Model Output Discussions 18z 31/01/2016

[nick sussex]

I think Singularity highlights the issue at present with some on the face of it good synoptics but a lack of cold to tap into. The continent at this time of year can't generate its own cold pools as you might get during Dec/Jan so you are reliant on an injection of cold into the circulation.

Preferably a lobe of the PV has to head south to inject that cold. The ECM T240hrs output is very good but we're missing the colder 850's.

The level of cold to the ne however is likely to chop and change between outputs so something colder might pop up if the trend remains the same to build a block to the ne.

 

[Singularity]

Shorter term, just noticed ARPEGE sides with UKMO in terms of having that little low running east under a mid-Atlantic 'wedge' as opposed to engaging with the polar jet exiting the U.S.

Something to keep us entertained while the models figure out the HLB potential end-month.

Also, hints of a secondary band of precip on Sunday from ARPEGE which is embedded in the cold air:

That area across N. Ireland approaches as a distinct line. A possible trough in the cold air which may explain the snow that keeps coming and going on the GFS runs (the 3 hour time-step leads to issues because this feature moves so fast).

[nick sussex]

23 minutes ago, Singularity said:

Shorter term, just noticed ARPEGE sides with UKMO in terms of having that little low running east under a mid-Atlantic 'wedge' as opposed to engaging with the polar jet exiting the U.S.

Something to keep us entertained while the models figure out the HLB potential end-month.

Also, hints of a secondary band of precip on Sunday from ARPEGE which is embedded in the cold air:

That area across N. Ireland approaches as a distinct line. A possible trough in the cold air which may explain the snow that keeps coming and going on the GFS runs (the 3 hour time-step leads to issues because this feature moves so fast).

Theres not much support in the ECM postage stamps for the UKMO solution. The interest with the UKMO is that cold air heads south and is more likely to engage a front, as opposed to that damp squib PM undercut which imploded as soon as the UKMO put the jinx on it by suggesting 2-5 cms of snow for some favoured locations! Just shows you when even the UKMO can't get it right at T24hrs and they have a wealth more in terms of info. Its a shame that it wasn't an undercut from the se where the dew points were favourable.

Anyway that's old news now and yet another let down for some who were hoping to see a snowflake. As I said a few days ago I really don't want to see some 5 star synoptics delivering 1 star 850 temps so we have to hope that we can find a deeper cold pool to tap into.

Edited February 18, 2016 by nick sussex

[IDO]

Jma update today offers no sign of any watershed towards a cold spell, w3-w4 showing uppers around or above average as a whole with the Azores omnipresent still. Very similar to GFS and CFS LR:

week 2:   Week 3-4:

Attempted ridge formation a constant tease from that Azores positive anomaly with the Euro trough to the east, but little sign we get the  Atlantic ridge and a block to the NW (yet). 

[Tim Brawn]

what happened to Sundays SNOW , yet again another wrong predication by most , i just dont get it why can t they get it more accurate  

[NorthYorksWeather]

11 minutes ago, Tim Brawn said:

what happened to Sundays SNOW , yet again another wrong predication by most , i just dont get it why can t they get it more accurate  

Never saw snow forecast for Sunday on the models other than elevated North/western areas, unless I've completely missed something?

[mushymanrob]

28 minutes ago, vizzy2004 said:

Never saw snow forecast for Sunday on the models other than elevated North/western areas, unless I've completely missed something?

i think some members suggested there might be a snow event on the back edge of the front as cold pm air tucks in behind it.  and they were right, in as much that the models they were referring to would have allowed the possibility of it.

but these things are only a forecast, a prediction, and are subject to change which is what some folks might not quite get?

[Captain Shortwave]

Well differences at 4 days out again, it always seems to be the way these days.

GFS/UKMO

     

It is all about that Atlantic low, the GFS runs this over the building Atlantic ridge whilst the UKMO has already pushed this east with the ridge building behind it. So a similar story to this morning with the UKMO probably offering a slower route to a cold shot but with better longer term potential.

Edit - Day 6 charts

     

The GFS tries to keep a westerly pattern going whilst the UKMO has cut off a large area of low heights over Scandinavia with a northerly flow developing through the UK.

Edited February 18, 2016 by Captain Shortwave

[feb1991blizzard]

10 minutes ago, Captain Shortwave said:

Well differences at 4 days out again, it always seems to be the way these days.

GFS/UKMO

     

It is all about that Atlantic low, the GFS runs this over the building Atlantic ridge whilst the UKMO has already pushed this east with the ridge building behind it. So a similar story to this morning with the UKMO probably offering a slower route to a cold shot but with better longer term potential.

Edit - Day 6 charts

     

The GFS tries to keep a westerly pattern going whilst the UKMO has cut off a large area of low heights over Scandinavia with a northerly flow developing through the UK.

The 144 UKMO very promising although admittedly not worth getting exited unless another 1 of the top 3 models offers some support.

[Yarmy]

1 minute ago, feb1991blizzard said:

The 144 UKMO very promising although admittedly not worth getting exited unless another 1 of the top 3 models offers some support.

It looks great synoptically, but I suspect the 850hpa temps are still not cold enough even sourced from Northern Scandinavia. As you say, not even worth worrying about though until the other models are interested. 

[feb1991blizzard]

Just now, Yarmy said:

It looks great synoptically, but I suspect the 850hpa temps are still not cold enough even sourced from Northern Scandinavia. As you say, not even worth worrying about though until the other models are interested. 

