Model Output Discussion - Snow for some, but what else is in store?

[Captain Shortwave]

Maybe as much as anything the series of recent poorer runs are the result of an extremely aggressive undercut of the Atlantic ridge from both Canada and cold air extending from the trough near the U.K. possibly upstream the split jet might end up with a weaker southern arm and as such allow the Atlantic ridge to reamplify and as such allow the U.K. trough to extend southwards to bring colder air through the U.K.

GFS control for instance

So by day 7/8 we are seeing heights from the Azores stretch northwards again instead of a strong jet streak running north east towards the U.K. under a cut of Greenland high. 
Just a general musing here, one that is often contrary to the usual hopes when a split in the jet is modelled where a stronger southern arm is usually better.

[Scott Ingham]

24 minutes ago, Met4Cast said:

Apologises, I mean to say Greenland blocking rather than Scandi blocking. 

Sizeable shift in todays GEFS mean towards a stronger Greenland block, as @Catacol mentioned either earlier or yesterday, models will now be starting to factor in the SSW in real time & will be able to begin modelling that into the trop patterns we see appearing. This run is evidence of that in quite a large shift towards an Arctic high in the mid-term.

I would expect the Det runs to go wild over the coming days, we'll probably see runs showing very mild almost spring like weather across the UK only for a BFTE style cold spell to appear on the next. 

Those of us who have been following the means these past few days have had a much more relaxed time of it, my advice for those of a nervous disposition would be to ignore the Det runs entirely beyond 120, and focus purely on the mean charts.

Best advice you could listen to right now!

[chris55]

1 hour ago, KTtom said:

Im guessing the usual suspects are in the regionals...so heres the ukmo day 6...not bad!? Gfs also 144, very similar.

Just catching up here.... last looked at 3pm lol. Trends are good so far, liking the UKMO very much. An easterly flow going into the mid term is not out of the question. SSW imprint Troph vs Strat may be slightly more disconnected than it seems. Although the overall effect is generally disruptive to the Troph.

[snowking]

I see the swings in mood continue on in here.

Probably best still yet not to take anything too literally I would have thought given how wildly even the ensemble suites have been swinging, though as noted yesterday I would hope that as of tomorrow, with the stratospheric vortex split into the initialisation data through the stratosphere we might get a slightly better handle on any trough disruption in the troposphere.

Another period of entropy to put up with though through until the 18th when the split vortices come back together again.

I would still advise taking any runs which dramatically remove higher heights over the arctic region too quickly with a pinch of salt - I'm slightly less confident in that assertion with recent runs I must say, but I'm still leaning more in that direction.

Let's see where we are at the end of tomorrow and try not to lose too much sleep in the meantime.

[chris55]

1 hour ago, Singularity said:

 

Guess I'm stepping in for the usual crew - though only partly; I'm not going to go much beyond this. 

We see more of a ridge holding on to the west and a better shape to the trough by the UK on the 12z run. Notice the slug of colder air moving just north of Norway on the 12z run and the cleaner sweep of the isobars down toward the UK from there. Might be fun to see whether that colder air can make it round or not - and if so how it interacts with the runners escaping the trough on the other side of the North Atlantic.

GFS 12 looking better. Atlantic profile edging south and west, flow from the Scandi trough more north east than north west. 

[Griff]

Ecm 96 and ukmo 

[chris55]

1 hour ago, Singularity said:

 

People bemoaning the 850s not being very low should consider the dewpoints.

Marginal Thu but low enough Fri pretty much everywhere.

As far as I can discern, the air behind the initial cold front starts out near the southern tip of Greenland.

Then, air from north of the UK starts to wrap around - this more efficiently done than in the previous few runs.

Take note people.

[ItNeverSnowsInWindsor]

3 minutes ago, chris55 said:

GFS 12 looking better. Atlantic profile edging south and west, flow from the Scandi trough more north east than north west. 

