Model output discussion 25th Jan - The final third of winter beckons..

[Summer Sun]

Every chance this cold weather will last for the vast majority of Feb

[EML Network]

Fantastic period of model watching this winter and finally it looks like we are generally in for a decent shout at the first decent country wide cold spell since March 2013, I did say earlier last week that I was getting excited for the first time this winter about the prospects of something really Wintery in the 2nd half of Feb and I can't wait to see the ensemble graph,some seriously cold charts being churned out. 

It's so good to see things ever so slightly ''upgrading'' from run to run, rather than the usual gradual downgrades. 

However, a word of caution, IMO the vast majority of us will once again need to be patient, as others have said the coming cold spell looks to be predominantly dry away from NE facing coats and this has been the likely outcome right from the outset.

 

Other posters who are under the delusion that the entire country will be sitting under 6 foot of snow by this time next week will look a little silly....by this time next week.

The 2nd bite of the cherry is by no means a certainty yet, but it's looking increasingly likely and IMO it's the 2nd bite that will pay dividends for some of us.

 

when you get charts like this being spat out of the machines you know something elsewhere in the world is not playing the normal rules of the game and something is amiss

Also looking through the GFS ensembles this morning (which I'm able to do for once as I'm off work sick and don't normally get opportunity to post on here these days)...

 

I can only find one run that supports the ECM evolution...(Run 16)

ECM

 

The good news ...the laughable news...is that this is run 16 just 3 days later...

 

So even if the ECM is on the money, the route to an Easterly still comes..

 

It seems right now that all roads lead to an Easterly that would deliver cold and snow for all (eventually)...this mornings 06 Suite is by far the best I have seen for a very very long time.

That's the biggest ramp from me for 6 years !!!!

 

[SLEETY]

21 minutes ago, Summer Sun said:

The GFS ens shows it becoming very cold later this week

Into next week it remains cold but real low 850's MAY move away with the UK seeing -2's or so instead of -8's to -10's

A week is a long time especially in an easterly setup  so  I changed your wording  regarding your comment that 850s are certain to rise in a weeks time ,the models still have to firm up exactly on how potent this easterly is yet or not fl is about t+ 72 in easterly setups .

[Summer Sun]

So at D10 after the 00z's / 06z we have a westerly, easterly and southwesterly

Plenty of cold weather to be had beforehand with some snow showers around later this week

Edited February 6, 2017 by Summer Sun

[Singularity]

45 minutes ago, bluearmy said:

Little time to comment but the extended ens are getting me interested now as they trend towards the Siberian vortex taking charge again and possible dropping troughing  south west towards scandi

the fi gfs ops (both normal and parallel ) headed this way

the mid range still uncertain but the 5/7 day period holds a lot of interest though pinning down exactly where that interest is greatest will prove a problem for the next 72/96 hours !

Indeed - plenty of scope for a standard 7-8 MJO + severely disrupted vortex response in the form of retrograde rotation of the broad setup with the big block heading west and the vortex lobe tucking in behind.

It is only potential of course and yes, I'm deliberately taking the opportunity to go lighter on the caveats and spanner-sense for once (but people should keep them in mind as always!).

 

[stotm]

3 minutes ago, Summer Sun said:

So at D10 after the 00z's / 06z we have a westerly, easterly and southwesterly

 

[stotm]

3 models at day 10, all different would you believe it?

[Methuselah]

Just now, stotm said:

 

Based simply upon how this year's cold spells have panned-out, those charts - sadly - mightn't be too far off the mark. I hope they are, though!

[chionomaniac]

51 minutes ago, bluearmy said:

Little time to comment but the extended ens are getting me interested now as they trend towards the Siberian vortex taking charge again and possible dropping troughing  south west towards scandi

the fi gfs ops (both normal and parallel ) headed this way

the mid range still uncertain but the 5/7 day period holds a lot of interest though pinning down exactly where that interest is greatest will prove a problem for the next 72/96 hours !

30 HPA chart supports this on latest GFS run. Can quite easily see the evolution from Scandi high to Greenland with this type of set up.

[Frosty.]

1 minute ago, stotm said:

3 models at day 10, all different would you believe it?

To be honest I'm just looking forward to the cold this week rather than worrying what the models show at day 10 but I'm cautiously optimistic our weather will stay predominantly cold for the rest of Feb once it arrives from midweek.

[Summer Sun]

Little update from Ian not sure what WBPT stands for?

