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Model Output Discussion - The Run In To Christmas


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Well except this

ECM1-216.GIF?17-0

Though it still looks cold at this point, I'm guessing other models want to place low pressure closer to the UK and introduce milder weather. It could of course be transient anyway if the forecast was specifically focusing on Boxing day.

We are a long way from sorting this in reality. Though surely a colder spell of sorts will do happen.

In all honesty I feel the Beeb are going with what a particular model is saying right at this moment, rather than appreciating a wide range of possibilities. Even if Dec 26th is mild, it may well be that the 27th/28th are cold. They're trying to be too specific. Can I dare say that?

Best odds right now for 25th-28th IMO is a snow-line somewhere between the borders and the south coast - a line which could move further north or south with time depending on the developing synoptics.

Just to add about the GFS (P) - I think I'm right in saying that it has been consistent all day long in putting a deep low in the North Sea at T240ish - so this will be a really good test of how it deals with a cold solution for the UK, how close will it get?

Edited by rjbw
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I think the options for Christmas towards New Year stack up like this:

 

The GFS P, more eastern based NAO, northerly then possible ne/e flow.

 

A western based negative NAO but not too far west, low pressure skirting into the UK but further se, lots of snow for favoured areas.

 

A western based negative NAO but too far west, milder sw'erly, the fish in the mid Atlantic freeze as the cold gets directed sw well to the west, basically crap then!

 

A more eastern based negative NAO with block holding, troughing over Scandi.

 

The colder western based negative NAO has the least margin for error, generally that goes one of two ways eventually you either get the block pushing further east with time or the initial more snowier version ends up with the milder sw'erly.

 

Overall given the timeframes it's impossible to side with any output, we've seen these types of situations in the past, even the great spell of end of Nov/Dec 2010 had a spell of a more western based negative NAO, however because of the good NH set up this was more shortlived.

 

I think the problem isn't the chance of a possible western based negative NAO, of course its annoying but its a case of will those background factors mean its an irritation to be forgotten as the cold finally arrives later or is it a case of a missed opportunity.

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Well, unlike many other members in here tonight, I am going to nail my colours to the mast. The GFSP is barking up the wrong tree. I will explain my conclusions shortly. Firstly though, assuming I am correct, you really do have to question these so called upgraded models. The GEM and now the GFS! How are they being upgraded and what so called improved mechanisms are being implemented? Okay, so now on to the reasonings behind my conclusions. Two ECM 12z ops on the bounce showing anticyclonic breakdown leading to west based negative nao. Last night's GFS 18z control agreeing with this solution and now tonight's GFS 18z op and control agreeing. Final nail in the coffin being the meto view which concurs with the above. I, along with most on here, hope I am terribly wrong with my analysis.

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Well, unlike many other members in here tonight, I am going to nail my colours to the mast. The GFSP is barking up the wrong tree. I will explain my conclusions shortly. Firstly though, assuming I am correct, you really do have to question these so called upgraded models. The GEM and now the GFS! How are they being upgraded and what so called improved mechanisms are being implemented? Okay, so now on to the reasonings behind my conclusions. Two ECM 12z ops on the bounce showing anticyclonic breakdown leading to west based negative nao. Last night's GFS 18z control agreeing with this solution and now tonight's GFS 18z op and control agreeing. Final nail in the coffin being the meto view which concurs with the above. I, along with most on here, hope I am terribly wrong with my analysis.

The thing is there are variations on a west negative NAO, theres westish, and too far west! The UKMO are just as in the dark as the rest of us because its impossible this far out to say which one it could be, and the GFS P might still be correct, given comments from Ian F the ensembles show either troughing over the UK or to the east, the former is likely to be more average in terms of temps the latter colder.

 

The positive at least is that theres a signal for blocking to the west, it might be west neg NAO slowly edging east.

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18Z Ens CET 2M Temps see's the GFS op very much on the milder side in FI

 

Also note a -10 in there!

 

graphe6_1000___-1.6037735849056602_52.42

 

Let's hope the 0Z reverts back to one of the colder options.

 

It's been a long day. Let's all hope for upgrades tomorrow. 

 

Goodnight.

Edited by SE Blizzards
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I don't think there's been enough positivity spun on IF's comments above. High to the West - Trough over or to the East. This doesn't sound like a West based - NAO at all!

 

Two other things to decipher:

 

1) A very firm NO to Bluearmy suggesting a west based - NAO

2) The date of the 28th (The met don't see a snowfest on the 24th,25th,26th or 27th.......) They have however for a while seen a signal for a deeper more prolonged cold spell from the 28th upto +360 hours. Any snow before this date was always a bonus squeezed about by unexpected amplification before then. This is something Tamara has been banging on and on about. It's the post Christmas into first week of January where the colder charts will come from

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Its going to be interesting how the models will deal with the xmas period, I must admit, despite my uncertainty, more runs do seem to trend to a cool/cold set up rather than a mild one for the big day itself but as we know, when it comes to ridging in the Atlantic then a lot of caution is needed

 

I suspect a lot of changes in the detail will be the order of the day in the models which will lead to a wide range of emotions no doubt in here. 

Edited by ajpoolshark
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But...You will see a (suitably measured) change in emphasis herein based on new UKMO guidance for period circa 26th onwards for few days. Initial areas being watched are N England - N Ireland, then focus to SW UK, based especially on MOGREPS-15 ENS. A 'very dynamic situation' as Exeter say, but confidence still low on eventual outcome.

sounds intriguing so maybe low pressure moving into the sw and bumping into the cold air and producing snow sw initially then moving across to other parts of England and Wales.sounds like blocking high eventually forming over scandi for this scenario to play out.interesting!

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Gfs has gone completely and utterly mad as early as 73 hours and its not looking good folks!! Shortwave drama once again!! Got a bad feeling once again! !but somehow manages to get there in the end!!

Edited by shaky
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Actually i was too early in commenting!! Very good output this morning including ukmo! ! All 3 so far very similar sending heights into greenland/canada with trough coming down over the uk and a northwesterly air flow!!

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Unless it moves south in a hurry of course ... have been amusing myself watching the 00z GFS coming in and clicking on the last standing remnant of the 18z, my last such exercise reveals that the GFS has narrowed down the pressure at Valentia to the range of 970 to 1035 mbs. Well done modern technology.

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Unless it moves south in a hurry of course ... have been amusing myself watching the 00z GFS coming in and clicking on the last standing remnant of the 18z, my last such exercise reveals that the GFS has narrowed down the pressure at Valentia to the range of 970 to 1035 mbs. Well done modern technology.

 

Yes Roger eventually if it slips south (thankfully the jet still plays ball) it's good however don't forget the two "d's" - dilution and delay. The former dilution and attrition of cold air and the latter simple delay.

Edited by The Eagle
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synoptically speaking, at day 9 the GFS P is a work of art. Snow, snow and more snow. GFS not quite so good in FI with a struggling attempt once again at Scandi heights.

Day 10 GFS P....some places would probably need a tractor to dig themselves out. Absolutely stunning charts on this run.

 

 CC

 

Just about to post the same GFS P is a thing of beauty,like you say Absolutely stunning charts

 

C.S

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