Model Output Discussion - The Run In To Christmas

[Polar Maritime]

I have a question please: the low around the 27th looks different all the time. Will the final placement of it have a major impact on the weather after it, depending where it tracks?

 

Yes dragan, As i said in my post before last, Until the Models have got a handle on the track of this storm i expect further wild swings. A few miles E/W will make a big difference regarding the outcome further down the line.

 

As TEITS above says this storm needs to be taken seriously.

Edited December 21, 2014 by Polar Maritime

[karlos1983]

Yes Tinyb, Some heavy snow model'd for the South, With sever gales for the UK. 

 

Personally I would love for that chart to verify. extreme weather is right up my alley, blizzards would be a bonus!

[tinybill]

Forget about snow, cold spells as im now more concerned about severe gales and more importantly storm surge for those living on the N Norfolk coast. Now the UKMO is predicting such a storm it must be taken more seriously especially as the next frame of the UKMO would see low pressure move SE and deepen further!

 

As for the potential cold spell and the ECM/GFSP are nowhere near as good as yesterdays 12Zs for the longer term. However its futile to discuss the longer term when the shorter term remains unresolved.

we all know  what happened  last year here down the east  coast !!

[alexisj9]

I have a question please: the low around the 27th looks different all the time. Will the final placement of it have a major impact on the weather after it, depending where it tracks?

Simple answer is yes, which is why I'm not really looking past that storm at the moment, until there is some consistency in the placement of the low anything past there will flip flop all over the place.

[Polar Maritime]

Personally I would love for that chart to verify. extreme weather is right up my alley, blizzards would be a bonus!

 

Yes Karlos, For weather enthusiasts very interesting indeed, It could be another one of RJS's 'Snow Hurricanes' :smiliz19:

 

-8 uppers over the South -10 in the North. And check that Wind Chill out..

 

Edited December 21, 2014 by Polar Maritime

[karlos1983]

Yes Karlos, For weather enthusiasts very interesting indeed, It could be another one of RJS's 'Snow Hurricanes' :smiliz19:

I bet the Express or the prat that writes for them can't wait to jump on this!

[West is Best]

Forget about snow

 

No

 

I bet the Express or the prat that writes for them can't wait to jump on this!

 

I think it's this bloke:

 

royals_houseprices_dementiacures_severestweatherever_maddie @dailyexpressanyrubbishwecanmakeup.co.uk

Edited December 21, 2014 by West is Best

[bluearmy]

Yes Karlos, For weather enthusiasts very interesting indeed, It could be another one of RJS's 'Snow Hurricanes' :smiliz19:

 

-8 uppers over the South -10 in the North. And check that Wind Chill out..

 0]

You mean the 'snow hurricane' that's just windy! great description but normally lacking one key ingredient. actually given that it's never windy enough, probably two!

wouldn't want to be stood out in my undies though!

As nick s posted last evening, upstream is very uncertain. I would be quite confident in calling the ops this morning 'over progressive' but the gefs have not been keen to maintain a mid Atlantic ridge over their past couple runs so I won't. Favoured call would be a short sharp blast of cold followed by either a cool mid lat high or a more zonal westerly with more ridge/troughs to follow. But it never quite works out like that does it..........

[Polar Maritime]

You mean the 'snow hurricane' that's just windy!

 

That's the one Nick  

Edited December 21, 2014 by Polar Maritime

[Weather-history]

Snap shot from history. Some similarities in the snapshots with some models.

[slater]

we all know  what happened  last year here down the east  coast !!

If this storm did happen on East coast there is no spring tide due next weekend on the norfolk Coast, in dec 2013 there was. So if the storm happens at low tide it would be nowhere near as much impact or even normal high tide come to that. It will be all in the timing of it.

[West is Best]

Yes Karlos, For weather enthusiasts very interesting indeed, It could be another one of RJS's 'Snow Hurricanes' :smiliz19:

 

-8 uppers over the South -10 in the North. And check that Wind Chill out..

 

 

Couple of great posts from you this morning. For fans of cold and storms there should be no place for despondence. This could be huge fun. Mind you, I do now live in north Norfolk  Bring it on.