Not over the UK on that chart but they soon would be afterwards, that's as good a PV split as you can get for the UK, apart from 17th Dec 2010.

[Yarmy]

Just now, feb1991blizzard said:

Not over the UK on that chart but they soon would be afterwards, that's as good a PV split as you can get for the UK, apart from 17th Dec 2010.

I don't know, it just seems there isn't enough of a cold pool in the Svalbard/Scandi region to draw upon and then there's modification:

 

-ve anomaly at source, but heading +ve in the North sea. If the ECM goes this route, we'll get a better idea as we will be able to view the 850s.

 

[feb1991blizzard]

1 minute ago, Yarmy said:

I don't know, it just seems there isn't enough of a cold pool in the Svalbard/Scandi region to draw upon and then there's modification:

 

-ve anomaly at source, but heading +ve in the North sea. If the ECM goes this route, we'll get a better idea as we will be able to view the 850s.

 

We could do with a trough to drop straight down from the Arctic into continental Europe!!  I wouldn't worry about the SST's I would rather have them on the warm side  to generate convection, I will just be happy to see the ECM go in that direction, cant help feeling if we could get to that split, at some point we would get blasted.

[Cloud 10]

A few of the GEFS ensembles look quite similar to the UKMO 144 hrs chart,although none quite as "clean"

 

 

ukmo..

[Mucka]

5 minutes ago, Cloud 10 said:

A few of the GEFS ensembles look quite similar to the UKMO 144 hrs chart,although none quite as "clean"

 

 

ukmo..

Yeah but many more are flat. 

One thing though, if it did happen, we wouldn't have to worry about a lack of cold air IMO. It would get very cold very fast with that feed,

Edited February 18, 2016 by Mucka

[SMU]

Afternoon

The UKMO is certainly a peach of a run & loading the cold into the UK in the later stages

however to get there ( T96 ) is wants to bring that atlantic low through a ridge of high pressure - This scenario has been modelled before but with very minimal success - the model that gets the low over the top of the ridge with flattening has historically been correct 

so its the GFS ( sadly ) that would usually be in favour here however the UKMO would certainly signal a profound pattern change....

s

[chris55]

UKMO is a peach of a run really!!

I know uppers are not amazing but IMO just looking at the evolution there would surely be some snow (away from Scotland that is) as the colder uppers chase away the front at 144.

At 96 colder air moving into Scotland, pretty settled and average temps in England and Wales

At 120 still cold in Scotland less cold in England and wales. but not mild (the low a touch further south and that would be different)

At 144 the cold air has won out and between 120 and 144 the front will have pushed south with the colder air engaging. And beyond things would get colder.

 

If this UKMO run was at the start of winter this thread would be very busy lols.

Ill just sit back and see what unfolds as always, no confidence placed in any runs past days 3-4, though that UKMO looks very very nice! 

 

[nick sussex]

The UKMO refusing to back down this evening, the ECM has trended towards it especially with heights rising to the ne at T120hrs.

The ECM we want as long as it disrupts energy se at T144hrs  or UKMO would be great, the GFS we definitely don't want!

[Cloud 10]

ECM 120hrs with some slider potential?

 

[Mucka]

All a bit crash bang wallop from ECM

Good potential and possible snow event, especially for the NE 144 but not as good as UKMO.

[nick sussex]

The biggest difference tonight is how much cold there would be to tap into. Previously the models wanted to pull the deeper cold nw, now the ECM/UKMO leave a cold pool over Scandi so if a ne flow does develop it would be an upgrade on previous runs.

[chris55]

One of these will eventually deliver i hope!!!!!!!!!!

 

[nick sussex]

Well the ECM is sort of good but it still finds a way to avoid advecting the deeper cold into the UK. Ironically this mornings run had a better block to the ne but less cold to tap into. We want this mornings block to the ne with tonights colder pool!

Still if we follow the likely evolution then the UKMO is still much better, its likely it will follow the others with that low in southern Greenland cutting se however it would be further west with energy going into southern Europe. It also has that shortwave tracking slowly ese and this unlike that PM damp squib yesterday would deliver some snow.

The GFS is to be frank crxp compared to the ECM/UKMO and if that verifies my laptop will meet a grisly end out of the window!

If you're going on trends the ECM has moved towards the UKMO and the GFS has made a small step upstream before hitting the buffers.

I'm not sure we might quite manage the UKMO solution but at least the ECM would be a palatable second option as that wouldn't need much to improve, the GFS would give me indigestion!

Edited February 18, 2016 by nick sussex

[Nigerian Prince]

The  very fact that poster are not getting excited, over the current output that the models are showing is a good sign, it shows that most posters are getting more wiser to the fact that in these block set ups, Fi begins at 72 hours, and we cannot fully trust the output beyond, unless we get full agreement at 48 hours. Location, Battersea, London Gender, Male.

[Mucka]

8 minutes ago, Nigerian Prince said:

The  very fact that poster are not getting excited, over the current output that the models are showing is a good sign, it shows that most posters are getting more wiser to the fact that in these block set ups, Fi begins at 72 hours, and we cannot fully trust the output beyond, unless we get full agreement at 48 hours. Location, Battersea, London Gender, Male.

Because we all only joined the forum this Winter?

Some years are especially frustrating but next year it might be as soon as we see a block modeled it gets upgraded.

Just the atmosphere (teleconnections) haven't been conducive to blocking this winter and the enthusiasm has suffered over time 

Edited February 18, 2016 by Mucka