Model Output Discussions 18z 31/01/2016

[Lukesluckybunch]

3 minutes ago, Lukesluckybunch said:

Yes this evening ecm is quite good,with a lot of the UK still in -4 uppers Wednesday midday..I'm just asking when will the gfs back this,or will it at all..maybe a different looking 18z coming up??

 

2 minutes ago, feb1991blizzard said:

I think we are past the point of no return wrt any nationwide event down the spine of the country, its just seeing if the models can just hold back the front for a tiny bit longer and get a few favoured places some snow, it would take too much of a climbdown now at too later stage for anything better.

Hmm I kind of agree,but the interesting thing is it turns quickly colder again behind the front,Thursday has us back in -4/6 uppers nationwide

[ANYWEATHER]

43 minutes ago, shaky said:

Gota say after looking at the ecm for midweek not all is lost snow wise!!i was surprised with the ecm actually and the 850s are far better than this mornings run!!winds back southerly ahead of it aswell so might even import even colder dew points ahead of the front!!

Hi, Gfs  has cold rain for most on Wednesday, but the good news for coldies  is gfs and ecm  are  portraying colder than average weather for the end of winter,,,,,,,

[Nick F]

29 minutes ago, nick sussex said:

The midweek is looking a bit of a mess with a lot of uncertainty.

The UKMO if you look at the fax chart has the fronts slow moving over central areas, the surface flow is important because on one side you've got some PM air and the other drier continental. I think the issue is whether some of that drier air with lower dew points gets pulled back into the UK.

Its quite an unusual set up, often with these you've got milder air trying to displace the cold but here you've got some PM air trying to displace the surface cold over the se.

Chances increase if a shortwave develops on the front towards the Channel as that could help steer the drier continental flow back into the UK.

It could go either way  here in terms of snow.

12z ECMWF shows a back edge snow event along the frontal boundary on weatherbell across England, even as far southeast as London area and E Anglia between 00z - 06z Thursday. So most likely the model has the air ahead of the frontal boundary too mixed out to have preceding snow. The slowing of the front as it arrives in the E/SE allowing colder and drier (dew points of AOB 0C) Pm flow to catch with the front.

However, the rain/snow margin will probably change with the next run ... and I lose count of the amount of times GFS or ECM has shown back edge lowland snow from Pm cold following a front 3-4 days out or more - only for it end up an all-rain event.

Still, I'm open to a surprise for mid-week. And for now, nice to see snow showers making it down close to east London this evening.

Edited February 14, 2016 by Nick F

[shaky]

12 minutes ago, Nick F said:

12z ECMWF shows a back edge snow event along the frontal boundary on weatherbell across England, even as far southeast as London area and E Anglia between 00z - 06z Thursday. So most likely the model has the air ahead of the frontal boundary too mixed out to have preceding snow. The slowing of the front as it arrives in the E/SE allowing colder and drier (dew points of AOB 0C) Pm flow to catch with the front.

However, the rain/snow margin will probably change with the next run ... and I lose count of the amount of times GFS or ECM has shown back edge lowland snow from Pm cold following a front 3-4 days out or more - only for it end up an all-rain event.

Still, I'm open to a surprise for mid-week. And for now, nice to see snow showers making it down close to east London this evening.

Just to add arpege has it as all snow across midlands and northern england!!only this morning it was showing all rain lol!!

[Singularity]

From that ECM 12z it's not hard to see how the theme of a NW-SE jet orientation in our vicinity could be retained for much of the foreseeable, with this weekend the only real exception - and even then the jet barely escapes the NW-SE alignment on Saturday before returning toward it on Sunday.

With this comes the continued potential for Atlantic troughs to undergo disruption and allow us to play the wintry weather game as ridges attempt to gain a foothold in the middle of the North Atlantic. In time, the area N and NE of the UK may become an increasingly viable target for HLB, based on the MJO expectations.

[karyo]

18 minutes ago, shaky said:

Just to add arpege has it as all snow across midlands and northern england!!only this morning it was showing all rain lol!!

That sounds good. Do you have a link for the arpege please?

[Liam J]

24 minutes ago, shaky said:

Just to add arpege has it as all snow across midlands and northern england!!only this morning it was showing all rain lol!!

Doesn't look all snow to me, high ground maybe.

http://www.meteociel.fr/modeles/arpege.php?ech=3&mode=1&map=330

Edited February 14, 2016 by *Sub*Zero*

[chris pawsey]

7 minutes ago, *Sub*Zero* said:

Doesn't look all snow to me, high ground maybe.

http://www.meteociel.fr/modeles/arpege.php?ech=3&mode=1&map=330

That's at 75hr, move on a few frames to 81hr and shaky is right with the front stalling and fizzing out over the midlands, the roller coaster continues. This I'm sure will go down to a now casting event with more ups and downs to come ☺

[Liam J]

1 minute ago, chris pawsey said:

That's at 75hr, move on a few frames to 81hr and shaky is right with the front stalling and fizzing out over the midlands, the roller coaster continues. This I'm sure will go down to a now casting event with more ups and downs to come ☺

Yeah, it turns very light and fizzles out but saying the ARPEGE was an all snow event is incorrect, it isn't as it shows rain possibly turning more to snow. We'll find out soon enough!

[shaky]

Jesus gfs 18z has the band of rain approaching west coast of wales at 42 hours whereas euro4 has it still approaching west  coast of ireland!!gfs could be right here of course or it could be way of the mark and too fast with the front!!!just checked ecm and that agrees with euro4 with the timing of the front aswell!!

