Model output discussion - into 2018

[markw2680]

23 minutes ago, ArHu3 said:

You can be fairly certain the high will sink southeast and the cold spell will end before any deep cold from Siberia /Scandinavia arrives 

Would normally pretty much agree with this but I just feel the models actually don’t have a clue what’s going to happen next week, they will look completely different come Sunday for next week I’m pretty sure of that

[Frosty.]

I don't think the progressive Ecm 00z op will verify with its mild unsettled spell, more likely something similar to the ukmo 00z / Gfs 6z blended solution with temps below average, a lot of dry weather, especially further east with overnight frosts and occasional bands of ☔rain edging in erratically from the west with a risk of ❄❄❄ snow in places, especially on higher ground further west..I think the cold block will prove stronger and more stubborn than some think.

Edited January 5, 2018 by Frosty.

[karlos1983]

I’ve always liked an underdog 

[FetchCB]

2 hours ago, TEITS said:

If im going to have the Tut taken out of me then I won't bother.

Suffice to say the mistake everyone is making is they are ignoring the fact the UKMO at +144 is very different to every model at that timeframe. The +144 like last night is a text book classic of an impending 1980s type E,ly. Just wait and watch how the high to the N will extend SW with its associated cold pool whilst at the same time any atlantic intrusion heads SE. The date of arrival for a classic 1980s E,ly is around 15th Jan!

I agree TEITS and understand what you mean. When you look at the extended text forecast issued at 2am  from the Met Office they do seem to be describing a classic easterly with a slow attempt at a breakdown from the West.

The period of interest on UKMO is the 48 hr mark

With the low pressure in Iberia. 48 hours later UKMO moves this low pressure North eastwards in response to the energy coming from the Southern tip of greenland. If however it moves West to Italy then we could end up with something similar to this

 

http://old.wetterzentrale.de/archive/ra/1991/Rrea00119910206.gif

 

Interesting times ahead

[Scandinavian High.]

1 hour ago, SLEETY said:

Why this cold spell being written off now?? It’s turning colder soon and the met talking about severe frosts and the threat of snow next week with PERHAPS milder weather into parts of the WEST later.

 

I wouldn’t go writing off any cold spell yet and the ukmo 144 timeframe showed bags of potential .fronts stalling against a cold block usually provide plenty of snow for some .

Watch this space ....

I've been  scratching my head why folk on here are disconnecting cold spell maybe not the deep cold yet from east with -10 uppers just yet.  For now it's going turn  cold from north east and as we go on there chance of snow with weather fronts coming in from south and west I say that's very  encouraging .great post sleety.

Edited January 5, 2018 by abbie123

[karyo]

10 minutes ago, FetchCB said:

 

With the low pressure in Iberia. 48 hours later UKMO moves this low pressure North eastwards in response to the energy coming from the Southern tip of greenland. If however it moves West to Italy then we could end up with something similar to this

 

http://old.wetterzentrale.de/archive/ra/1991/Rrea00119910206.gif

 

Interesting times ahead

I guess you mean if it moves East to Italy. I think that's unlikely because the strong high pressure over the Balkans and Greece blocks the eastward progression of the low and instead it joins forces with the Atlantic low.

[Man With Beard]

The Icelandic clusters this morning confirmed a switch in the whole ECM suite to a situation where the Atlantic front is either over the UK, or pushes right through the UK by T144.

I thought I'd also take a moment to highlight some key things to be aware of when using these particular cluster charts! First - use the anomaly colours with great, great care!! The clusters chart have very sexy colours on them - ones instinct might be to think "Deep positive anomalies at the top right of the chart = strong NE blocking". Not necessarily!! I think a comparison of actual vs anomaly charts on Meteociel demonstrates this nicely. Take the T144 ECM op charts as an example:

     

Looking at the Z500s (the green/blue colours), you'd think there's just a transitory wedge of heights that is unlikely to stand in the way of the Atlantic. But looking at the anomaly chart in isolation you could rush to the conclusion that there was blocking all the way from Scandi. As you can see, not so!! The thing to remember is - in winter, the norm is for the north to have low heights. Therefore, positive anomalies could merely mean an absence of low heights. You need very positive anomalies to indicate a block. Take the ECM op from Wednesday (which did show a block):

   

Using the clusters view for the same chart (see the chart under "op"), there is a very large area with the deepest red available directly to our NE (they don't do black holes on these cluster charts!)

