Model Output Discussion - Christmas and New Year

[Beanz]

6 minutes ago, markw2680 said:

I do think there will be movements of about 50-100 miles yet east or west and where it pivots could well be in for quite a bit, just my view , it won’t be nailed completely even this time tomorrow so expect the unexpected 

There had better not be, west is best!! 

[sheikhy]

Has gfs just moved east at 24 hours

[Guest]

6 minutes ago, markw2680 said:

I do think there will be movements of about 50-100 miles yet east or west and where it pivots could well be in for quite a bit, just my view , it won’t be nailed completely even this time tomorrow so expect the unexpected 

Was thinking the same thing regarding the pivoting. Should precip be heavy enough at the pivot point, a favoured location could see a fair amount of accumulating snow. Speculation at this stage but it is one to watch as the hi-res models try to get a handle on the precipitation track.

[Mapantz]

Can we keep to model discussions please?!

Please use the regional threads, or the moans/ramps/chat thread for asking if it'll snow in your location.

Edited December 26, 2020 by Mapantz

[Spah1]

16 minutes ago, sheikhy said:

My god that latest ukv looks similar to icon!!is the midlands back in it last minute!!

Arpege takes it south through Wales and misses NW and Midlands out. 

[Nick F]

So, the 18z ICON has flipped and now backs 18z UKV, 12z EURO4 and AROME with taking low and snow east from Wales/W England across S England and Midlands on Monday. I guess EC will jump on board tomorrow.

Really interesting watching how the models behave, the high-res models, apart from EC, seem to be the ones to follow when there's uncertainty in track of lows within T+60-72. 

Also really interesting seeing the longer term growing prospects of prolonging the cold into early January, with high latitude blocking and -NAO signal from extended 12z EPS.

Lots to look forward to for coldies. 

Edited December 26, 2020 by Nick F

[MattStoke]

GFS joins the ICON, UKV and Euro4.

[SMU]

18z GFS

[Kasim Awan]

4 minutes ago, Steve Murr said:

It would be nice to have some QPF forecasts for the Uk...  & some basic SLRs 

I think weatheronline Euro4 algorithmn uses an SLR

[sheikhy]

2 minutes ago, Steve Murr said:

18z GFS

Steve at this rate the whole of england gona get smashed!!❄

[kold weather]

Very interesting and somewhat rare to see the models shift back northwards are flirting taking it further south, definitely a better evolution though for a bigger chunk of the country.

The evolution for the south is something of a knife edge in particular, timing really will be vital. IMO if it arrives in the south before say 10am, snow is likely, if it arrives to co-incide with peak heating, then ot my end up just as a wintry mess.

Further north looks increqasingly less marginal as you'd expect.

[Allseasons-Si]

Yep,18z gfs a lot further NE than the 12z.

[Kasim Awan]

Just now, sheikhy said:

Steve at this rate the whole of england gona get smashed!!❄

The problem is once the shortwave precip area reaches a certain size more moderation will become entrained into it = more marginality. This is now a risk.

[Tim Bland]

GFS snow depth mon eve (t+48) slightly west of icon / euro4

[kold weather]

4 minutes ago, Steve Murr said:

18z GFS

One other thing to note Steve is to watch to see if we end up getting a cyclonic loop out of this low pressure as a secondary low tries to form around it.

The models won't clock this till late in the day but such evolution have led to some really big snowfalls in the past. Bit of a lottery as to where the pivot point would be mind you!

[Cymro]

Just now, Mapantz said:

Can we keep to model discussions please?!

Please use the regional threads, or the moans/ramps/chat thread for asking if it'll snow in your location.

This is a fair point it’s important that this thread doesn’t become derailed from the brilliant commentry in here from longstanding experienced posters. 

But could I kindly ask for some consistency? I.e when snow is likely in the South East of England posts tend to concentrate on that and the thread quickly becomes focussed on that however when the threat of snow is say in Wales or the Midlands or northern England and posts comment on this we see the disappearance of said posts and kind reminders to stick to the regionals such as this one. 

I understand the importance of the regionals but please don’t allow this thread to become derailed likewise by those from the South east of England. 

[I remember Atlantic 252]

looks good, further NE

[Kasim Awan]

M4 north with gfs 18z. Model consistency equillibrium pretty much hit. Amounts varing with precip longevity latitude & elevation. 

[Snowman.]

1 minute ago, Kasim Awan said:

M4 north with gfs 18z. Model consistency equillibrium pretty much hit. Amounts varing with precip longevity latitude & elevation. 

Know it's likely to be accurate because its north of the M4 

Edited December 26, 2020 by Snowman.

[Cheshire Freeze]

1 minute ago, Kasim Awan said:

M4 north with gfs 18z. Model consistency equillibrium pretty much hit. Amounts varing with precip longevity latitude & elevation. 

Some elevation will be key (for accumulation)...100m+ I'd suggest. You can see the Cheshire/Shropshire plain there with no accumulation

Edited December 26, 2020 by CreweCold

[danm]

3 minutes ago, Cymro said:

This is a fair point it’s important that this thread doesn’t become derailed from the brilliant commentry in here from longstanding experienced posters. 

But could I kindly ask for some consistency? I.e when snow is likely in the South East of England posts tend to concentrate on that and the thread quickly becomes focussed on that however when the threat of snow is say in Wales or the Midlands or northern England and posts comment on this we see the disappearance of said posts and kind reminders to stick to the regionals such as this one. 

I understand the importance of the regionals but please don’t allow this thread to become derailed likewise by those from the South east of England. 

Ah this old chestnut again. Hear it every winter (apparent SE bias). 
 

One thing I’ve learned over the years is that the track will continually change and end up becoming a nowcasting event. We’ll get an envelope of possible tracks, within a few hundred miles, and it won’t be firmed up until 12-18 hours beforehand, but even then things will change. 

[Allseasons-Si]

The ICON in the latter stages(low res)has another feature coming down from the NE coast and running through Yorkshire and down through the the midlands then down into the SE,speculation at this stage but at least it is showing another snow event.

Oh!,and a possible channel runner too.

Edited December 26, 2020 by Allseasons-si

[Scott Ingham]

1 minute ago, CreweCold said:

Some elevation will be key...100m+ I'd suggest. You can see the Cheshire/Shropshire plain there with no accumulation

The higher res outputs put the freezing level much lower than the lower res gfs so i wouldnt rule out these areas just yet but obviously the accunaltions will be much lower. As stated by the met office.

1-3 cm on low elevation

5-10 on higher elevation

This was based on high res models which have actually increased these amounts closer to 2-5cm lower and 10-15cm

Glad to see a situation improve closer to the end for a change!! 

[Cymro]

Just now, danm said:

Ah this old chestnut again. Hear it every winter (apparent SE bias). 
 

One thing I’ve learned over the years is that the track will continually change and end up becoming a nowcasting event. We’ll get an envelope of possible tracks, within a few hundred miles, and it won’t be firmed up until 12-18 hours beforehand, but even then things will change. 

I agree the track of this secondary system remains far from resolved. 

But might I suggest that the reason this old chestnut fails to relent is because it is a valid concern based on years of observation. 

[I remember Atlantic 252]

Pivot around S/SW Midlands?