Model output discussion - into Christmas

[Jordan S]

Remaining mostly dry further north tonight with frost and fog patches for northern areas with just the odd shower. 

High resolution models backed away from the widespread slow moving rainfall for England today earlier this morning so a poor handle on it. But anyway drier spells in places tonight compared to last night but some showery rain moving northeast for England and Wales not good for flood effected areas a few mm's in places. 

Tomorrow starts dry for most but heavy rain moves into southwest England then spreads to other southern parts of England and Wales during tomorrow evening and then overnight.. uncertainty with how far north this will reach but the heaviest rain generally for southern and southeast England with perhaps as much as 20-25mm in one or two places but mostly 5-10mm for most areas effected. 

Drier further north with a frost and perhaps a few fog patches. 

Edited December 20, 2019 by jordan smith

[Jordan S]

6 minutes ago, Walsall Wood Snow said:

Yes you're right. The cold returned sometime mid month and gave us another blizzard with drifting which stuck around for maybe 2 or 3 days I think. Some of the drifts took a while longer to completely thaw too. 

As @Mapantz has said let's just focus on weather that's happening atm and the next couple of weeks on here there's other threads to discuss historic weather..

Edited December 20, 2019 by jordan smith

[Mike Poole]

First view of the 18s, v the 12s:  ICON T90 v UKMO T96:

Looks like ICON is going to develop the shortwave.

Edit: T120

Nope, wrong again Mike!  Pretty much in line with UKMO, clean WAA.  Over to GFS...

Further edit: this really is the key difference, until the models decide this between T96 and T120, the rest of the run of any of them is just flights of fancy. 

Edited December 20, 2019 by Mike Poole

[syed2878]

my word such poor showing on the models today I can’t even use the data issue excuse if only it was the 25th today then the lack of data use excuse could have been used 

[SouthLondonCold]

Maybe clutching at straws but icon seems a bit better with less of a boxing day storm, Everything also seems a bit further west with higher pressure to our North West Big changes at only day 5 which can only mean positive things given the current state of the models!

12z vs 18z

[SMU]

The ICON 18z would bring the threat of snow on the northern edge of the low as it filters into the cold air feeding down from the North-

Lets give the evolution another 24 hours...

[weatherguy]

Good evening all!

The output is, basically, a complete mess with major uncertainty on how things will play out even at +144h. Not necessarily the longwave pattern, but definitely in terms of how things set up in our small section of the NH.  See the GFS/ECM/UKMO below:

The GFS is the most amplified in terms of getting that negative tilt on the incoming LP, but even here the block is transient at best and it isn't strong enough to avoid being toppled in due course.  The UKMO offers a somewhat more robust high, but the angle of attack from the west is worse, so, another toppler.  The less said about the ECM, the better.

192h

While both models produce a secondary LP, the GFS combines it with the main trough to the west, which delays the flattening of the ridge.  This is only to be a delay though, because the jet is then positioned SW-NE...less than ideal.  The ECM does not model this as such; due to the ridge being weaker and further east, it is allowed to simply run east and barrel over the ridge, heralding a return of zonality.

240h

The GFS, despite the escape at 192h, then powers up the jet, aided by the migration of the main portion of the PV over to Greenland, creating something of a doomsday scenario for us coldies with an Atlantic profile as flat as a pancake.  The ECM offers up limited amplification, which may present the opportunity of a PM flow at times.

Overall thoughts:

What we know for certain is that there is an opportunity for a ridge forming roughly around the UK/Iceland/Scandi sector around the 27th Dec.  The models cannot agree on the exact setup, but none of the big 3 are showing a scenario where the Atlantic is held at bay, or undercuts.  Given the uncertainty however, there does remain a small chance that the LP positioning may be more favourable and we can prevent what follows should this buckle (more rain, and more despair for those of us who wish to see some more seasonal weather).  Again, this is very unlikely, and the strat profile at the minute doesn't suggest that the TPV will be lacking the strength to simply flatten out what is a rather weak ridge. 

