Most of the ENS show the Atlantic storming back in ( up to 168 )

 

Not a good day for model watching IMO

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The GFS is a pile of shyte.

That's my contribution for the day.

But seriously - the difference between yesterday's 18Z and today's is completely ridiculous. How is anyone supposed to have an idea of what's going to happen when every day is offering something completely different?

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Very much appreciated ..........................and have to agree.

 

 

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The models seem to be firming up on the prospect of a December reset as we head into next week. If we do, then the pattern could be locked in for some time, with high pressure over the Azores and continent being hard to shift again. In terms of averting this pattern, it seems there are 2 straws left to clutch this evening:

1. We are still a week away and there's plenty time for different patterns to emerge; and


2. There still seems to be a chance at around t120-144 for an undercut of the high over the UK at that time, which would give a very different evolution. It will be interesting to see how many of the GEFS members support this scenario in the coming runs.

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Post of the Day

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I fear it is likely UKMO will catch up to what GFS has been trying to do for a few days now and finally concede to flattening the pattern and allow the Atlantic properly back in at 144 by it's runs on Wednesday.
There is no denying the GFS set has been steadily waning from the idea of sustained HLB.
Shame as the set-up did look very promising for cold weather at one stage.

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ECM 12z enesmbles for London:

http://www.weathercast.co.uk/services/ensemble-forecast.html

 

The Operational was very much at the mild end of the range of outcomes from Tuesday - up in the top 10% on 20th and 21st.

The cold cluster has remained broadly as was, with a marked warming and weakening of support after the middle of next week. A few runs maintain the very cold theme but less than 10%.

From the ensembles you would conclude that we will see a return to average temperatures for the second half of January from around the middle of next week, give or take a day.  Not as rapidly as either the GFS 12z or 18z would indicate. High pressure looks to be in charge with only a minority of runs showing much precipitation from this weekend on.

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Yep, been through them and it looks like curtains, based on the 18z ENS at least. There only seems to be 1 run offering any kind of undercut (no 11 ).

Oh well, let's see what tomorrow brings.

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That's possible but not nailed on just yet.

Someone posted an ECM ensemble spread chart earlier.  They're very telling with huge uncertainties by Sunday in an area through the mid-Atlantic up to the Arctic.  I assume that's to do with the behaviour and timing of the predicted return of the Atlantic - it may be all about timing. The modelling of the ridging into the south of the UK seems pretty solid though.

T+240 chart shows the vast areas of great uncertainty our side of the Pole & into central northern Russia (and the strong support for the ridge over the south of the UK)

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that ecm ensemble chart shows we look to be to the west of a block over scandi. but we are held on the very mild flow up the side of it. it wouldnt take much to see that block shift slightly and we end up in the colder side.

other charts show an easterly option

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UKMO sticking to its guns this morning with High Pressure centred over Scotland at T144 with a short fetch easterly covering much of the UK with low pressure diving south east across the Atlantic into Spain and France. GEM not quite so good has a rather more squashed High Pressure centred over Ireland preventing pressure dropping to the south with a generally slack or easterly flow across the UK, the compromise option of the three. That leaves GFS following on from the 18z with a repeat of the Atlantic pushing through by T144 and any remaining high pressure retreating across the North Sea. Still all up for grabs over the next 5-7 days IMHO but not currently looking like a severe cold spell for the UK.

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I can't remember such a prolonged period of disagreement between the models at such a short range!

Here's last night's ECM meteogram for Reading. For the first time in ages the milder cluster are now in the majority towards the end.

Last night's control has southerlies and SW'lies moving across the UK from 204 onwards, it's surface cold only at the end of the run.

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GEFS 0z shorts are a slight improvement on the 18z set with about eight runs retaining -6 to -8 850hPA in the south-east until Day 5 or 6. The Op is at or slightly above the mean.

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Looks to me like its heading the other way this morning.  GFS has made incremental changes towards UKMO.

I think we are looking at a cold period with wintry showers, and frost latterly, starting Thursday and lasting well into next week.  I think GFS will continue to grudgingly concede ground, it appears only to have the capacity to concede ground for about 12 hours or so, every  other run.

ECM will be useful out to t96, thereafter it will be a wait to see where it sits in the ensemble.

Cold weather in this westerly-NAO set up = massive uncertainty.

Gandalf, if I get the time I will post another one of the GFS spread charts later.

 

WI

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I'm afraid I don't see that , to me its pretty similar to last night with regards GFS, the Atlantic looks on its way ??

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It's weather! The likely weather at your chosen t+ was one thing yesterday, another today. It is myopic to see this variability solely as an outcome of model inaccuracy. Weather is not a deterministic system like the movement of the planets. What's going to happen changes; it doesn't follow a set path. From the setup we have today, many different outcomes are clearly possible...

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The UKMO has 'nearly' stuck to its guns but by 144 the high has declined slightly to the SE suggesting that the writing is on the wall with an inevitable slow erosion from the atlantic from the NW with time. However, as Whether Idle has eluded the 0z GFS has made a minor step change towards the UKMO. 

Its looking like an extension of the cold and dry spell has been granted for a couple of extra days this morning. The added bonus is that the snow starved SE, especially Kent may get to see a little snow from 1. Some convective stuff if the flow does back NE'ly for a time or 2. A transitory event as the mild air tries to push in early next week.

Fascinating times continue.

 

 

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My trough is coming

ECM 144

http://www.wetterzentrale.de/pics/Recm1441.gif

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Morning all

updating my post from last night ( & reinforcing what I said around 10 days ago when I said the models would flip - when they partially did ) is one of the biggest model failures ( or bias ) - especially the GFS is to move energy NE through a block - then as we approach real time so the final distribution often sees that replaced more & more By SE movement & the potential for prolonging the cold

The overnight model suite has seen fairly moderate model changes & fine tuning - but notable very positive moves ( a slight whiff of 96 in the air ) towards the colder solution ...

so,

UKMO has back peddled the least but ever so slightly reduced the northern extent of the blocking - but crucially gets enough of a trivial persuit size wedge in there that at 144 theres the majority of the atlantic energy is moving SE - delivering a dead cert snow event for the SW - ( if the low ever gets that far )

I would also say the East & SE is covered by the -10c isotherm at day 6 ( slight resemblance to Jan 85 in its most positive light ) & would see a continuation of the cold spell out well past day 6

UKMO ( the new anti global warming model ) - A+

The GFS & ECM blend are less amplified & send a more even distribution of energy NE & SE allowing less undercutting - crucially though both models get enough SE to hold a cold SE flow into the front to see a snowy breakdown over the UK but eventually topple it all away -

B- which is a big swing to cold after yesterdays C-



In my experience where models are swinging to more energy going SE at day 6 against the block the trend for day 5 ( backing into day 4 ) shows the biggest continued trend of swinging to more energy SE so todays the day where if its going to happen the UKMO becomes the hero....

S

Spot on.  However I'm afraid for quite a few its like a drug, uppers one day downers the next, its what floats the boat.

Have to say, the Atlantic isn't the only option in the ENS

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I'm afraid I think we are going to have to accept the sinking of the High and energy going over the top, hopefully the High can be far enough North to prevent copious rainfall for the NW.

Recent history suggests on average 4 weeks longevity from the beginning of such zonality...

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Oof...and you'd been doing so well recently.

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GEFS0z update does have some colder options.

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John some of the periods have beem longer my point is I think its a battle lost here, let's accept it and begin the next chase.

If the Strat boys are right, then it won't be 4 weeks of zonality.

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