Edited February 6, 2017 by Summer Sun

[bluearmy]

1 minute ago, Summer Sun said:

Little update from Ian not sure what WBPT stands for?

Wet bulb pot temps  gav 

dictates where dp's will stay low enough for snowfall 

[stotm]

7 minutes ago, stotm said:

3 models at day 10, all different would you believe it?

Sorry what I wanted to says has there ever been 3 models at day 10 the same? Lol

[Iceaxecrampon]

06z

Fun and games start as early as T+51 Wednesday for the East Coast

 

Can someone inform me why does all the ppn seem to hang for two days in the North Sea? obviously these are only guideline charts.

 

Bonkers in FI

[pyrotech]

7 minutes ago, Iceaxecrampon said:

06z

Fun and games start as early as T+51 Wednesday for the East Coast

 

Can someone inform me why does all the ppn seem to hang for two days in the North Sea? obviously these are only guideline charts.

 

Bonkers in FI

The models are showing dry cold air crossing the continent and into a relatively warm North sea, the warm air from the North sea adds moisture to the air which the cold air can not hold and so we see snow showers as the cold air crosses the north sea and potentially inland for around 15 miles depending on wind speed. At that time the Cold air is unable to hold enough moisture to maintain showers further inland although streamers will occur in prone places. 

East coast may get slight covering from this and is why Far Eastern counties are much better in this Scenario where the models later show options to open doors for other areas.

[Met4Cast]

13 minutes ago, Iceaxecrampon said:

06z

Fun and games start as early as T+51 Wednesday for the East Coast

 

Can someone inform me why does all the ppn seem to hang for two days in the North Sea? obviously these are only guideline charts.

 

Bonkers in FI

The PPN hangs on in the North Sea because the temperature boundary between the relatively milder ocean and the bitterly cold uppers aids convection and produces snowfall. Unfortunately as soon as these showers move over land they lose the convective element and the showers quickly die out, hence the models showing it hugging the East coast.

We need a trough or disturbance to develop in the flow, that'll give us more organised bands that would be able to push further inland, as per GFS at T150.

But, looking for features like this outside of a 2-3 day window is pointless, not only because they can appear suddenly but also because the GFS Precip charts are very often, completely useless. 

The models are trending the right way today, if we can see just a little more instability in the Easterly flow then they'll be a lot of snow lovers getting excited. We're not talking a particularly big upgrade for that to happen, either. 

If the ECM doesn't come on board with todays 12z I'll be honest, I will start to worry. I'm always on edge when one of the big 3 refuses to fall into line. 

Edited February 6, 2017 by Daniel Smith

[Man With Beard]

And having done the ramp, now for the "back to earth" bit!

That cold pool for next weekend looks good. BUT - it has to (i) get here and (ii) stall here.

No matter what model agreement there may appear to be right now, this won't be in the bag until at least T48. Nor will snow forecasts (which I can see upgrading as well as downgrading).The pattern we're looking for is too precise to hope for more than that.

And when you see that the GFS is colder than almost all members of the ECM ensembles for D7/D8/D9 - one has to prepare for the fact that it probably won't be as cold as presently being forecasted - sorry!

But notice that a good cluster stays cold throughout. Greenland - Scandi ridge???

[bluearmy]

13 minutes ago, Man With Beard said:

And having done the ramp, now for the "back to earth" bit!

That cold pool for next weekend looks good. BUT - it has to (i) get here and (ii) stall here.

No matter what model agreement there may appear to be right now, this won't be in the bag until at least T48. Nor will snow forecasts (which I can see upgrading as well as downgrading).The pattern we're looking for is too precise to hope for more than that.

And when you see that the GFS is colder than almost all members of the ECM ensembles for D7/D8/D9 - one has to prepare for the fact that it probably won't be as cold as presently being forecasted - sorry!

But notice that a good cluster stays cold throughout. Greenland - Scandi ridge???

The eps seem to be as useless as the ops recently

that Temp graph just indicates that the envelope is extremely large post the weekend and the weekend itself could be anything from snowy to frosty and even wet/damp or miserably grey and dry 

[Timmytour]

3 hours ago, Gustywind said:

I remember back in Jan 10 ( I think) the Beeb were calling up to 20cms of snow for SE, but they got rain instead. Steve Murr forecast this in advance I believe.

Upper air temps were sub -10 I think but the long fetch over the North Sea turned dew points the wrong side of marginal.

