Model output discussion - proper cold spell inbound?

[Chesil View]

Just now, bluearmy said:

Given the issues of strat/trop coupling and the modelling of the strat being at lower res with less layers, I think we need to be circumspect re nwp for later next week and beyond

 

Indeed Blue. Anything beyond 120/144 really is FI at the moment especially with the strat changes going on. Yesterdays gfs 12z showed how it should work i. an ideal world but this the uk of course.

[ICE COLD]

The GFS 6z and ECM day 9 are no where near each other . Pitch of salt everyone . 

 

GFS 

ECM

[stodge]

Morning all

One or two excellent comments last night to counterbalance the trolls. No one ever said the coming week was going to produce "feet of disruptive snow" and while my part of lowland East London is dry, very cold and clear currently, who knows what the day and the Thames Estuary might bring ?

On then to the medium term outlook and this morning we're looking at where we might be in the middle of next week - Thursday February 15th to be exact.

Starting with ECM 00Z OP at T+240:

A deep and quite vigorous LP (960 MB) is approaching the NW of Scotland. The frontal rain bands have crossed the British Isles leaving us in an unstable PM airflow from the NW or WNW. The 850s aren't very low though so any wintriness in the showers restricted to hills but there would be plenty of convective activity in that flow.

GEM 00Z OP at the same time:

As is often the case, GEM produces a very stormy run and it ends with an LP right over the British Isles. This has developed as a secondary feature from the main LP which moved to the south of Iceland and has now filled with the remnant over SE Greenland. A new LP is forming in the Atlantic and you'd imagine that would join the party or head SE into western Europe. Plenty of rain and showers for the south and west, colder further north and you'd think snow for the mountains.

GFS 00Z OP at the same time:

Quite different. While both ECM and GEM have completely suppressed the Azores HP and the ECM has a negative tilt on the trough, GFS is ridging the Azores HP into Europe and the trough has a positive tilt so a much milder and more benign outlook with the LP still well to the west of Iceland. Settled in the south, perhaps less so further north but nothing exceptional.

Further into FI and pressure starts to rise in mid Atlantic but it's slower than some of the FI output from the weekend suggesting the effects of the MJO and the splitting of the vortex appear to be lagging more than some might have hoped.

GFS Control at the same time:

Mild and benign for most especially in the south. Further into FI and Control also raises heights in mid-Atlantic and ends with southern England under a cold NE'ly airflow from an LP over the Low Countries.

Looking at the GEFS at T+240:

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240

A number of members starting to hint at mid Atlantic height rises but that translates only into an MLB near the British Isles with too much strength in the northern arm at this time but as Chio said in his superb post last night, the energy displacement from the current wave of warming is vital to ensure the vortex split (still scheduled for next weekend) and the resulting warming on both remaining vortices, That may limit any cold spell we have now but opens the door for more opportunities later in the month.

One note of further encouragement, the GEFS at T+312 are clearly showing signs of the Atlantic weakening and the jet amplifying and the OP is atypical at T+384 with almost all options having heights either to the NW or NE.

In summary, and it's a repetition of yesterday's message to some extent, the "failure" (as some of the trolls have called it) of this week's cold spell is going to work to our advantage as the Atlantic energy which kills it will in turn start to split the vortex which leads to a sustained Wave 2 attack as we move through the middle of the month. The tropospheric response to that isn't clear yet but the overwhelming majority of options in GEFS FI beyond T+312 are going cold in some form. Will it be feet of snow for all ? Probably not but snow for many is likely and wintry weather for all very likely but nothing can be called yet.

For now, GFS offers a mild and benign middle of the month but both GEM and ECM are keeping the energy close to the British Isles so a spell of cool if not cold zonality with wind and rain would be on offer. That medium term issue has still to be resolved but it won't interest the ultra-coldies that much. For them, all I can offer is patience in the short term.

[Nick F]

Looks like the Polar Vortex over Greenland wants to have one last laugh this winter before perhaps succumbing to downwelling of the SSW later in the month. No getting away from it, but looks like a more zonal / mobile spell of weather  off the Atlantic is on the cards from the weekend, albeit cold zonal. Just hope the trop PV blows itself out quicker than the GFS operationals have shown this morning.

Still, we have a week of cold weather ahead, not particularly noteworthy or memorable for the cold or snow, but most should see some snow this week, as band of snow moves SE tomorrow across most parts, then another Atlantic front moving SE on Thursday/Friday should bring snow for some, though looking more marginal for this late week event, with a rain/sleet/snow mix at lower levels.

Edited February 5, 2018 by Nick F

[Matty M]

Looks like heights will finally rise across Greenland by late Feb ensuring a very cold end to the winter.

 

But back to the more important thing, the prospect of FRONTAL snow for eastern Ireland tonight. A very very rare event.

[ITSY]

Another cracking ending, aided by a follow-on warming over Greenland which really kills off what remains of the PV. Patience. 

[ICE COLD]

5 minutes ago, Matty M said:

Looks like heights will finally rise across Greenland by late Feb ensuring a very cold end to the winter.

 

But back to the more important thing, the prospect of FRONTAL snow for eastern Ireland tonight. A very very rare event.

Yep in the far reaches of FI . If it went a few more frames it could of been stonking ?

[karlos1983]

Another nice ending to the GFS. Retrogression of UK high, PV non existent, plenty of cold Bottled up to the NE.

Things ticking along nicely.. sure some will find something to be pessimistic about though! 