So lesson one - when looking for a northern block in winter, you are looking for the most extreme level of positive anomaly - a modest anomaly will not be sufficient.

Secondly - the angles of the Icelandic charts and the Meteociel charts are not the same, and this makes a big difference!! I'll repost the current T144s to make the point:

   

again using cluster three (the one with "OP" above it) - on the right of the chart, you'll see the 546mb line over Southern Scandi, and then another line to its left is the 540mb line. The 540mb line is more or less represented on the Meteociel chart by the first light blue colour. If you look closely, you'll see that on both charts, this line runs through southern Sweeden, through Denmark, through the Low Countries, along the very north of France and finally clipping the SW of England and Ireland.

However, on Meteociel, the line from Sweden to around Paris runs from the top-right towards the bottom-left. But on the Icelandic clusters, it looks like a straight line from north to south.

If this difference is not appreciated, it may lead to a completely incorrect comparison of the two charts.

The reason why this happens is because the Icelandic charts are more like a globe, with everything running towards the pole - but the Meteociel charts we tend to see on here are more like a poster of the world one would put on the wall - with Greenland consequently stretched unrealistically. 

The consequence is that, by mistakenly thinking "right to left = east to west", what might look like a NEly flow on the Icelandic clusters might in reality be an Ely flow - and what might look like an Ely flow might be a SEly one.

So I hope that might help people interpret these EC clusters that we have free access to.

Let's hope tonight's 12Z charts resemble cluster 2 - much better attempt at the Scandi High   (though this one doesn't last either...)

 

 

Edited January 5, 2018 by Man With Beard

[carinthian]

2 hours ago, carinthian said:

Spoke to them this morning. There short term range of charts had a low forming off the SW of England by Thursday and temperature profile was below the anomaly average for much of the British Isles. Will get another update from the shift forecaster ( she) who speaks good English and get more thoughts on there longer term prognosis and snow model results, which by the way have produced some remarkable accurate results for the resort yesterday.

 C

As promised have an update from a foreign field. Firstly, latest snow model( outer perimeter results) still show some snow accumulation in a convergence zone at 6h Sat morning. Zone affects Manchester, Peak District, Cheshire, Shropshire and parts of Wales. Amounts non significant (1-5 cm )  Freezing level quite low. Specific to UK regarding next week. Still favour block over Southern Scandinavia lasting till Friday at least . Their short range charts still show low pressure development by Thursday to SW of England . Their own forecasting model indicates any Atlantic fronts making limited/no progress into the British Isles and temp profile for the next 7 days shows negative anomaly  for British Isles at least.. Interest remains especially to the Atlantic spin next week and development to the SW of England  . A long way off but something to watch. 

C

[FetchCB]

5 minutes ago, karyo said:

I guess you mean if it moves East to Italy. I think that's unlikely because the strong high pressure over the Balkans and Greece blocks the eastward progression of the low and instead it joins forces with the Atlantic low.

Yes apologies East.

I understand what you mean however i'm not sure its that strong, 48 hours later it is gone replaced by a general area of low pressure

As ever it is always a game of ifs and buts and the lack of organised low pressure in the med has seen many potential easterly's fail and for the high to sink

[Cheshire Freeze]

9 minutes ago, carinthian said:

As promised have an update from a foreign field. Firstly, latest snow model( outer perimeter results) still show some snow accumulation in a convergence zone at 6h Sat morning. Zone affects Manchester, Peak District, Cheshire, Shropshire and parts of Wales. Amounts non significant (1-5 cm )  Freezing level quite low. 

And here is the Metoffice text forecast for tonight (NW England) and tomorrow with the GFS concurring with the Metoffice prognosis

 

It will be a cold but increasingly cloudy night as a band of more persistent rain and possible hill snow edges slowly south. Minimum temperature 0 °C

Cloud and rain will clear south through the morning with colder, brighter and windier conditions following. There will be sunny spells and the odd wintry shower is possible. Maximum temperature 6 °C

 

 

Edited January 5, 2018 by CreweCold

[ArHu3]

15 minutes ago, Man With Beard said:

 

The reason why this happens is because the Icelandic charts are more like a globe, with everything running towards the pole - but the Meteociel charts we tend to see on here are more like a poster of the world one would put on the wall - with Greenland consequently stretched unrealistically. 

