Focussed Model Discussion

[kold weather 4,333]

6 minutes ago, feb1991blizzard said:

Is the ECM graph likely to show higher temperatures in the extended range then as a result? - everything was trending colder on the last few runs

Remember if we were to get a SE flow higher 850hpa temps won't be too much of an issue, though much wouyld depend on exactly how cyclonic the flow is as the more it becomes dominated by the upper low, the worse things get, especially for the south, which is always more susceptible to things going wrong from that angle without having any decent cold pooling at all levels of the atmosphere.

[feb1991blizzard 14,062]

Just now, kold weather said:

Remember if we were to get a SE flow higher 850hpa temps won't be too much of an issue, though much wouyld depend on exactly how cyclonic the flow is as the more it becomes dominated by the upper low, the worse things get, especially for the south, which is always more susceptible to things going wrong from that angle without having any decent cold pooling at all levels of the atmosphere.

Problem is, if the surface temps are too high on the London graph, any other variable is academic because its rain anyway.

[bluearmy 35,310]

Just now, feb1991blizzard said:

Problem is, if the surface temps are too high on the London graph, any other variable is academic because its rain anyway.

Remember you don’t need sub zero T2 for snowfall feb ..........it’s dp’s which are relevant 

[feb1991blizzard 14,062]

1 minute ago, bluearmy said:

Remember you don’t need sub zero T2 for snowfall feb ..........it’s dp’s which are relevant 

1c at a push to settle, unless its very very heavy continuous snowfall

[bluearmy 35,310]

10 minutes ago, feb1991blizzard said:

1c at a push to settle, unless its very very heavy continuous snowfall

You are looking at maxes ....snowfall brings it back down. Ground temps aren’t T2’s ....anyway, it’s derailing the thread feb so let’s move on .....

[kold weather 4,333]

Right so just had a look through at all the ECM ensembles (though not the arctic or snow, etc...yet!) at 500mbs and some key things emerge:

1: The PV lobe over Canada remains the key driver pretty much throughout on a large percentage of the runs and there are constant lows spinning off and moving towards our general direction. I can't comment on the surface reflection but I'd say most look far south enough that most would have a good shot at frontal snow.

2: The ensembles are not really showing any agreement on where to place any northern blocking. Nearly all runs do have varying degrees of blocking, though a few are purely a response to the upper lows dropping down, but they are there. I'd say the favoured area is probably due north of us, but there are genuine Greenland blocks and a couple of strong Scandi blocks as well. Also worth noting there are a few Euro blocks as well (aka a Bartlett looking set-up)

3: The other factor that does shine is a prevalence for Azores high ridging, which probably comes as no surprise given no.1. Azores high ridges and normally shears off to the east so even though not many runs have any true Scandi highs, the response at 500mbs is still the same. It'll be interesting to see is surface pressure matches what the 500mb level shows on that one.

Overall the ensembles are better than the GFS ensembles tonight, though both are full of promise for sure as we move into Feb.

[bluearmy 35,310]

The 18z is a decent illustration of the slightly flatter pattern with less Atlantic ridging ....results in a shorter track of the low uppers with less moderation and we see the fronts apporach on a slightly better trajectory .....slightly more snow than the earlier run.

[bluearmy 35,310]

Interesting news from the clusters. - far from being less amplified, one 20% flatter cluster does the damage whilst the other two 40% options actually amplify enough to build good cut off upper ridges to our north (griceland)  ....so the flatter mean is actually better re likely southerly jet flow ! 

Edited January 20 by bluearmy

[kold weather 4,333]

Several marginal snow set-ups on the 18z runs, though they become less marginal the further north you go and also the longer into the set-up we go. Some decent snowfall likely for the Midlands north in this run though I doubt snow hangs around for to long, a snow-rain mix likely for the south with probably little settling snow bar maybe transient stuff.

Upper low dropping over the UK by 240hrs, so even though upper temps are moderating, its still decently cold.

BA- interestingly the cluster with the flatter pattern is still fairly snowy from what I've been looking at.

Edited January 20 by kold weather

[karlos1983 21,595]

Apparently a lack of Data on the GFS18z

If you’re wondering What does this mean?:

“It shows the amount of data gone into the initial conditions. More data in usually means a better idea of atmosphere at starting condition.”