 

A long way out granted, but we are trying to get an idea of what might happen following the predicted SSW, so rather than detail, it's looking for the more general theme. Karlos likey! 

Edited February 5, 2018 by karlos1983

[Chief Wiggam]

As I write this the sun (Solent area) is streaming through the window and is clearly now starting to be a factor. Is there a model which gives any solar strength.... Please excuse me for a lack of technical terms.  Thanks 

[Methuselah]

1 minute ago, ICE COLD said:

Yep in the far reaches of FI . If it went a few more frames it could of been stonking ?

Aye, the three stages of the GFS: 0-5 days - reliable; 5-10 days - semi-reliable; 10-15 days - NARNIA!

[mike Meehan]

Isn't this really what we need for the summer months - the problem with this winter is that the HP's have been in the wrong place.

[Yarmy]

9 minutes ago, Chief Wiggam said:

As I write this the sun (Solent area) is streaming through the window and is clearly now starting to be a factor. Is there a model which gives any solar strength.... Please excuse me for a lack of technical terms.  Thanks 

Insolation? 

The red line is roughly suitable for the UK. Of course the actual Watts hitting the surface will depend on cloud cover.

Edit: Image is from here:

http://www.physicalgeography.net/fundamentals/6i.html

 

Edited February 5, 2018 by Yarmy
Credit image source

[MP-R]

2 minutes ago, mike Meehan said:

Isn't this really what we need for the summer months - the problem with this winter is that the HP's have been in the wrong place.

That's our climate summed up - 'right synoptics at the wrong time of year' lol. That chart is primed for high pressure sliding west and the low heights above it slipping southeastwards. On the day itself, however, probably very spring like.

[karlos1983]

29 minutes ago, mike Meehan said:

Isn't this really what we need for the summer months - the problem with this winter is that the HP's have been in the wrong place.

Many memorable UK cold spells have started with a UK High, which then slips off to Greenland, then scandi, then back to Greenland! 

Be interesting to see the ENS over the next few days. Will they start to smell the coffee! 

Yesterday's ECM extended not yet, but 00z will be out shortly! I'm going to start saving them and comparing runs from today!

EDIT: Here they are for 00z

more colder members in the middle of the run compared tom the 12z, other than that, not too much to get excited about yet on the ENS.

Edited February 5, 2018 by karlos1983

[ALL ABOARD]

By 150 we have two GEFS ensembles that go this route... 

 

Can we competly ignore these at such a short lead time? 

 

[frosty ground]

12 minutes ago, ALL ABOARD said:

By 150 we have two GEFS ensembles that go this route... 

 

Can we competly ignore these at such a short lead time? 

 

I think we can, just your typical outliers you get with most Ensemble sets.

Then again the Mild sector on Thursday started with support of just one or two runs. 

[ITSY]

Very cursory glance at work but 13 GEFS members with significant ridging towards Greenland/Iceland/N Atlantic by T+360. Given the background signals, that's quite a noticeable move in my mind...

Mean at 384 shows big tendency towards height rises over N Atlantic/Europe: 

 

Edited February 5, 2018 by ITSY

[karlos1983]

Well, the GEFS certainly looks like it's starting to smell the coffee already!

 

Take a look at the Mean!!

Edited February 5, 2018 by karlos1983

[Ice Day]

Lots of scatter at 144 so FI begins around 120.  Interesting to again see the GFS and Control very much on the mild side of the mean for most of the run after day 6.  I would think it's only a matter of time until we get a stonking FI run....getting it to verify is a different matter though!

 

[ALL ABOARD]

6 minutes ago, frosty ground said:

I think we can, just your typical outliers you get with most Ensemble sets.

Then again the Mild sector on Thursday started with support of just one or two runs. 

Agreed. But given continious updates from met with regards to the battleground conditions continuing across the UK, surely cant be discounted.

[bluearmy]

Just waiting to see the AO/NAO from that ens suite

the trend from the 00z suites was pretty clear and looking to see if subsequent runs firm up further

EDIT: nothing dramatic but the spread shrinking further approaching the 18th on a neg AO/NAO combo

Edited February 5, 2018 by bluearmy

[Daniel*]

5 hours ago, Chevron12345 said:

Quick Trop Response? Is it on that chart or are you just guessing? PV looks pretty organised to me.

I mean, I didn't any charts would be showing the effects of a SSW for a number of days yet.

Well somewhat ‘guessing’ but I think it’s conceivable. This is right now looks more organised to me, following a SSW or any big disruption at first I believe, we tend to see the jet stream retreat southwards and take a more meandering path. Before we see any HLB but I don’t really know. It could be to do with MJO but phase 7 composite isn’t a great match? Therefore I also think there is also some assistance there from strat developments. In keeping vortex away from roosting over Greenland we’ll see but GFS is consecutively giving real eye candy in FI. 

[Weather-history]

3 hours ago, TEITS said:

I have been keeping an eye on the GEFS SLP Mean for Iceland because to me around the 19th Feb we could well see the development of a Greenland HP.

The mean continues to rise and now stands a 1015mb. The 0Z GFS was clearly much lower than the mean.

Until then though I feel after this week the weather will turn more unsettled, less cold, less snow than some are suggesting including the Met O.

GFS 06z ensembles.

[winterof79]

Control run on the money 

The mean not miles away either

 

[mountain shadow]

Very good support for height rises near Iceland in the extended GEFS. Hopefully, we can start to get more agreement on future runs.