Edited December 21, 2014 by West is Best

[Severe Siberian icy blast]

Having seen that the ECM 12z was a temp outlier it is no surprise that the 0z moves towards the GFS with just transient ridge and trough in a less amplified pattern. The Greenland height bias anomaly on the ECM (last 5 runs) has been extraordinary, so it is impossible to take any block in that area seriously:

 

ensemble-tt6-london.gifNOAA_NWS_NCEP_WPC_MODEL_DIAGNOSTIC_-_INTERACTIVE_MODEL_BIAS_PAGE 2.png

 

D10 on the ECM is similar to a major cluster the GEFS have been showing for a while: 

 

ECM1-240.gif  GFS P: gfs-0-240 (1).png

 

As the mean has been suggesting this was only likely transient, a variation on the current pattern. The real pattern changing potential was always if the Pacific ridge developed (around D9) and the following upstream wave to our sector. With the US likely to dig a cold and wintry trough there is a good possibility we would get an associated ridge in our locale. Unfortunately the GEFS are downgrading the longevity of the Pacific Ridge and it looks like they are continuing with the amping up of the PV. The mean at D15:

 

gensnh-21-1-360.png

 

That is a fair resemblance of the clustering in the GEFS and it looks like Dr Cohen's 3-4 week analysis where the Pacific Ridge fails and we head into a neutral AO and positive NAO is showing up.

 

So wintry wise little away from the December norm. The real concern is the potential storm around D6. The LP system looks like being a smaller feature but the main cluster is fairly represented by the op:

 

gfs-0-144 (1).png

 

One to watch. As for snow for the south on the back edge as per the GFS P, the ensembles have this as a 10% risk and remains unlikely.

About cohens forecast , I feel sad saying this but I have to admit I'm a bit disappointed in the way things are turning out , december has been and is different synoptically to what they thought , the main difference been what's happened to our East over Asia really , but it also tells me that in reality yes we can look for signals going forward , but the weather really , has and continues to have different ideas , whilst some excellent posts by experienced ones on hear point toward a pattern change , it's clear that they are only forecasts , and the -PDO that looked to be a major pattern change going forward isn't really having the same implications down stream as one would expect , I no that there's still a lot of uncertainty but if I'm been honest with myself I just don't see an amplified ridge lasting, and more inclined to think it wil be more of a toppling mid atlanitc ridge , the wave 2 forecasts that we'r all looking for comes as a result from a very -PDO and a resultant Greenland high which will pump WAA into polar regions , then a trop led stratospheric response , so if these fail to materialise then that has knock on effects going forward .

So with Cohen now forecasting a restrengthening of the vortex , I ask myself can I trust any forecast going forward ? That answer unfortunately is no , however it's easy to see if this pattern upstream fails to materialis then big question marks are there for a cold spell at least for the first half of jan .

I'm been honest with how I see things and not saying the writings on the wall at all I'm just airing my thoughts .

[Captain Shortwave]

The ECM ens still prefer the slower track for that low

GFS ens

 

To be honest there might be a northerly following this, but this mornings ens seem to be backing a return to a westerly pattern by New Year.

Big shift from previous ens. It can go the other way but the theme this morning is similar across all the output pretty much.

 

The ECM suite does perhaps suggest a decent chance of wintry showers down coastal areas on Christmas day, a better chance than the other models anyway.

Edited December 21, 2014 by Captain shortwave

[nick sussex]

Oh dear what chaos!

 

So what solutions to believe, regardless of all the drama theres yet more problems upstream and this is in relation to an expected shortwave expected to run east across the USA between T120 and T144hrs , the models differ in the depth of this and the amplitude and this is now turning into yet another pile of uncertainty.

 

If you run the GFS P you'll clearly see the impact of this shortwave on the PV in ne Canada, shortwave runs east engages the PV and pulls it further nw, then look at the GFS, weak flat shortwave runs east, then energy piles east into Greenland.

 

At the same time theres still disagreement with the Atlantic low and shortwave ejection so all in all its to be frank complete chaos, even Christmas and Boxing Day have uncertainty in terms of cold so frustratingly we're just going to have to be patient and wait for agreement!

[Ali1977]

It definitely looks like after this short cold snap nothing cold is in the offering just yet. Not sure if this could quickly swing looking at today's charts neither, and definitely no beast from the east showing up in any FI suite. :-(

[craigore]

i.e  the people on the east coast will need to keep a eye on this beast with the possible big tidal surge which could come down the east coast  ,and looking at the latest models the east coast could  easy expect  heavy snow on the 27 at the moment

Wont be cold enough {just rain/sleet) meto are forcasting temps around 7c for me on east coast 27th.