[knocker 43,339]

Keeping in mind my final comment in the short range by Saturday the gfs has a wave that has formed on the front trailing back to the cut off low way to the south west deepening and tracking over the UK bringing some rain, sleet and snow. This quickly tracks into the low counties leaving Britain in a cold northerly on Sunday. This cold northerly, veering a tad, persists over the next couple of days with a large low pressure area over western Europe and the high pressure once more ridging to our west. Wintry showers in northern and eastern regions would be the order of the day

Edited January 21 by knocker

[knocker 43,339]

The ecm doesn't form a wave depression and track it over the UK but it does track the quite active front south east on Saturday accompanied by a belt of rain, sleet and snow. And by Sunday Britain is in a cold northerly with wintry showers. Then a very transient ridge before the next trough arrives south west of Iceland and Britain is in a very strong WNW flow, gales in exposed areas, and frequent showers. From this point further amplification of the subtropical high in mid Atlantic establishes a very large low pressure area over western Europe thus Britain unsettled and cold

And quite remarkable upstream with Arctic air plunging down over most of North America

Edited January 21 by knocker

[bluearmy 35,310]

8 hours ago, karlos1983 said:

Apparently a lack of Data on the GFS18z

If you’re wondering What does this mean?:

“It shows the amount of data gone into the initial conditions. More data in usually means a better idea of atmosphere at starting condition.”

Might be worth keeping an eye on ..... an almost complete absence of balloon data could be significant.  if it’s been occurring every run then presumably it hasn’t made much difference due to the poor nwp all round!

models as expected this morning .....Ukmo caught my eye with less ridging to the west and potential undercutting of a wedge as a consequence ....it’s a day 6 so nothing more than a cursory glance for now 

[bryan629 953]

May be barking up the wrong tree but something that has caught my eye is the development of a strong Russian high and seemingly westward movement across towards Scandi. 

Is it possible this could retrogress even further west across the top of the deep Euro low ? 

Below are the EC anomaly charts from the 0z days 9 and 10 , maybe clutching at straws but it is also visible on the GEM ( very last frames ) and the GFS just before it goes into low res and flattens the high. 

  

 

[knocker 43,339]

44 minutes ago, bluearmy said:

Might be worth keeping an eye on ..... an almost complete absence of balloon data could be significant.  if it’s been occurring every run then presumably it hasn’t made much difference due to the poor nwp all round!

models as expected this morning .....Ukmo caught my eye with less ridging to the west and potential undercutting of a wedge as a consequence ....it’s a day 6 so nothing more than a cursory glance for now 

Presumably lack of radiosonde data at 06 equally so

[knocker 43,339]

At the end of ext EPS this morning a high cell has been established over the western Arctic and the European ridge more or less extended into Greenland/ This has the effect of weakening and greatly increasing the negative tilt of the European trough Temps still below average There has been indications of this previously

Edited January 21 by knocker

[Paul 17,864]

Just copying a few posts from various members from this morning into here. 

2 hours ago, northwestsnow said:

I'm not going to post all the EC but its generally cold, moreso the further north you go with -7 uppers widely north of the midlands..

Ends at day 10 with uppers of -7/-8 widely as the jet sinks south, to leave 

Plus being the UK stays cold , downside we still cannot shake off the energy from the canadian vortex..

 

1 hour ago, Polar Maritime said:

GFSP showing a cold PM blast Mon/Tue next week, With -9/-10 uppers over the majority of the UK and possible widespread snowfall.

GFS making it more a Northerly flow..

Certainly a wintry outlook looking at the models this morning with temps mainly keeping below avg.

 

1 hour ago, nick sussex said:

Not much change this morning .

Same pattern out to day ten which comprises an amplified ridge in the west USA, trough in the east . And jet track se into the UK.

Although that’s set the uncertainty is in relation to what shortwaves do as they encounter the PV lobe over ne Canada and run into the Atlantic .

This makes a difference for the UK because it’s these that effect the development of small wedges of high pressure ahead .

You can already see these differences between the models at day 6.

 

1 hour ago, IDO said:

The GFS 0z run is a lot slower with the Atlantic compared to the 18z, quite the opposite ends of the envelope for the upcoming pattern. The nascent Atlantic ridge starts climbing at T138 and takes to T288 to topple and allow another chunk from the Canadian PV lobe to slide SE!

Clearly, some fine tuning needed by the models to nail this developing pattern and TBH would not rule the 0z out.

The ECM has another run with the Siberian High blocking the eastward slippage of the euro trough, but GFS already toned this down. ECM is known to overplay its hand with new patterns, blowing up highs, so I expect the Siberian High to moderate accordingly in future runs, and that would collapse the Atlantic ridge faster and a trend towards the GFS. The GFS op has solid cluster support.

With the D16 mean suggesting any HLB is going to be on the Asian side of the NH, with the PV lobe in Canada, we are really looking at scraps of cold, with any brutal cold way away from our quadrant:

At the moment it looks like the cards have been dealt and our opening gambit is pretty average! 

