Model Output Discussion 19th January 2014-18z onwards.

[Man With Beard]

http://www.meteociel.fr/ukmo/runs/2014012312/UN144-21.GIF?23-17

UKMO raw 144-

 

UKMO Raw tonight is 9.5/10 if the ooz was 10/10.

Although troublesome snow for the SE if that verifies- not that it will at this range.

 

S

I think a few people would love to know how you see troublesome snow on that chart - I see uppers -4/-5C in a low which has drawn in a lot of Atlantic air, I would have though it was "high ground" or margin?

(edit - "marginal")

Edited January 23, 2014 by rjbw

[Mucka]

I'm still wondering about that second Arctic high that is modelled to move across the pole post day 7 that I mentioned as a strengthening signal recently (It has not been modelled by ECM this morning so expect this evenings output to look quite different re the NH post 120/144)

 

 

If the Atlantic does not break through and that links up favourably once more with the block over Scandinavia then the MetO could be waiting a long time for the zonal pattern that has dominated this winter so far to re-establish itself.

 

Clearly the balance of data so far must show that it can not exert enough influence within the required time-frame but that was exactly the case with the current set up when I was talking about a race against time to get Arctic block to link up with the Scand high for this current situation, stating that if it didn't happen we would be looking at a zonal picture but if it did it was game on. This looks like a similar situation developing to me, will the Atlantic overwhelm the block before reinforcements arrive?

 

GEM shows only a weak high with a belated link up due to energy pushing through NE, this is probably what the majority of ensembles (that actually model it) will be doing too but pay close attention to this evenings ECM and JMA and all the output through the next few runs to see if that develops further.

Edited January 23, 2014 by Mucka

[gottolovethisweather]

The Easterly is certainly on as this particular GFS run is peachy in its early stages once the four consecutive days of flooding rain and showers are out of the way. Much better prospects for a period of cold weather unfolding IMHO.

 

To update this posting, currently it is just a three day Easterly with Friday seeing the return of the Atlantic. We still have other runs to run and a lot of water under the bridge to come but kudos to fergies post from earlier as that is indeed how they (the Beeb/UKMO etc.) suggested it would evolve. Still, I feel "more runs needed" will be the much-quoted phrase passed about before this saga is over for sure.

[Ali1977]

Maybe further in FI is where we need to look, high pressure building over Labrador, and a big one moving towards the Arctic from Alaske. If they could stay there the PV and westerly's days are surely numbered.

 

Wrong, high mown down...again

Edited January 23, 2014 by Ali1977

[mickpips]

I think a few people would love to know how you see troublesome snow on that chart - I see uppers -4/-5C in a low which has drawn in a lot of Atlantic air, I would have though it was "high ground" or margin?

We have seen heavy snow showers on and off all day here with air temps around 5/6 degrees and 850's not much to write home about. -4/-5 uppers are more than sufficient in providing snowfall , even to low levels. I am pretty confident that both the gfs and ukmo 12z output will provide snow to many next week and not just the North / Ne as indicated by many including the Met.

[Panayiotis]

Evaporative cooling would take place in the SE (due to lack of wind) on the 144hrs chart , and with widespread -4/-5C uppers and low thickness values, a lot of places have the potential to SEE snow fall even at lower levels:

Edited January 23, 2014 by Panayiotis

[swfc]

Not really, it backs the pattern westwards and there's nothing wrong with that to be honest. It delays the arrival of the cold a bit, but gives us more room for error

Tbh this upcoming spell of cooler-colder weather is atm transient before the usuall unsettled  atlantic moves in.The arrival of cold air as you say is nothing out of the ordinary "well for this winter maybe"lol but its a fleeting blow imo.The ukmo actually looks to more akin now to the gfs 12z which itself blows up.I think ians post sums things up for me with rain being the main player and cold wintry weather not being of much interest

[Joe Levy]