There’s nothing NE about the flow - more a W to NW’. 
 

The pattern needs a few changes to benefit the U.K. A -ve NAO is a start.

[bluearmy]

Dp’s sat pm .....just in case anyone posts a snow map 

 

[Tim Bland]

ECM take on Saturdays rain preceded by snow - mainly East Anglia & North East 

[Tim Bland]

2 minutes ago, bluearmy said:

Dp’s sat pm .....just in case anyone posts a snow map 

 

Comedy timing there Have you got those for early Am? That’s when most of the above is show to fall...albeit turning to rain 

Edited January 14, 2021 by Tim Bland

[Griff]

4 minutes ago, Griff said:

Ecm 96 and ukmo 

And 120...

What were people commenting about the tilt on ukmo?  

[MJB]

Not a bad Control

GFSP not bad either 

[BLAST FROM THE PAST]

this is the point that makes the difference going forward.  The LP off southern tip of Greenland around t144

 

 

Move to around t156 to 162

The core has is ‘retreating’ up west side of Greenland and a wedge of trough disrupting against the block not being able to connect with the main North Sea trough.  This moves towards cold set up elongation with the chance of deeper cold to start digging in.  The run doesn’t go onto produce the depth of cold but the NH Synoptics are incredible.  It’s great model watching and until we see successive like for like 24 hr inter run down grading, don’t panic with the swings...and wild ones at that currently.  All to play still IMO

ECM t144

 

let’s see what happens to the LP southwest tip of Greenland

BFTP

 

 

Edited January 14, 2021 by BLAST FROM THE PAST

[bluearmy]

2 minutes ago, Tim Bland said:

Comedy timing there Have you got those for early Am? That’s when most of the above is show to fall...albeit turning to rain 

Probably ok till late morning Tim - I’m sure some lucky peeps will get out with some cover but those Dp’s say it will melt 

[chris55]

5 minutes ago, prolongedSnowLover said:

There’s nothing NE about the flow - more a W to NW’. 
 

The pattern needs a few changes to benefit the U.K. A -ve NAO is a start.

I know the actual surface flow is not a direct correlation to the 500 charts, but comparing the 6z to the 12z the "flow" as I said, is more north east on the 12z than the more north/north west flow on the 6z

12z

6z

[Griff]

6 minutes ago, Griff said:

And 120...

What were people commenting about the tilt on ukmo?  

144... 

Differences rather than similarities? 

[Alexis]

12 minutes ago, chris55 said:

Take note people.

Yep, often see lovely nice low dew point charts - when it's dry as a bone!

[Snowman.]

If the ECM can reamplify behind that small low we may stand a better chance.

[Griff]

Just now, Snowman. said:

If the ECM can reamplify behind that small low we may stand a better chance.

Yes, more gfs than gem 12z, small pluses 

[TSNWK]

6 minutes ago, Griff said:

144... 

Differences rather than similarities? 

I think I actually prefer ECM just looks a slightly sharper on heights into Greenland to my eyes.  

[Griff]

Just now, TSNWK said:

I think I actually prefer ECM just looks a slightly sharper on heights into Greenland to my eyes.  

I thought it was heading for the gem, it might still yet?  

My glass might be half empty though after a challenging week. 

[TSNWK]

1 minute ago, Snowman. said:

If the ECM can reamplify behind that small low we may stand a better chance.

Why will you not drop North sea trough....

[chris55]

EC 168. 

Pattern being forced south, nothing extreme, but nice to see.

[KTtom]

16 minutes ago, bluearmy said:

Dp’s sat pm .....just in case anyone posts a snow map 

 

Yes, i did mention some surprise when someone mentioned a snowy saturday earlier in the week (cant mention names as hes the boss !)Weather after the BBC news didnt even mention the word sleet for saturday, let alone snow...very rare in my memory have i known snow falling from a front preceeded by southwesterlies, normally you need more of a nw/se tilt on the front.