Winter Model Discussion 18Z 12/2/13 onwards.

[Earth Wind and Snow]

There is now broad consistency within the full Operational model suite, ECM ensemble suite & I guess the MOGREPS ensembles-

Rather than comment on whats infront of us I though I would highlight the 4 key things to look for when homing in on a potent Easterly.

Here taken from the 06z- I believe the 06z represents the general super ensemble mean of the all the models.

1) The core of the low heights & Unstable air, this will also be the lowest temps of the upper air cold pool. These upper air cold pools rarely reach the UK & are often stalled or swerved away into france-

They are driven by the Upper level high & will only reach the UK if squeezed west by the Upper & high-

**IF** this makes it to the UK it will 100% bring a period of snow on its northern flank- & the convection will fire further North.

This happens on the 06z ( but was stronger on the 00z GFS) - very close similarities with Dec 26 2005 & Feb 1 2009-

here is where it lands on the 06z.

http://modeles.meteo...gfs-0-186.png?6

Whats also important is the track of this low- the further East & its influence will be low over the UK, my favoured track again for reference is:

Norway, Southern Finland, North Germany- where it may remain in situ for a day- then westwards again- after being squeezed.

2) The upper high that moves North out of the UK must gain the correct latitude, it will eventually be sheared & elongated East- which is good, but for people that still desire snow & live in places like Yorkshire then the highs lattitude is everything!

Whats more critical as well is the western end of the block - being 'lifted' to the right lattitude- we dont want the western end saggy - like the UKMO

http://www.meteociel...20-21.GIF?15-06

This will modify the initial CAA from europe.

3) Iberian Energy, People often overlook this in favour of the eyeline always on the Scandi high- however the energy moving North out of Iberia is whats supporting the high-

The best & most prolific Easterlies come with the sqeeze of isobars across europe to the UK are a result of the polar cell force moving south V the energy within the ferrell cell moving North-

that way the high is 'stuck' it cant sink.

Heres 3 classics-

http://modeles.meteo...52-3-29-0-0.png

http://modeles.meteo...87-1-12-0-0.png

http://modeles.meteo...991-2-7-0-0.png

This is usually the weakest of all features modelled, & also one that invariably is our stumbling block- notably because the energy isnt always deep enough to compensate the force moving south out the pole-

4)Southern Atlantic energy- Often ABSENT in recent winters & being replaced by the ever present Azorews high ridging North to kill the convection.- This seems to be well placed this time around-

Again, to build & sustain a decent easterly the track across Europe we need 'forcing' moving the cold west, then another area of energy across the Brest peninsula.

What will happen is the energy will drive north, but stop somewhere in this location due to the force of the high-

In recent winters the scandi high has had LOW heights positioned on the western end of Norway-

http://modeles.meteo...012-2-3-0-0.png shown here-

Which impedes the blocking-

this is so crucial that this region is blocked as the ridge will normally extend out towards iceland- as a result the southern energy can slide south under the block, where as no blocking the energy will recurve north over the UK = end of cold.

This is the GFS energy plot at 174

http://modeles.meteo...gfs-5-162.png?6

notice the energy approaching the UK from the SW & then being sheared away east again.

So in summary-

The pattern longwave is nailed- Upper high over scandi & low heights into europe-

What we need is consistency of the 4 key features of a snowy easterly to varify.

1) Upper high in the right lattitude

2) Iberian Energy

3) Southern jet energy

4) Upper air cold pool moving west to the UK & a westerly track of the low.

I hope this insight has helped some viewers.-

This is also why the UKMO are tentative around forecasting cold & snow from the east, because without a CLEAR signal of all these coming together at day 6/7 then its pointless.

Even at day 5 the track of the low can vary quite a bit- so UKMO sitting on the fence is the right choice.

regards

S

What a brilliant analysis Steve - it is a pleasure to visit this forum to view brilliant posts like this thanks from the likes of SM, GP, Chino, TEITS, John Holmes etc. - keep up the good work all

EWS

[Methuselah]

Frosty's post was tongue in cheek....

No probs. So was mine...