Tbh this upcoming spell of cooler-colder weather is atm transient before the usuall unsettled  atlantic moves in.The arrival of cold air as you say is nothing out of the ordinary "well for this winter maybe"lol but its a fleeting blow imo.The ukmo actually looks to more akin now to the gfs 12z which itself blows up.I think ians post sums things up for me with rain being the main player and cold wintry weather not being of much interest

I never said that in any case, I would be careful about being decisive about a situation that has yet to happen. The official forecast is certainly worth heeding, and currently a return to cool/cold zonality is the favoured option, but since we don't decide the weather, that is prone to changing and fluctuating. Where there is uncertainty, sometimes turning to previous examples can help a bit. If the low sinks south quick enough, then blocking to the north of us could strengthen. Cold air, as I'm sure you've heard hundreds of times, is denser than mild air, so it is harder to shift. For the time being, let's hope for a cold snap if that's what you're after, and see what happens. 

[IDO]

The GFS ensembles picked this flatter pattern out several days ago with a good cluster. The ECM op came on board a day later and has been resolute since with a return to zonality once the quasi easterly low sinks through the UK next week.

 

Other options were on the table but the upper ridging of the AH has now been modelled by GFS 12z similar to the ECM op and this cuts off the upper flow to the lower heights sinking SE.

 

UKMO at T144:   GFS at same time: 

 

The lower heights go over the top on the GFS whilst the UKMO keeps that flow longer and the longer that flow of undercutting goes on, the better chance for the upper heights to the NE to retrogress.

 

GFS is then zonal, as the Atlantic rushes in, and again the UK is at the end of the zonal train=more wet weather. It stays zonal till T384 (cooler variety). This is the so called tipping point in its full glory:

 

T384: 

 

GEM has the same problem. It's Atlantic ridging cuts off the upper flow to the trough:  

 

And from there it follows the GFS, so by T240 we are zonal:

 

Has the UKMO modelled this correctly? We will see.

Edited January 23, 2014 by i'm dreaming of...

[Alexis]

Evaporative cooling would take place in the SE (due to lack of wind) on the 144hrs chart , and with widespread -4/-5C uppers and low thickness values, a lot of places have the potential to SEE snow fall even at lower levels:

 

-4 uppers are usually insufficient for low ground, even with a continental flow. -7 is a good indicator in most situations, but even -8 is preferable. I can't see anything other than cold rain on that chart. We're only really wanting the low to slide to try and get get heights to build behind - the low itself is going to be a miserable affair to be under. And lets face it, we're still waiting for a single chart to appear to show what we need at this stage. Maybe over the weekend, but not at the moment, no matter how favourable the pressure looks over the pole and the Pacific ridge.

[Joe Levy]

-4 uppers are usually insufficient for low ground, even with a continental flow. -7 is a good indicator in most situations, but even -8 is preferable. I can't see anything other than cold rain on that chart. We're only really wanting the low to slide to try and get get heights to build behind - the low itself is going to be a miserable affair to be under. And lets face it, we're still waiting for a single chart to appear to show what we need at this stage. Maybe over the weekend, but not at the moment, no matter how favourable the pressure looks over the pole and the Pacific ridge.

That's not actually true. There has been snowfall in lowland Britain in -2 uppers before, due to low dewpoints and/or low thicknesses. Last year, in fact, there was snow in the South West with uppers of around -2/-3 if I remember correctly

Edited January 23, 2014 by Joe Levy

[Cheese Rice]

I'm getting pretty excited that there might be some really wintry weather across the high ground of northern England and Scotland.

 

BBC weather forecasts showed two blobs of snow over N.England/Scotland for Sunday

 

 

 

 

 

 

[SMU]

I think a few people would love to know how you see troublesome snow on that chart - I see uppers -4/-5C in a low which has drawn in a lot of Atlantic air, I would have though it was "high ground" or margin?

(edit - "marginal")

That should have been the NE not SE

 

S

[Cheese Rice]

ECM shows snow for Sunday 

 

[Paul White.]