 

 

 

You could say they are like a cut out of the northern horizon view of meteociel, with the center on the meridian running through Iceland instead of the one running through Greenwich (so rotated 15 degrees east) 

[captaincroc]

13 minutes ago, carinthian said:

As promised have an update from a foreign field. Firstly, latest snow model( outer perimeter results) still show some snow accumulation in a convergence zone at 6h Sat morning. Zone affects Manchester, Peak District, Cheshire, Shropshire and parts of Wales. Amounts non significant (1-5 cm )  Freezing level quite low. Specific to UK regarding next week. Still favour block over Southern Scandinavia lasting till Friday at least . Their short range charts still show low pressure development by Thursday to SW of England . Their own forecasting model indicates any Atlantic fronts making limited/no progress into the British Isles and temp profile for the next 7 days shows negative anomaly  for British Isles at least.. Interest remains especially to the Atlantic spin next week and development to the SW of England  . A long way off but something to watch. 

C

Thank you for this update, especially as it looks like we could be in for a sprinkling of snow. Which models/data is this forecast (short and longer range)based on?

[bluearmy]

We need a bit of clarity here - the models show a bit of a stand off, but the upper air temps to begin with are way high. So that could mean surface cold but it won’t mean any snowfall once fronts try and make progress from the west 

if they do, then ironically they bring some colder upper air with them than the continental flow which could then make the situation more conducive to some snowfall if the block fights back and further attempts from the west/southwest ensue. 

We also have ec being quite progressive once the Atlantic makes headway east of the meridian although there remains the lesser chance that the second wave of the Atlantic could head more se than the first

[frosty ground]

1 minute ago, bluearmy said:

We need a bit of clarity here - the models show a bit of a stand off, but the upper air temps to begin with are way high. So that could mean surface cold but it won’t mean any snowfall once fronts try and make progress from the west 

if they do, then ironically they bring some colder upper air with them than the continental flow which could then make the situation more conducive to some snowfall if the block fights back and further attempts from the west/southwest ensue. 

We also have ec being quite progressive once the Atlantic makes headway east of the meridian although there remains the lesser chance that the second wave of the Atlantic could head more se than the first

So if the Upper flow is of the atlantic with Sub zero 850's (say -2) but the surface feed is still of Europe, those conditions could be conducive to Snow.

So if I am getting this right, as low 850 move in of the Atlantic you would get rain turning to snow from the west?

This is of course without taking all the other parameters into consideration.

[bluearmy]

12 minutes ago, frosty ground said:

So if the Upper flow is of the atlantic with Sub zero 850's (say -2) but the surface feed is still of Europe, those conditions could be conducive to Snow.

So if I am getting this right, as low 850 move in of the Atlantic you would get rain turning to snow from the west?

This is of course without taking all the other parameters into consideration.

Possibly with elevation but I think much more likely second time around so that any se surface feed ahead of frontal incursion is from upper air below zero 

[shaky]

3 hours ago, Steve Murr said:

Morning.

The Forecast has ( & still is ) the original GEM / ECM blend from day 1 with a possible slightly more SE flow.

This is one of the 06z ENS which still feels about right.

 

 

Latest icon digs colder air further into the netherlands at 40 hours compared to the previous run!!might not be much but might help keep colder air for longer over us!

[SMU]

Just now, shaky said:

Latest icon digs colder air further into the netherlands at 40 hours compared to the previous run!!might not be much but might help keep colder air for longer over us!

Yes the colder air is not that relevant but the flow & alligment is important -

[Dean E]

A trend that is becoming more likely now is the US (especially the North East) is likely to return to just above normal temperatures from Monday onwards, with the bitter weather being replaced. Would expect the jet to react to this change slightly around the middle of next week.

However, (Using the GFS) there is still stubborn cold pool over Northern Canada that does keep the Jet amplified, however, increasing interest from the North Pacific (heights transferring into the Poles *See red area) does seem to be 'shunting' the jet towards Iberia, leaving a week arm going towards Iceland.

   

IMO this is an area I have been watching closely for the past few days and from past experience the GFS models very well over the Pacific during the winter months. A low does appear post +144h that cuts off the ridge, but I don't buy that right now.

NOAA is now pretty confident of this pattern change across the US, so I believe this could be a player for model agreement post +144h and beyond.

