Model output discussion - 5th December 2016 - Into Winter we go

[Singularity]

2 minutes ago, CreweCold said:

Look at heights to the S of the UK...sorry but you've not got a cat in hells chance of any meaningful disruption with a set up like that. Height are anchored all the way down to Africa! Couple that with a strong jet streak....Don't understand why the possibility is even being discussed. 

As I said last night, we're on hold now until the latter stages of December.

This jet stream chart shows why it's certainly possible. Disruption occurs on the west flank of the ridge to help pump it up and encourage a northward drift over the following week or so.

I presume you mean on hold for significant snow events, in which case we probably are unless by some currently veiled luck the block gains latitude remarkably quickly.

[whitestuff]

31 minutes ago, Steve Murr said:

 

Theres a world of difference between commenting on a day 16 chart than making a forecast with specifics for day 26 through 33.

Stewart - week 4- instability? Whats that supposed to mean-? Pretty pointless by anyone's standards -

we are almost in the realms of Piers Corbyn fantasy nonsence...

As far as I can see there is no difference in commenting on day 16 and 26 when the flip about day to day! A week or so people were saying they see a cold run up to Christmas and now it seems winter is over....again.

The models are like a crystal ball and you see what you want to see in them. Coldie and mildie alike!

[johnholmes]

28 minutes ago, karlos1983 said:

Well if I was reading it wrong then fair enough, not sure it was a "why on earth would it do x,y,z" warranted comment. Blimey, shoot me down 

my apologies for being somewhat insensitive 

 

[Mucka]

GFS ensembles day 10 possibilities.

I would say around 50% are pretty flat and the rest more amplified with a mix of UK high and something more interesting as far as possible cold/snow possibilities could go from there.

That spread becomes more favourable as we move out into deeper FI so that by day 13/14 there is virtually no zonal on offer and a lot of mid lat blocking, some with good cold potential.

Edited December 6, 2016 by Mucka

[frosty ground]

24 minutes ago, Steve Murr said:

I will a final comment like this-

If the forecast for Jan is that easy to predict with so much confidence to paint any detail around then it would indicate its pretty straight forward with minimal variability -

However just yesterday at 315 we see a post claiming that 12z data had significantly different initialised data around   Indian ocean convection than the 00z & 06z - & the ramifications of this could effect the UK down the line at say day 8-12 ...

So in one breath there is a confident post about specifics at the period 26 - 33 ( T624 - 792 ) yet just 24 hours before we have a massive potential swing in outputs as a result of different starting data covering 12hours - 

So if that disparity can occur in just 12 hours having a exponential effect at just day 8 how does one arrive with such bold statements at day 26....

The seasonal models - like the CFS swing around daily from run to run all because the starting data is slightly different from the run before leading to huge hemispheric change at week 4..

I will leave people to make up their own minds...

So far - The glosea long range has been not very good, the assumption of a front loaded winter looks to bomb ( which includes me as well ) & were just 6 days in ...

Anyway enjoy the eve 

Could it be more that one is stating what the data is showing and you are confusing this with a forecast?

[Scandinavian High.]

Looking cold and crisp run up to Christmas even  colder air pushing in to south east England but dry and frosty .no snow yet  but can change.

Edited December 6, 2016 by abbie123

[SMU]

27 minutes ago, whitestuff said:

As far as I can see there is no difference in commenting on day 16 and 26 when the flip about day to day! A week or so people were saying they see a cold run up to Christmas and now it seems winter is over....again.

The models are like a crystal ball and you see what you want to see in them. Coldie and mildie alike!

I think you misunderstood the difference between commenting on a chart @16  & forecasting on a date well past it anyway...

talking of trending the GFS midterm is now up to 12 members over the ERA long term zonal mean average & the daily ( think 00z ) CFS run & perturbed run both peak the forecasted zonal mean wind speeds around the 20th of Jan ( one of them has a peak of about 57 M/S ) which is HIGHER than 2015 - that would pretty much nail all of dec & Jan as bad as last winter -

Because the data on the image only uses 1 run of daily data its a little less volatile however the trend for the last 10 days has crept up & up in lines with the short term GFS ENS-

Whilst there not the be all & end all you would expect leas chopping & changing unlike reviewing a fixed point on the map.

Not great reading TBH

 

* FG Possibly but seeing as it was against the meto then theres not much other data around other than the EC46/Glosea & the seasonal models- 

Edited December 6, 2016 by Steve Murr

[Ali1977]

Some fantastic ENS, Dec isn't done yet folks.

[northwestsnow]

Im not overly bothered about the zonal wind speeds steve, they have been very low since mid Nov,and we have seen little or zero high lat blocking across the NWP thus far....:)

Edited December 6, 2016 by northwestsnow

[feb1991blizzard]

Just now, Ali1977 said:

Some fantastic ENS, Dec isn't done yet folks.

There is some 5H!T in there as well though.