Possibly you refer to 2009 when, on having received 8 unforecast inches of snow from a Streamer first, some of us waited breathlessly for another 8 inches to fall as forecast by the BBC (Met) only for it to disappoint and fall as sleety rain.  What we did have lasted most of the week but we never got further falls. However areas that missed out then picked up substantial falls in the next few days.  Not sure if currently projected scenario will be similar....looks as if the block will keep the fronts that kept trying to encroach back then well away this time...

[danm]

6 minutes ago, Timmytour said:

Possibly you refer to 2009 when, on having received 8 unforecast inches of snow from a Streamer first, some of us waited breathlessly for another 8 inches to fall as forecast by the BBC (Met) only for it to disappoint and fall as sleety rain.  What we did have lasted most of the week but we never got further falls. However areas that missed out then picked up substantial falls in the next few days.  Not sure if currently projected scenario will be similar....looks as if the block will keep the fronts that kept trying to encroach back then well away this time...

Yep think you're right here. 

Feb 2009, the main event was meant to be an area of PPN moving up from France that was to give heavy snow, but turned out to be sleety wet snow. The previous night however, a streamer set up that was only forecast at relatively short notice which gave 6-8 inches of powdery snow. 

Shows how difficult it is to forecast snow in the UK.

Edited February 6, 2017 by danm

[East_England_Stormchaser91]

11 minutes ago, danm said:

Yep think you're right here. 

Feb 2009, the main event was meant to be an area of PPN moving up from France that was to give heavy snow, but turned out to be sleety wet snow. The previous night however, a streamer set up that was only forecast at relatively short notice which gave 6-8 inches of powdery snow. 

Shows how difficult it is to forecast snow in the UK.

Yes, that would've been the 'winter storm' that swept up the channel from the BoB. I think that the warmer air within that system mixed out the cold uppers just to the wrong side of marginal! 

Another example was in January 2010 when Rutland and Leicestershire saw regular snowfall, but from the coast to 20 miles inland saw not a flake and just steady rain. Quite frustrating! 

Noticing with each run on the GFS as it goes on, the cold pool is being corrected 50 miles further south and west every time, thus increasing the likelihood of snow more widely in the short term outlook. 

If you have been watching the daily now cast updates by 62-63, you'll see the reasoning for this! The cold pool over Russia has been advancing more quickly and ripely than most of the models suggested beforehand. 

[sparky1972]

well, nearly that time of day where dreams are dashed, toys are thrown and at times a nice surprise forecast is handed to us cold lovers, my hunch is the next few days will be chilly/cold rather than cold/very cold, but so hoping im wrong, maybe this Feb will be winters saviour and give us coldies something to remember, to all those who post the views etc here, keep up the good work, i for one who has no understanding of model reading etc love being here just to read and enjoy the emotional rollercoaster that is British weather

[Dennis]

Latest MJO -

[Chris K]

2 minutes ago, sparky1972 said:

well, nearly that time of day where dreams are dashed, toys are thrown and at times a nice surprise forecast is handed to us cold lovers, my hunch is the next few days will be chilly/cold rather than cold/very cold, but so hoping im wrong, maybe this Feb will be winters saviour and give us coldies something to remember, to all those who post the views etc here, keep up the good work, i for one who has no understanding of model reading etc love being here just to read and enjoy the emotional rollercoaster that is British weather

"Less grey, more sleigh" is what I'd like to see. 

[Nouska]

Since there is a lull between model runs, let's take the link for the UKMO 168 hour forecast and use it for what it is designed for - ie tropical weather forecasting.

The three main models at the day seven period. You may wonder why I'm using a southern hemisphere view - it is best for looking at the broader picture MJO as it spans the equator.

GFS    UKMO

                                                    ECM

That all looks in good agreement - there's a function, top left, (pink strip right above chart) for looping comparison of the models for each day of forecast; very useful!

Anybody spot some tropical situation for ECM to be out of step?

https://ruc.noaa.gov/hfip/tcgen/

For people new to this, Adrian Matthews offers simple to understand discussion and animations of how the atmosphere responds.

http://envam1.env.uea.ac.uk/mjo.html

On the subject of what interactions are taking place above the North sea and the land mass of the east coast - try using the vertical atmosphere forecast from the GFS. Main page for making your own cut.

http://www.meteociel.fr/modeles/coupes_gfs.php

I've done one from Lincolnshire out into the sea to let you use the parameters without fiddling about.

http://www.meteociel.fr/modeles/coupe2.php?mode=1&archive=0&ech=81&x1=258&x2=441&y1=52&y2=51&latlon=&newmode=1&couchehaut=250&couchebas=1000