[Gary_R_Walker]

The 00z UKMO-GM now looking much more in tune with other solutions mid next-week and contra it's predecessors has received no modifications this time around from Exeter.

You will recall how yesterday’s 12z GM - with faster CAA and considered something of an outlier - wanted a greater degree of upper trough disruption across the Biscay/NW Iberia area through late Sunday into early Monday... consequently, this resulted in backing the continental flow into the UK more by mId-week. However, also recall how (despite fans here!) this more potent-looking solution had scant support from other models, i.e. for a faster transition to a more pronounced E’ly. For that reason, Exeter stayed cautious but the 00z GM is thought to represent a much more realistic fit to the most probable evolution - especially given the support from 00z NCEP and EC Det runs. Thus, Exeter will run with what you see in the raw fields, and little significant modification.... at least for now.

This is probably an excellent post, but sadly makes as much sense to me as paying a footballer £200,000 a week. Any chance one of the experts could give an idiot proof explanation? Thanks.

[Captain Shortwave]

But, if the weather treats the current batch 'stellar runs' with the same degree of contempt as it did those that have preceded it, they might (again) all need binned?

No idea at this point but given good model agreement at T120 now we should at least give it a chance to redeem itself. The orientation and placement of heights is still up for grabs and starts to deviate from this point. For now we should treat each run with the same level of scrutiny, the weather will do what it likes and until all models agree on one outcome we should treat them as equals, as much as we would like to declare GFS as the village idiot.

GFS 06z at T138

http://modeles.meteo...gfs-0-138.png?6

UKMO at T144

http://www.meteociel...44-21.GIF?15-06

ECM at T144

http://www.meteociel...1-144.GIF?15-12

Edited February 15, 2013 by Captain shortwave

[No Balls Like Snow Balls]

This is probably an excellent post, but sadly makes as much sense to me as paying a footballer £200,000 a week. Any chance one of the experts could give an idiot proof explanation? Thanks.

In other words the Easterly isn't gonna be as good as we would all like it to be .

Obviously subject to change though as always, especially this far out

[Methuselah]

In other words the Easterly isn't gonna be as good as we would all like it to be .

Obviously subject to change though as always, especially this far out

That's what comes from being human - we all the remember the most memorable. Excuse the obvious tautology.

Edited February 15, 2013 by Rybris Ponce

[Tim Bland]

WOW Meto are actualy using the 'S' Word now !

"Late next week and into the weekend some more persistent rain or snow may reach some southern parts of the UK."

"Also some signs of conditions turning a little more unsettled during the early part of this forecast period, perhaps with a slightly greater than average chance of snow"

Good news from Ian that we can start trusting the Operations more now. Shame the ECM watered down the Easterly. Hopefully this will upgrade and we can see a strenthening signal for a channel low scenario

[swfc]

That's was comes from being human - we all the remember the most memorable. Excuse the obvious tautology.

can you say that in English now! sorry Edited February 15, 2013 by Rybris Ponce
Wrong damn button. Soz!

[Gary_R_Walker]

In other words the Easterly isn't gonna be as good as we would all like it to be .

Obviously subject to change though as always, especially this far out

So in brief this easterly will be like the last easterly. Thanks for the explanation.

[snowking]

This is probably an excellent post, but sadly makes as much sense to me as paying a footballer £200,000 a week. Any chance one of the experts could give an idiot proof explanation? Thanks.

