Model Output Discussion - 05/01/2016 18z onwards

[Cheshire Freeze]

Another nudge N of the 552 isopleth at 96 hours. The further N this gets the better

[Radiating Dendrite]

4 minutes ago, The Enforcer said:

Not only has GFS been a bit out on a limb with the westwards progression of atlantic air, but it also seems to have some glaring errors in the detail. Take next Monday, when the 12z is predicting a transitional snow event:

Mostly rain over my location, yet snow over France. However, when you look at the 850's:

The -5C isotherm is over my location and the mass of snow over France is above 0C. It certainly doesn't inspire confidence. And of course, the ensembles show that the operational is one of a handful of milder runs on 18th:

 

I was led to believe that the 0c degree isotherm was good enough for low level snow on the continent due to it being a continental landmass and not an island - lower DPs etc. 

[Ali1977]

Incoming rain proceeded by snow again at 132, this has shown a few time. Could be our best chance of snow down South, even if it does turn back to rain. It would be great to stall against the cold and give us a decent covering. All for fun at this range though - and without support of other models as of yet.

kind of stalls over the SW against the cold, this type of scenario could be interesting depending how far inland the moisture gets.

Edited January 12, 2016 by Ali1977

[Mark Neal.]

3 minutes ago, Ali1977 said:

Incoming rain proceeded by snow again at 126, this has shown a few time. Could be our best chance of snow down South, even if it does turn back to rain. It would be great to stall against the cold and give us a decent covering. All for fun at this range though - and without support of other models as of yet.

Very true, but its been consistent of late by GFS Op runs. But obviously at 6 days away, still looong way for it go and plenty of model runs before it comes to fruition. 

It also seems to be fragmenting all the time, as it hits UK. Probably down to trough distruption. 

Edited January 12, 2016 by Mark N

[bradymk]

4 minutes ago, Ali1977 said:

Incoming rain proceeded by snow again at 126, this has shown a few time. Could be our best chance of snow down South, even if it does turn back to rain. It would be great to stall against the cold and give us a decent covering. All for fun at this range though - and without support of other models as of yet.

When we get to reality Ali, i doubt that precip will even make 90% of mainland UK.

Look at 12z compared to 18z, further west and this has been the case the last few runs. Wonder if by this time tomorrow, it will even make it to Wales?

Even on the 18z it fades out over Wales 

Edited January 12, 2016 by bradythemole

[I remember Atlantic 252]

As expected GFS 18Z shoved things West, not looking like any snow on Monday now away from Ireland, disappointing run really if snow is what you are after

 

[Snowman.]

On 08/01/2016 at 6:36 AM, shaky said:

Ukmo odd one out am afraid and well done gfs!!!still get some cold and snow before it all goes west based so not bad!!

 

2 minutes ago, I remember Atlantic 252 said:

As expected GFS 18Z shoved things West, not looking like any snow on Monday now away from Ireland, disappointing run really if snow is what you are after

 

Not really disappointing as cold is now locked in and the atlantic onslaught pushed back more get the cold in first then look for the snow.

 

Also on phone and cant delete the first quote so sorry about that

[Mair Snaw]

On 10/01/2016 at 4:45 PM, Ed Stone said:

 

But surely everything being shunted west means the cold stays in longer and that must be a good thing right??  also no idea why i cant get shot of the quote post thing...

[bradymk]

Pointing out the obvious really but the 0c 850 is around 300-350 miles further west at 162 than it was on the 12z and around 800-1000 miles further west than it was compared to Sunday 12z run. Just proves how the models do struggle with the return of milder air.

[cornish snow]

4 minutes ago, I remember Atlantic 252 said:

As expected GFS 18Z shoved things West, not looking like any snow on Monday now away from Ireland, disappointing run really if snow is what you are after

 

Looking good. Just need a further correction west and thing's could get exiting for us in the south west

 

[Banbury]

At 168 we are still under the HP well into FI in this sort of set up

[SMU]

The great GFS over 4 runs

so this is the theta E charts across the 4 runs of the day starting at 162,156,150 & now 144 on the 18z

The typical GFS backtrack..,.

 

It also shows the sudden emergence of High pressure to the East that gets further north & west with time...

another day or so it its in UKMO territory.....

S

[Dancerwithwings]

2 minutes ago, Banbury said:

At 168 we are still under the HP well into FI in this sort of set up

Best not to even look past 144h! Like you said "in these sort of set up"

 

[Banbury]

1 minute ago, Dancerwithwings said:

Best not to even look past 144h! Like you said "in these sort of set up"

 

Totally agree ......I'm looking at that large HP out to the East

[Dancerwithwings]

5 minutes ago, Steve Murr said:

The great GFS over 4 runs

so this is the theta E charts across the 4 runs of the day starting at 162,156,150 & now 144 on the 18z

The typical GFS backtrack..,.

 

It also shows the sudden emergence of High pressure to the East that gets further north & west with time...

another day or so it its in UKMO territory.....

S

Oh! yes .. GFS                     You know it makes sense!

[chionomaniac]

Two/three days ago the GFS had the cold air (-5ºC 850's) to be cleared away from the country by Sunday. Now it is Tuesday. If for every day the cold clearing is delayed a day then most will be happy with that!

[damianslaw]

Another day and lots more changes and possibilities - as others have said this past week has been excellent for model watching.. reliable timeframe always has been short, yet many have got hung up on one model run beyond the 144 hr timeframe..

UKMO has been the most bullish of all the models sticking with its persistant cold theme, GFS has backtracked and yo-yoed a bit on a generally more fluid flow, but is now backing everything westwards - markedly so.. ECM sitting inbetween somewhat but siding more with UKMO.