[bobbydog]

silly comment in my view-will post in more detail tomorrow

i'd be worried if you didn't think it was silly john!

[Eugene]

ECM 00Z T+240 hrs looks like it could lead to a pressure build over us and the near continent, good runs this morning apart from GFS 00Z OP.

[No Balls Like Snow Balls]

19 of the 20 GFS ensemble members show LP affecting the UK on the 27th. out of the 20 members 12 Also show the LP to be deep and affect the East Coast the severest.

[mushymanrob]

it appears the models are firming up on the general pattern expected over the next ten days or so...

it turns milder, cloudier, wetter today and that lasts until crimbo eve

 

when this complicated system departs eastward and a temporary ridge builds from the southwest giving us a bright, crisp, cold crimbo day... i guess theres a chance of a snow shower down the eastern exposed coasts but most of us wont get a white crimbo or even see any snow

 

 

the ridge collapses as a vigourous and deepening trough 'ejects' (the new buzzword) off the main parent low west of the azores, and crosses the uk, somewhere (timing and severity uncertain but could be a signbificant storm next weekend)

 

 

after which we might get a cold snap., blink and youll miss it, after the very cold air thats been locked up to our north finaly gets a shot at a proper southern drift. so next sunday/monday might be a cold snap

 

before its looking like the atlantic kicks back in for the new year

 

so a very volatile period with dramatic swings between mild and cold, with no one weather type becoming dominant (no big freeze, no endless mildness).

Edited December 21, 2014 by mushymanrob

[bluearmy]

read all about it....  read all about it.....  ecm suite in greenland over amplification shock !

 

ecm ens mean now in line with naefs. cancel the snow event before new year. the pendulum swing on yesterdays 12z was a last hurrah and the direction of travel prior to this (which the gefs and naefs were already on) is resumed.  of course we have a potential winter storm to contend with and possible snow for the scots/northern hills  (not sustained). we could well be looking at a cool and frosty period to follow but a decent snowfall seems a long shot now.

[nick sussex]

read all about it....  read all about it.....  ecm suite in greenland over amplification shock !

 

ecm ens mean now in line with naefs. cancel the snow event before new year. the pendulum swing on yesterdays 12z was a last hurrah and the direction of travel prior to this (which the gefs and naefs were already on) is resumed.  of course we have a potential winter storm to contend with and possible snow for the scots/northern hills  (not sustained). we could well be looking at a cool and frosty period to follow but a decent snowfall seems a long shot now.

Yes disappointing but given the ECM's bias not that much of a shock. The GFS P might be the best possible solution upto T240hrs, still some leeway possible with snow but any ideas of some resilient Greenland block at this point look unlikely. 

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY SUNDAY DECEMBER 21ST 2014.

NEXT UPDATE MONDAY DECEMBER 22ND 08:00

THE CURRENT GENERAL SITUATION A mild SW flow will become established over England and Wales while a cold front slips slowly South over Scotland tomorrow becoming slow moving over Northern England.

MODELS-2 WEEK HEADLINE Remaining changeable with rain at times especially across the North and West. Possibly becoming more generally colder and unsettled post Christmas with some snow and ice in places, at least for a time and chiefly over the North.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Foreecast is for the flow to gradually settle into a familiar pattern of becoming quite flat, crossing West to East in the vicinity of the UK between a large Azores anticyclone and Low pressure to the North and NW.

GFS OPERATIONAL The GFS operational this morning in general reflects the pattern that we have seen throughout the Winter so far and that is that repeated attempts of cold NW winds come down over the UK to be followed by a collapsing ridge of High pressure crossing from the West and being replaced by renewed spells of SW or West winds with rain at times in mild air. The two pronged cold attack both at Christmas and again towards the New Year have been reduced to no more than brief affairs on this run today.

THE GFS PARALLEL RUN The Parallel run is somewhat different in asmuch as the second attac post Christmas is much more potent being driven by an intense depression crossing SE down the North Sea and on into Europe. Cold and wintry weather with snow for some would then slowly be replaced by quiet and calm conditions under a strong Winter High with widespread harsh frosts and freezing fog before milder SW winds and rain at times are shown to take over at the end of the run.

