets chance to establish judging by the mean later on..

GEFS also look cold mid term but again a signal for the high to get shunted out of the way longerterm..

So, easterly looks fairly certain, but it might be brief..

 

 

[snowray]

22 minutes ago, Bristle boy said:

Erm....March 2018?! 6-8ins of Snow and below zero temps at 14.00 here in Bristol, SW England? Short memories and all that!

Yes but how long did it stick around for Bb?

Of course we can get heavy snowfall in March, and April sometimes, but it's the rate at which it melts that I was referring to, the longer days and strength of the sun by then usually mean that its all gone in a day or two away from any shaded areas, particularly in the South of the country. Having said this it goes without saying that if you get a foot of snow in March it will take longer to melt, but a foot of snow in mid December can hang around with very little melt through til Christmas quite easily, as long as conditions stay relatively cold.

 

Anyway enough of that.

 

GFS 00z Ensembles still looking very good, hopefully the 06z will eradicate a few of the milder members there.

[Weathizard]

10 minutes ago, SLEETY said:

Most of us had  lying snow and temps below freezing all day in March this year ,you have forgotten that ? and mid March 2013 3f snow drifts at sea level and about 4inches of lying  snow here,so don’t know how from mid FEBUARY you think we can’t get a decent cold spell.FEB 86 was colder 2nd half of month.lots of examples of deep cold in late Febuary.

OT, but here on the south coast even though we’ve had lying snow and a fair amount of it in the later winter months as soon as the sun comes out it melts very very fast, what most people crave is snow that comes and stays for a while, not the type that melts straight away even at very low temps.

 

Think caution should be advised this morning, things are getting very interesting but we must remember how knife edge these set ups are, a bit too much energy in the jet or a bit of energy spilling over the top and it all goes Pete tong!

Edited December 4, 2018 by Weathizard

[snowray]

3 minutes ago, Weathizard said:

OT, but here on the south coast even though we’ve had lying snow and a fair amount of it in the later winter months as soon as the sun comes out it melts very very fast, what most people crave is snow that comes and stays for a while, not the type that melts straight away even at very low temps.

 

Think caution should be advised this morning, things are getting very interesting but we must remember how knife edge these set ups are, a bit too much energy in the jet or a bit of energy spilling over the top and it all goes Pete tong!

Thank heavens, someone actually gets my point Weathizard!

[daz_4]

It seems the uppers won't be that cold. This will probably be a borderline situation even here in Central Europe. Mix of rain and snow, temps around zero. Nothing extraordinary but better than raging southwesterlies, that's for sure.

[I remember Atlantic 252]

11 minutes ago, daz_4 said:

It seems the uppers won't be that cold. This will probably be a borderline situation even here in Central Europe. Mix of rain and snow, temps around zero. Nothing extraordinary but better than raging southwesterlies, that's for sure.

Problem with Dec, needs to be late Jan to late March, everything much colder then if E'lys arrive

[Met4Cast]

Quite a clear and supported warming trend on the 00z GFS ensembles after the initial bout of colder air

 

[carinthian]

On ‎03‎/‎12‎/‎2018 at 08:23, carinthian said:

Morning all from a cloudy but mild Austrian Alps. 24 hours on from yesterdays post and the same consistency on route to cold being shown on most models now at 168t  as shown on the latest GFS control run. Remember , I did mention there will be variations on the more frequent op runs as shown this morning with GFS against ECM at 240t. The former with the high sinking and the other with an undercut . Tomorrows comparison at 144t will be important as to determine the type of cold spell now likely to develop next week for many in Europe and decrease or increase the probability of a sustained cold spell. A crucial 24 hours coming . I will talk to the team over here in a hour or so as they will have a update on their singular NWP model and will get back with specifics for you lot back in blighty.

Morning all, basically the big three models operational runs in agreement at 144t, with possibly ECM run showing the sharpest of the ridging  over the British Isles.  The UKMO looks like the least favourable at this stage with a possible delay to draw in the colder Easterly flow. Maybe the Atlantic spurning a short wave into the equation in the period 144-168T. The ensemble runs not as good this morning in the longer term from GFS and ECM. That just my view on things at the moment, so none the wiser if a sustained cold well will evolve . Will get an update from the team over here later this morning to see what their model is showing.  A  very frustrating but sure we will know better by the end of today.

C