 

Edited January 5, 2018 by Dean E

[SMU]

Just now, shaky said:

Latest icon digs colder air further into the netherlands at 40 hours compared to the previous run!!might not be much but might help keep colder air for longer over us!

Yes the colder air is not that relevant but the flow & alligment is important -

[markw2680]

1 minute ago, Steve Murr said:

Yes the colder air is not that relevant but the flow & alligment is important -

If only that area of low heights around Russia could join up with the stuff coming around the south from the south west, would then be bingo imo, you just never no

[Mucka]

The darkest hour is just before the dawn.

ECM has gone from hero to zero but as others have pointed out, this mornings run looks very suspect.

Given the Op has been bouncing around from one extreme to the other it is probably better to stick with ensemble guidance and any consistency within UKMO, GFS Ops for now to determine where we may be heading.

The teased Easterly of a couple of days ago has clearly failed but post day 6 still holds possibilities.

We should have some form of Scandi blocking reaching NW toward Greenland, too far East to bring cold to us but if upsteam plays ball it is a good building block.

It is all about the distribution of energy coming in off the Atlantic from day 7+ and the same old theme, if it goes NE the pattern flattens out and the Atlantic roars in, if it splits favourable or undercuts then it is game on.

I would actually be surprised if another Easterly does not get modelled by GEM/ECM over the next few days for mid month or just after.

This could be a long Winter, buckle up and strap in for the next crazy rollercoaster - I feel pretty confident it is coming.

 

 

 

[carinthian]

49 minutes ago, captaincroc said:

Thank you for this update, especially as it looks like we could be in for a sprinkling of snow. Which models/data is this forecast (short and longer range)based on?

Yes, it rather hard to predict lowland snowfall as opposed to being 1 mile up in the atmosphere of the Eastern Alps. Own model with specifics for Austrian Alps , independent of data from GFS/ECM. High res fine mesh produces forecast for periods 36h and 72h advanced. Mechanism for out perimeter results as well but the main detail is focused with-in the local confines of a few square KM and produces amazing accuracy in the short term. Think the snow is from medium level clouds associated with a slow moving and decay front with an undercut of cold NEly flow creating a bit of a convergence zone. I remember a similar instant, think it was one Christmas Eve back in the early 70s that produced a bit more than a few cms of snow in the Manchester area. On that occasion there was non forecast ( I know as I was on duty) Sometimes the best snowfalls are never predicted ! However, if you are lucky enough the wake up to even a light covering, not to be surprised.

C

Edited January 5, 2018 by carinthian

[Ali1977]

Another step colder again please 12zs

[SMU]

4 hours ago, fat chad said:

Hello Steve. Thanks for posting. Just a quick question from me. What are the 850s temps for that timeframe please? I only ask as the best falls in recent history barring 2010, for my area (Portsmouth) have come from a windflow coming off of a frigid continent. And would the continent have cooled enough in time in your opinion?

@fat chad

 & Everyone

I am still basing my forecast on the below image with 2 caveats for expected change -

 

1) heights & cold pool ... > If you draw a big circle around Central Europe on that meteociel chart the height are 544-548 ( green ) with a cold pool around 0c to -4c

** History indicates that the GFS over estimates these heights by 4-8 dam sometimes even 12 dam which is another reason why it looked so tame V the euros-

assumjng The Easterly lands as predicted above then expect that Green to change to the first colour of blue with even a central pool of lower heights into the next layer of blue - so a forecast to drop from 544-548 to 536-540 ( core pool 532 dam) 

This will also signify a reduction of upper temps along a similar gradient so instead of 0 to -4c you get -2 to -8c

* Secondly the glow allignment is SEasterly - this can also be a GFS bias of the strength of the southern arm not being identified to sub T120

below is the T156 Jet chart from 06z

look as we get nearer 120 & below for more of an Arc / n shape across Italy - more amplification- this will enhance the easterly allignment-

if you look at T54 that’s why the Easterly is getting sharper now because of the upwards flow

 

so these would Be my pointers to everyone looking in on the models looking for a more classical Easterly @168..

The forecast for this period (144-192) is my representation research & acknowledgment of bias - no one else’s.

 

thanks

S

 

[karyo]

A slight improvement from the ICON. Although a low pressure makes it through the UK from the Atlantic, it then dies over the north sea and a ridge of high pressure from the southwest tries to link with heights to the northeast at 135 hours. It may not make it in this run but the Atlantic is slower and further west.