You know all of this talk about a bit of rain down South for Sunday we have taken our eyes off of the ball for what's happened today in the last hour, between this thread and the met office I feel let down, not a single warning about the blizzard I have just had to battle through to get home.. I can also confirm to shedhead that they weren't "wet snow flakes" as he alluded to earlier. Maybe Frosty can confirm if Wakefield experienced anything like we just received in Huddersfield ? Wrt whatever the models shows next week if it's westerly bring it on because if this is the mild Atlantic it ain't that mild

[LomondSnowstorm]

That's not actually true. There has been snowfall in lowland Britain in -2 uppers before, due to low dewpoints and/or low thicknesses. Last year, in fact, there was snow in the South West with uppers of around -2/-3 if I remember correctly

The bottom line is it absolutely depends on the circumstances - in a slack flow with embedded cold air the uppers only need to be just below 0C for snow to fall, but if you live right on the coast with a strong onshore breeze then even -8C might not cut it, especially if the airmass is not Arctic or cold continental in origin.

With the slack low pressure on the UKMO +144 in the SE you might just be able to eek out some snow with with those uppers:

bearing in mind the flow is a (localised) continental one. For eastern Scotland, for example, those uppers are and have been touch and go for convective stuff - usually -8C is the cut off point for us from an easterly between a wintry mix and proper lying snow, so it wouldn't take much for that to be achieved by midweek. However, inland in central England you generally don't need uppers quite as low as that because you don't get the same degree of coastal mixing.

However, inland northeast Scotland still looks the place to be if you're looking for decent snowfall in the next week or so.

Edited January 23, 2014 by LomondSnowstorm

[i luv snow]

You know all of this talk about a bit of rain down South for Sunday we have taken our eyes off of the ball for what's happened today in the last hour, between this thread and the met office I feel let down, not a single warning about the blizzard I have just had to battle through to get home.. I can also confirm to shedhead that they weren't "wet snow flakes" as he alluded to earlier. Maybe Frosty can confirm if Wakefield experienced anything like we just received in Huddersfield ? Wrt whatever the models shows next week if it's westerly bring it on because if this is the mild Atlantic it ain't that mild

Further to this, If it interests anyone, it's also sleeting/wet snowing/hailing (as well as Thunder/Lightning!) in Central Manchester at the moment. So as you say, if this is the 'mild' Atlantic, bring it on next week.

Edited January 23, 2014 by i luv snow

[SnowObsessor90]

I haven't seen the word 'downgrade' used yet but that's the impression I'm getting, ah well it's not as I should have been expecting anything different.

[jvenge]

Leeds also had a heavy snow shower as well.

[Wadey]

-4 uppers are usually insufficient for low ground, even with a continental flow. -7 is a good indicator in most situations, but even -8 is preferable. I can't see anything other than cold rain on that chart. We're only really wanting the low to slide to try and get get heights to build behind - the low itself is going to be a miserable affair to be under. And lets face it, we're still waiting for a single chart to appear to show what we need at this stage. Maybe over the weekend, but not at the moment, no matter how favourable the pressure looks over the pole and the Pacific ridge.

There was snow in the midlands at about -2/-3 uppers about a week ago so not impossible and there is snow about today and it's not on top of Ben Nevis either

[fergieweather]

Hmmm.. How does one have high confidence circa 10 days in advance to a return of Zonal & no issues regards lowland snow, but a 30% probability of 10-15mm of rain for the next day?

 

I would take it with a pinch of salt re snow issues next week, especially amounts/quantities. I can count a lot of times the forecast has been "Little snow" and turned out to be quite a lot.

Hi - I think you misread the prognosis tomorrow: 10-15mm widely  30% probability locally rising to 20mm.. The uncertainty due to the complex inner (warm) front structures and potential wave / triple-point development shearing-away SE across Wales/SW, which is likely to offer the highest ppn totals.

 

The change back to an Atlantic-dominated story circa Thurs-Fri onwards is well-signalled across the models and ENS, so can't really be open to other interpretation as things stand. That's the underpinning of the UKMO thoughts (as reflected by others on this forum who see the same net result). Beyond that into trend period, again to cite the Dep. Chief based on 00z suites:

"....examination of EPS members indicates that the vast majority of solutions support a continuation of the zonal pattern, with only a small minority (of the order of 10% or so) suggesting non-zonal patterns (typically, intense lows or highs, some leading to E’ly flow)."