You will recall how yesterday’s 12z GM (YESTERDAYS 12Z UKMO) - with faster CAA (FASTER ONSET OF THE COLD FROM THE EAST) and considered something of an outlier - wanted a greater degree of upper trough disruption across the Biscay/NW Iberia area through late Sunday into early Monday... consequently, this resulted in backing the continental flow into the UK more by mId-week (THE WHOLE PATTERN WAS FURTHER WEST ON YESTERDAYS 12Z UKMO THAN LOOKS LIKELY TO BE THE REALITY). However, also recall how (despite fans here!)(THERES A SMALL CHANCE A FEW OF US MAY BE PARTIAL TO THE ODD FLAKE OF SNOW OR TWO) this more potent-looking solution had scant support from other models, i.e. for a faster transition to a more pronounced E’ly (12Z UKMO YESTERDAY WAS MOST AGGRESSIVE WITH POTENTIAL EASTERLY). For that reason, Exeter stayed cautious (ALL THE MET OFFICE STAFF SAID STUFF THIS, LETS GO TO THE WINCHESTER, HAVE A PINT, AND WAIT FOR ALL OF THIS TO BLOW OVER) but the 00z GM is thought to represent a much more realistic fit to the most probable evolution (0Z UKMO IS CONSIDERED THE MOST LIKELY OUTCOME AT PRESENT) - especially given the support from 00z NCEP and EC Det runs (SUPPORT FROM GFS AND ECMWF OP RUN). Thus, Exeter will run with what you see in the raw fields, and little significant modification (VERY FEW IN-HOUSE CHANGES MADE TO THE UKMO 0Z RUN THAT WE GET TO SEE).... at least for now (UNTIL THE BLIZZARD TO END ALL BLIZZARDS COMES IN FROM THE SOUTH-WEST MAKING THE STORM IN THE NORTH-EAST USA LOOK LIKE A QUICK FLURRY***).

SK

*** N.B. - the last point may be open to changes/completely fictitious

Edited February 15, 2013 by snowking

[fergieweather]

SK

*** N.B. - the last point may be open to changes/completely fictitious

Love it, especially re the pub!!!

Yes, the potential snow issue later from SW/S is the key focal point a tad further away into the MRF.

[johnholmes]

Love it, especially re the pub!!!

Yes, the potential snow issue later from SW/S is the key focal point a tad further away into the MRF.

yes good to have a touch of humour in this thread not personal

[CanadaAl]

I know to take a barrel of salt with the precip charts but the latest gfs charts do seem to indicate higher snow risk for the east from weds onwards, subject to change at this range obviously

[bluearmy]

the UKMO GM t144 is quite a slack flow so the fact that exeter are happy to go with this for the time being means they still remain on the cautious side re late next week. clearly the text from the 6/15 dayer adds the caveats that the other model guidance from those ops we see offers a slightly more unsettled picture with a stronger flow and therefore more CAA.

gary's comment that this may not be so far from the previous cold spell may not be too far from reality. i have thought for a while that this was all heading toward a similar end game re blocking/sliders and undercuts. this time we look to get a decent flow of v cold uppers and low dp's to begin with before the flow is sharpened ahead of any attempted incursion. still looks to be no more than a week or so and any snow bearing cold will struggle to make it into march. a good fall with a few days cover to finish the winter would do me fine.

[DTHFCJ]

SK

*** N.B. - the last point may be open to changes/completely fictitious

That Sir is quality

so it seems the back end of winter could throw up some of the white stuff again for some,the last few years,well since 2007 things seem to have changed poorer summers and whiter winters......i wonder if this summer will buck the trend following on from another at times white(ish) winter (for some)..........

[Frosty.]

Hmmm, mainly light wintry showers as next week goes on, my experience of easterlies is those light wintry showers then become heavier and more prolonged and bring accumulations. It sounds like we are in for a prolonged cold spell, the snow showers mainly for the eastern half of the uk and then a risk of persistent snow spreading up from the south. What a difference a few days make, early this week the GEFS mean was showing persistent swly winds for the next 2 weeks, how things have changed.

[No Balls Like Snow Balls]

Hmmm, mainly light wintry showers as next week goes on, my experience of easterlies is those light wintry showers then become heavier and more prolonged and bring accumulations. It sounds like we are in for a prolonged cold spell, the snow showers mainly for the eastern half of the uk and then a risk of persistent snow spreading up from the south. What a difference a few days make, early this week the GEFS mean was showing persistent swly winds for the next 2 weeks, how things have changed.

The current models and huge potential they may bring make the old chocolate star fish quiver with excitement, although in the back of mind i do hold the failed Easterly of December.