Ever the optimist, I will be looking for any signs that this period is to be modelled more favourably for us.  However, my sights are definitely set more towards what fun and games may be had in the SPV potentially by mid-Jan - there's certainly plenty of members going for a dive in zonal wind speeds, so I shall leave this here to end on a more positive note!

[Allseasons-Si]

ICON is a better run at 120 v 126 12z

key points:-

better vertical WAA...check(black arrow)

better trough seperation...check(red line)

trough/low south of the UK...check(blue arrow)

i do hope it pans out like this then we will miss the rain that we don't want

also the 0c isotherm is clear of the south coast on this run so a cooler crispier Christmas day coming up if it's right

do you spot the -4 there over NW England

 

 

[feb1991blizzard]

9 minutes ago, weatherguy said:

 

I am liking that CFS plot, and in line with my thinking.

[SLEETY]

5 hours ago, SLEETY said:

 

Yes not over yet.,ECM keeps throwing out mild operational runs ,last few days,nearly always the mildest run in the suite,GFS has backed the pattern further west in the semi reliable .last couple of runs..

No point looking beyond that timescale  on GFS,as it's mostly sypnotic garbage that never ever verifies ,same as ecm,after t168 hours.

[Mike Poole]

Early doors on the pub run, but I can't see this one going to be anything but an improvement, T96:

Less hint of shortwave drama, let's see...

Edited December 20, 2019 by Mike Poole

[northwestsnow]

18Z much better and less progressive than the EC..

[Mike Poole]

Now we're lovin' it, GFS T132:

[shaky]

Just now, northwestsnow said:

18Z much better and less progressive than the EC..

Much better is an understatement!!its absolutely fantastic at 138 hours!!heights further west and cold air coming in and building in the east!

[Allseasons-Si]

5 minutes ago, Mike Poole said:

Early doors on the pub run, but I can't see this one going to be anything but an improvement, T96:

Less hint of shortwave drama, let's see...

Yes a better run than the 12z and sort of like the ICON  but not quiet there,the Azures shortwave has better separation on this run.

120 v 126

 

 

[northwestsnow]

18Z looks cold next week.

Can it be believed?

[northwestsnow]

LOL its a cruel existence being a cold weather fan-

Its a long shot, but lets hope GFS has somehow, against all the odds, picked out the correct progression.

[Allseasons-Si]

1 minute ago, northwestsnow said:

18Z looks cold next week.

Can it be believed?

We believe

[swfc]

2 minutes ago, northwestsnow said:

LOL its a cruel existence being a cold weather fan-

Its a long shot, but lets hope GFS has somehow, against all the odds, picked out the correct progression.

App it's 3rd in the pecking order sometimes 4th???who knows it's a big leap of faith after the gfs-ec 12z

Edited December 20, 2019 by swfc

[northwestsnow]

1 minute ago, swfc said:

App it's 3rd in the pecking order sometimes 4th???

Yep, precisely why i questioned if it can be trusted- in other words, i don't!!!

That said, it has occasionally trumped the others.

Its a million miles away from EC though so...

[SMU]

100% under cutter here will look for poss snow northern edge-

Could this be another triumph for ICON / UKMO over GFS / ECM

Look at jet 18Z Vertical V 12z NE

Edited December 20, 2019 by Steve Murr

[feb1991blizzard]

That shortwave is the feature Steve was on about on the Icon i think - looks primed for snow but nothing white on the PPN charts yet but as it runs into colder air.....

[Ali1977]

There’s a hint of yellow in that WAA at 150, what’s about to happen here, a proper high rather than a bit of WAA - bloody hope so!!

[ICE COLD]

Mate please be right gfs 18z please 

[Allseasons-Si]

Erm!!!

an easterly is not far off at just 144hrs

this at 150.

come ooooon!!!!