THE GFS CONTROL The GFS control run appears to follow a similar trend to the operational in making less of the storm cell after Christmas and keeping the pattern rather flatter, alternating the periods of mild and damp weather with colder and brighter weather with wintry showers in the North going well into 2015.

THE GEFS ENSEMBLES The GFS Ensembles do show the temporary chance of cold weather from quite a few members post Christmas with the overlying trend thereafter for the cold to lift out in preference to milder Westerly winds between High to the South and Low to the North into the New Year.

UKMO UKMO today maintains the colder push into Christmas quickly followed by a powerful storm system close to Northern Scotland soon after Christmas with severe or even storm force Westerly winds and heavy rain likely by Day 6 across the British Isles.

THE FAX CHARTS The Fax Charts today show a couple of cold fronts straddling the UK as they edge very slowly SE over the next 72 hours. By Christmas they clear the SE making for colder NW flow with scattered wintry showers over the North for Christmas with High pressure building from the SW.

GEM GEM today shows the smae attern as the rest of the output. In regard to the storm post Christmas it develops West of Ireland after which it drifts East over the UK with strong winds and heavy rain being replaced by cold North winds briefly as we approach the New Year with snow showers quite widely. At the end of the run a ridge os collapsing across the UK being the precursor of a pattern reset to milder west winds and rain at times soon after.

NAVGEM NAVGEM's runshows the storm developing to the North and ttansferring to Scandinavia in a weeks time with severe gales and heavy rain being replaced by cold North or NW winds and snow showers particularly over the North.

ECM ECM this morning shows that the mild SW winds after Christmas quickly become replaced by cold weather behind the storm which transfers East quickly to Europe with a strong pressure rise close to the SW by the end of the run. Heavy rain and gales post Christmas would be replaced by snow showers for many before quieter frosty weather slowly takes control by the end of the run in much lighter North or NW'lies.

ECM 10 DAY MEAN The ECM 10 Day Mean Chart reflects a pattern made up of the majority of members showing High pressure down to the SW and lower or Low pressure remaining to the NW, North and possibly East of the UK with the mix of milder and wetter conditions alternating with colder conditions with wintry showers at times in the North.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS Trends this morning show strong support for a cold and potentially stormy interlude post Christmas with the strongest trend being for this to be short-lived to a likely return of milder Atlantic Westerly winds again as we move into 2015.

MY THOUGHTS The models remain all over the place with regard to the development and positioning of a Post Christmas Storm which is shown in some shape or form by all models this morning. As a result of this the evolutions following this point in time could be thrown into turmoil by models not being able to nail down the intensity, movement and engagement of cold air around it. The general theme remains for a deep Low to develop near Northern Britain before it quickly moves off into Northern Europe. There looks a good chance that all areas will see a good blow from this with potential for severe gales and heavy rain. There is also of course potential for snow, probably unproblematic for many Southern areas but as the cold polar flow behind the Low gets pulled strongly South blizzards in shower form is expected to affect the Northern hills and mountains. The weather thereafter as hinted at earlier will be driven by the final resting place of this storm in relation to what remains of High pressure over the Atlantic by that point. The most favoured and less desirable option appears to be for any High pressure in the Atlantic at the end of the year will likely drift SE in the form of a ridge with a period of cold and frosty weather before mild Atlantic winds take hold again with rain at times. The pattern though is very fluid and any changes in model thoughts on the behaviour in the development of the post Christmas storm event could continue to throw very different evolutions into the mix over model runs of the coming days. However, to bring a sustained cold weather event we need to somehow hold higher pressure up to the NW and less power to the Azores High and in neither instance within the ensembles does that look likely currently so my best stab goes with a short and sharp cold snap post Christmas before a mobile Atlantic feed takes back over control as we move into 2015.

[bluearmy]

Yes disappointing but given the ECM's bias not that much of a shock. The GFS P might be the best possible solution upto T240hrs, still some leeway possible with snow but any ideas of some resilient Greenland block at this point look unlikely. 

 

the extended ens ins some agreement now nick and it looks cool zonal with the south closest to building euro heights and scotland to any incursions of really cold air. the scottish ski resorts could be looking at a decent period if everything can be tied down! 

 

n america still looking amplified so something could crop up out of somewhere.