Edited February 15, 2013 by No balls like Snow Balls

[Purga]

the UKMO GM t144 is quite a slack flow so the fact that exeter are happy to go with this for the time being means they still remain on the cautious side re late next week. clearly the text from the 6/15 dayer adds the caveats that the other model guidance from those ops we see offers a slightly more unsettled picture with a stronger flow and therefore more CAA.

gary's comment that this may not be so far from the previous cold spell may not be too far from reality. i have thought for a while that this was all heading toward a similar end game re blocking/sliders and undercuts. this time we look to get a decent flow of v cold uppers and low dp's to begin with before the flow is sharpened ahead of any attempted incursion. still looks to be no more than a week or so and any snow bearing cold will struggle to make it into march. a good fall with a few days cover to finish the winter would do me fine.

So we could end up with another relatively tame affair?

[Ian Brown]

Hmmm, mainly light wintry showers as next week goes on, my experience of easterlies is those light wintry showers then become heavier and more prolonged and bring accumulations. It sounds like we are in for a prolonged cold spell, the snow showers mainly for the eastern half of the uk and then a risk of persistent snow spreading up from the south. What a difference a few days make, early this week the GEFS mean was showing persistent swly winds for the next 2 weeks, how things have changed.

The METO update is reflective of the ECM, they don't at this stage see the GFS as the likely scenario. The ECM gives a window for wintry showers in the East before winds turn SE ahead of possible Atlantic attacks.

Still as SM outlined in his excellent post, there are still time for changes in positioning and orientation of the High.

[mushymanrob]

not sure what all the fuss is about tbh. a 'big freeze' with dumpings of snow that last longer then a day or two are quite rare from mid feb onwards. what i see in the models is typical of what we got in feb 83, or march 69... ok, i might be way off the mark here, but at this time of the year, raw, bitter, overcast, largely dry scenario is more common then a wintery one. this mornings ecm in particular has winds from a more south of east origin. ok, the 00z gfs was more favourable for a wintry picture , but last time i looked here the gfs was being ignored and rubbished!

for a month now the ecm has been predicting the mother of all winters, the gfs mainly a milder average picture. we got something in between, and today is a beautiful day. i think that those expecting something spectacularly wintry are likely to be as dissappointed with what we eventually get as those of us who dont want any cold at all.

[Timmytour]

There is some understandable worry about the flow being too slack to deliver the narnia like winter spell so many of us love.

I'm with the GFS here though.....this time i think the ECM and UKMO, instead of slowly diluting epic charts, will revisit them in the nearer timefame. The GFS is swinging that way so I have more faith than usual in next week delivering a real winter sting

[mushymanrob]

Still as SM outlined in his excellent post, there are still time for changes in positioning and orientation of the High.

.... and changes work both ways

[bluearmy]

So we could end up with another relatively tame affair?

actually, given the stronger blocking, i think we could see a rather more snowy period than the last two spells. the time of year not too helpful if we lose a continental flow at any point but there are plenty of signs that this period could see a really effective slider/undercutter into proper cold uppers. i read the extended metoffice forecast with interest as it seems to indicate march beginning with a block to the east/north slowly giving way to the atlantic (but with some battleground stuff along the way).

[legritter]

Well my glass is half full on the weather front .regards todays [so far ] Modells .im not hoping for a Stella run from ECM or Met office later just a gradual increase of the chance of a good easterly with a bit of bite to it and of course some snow chances .as far as snow showers into the east i think we can say that is 5days away .as for an attack from s/west, south ,or west there is the possibility from next thursday onwards .as is the case more runs needed so keep blades ,prozack ,and a bottle of bubbly at hand .apart from the fact that im [iMBY]hoping for one or two real classic snow events another reason i want two dices showing double SIX is because some of my circle of friends are under the impression that you would not get Major blizzards like yester year because theres no ice in the arctic and the world is getting warmer .as i tell them, they arent that common its a case of just waiting .as for the posters who say its getting late ,early to mid April 1908 delivered a lot of snow to low lying ground in southern britain ,MARCH 4th 1947 widespread snow and blizzards ,although this was on the back of well established cold .thanks again to regular posters for data etc ,only 6hrs till next ECM ,HOLD TIGHT .

[Rollo]

Looking at this mornings charts I feel that alls to play for.Obviously things will change,probably right up to the last minute but at least we are in with a shout,Its time we had a good old fashioned snowfall on low ground in February.