 

45 minutes ago, winterof79 said:

In my opinion there is no trend for Greenland heights but a move towards Scandi/Western based Siberian  Heights building as the trough constantly drops to our East

GEFS

GEM 240Z

Navegem

ECM

 

 

 

[winterof79 5,300]

30 minutes ago, Paul said:

Just copying a few posts from various members from this morning into here. 

 

 

 

 

 

Thanks Paul I couldn't copy it across 

[Singularity 10,785]

Copied over on request 🙂

 

On the other side of the pond there is much scepticism over the models de-amplifying the PNA ridge formation past about a week’s time. The tropical cycle shouldn’t force that to happen so much as the MJO either reaches P6 or decays away. This has implications for sustained HLB in the NAOregion too... models may be missing this if they do have the PNA pattern wrong.

Something to bear in mind over the coming days.

[mb018538 3,479]

We had 100% ensemble agreement yesterday...



Now we're back to a dogs dinner again. You just get that sinking feeling that it'll just flatten out without any significant ridging to send us colder.

[IDO 5,713]

1 hour ago, Singularity said:

Copied over on request 🙂

 

On the other side of the pond there is much scepticism over the models de-amplifying the PNA ridge formation past about a week’s time. The tropical cycle shouldn’t force that to happen so much as the MJO either reaches P6 or decays away. This has implications for sustained HLB in the NAOregion too... models may be missing this if they do have the PNA pattern wrong.

Something to bear in mind over the coming days.

The problem with background signals are not that they are wrong, is that they are assumed to imprint without interference. Just looking at the D10 charts we can see why the Pacific Ridge fails on both ECM and GFS:

Spoiler upper lows forced off the Asia trough due to the upstream blocking. These stop the Pacific wave and sends a wedge north into the flow. 

Of course, this feature may be wrong, but bearing in mind we have one in the Atlantic modelled, they may be a direct result of the upper pattern? 

[bluearmy 35,310]

16 minutes ago, mb018538 said:

We had 100% ensemble agreement yesterday...



Now we're back to a dogs dinner again. You just get that sinking feeling that it'll just flatten out without any significant ridging to send us colder.

Seriously- how many times do I have to post that one cluster means that there really isn’t any agreement !!!!!!!

for the second consecutive run we see a propensity to build wedges to our north and to undercut the Canadian splurge across the Atlantic ..... knocker has already shown that in mean chart form .... how far south we can get the jet would be the question - my guess at the moment would be a snow line traversing the country which is going to lead to all sorts of nonsense on the other thread! 

Would be a high risk, high reward pattern and reliant on the strength of that wedge of higher heights to our north .......taking out the Azores is a good thing imo ... it’s doing us no favours as it injects warm sectors into each cycle of the current pattern 

[feb1991blizzard 14,062]

15 minutes ago, bluearmy said:

Seriously- how many times do I have to post that one cluster means that there really isn’t any agreement !!!!!!!

for the second consecutive run we see a propensity to build wedges to our north and to undercut the Canadian splurge across the Atlantic ..... knocker has already shown that in mean chart form .... how far south we can get the jet would be the question - my guess at the moment would be a snow line traversing the country which is going to lead to all sorts of nonsense on the other thread! 

Would be a high risk, high reward pattern and reliant on the strength of that wedge of higher heights to our north .......taking out the Azores is a good thing imo ... it’s doing us no favours as it injects warm sectors into each cycle of the current pattern 

Feel this Nick - this mean elongated trough on the GEFS mean is very decent, take out some outlier solutions that probably show no such scenario and it would probably even further South, but the real aim from that position would ultimately be one last go at a scandi / Iceandi high, but then could we get the frigid uppers to our East back?

[bluearmy 35,310]

12 minutes ago, feb1991blizzard said:

Feel this Nick - this mean elongated trough on the GEFS mean is very decent, take out some outlier solutions that probably show no such scenario and it would probably even further South, but the real aim from that position would ultimately be one last go at a scandi / Iceandi high, but then could we get the frigid uppers to our East back?

Development of a sustained strong block up there still unlikely within next fortnight .... wedges will work for snowfall but need that Azores ridge to pull back so the jet can approach on a less rounded route and drive the wedge to its ne to pull the flow se ahead of it.

anyway .... no sign this will be an easy evolution unless ukmo has successfully picked it early 

[Sperrin 1,008]

Would @bluearmy or anyone else have time to give a quick explanation of a wedge? Am I right in thinking its an increase in application of a high pressure cell that causes the jet to come in on a NW/SE axis causing a PM flow as opposed to full on Greenland block?