[feb1991blizzard]

Just now, *Sub*Zero* said:

Yeah, it turns very light and fizzles out but saying the ARPEGE was an all snow event is incorrect, it isn't as it shows rain possibly turning more to snow. We'll find out soon enough!

Yes, in fact there was next to bugger all snow over the midlands.

[Sweatyman]

35 minutes ago, feb1991blizzard said:

Yes, in fact there was next to bugger all snow over the midlands.

Nothing new there then !

[snowray]

The new UKMO T120 fax looks nothing like the GFS...More mystery and suspense in the models.

[shaky]

Latest 18z arpege continues to look interesting for wednesday!!shame its goes out to only 60 hours but very similar to 12z run!!dew points of 0 to -2 across northern england and midlands with the front approaching!!temps of around 1 degrees!!!also continental air incoming from france!!

[Banbury]

Snow on the back edge if GFS is to believed

[Cheshire Freeze]

Quite a decent little rain to snow event Wed eve/night on the 0z as the front stalls and fizzles across England and parts of E Wales. Doesn't make it as far E as the 18z had it (not initially anyway) Will be interesting to see if we could perhaps get a little wave on the front as the 0z hints at...could serve to hold the front up further W so that the colder air can dig in more efficiently.

Edited February 15, 2016 by CreweCold

[Nick L]

14 minutes ago, CreweCold said:

Quite a decent little rain to snow event Wed eve/night on the 0z as the front stalls and fizzles across England and parts of E Wales. Doesn't make it as far E as the 18z had it (not initially anyway) Will be interesting to see if we could perhaps get a little wave on the front as the 0z hints at...could serve to hold the front up further W so that the colder air can dig in more efficiently.

Not particularly consistent with this, the GFS. If it can stall like it does here then perhaps there's a possibility of some snowfall, yes. But the EC has been consistent in racing it through with virtually nil snow potential, even for higher ground in most areas. GEM is the same as the EC as well, for what it's worth (probably very little!).

[Cheshire Freeze]

1 minute ago, Nick L said:

Not particularly consistent with this, the GFS. If it can stall like it does here then perhaps there's a possibility of some snowfall, yes. But the EC has been consistent in racing it through with virtually nil snow potential, even for higher ground in most areas. GEM is the same as the EC as well, for what it's worth (probably very little!).

Interestingly, however, Metoffice still talking about snow midweek. Can't be snow preceding the rain because the mild air mixes well ahead of the front. This is still very much up in the air and it's interesting that the GFS follows the 18z Arpege run almost to a tee.

[Nick L]

Just now, CreweCold said:

Interestingly, however, Metoffice still talking about snow midweek. Can't be snow preceding the rain because the mild air mixes well ahead of the front. This is still very much up in the air and it's interesting that the GFS follows the 18z Arpege run almost to a tee.

Yes if there is to be snow it will be backedge. I think the Met are simply covering all bases as it could still go either way, but my money is on the less fun option at the moment. Will be interesting to see if the 00z EC sniffs the same trend.

[joggs]

24 minutes ago, CreweCold said:

Interestingly, however, Metoffice still talking about snow midweek. Can't be snow preceding the rain because the mild air mixes well ahead of the front. This is still very much up in the air and it's interesting that the GFS follows the 18z Arpege run almost to a tee.

Mainly on higher ground,they're talking.

[Nick L]

EC has trended towards the GFS for Wednesday. Really slows this thing down, has heavy precip over the Midlands on Wednesday night at 72h, DPs of +1C so it is as marginal as marginal can be. 

[snowangel32]

3 minutes ago, Nick L said:

EC has trended towards the GFS for Wednesday. Really slows this thing down, has heavy precip over the Midlands on Wednesday night at 72h, DPs of +1C so it is as marginal as marginal can be. 

Hi Nick with your experience which way do you think it will go Gfs 00z ppn charts show snow through wed night into Thursday right through the heart of the UK. Like you said it couldn't be more marginal hence sleet forecast from met for me hedging there bets I think. 

[Nick L]

2 minutes ago, snowangel32 said:

Hi Nick with your experience which way do you think it will go Gfs 00z ppn charts show snow through wed night into Thursday right through the heart of the UK. Like you said it couldn't be more marginal hence sleet forecast from met for me hedging there bets I think. 

6 hours ago I would have flat out said rain, but now I'm really not sure. However, even this morning's output isn't great for low-lying areas, still looking like mostly cold rain at the moment but it's trending in the right direction. Couldn't possibly say which way it's going to go next!

The EC just lingers it over the south Midlands for quite a while with pretty heavy precip. The winds are light so evaporative cooling could come into play.

Edited February 15, 2016 by Nick L

[snowangel32]

Just now, Nick L said:

6 hours ago I would have flat out said rain, but now I'm really not sure. However, even this morning's output isn't great for low-lying areas, still looking like mostly cold rain at the moment but it's trending in the right direction. Couldn't possibly say which way it's going to go next!

It's quite a big shift as well in terms of the time the front hits the UK and then almost grinds to a halt, and although off topic the BBC have definitely changed there forecast this morning. So some nice upgrades for people to wake up to. 

[Man With Beard]

The Weds/Thurs rain/snow event is even more of a forecasting nightmare than before on the 00Zs. Quite a dramatic change to halt the front even further west, and perhaps even push the front backwards for a short time. Central areas are now back in the picture for snow. Need to be very wary for believing the GFS snow charts though, and rather look at other markers e.g. uppers, few points etc, and as Nick points out, they are so marginal that you couldn't predict snowfall at T6 even if the charts we have this morning are right.