[The PIT]

Well we get or rather cold shot next week but it doesn't seem to last long as the next set of lows beat the high pressure up fairly easily in deep FI which what the ECM was showing this morning. Pity as a series of undercutting lows would be nice. The models may still lurch back to that idea in future runs. 

[Barking_Mad]

Snow in Bolton - some heavy ppn passing to the SE over Lancashire and Yorkshire - clearly not forecast. 

 

 

https://pbs.twimg.com/media/BeriTJgCUAAF953.jpg

 

https://pbs.twimg.com/media/BerhIRmCYAIkVG3.jpg:large

[terrier]

Really value Ian's output on this thread. And they certainly have more acess to data than we do and it seems obvious that the mogreps model isn't buying any real cold outbreak past Thursday next week. With nearly 90% of the eps members going for a return to Atlantic winning through. And for them not to be backing there own model ukmo at moment that should really tell us all we need to know.

[Catacol]

If....and a bif IF,,,,the Easterly gets in post T144....it's hard to see the Atlantic coming back easily with the way things are shaping up on the GFS

 

I'm afraid that's nonsense. The models are still operating under a background signal of vortex energy over Canada, cold air spilling into the atlantic encouraging strong cyclogenesis and an azores high that is prominent enough over Biscay that it is preventing lows from sliding genuinely to the south. In this situation it is quite hard to see how the atlantic WONT come back.

 

The pattern is really very entrenched now. To break out of it we need the main driver of the pattern - the persistent deep low pressure anchored over Canada - to relent in its domination of the atlantic. We could also do with the azores high moving away - Steve is right that we need it to be displaced as it is an ever present feature of our weather... but right now it is in exactly the wrong place.

 

In theory changes should already be happening: the vortex isnt as strong as it was before and there is a general warming and disruption of the strat ongoing... but the effects at the trop level so far are limited as we will see over the next 4 days. To my eye the changes that many called for at the start of winter are now happening only slowly and it is increasingly looking like the very very cold strat (and it nearly went off the scale it got so cold...) has created a beast of a vortex that just isnt going to bust quickly enough for us. The subtext of some of the posts over on the strat thread are now pointing to proper displacement and/or disruption not happening until mid Feb or later... or possibly indeed not at all. And given the reasonable chance for the effects to be only slowly felt I am beginning to doubt whether February is going to deliver.

 

It is still relatively finely balanced and it would be folly to think that any forecast or trend is ever carved in stone. I think the chances of cold next week now are gone - watch the TV instead and look out for pictures of the Somerset Levels disappearing under water - amongst other places of course. We may get a transient easterly of 24-48 hours but it will soon be blown away by more atlantic systems. Beyond that, if by 1st Feb we are not seeing proper modelling of stratospheric vortex displacement or breakup within the 240h bracket then it will nearly be game over for this winter. By then I think a lot will be clear and the last 4 weeks of our winter will be laid out in front of us. We may get the odd day here and there of arctic air in the mix and there is always a chance that the scandy high that is also digging its heels into the pattern may ridge our way off an on - but a proper cold blast with a dominant high latitude block is what many coldies (including me) are looking for and the clock is ticking.

 

I suspect the Met call of the coming week being a genuine tipping point is pretty close to the mark - not just for the actual pattern of the next 7 - 10 days but also in terms of medium term modelling out to Feb 10-15. I got a bit of flak back in November for stating that nothing looked good in the run up to Xmas. I'm braced for a similar response to this post but I think we must be prepared for the possibility that, for the South of England at least, the winter of 2013/14 will be memorable only for its water levels and the fact that we will want to do our best to forget that it ever happened.

 

Cue... the most powerful wave 1 warming of the winter on the horizon, the modelling of a strong Greeny block at 240h on the next run, and an about turn by the Met in the long range forecast by the end of the weekend. Come on Commentator's Curse - strike me down...! Please!!!!