[Paul]

The latest synoptic guidance from @MattHugo is online:

Synoptic Guidance: Unsettled For Now - Potential Pattern Change Later

[SMU]

25 minutes ago, frosty ground said:

Could it be more that one is stating what the data is showing and you are confusing this with a forecast?

 

18 minutes ago, northwestsnow said:

Im not overly bothered about the zonal wind speeds steve, they have been very low since mid Nov,and we have seen little or zero high lat blocking across the NWP thus far....:)

I know - however if they go north of 40M/S you can forget any going forward!

just to emphasize how important it is though- todays date record of -0.7 is for Dec 81

& why I was so excited to see the GFS mean forecasting -3 ish for Nov 30th....

coincidentally the date positive record is 2015 @ +52.9 M/S & the PV looking like this

today initialised at 16.3 M/S with a 5 day forecast up 36M/S ...

 

Edited December 6, 2016 by Steve Murr

[pip22]

Matthew Hugo ‏@MattHugo81 1m1 minute ago

850mb temps not always of worth during high pressure (HP) but theta-e is with a downward trend as HP becomes established. #coldandsettled

 

[nick sussex]

I think we can't avoid a raging PV, the issue is how far into Greenland it will get and looking at the GEFS upto T240hrs theres still some uncertainty there. The best case scenario within the next two weeks or least worst is a high far enough north to cut off the TM flow and bring some surface cold.

If we can get more amplification upstream which could help pull some of that PV further to the nw then the outside chance of a Scandi high.

The GFS op is of course possible but the less said about that the better!

[feb1991blizzard]

9 minutes ago, Ali1977 said:

Some fantastic ENS, Dec isn't done yet folks.

There is some really good ones at the end to be fair.

[Summer Sun]

Cold and settled looks to be the way still as we move to Christmas

[Frosty.]

6 minutes ago, feb1991blizzard said:

There is some 5H!T in there as well though.

There always is but crucially it looks like support is growing for a colder spell towards / during xmas..perfect timing that would be!

[Seasonality]

2 minutes ago, nick sussex said:

I think we can't avoid a raging PV, the issue is how far into Greenland it will get and looking at the GEFS upto T240hrs theres still some uncertainty there. The best case scenario within the next two weeks or least worst is a high far enough north to cut off the TM flow and bring some surface cold.

If we can get more amplification upstream which could help pull some of that PV further to the nw then the outside chance of a Scandi high.

The GFS op is of course possible but the less said about that the better!

Raging? The run ends with an arctic high spreading the vortex out nicely.

 

[northwestsnow]

I know patience is a hated word the world over but we really are going to need plenty of it again.

Imho the next couple of days are huge - the further north the azores high can ridge in the 96-120 timeframe the better for coldies, we do not want to see the azores high ridging into the UK and the jet rolling over the top!

[chris55]

I think the 12z GFS ens highlight Ians comments from earlier on today.

The longer range suits are split between milder than average, and colder than average. Some members taking us into a much more pronounced colder scenario, while others take us mild. This will skew the mean as the trend is not for an average period, its either cold or mild.

Taking op runs with any confidence beyond day five is more futile than normal at present until we get a clear signal in the ens.

Here are the GFS 12z ens

 

[nick sussex]

7 minutes ago, pip22 said:

Matthew Hugo ‏@MattHugo81 1m1 minute ago

850mb temps not always of worth during high pressure (HP) but theta-e is with a downward trend as HP becomes established. #coldandsettled

 

Lmao! You know we're scraping the bottom of the barrel when the theta-e gets rolled out! Basically cold at the surface warm aloft, zip chance for snow. If we're going to have a raging PV it needs to elongate  and run sw/ne far enough north to allow a Scandi high, barring that we're feeding off scraps.

[Stuie]

Probably Nick why the hashtag is cold and settled and not cold and snow....

[I remember Atlantic 252]

Pressure not bad either on GEFS, avg around 1030, a few stinkers but seen miles worse, like mean of 980 etc

[AWD]

6 minutes ago, feb1991blizzard said:

There is some really good ones at the end to be fair.

I take it you are referring to perb 3?

Although, as per the above tweet, if HP does indeed settle over the UK as a number of ens suggest, then the 850mb temps become less useful in determining the surface temp so I've included the 2m temp ens;

And the pressure ens, which to be fair, show a distinct favouring of settled rather than unsettled conditions over the UK;

I think upper level cold with widespread snow conditions look unlikely for the foreseeable, but also unlikely after the next week or so, is stormy, mild conditions.  Based on the above, I stick with my hunch for a cool/surface cold & settled Christmas period.

[Seasonality]

4 minutes ago, nick sussex said:

Lmao! You know we're scraping the bottom of the barrel when the theta-e gets rolled out! Basically cold at the surface warm aloft, zip chance for snow. If we're going to have a raging PV it needs to elongate  and run sw/ne far enough north to allow a Scandi high, barring that we're feeding off scraps.

But cold at the surface is exactly what Matt is referring to, hence why theta-e's are relevant. No barrel scraping, just telling it like it is. Not sure why you think it is 'lmao'