Back to the here and now, we have a potential low level snow event for some parts tomorrow night and into Thursday as we see a front engage the cold air over northern parts. Thereafter we see cold thicknesses finally sweep down to the south coast.

The weekend is looking good, a dry cold one with lots of frost..

Early next week - strong indications the cold will stay in residence with heights remaining robust and a significant cold pool developing to our NE. UKMO shows a classic trough disruption event which would prolong the cold and embed it further. As some have said we have seen many such scenarios in years gone by, the atlantic struggling to break through, especially when the Jetstream is rather sluggish. We shall see if this theme continues..

[Jason T]

Hi All,

Well Well..The excitement really begins. For those that like to go compare so to speak. Excellent link to diff model postage stamp time frames, Also 3d jet stream/Wind map global. Winter is about to embrace us all.

http://www.meteociel.fr/cartes_obs/comp_panel.php?mode=1&ech=54&size=1

http://earth.nullschool.net/#current/wind/isobaric/700hPa/orthographic=1.73,49.05,562

 

[Panayiotis]

So this cold spell has almost finally arrived, so my attention turns to where our snow will come from!... this week the biggest snowfalls would be for the Pennines and high ground over Wales as a low pressure system tracks itself W to E on Wednesday night with totals over 10cm likely. After this, snow showers will be hit and miss across the UK (more likely towards the coasts) but this isn't ideal for a widespread event that were all looking for!  

The one event that were all looking towards and has already been spotted is the potential undercut shown by the GFS especially and some of the other models. And although I would prefer the evolution shown by the UKMO, atleast the GFS shows a snowy breakdown for some in the south! So looking at the undercut, one would expect not to see snow from a chart like this:

However with the cold already in place (for more than a few days), the precipitation bumping into it can readily fall as snow,  looking at the 850hPa we have the bulk of the country under -4c/-5c with the far W and SW seeing uppers around -2c:  

And although we generally say we need uppers of below -6c, in these conditions we can see snow to lower levels even with uppers of -2c/-3c as the feed is off the continent, so dew points will be lower and most probably negative as the air is drier:

And finally the snow chart to show this, but not to be taken for gospel as things would probably change by then:

v

 

[Mucka]

When evaluating the models I don't think anthropomorphism helps us or cherry picking success or highlighting individual failures but for sure take on board the various models bias.

Yes I do it myself, pot kettle and all that, but worth remembering GFS got an awful lot right the other  models failed with before this latest episode (assuming it is wrong)

I'm 99% sure on these;

• It was the first to push the pattern west. 
• The first with the Icelandic shortwave.
• The first to have energy break through the first ridge.
• The first to downgrade the uppers.
• The first to bring the Azores low North as we see now.

They all have strengths and weaknesses and it is probably GFS's progressive nature that causes it to be on the end of more of our bad feeling as it will usually be the model that will least likely give us the amplification we want.

Edited January 12, 2016 by Mucka

[Severe Siberian icy blast]

12 minutes ago, damianslaw said:

Another day and lots more changes and possibilities - as others have said this past week has been excellent for model watching.. reliable timeframe always has been short, yet many have got hung up on one model run beyond the 144 hr timeframe..

UKMO has been the most bullish of all the models sticking with its persistant cold theme, GFS has backtracked and yo-yoed a bit on a generally more fluid flow, but is now backing everything westwards - markedly so.. ECM sitting inbetween somewhat but siding more with UKMO.

Back to the here and now, we have a potential low level snow event for some parts tomorrow night and into Thursday as we see a front engage the cold air over northern parts. Thereafter we see cold thicknesses finally sweep down to the south coast.

The weekend is looking good, a dry cold one with lots of frost..

Early next week - strong indications the cold will stay in residence with heights remaining robust and a significant cold pool developing to our NE. UKMO shows a classic trough disruption event which would prolong the cold and embed it further. As some have said we have seen many such scenarios in years gone by, the atlantic struggling to break through, especially when the Jetstream is rather sluggish. We shall see if this theme continues..

i haven't saw one forecast that's going for low level snow tomorrow night , the bbc have really talked it all down from last wk when they did talk about snow . 

And for any places south of Stoke there's not even the sniff of any wintyness at all on the bbc graphics or the euro4 Hi res . 

I hope to be proved wrong . 

But yes re the cold spell , it's looking increasingly likely we will sell an extension to the so called cold snap . Should be getting colder as we move deeper into it . It will be nice to get.a traditional undercutting low bringing snow but I doubt any trough disruption will get to the uk , but interesting none the less .

[Daniel*]

Bit by bit GFS is getting closer to UKMO with these westward adjustments, all models tend to overdo the energy of Atlantic pushing through against cold air which is not too easily displaced, the models have always struggled on this. UKMO has made some mistakes as has ECM, but it has been the superior model GFS, has been like a stuck record over the past few days. 

ECM Dutch ens are very impressive the momentum has shifted greatly.

Bit premature, reasons to be happy but what a tune!

Hopefully excusable considering, RIP Legend 

 

[Midlands Ice Age]

Just watched Alex Deakin at 10:40 on BBC1.

He stated that the milder air May well arrive by midweek.

At the time he was standing in front of a chart showing a 1035Mb high from Scotland upto the West Coast of Norway.

Interesting because I haven't see the high that far north east on any of the charts that have been published on here.

This evenings Fax chart my be better than expected.

[Mark Neal.]

120hr Fax.

[Midlands Ice Age]

7 minutes ago, Mark N said:

120hr Fax.

Thanks Mark..

That screams to me of energy going into France  and pushing our high northwards as it does so. Possibly explaining Alex D charts.

It also screams an easterly as the high to the north west doesn't look to be collapsing, hence turning the energy emerging off the states more easterly and then undercutting.