To be fair, Rob did say it would certainly be chilly. As you point out, even down down here I'd be enjoying 528 decametre air off that ECM 240 hr chart. But also, as Rob alludes, not much precipitation-wise.

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Maybe it comes of being spolt in recent winters, but I don't even feel even a tinge of excitement with this potential cold snap/spell:

1) It's still in FI

2) Lack of substantial northern blocking means it will be a snap rather than a spell

3) It's cold yes, but not especially so compared to recent winters

4) Snowfall, IMBY at least, seems unlikely (OK, the GFS Op at T+300 delivers, but thats far too far out to take seriously)

Andrew

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A very poor ensemble mean 10 day chart which is even poorer than this morning's with High pressure close to the South and a Westerly feed across the UK.

http://www.wetterzentrale.de/pics/Reem2401.gif

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It seems to me that extrapolating wind direction from ensemble charts is a pretty misleading thing to do. The ensemble chart is an average. No one individual chart is likely to look anything like that - the pressure patterns shown on an ensemble chart are a big red herring IMO.

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Yes I agree but there is no getting away from the fact that the general consensus between ECM's ensemble members tonight from it's 12z suite point to a bias of High pressure to the South and lower pressure to the North with temperatures pretty average overall.

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Yes, you're right Rob.

To be honest at this time scale almost anything could happen but the outlook is not a bad one from a cold perspective. This is reflected in the Met Office outlook. In the medium to long term things look being on the cold (rather than mild) side of average. Given the time of year wintry conditions are therefore quite likely. On a more specific FI note both the GFS and ECM op runs this evening have circa 510dam (500-1000hPa thicknesses) here around the 9 to 12 day period.

Essentially there are cold options in the output in early December and it is therefore worth watching this period for developments if you a wintry weather fan.

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The reason the ECMWF12z wasn't too good, was due to quite a major pattern change in canada imo. The polar vortex, instead of being split and isolated was actually strengthened and moved south east. The bearing high was forced into the western part of the continent where its influence became significantly reduced. This meant there was virtually no communication between the atlantic and the pacific, so it should not be suprising that the collapse occured. 

However if you look at the error charts for that part of canada

http://www.meteociel.fr/modeles/ecmwf/runs/2013112712/EEH1-216.GIF?27-0

then its apparant that there is alot of uncertainty regarding the heights. In the 850 chart the difference is even more apparant.

http://www.meteociel.fr/modeles/ecmwf/runs/2013112712/EEH0-216.GIF?27-0

If this ECMWF chart represents a trend setter then I would be very worried. I don't think any other chart has produced something so different in terms of the position of that high in a while. Perhaps that is evidence that it is an anomoly, especially since there is so little intramodel agreement. But to be clear, the ECM is alone today in its positioning of the PV in the key area; I personally wouldn't accept its word over every other chart, though it doesn't exactly make me happy either.

 

Even so the ECM216 and 240 charts are very wintry. With such low uppers, heavy snow would be a major feature to anyone exposed to the wind. 

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Err Quantum - why do you persist in referring to the mythical bearing high?

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And why do his links not work?

 

 

 

 

 

 

 

 

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I still can't get the links to work. I really don't know why, but they are valid URLs, just copy and paste them rather than click! The bering high isn't mythical, the reason I am mentioning it, is because it is having a substantial impact on blocking in our part of the world at the moment. When we are beyond 192h, the most important thing, imo, is to concentrate on major (particularly upper) features and not get bogged down in literal interpretation of synoptics.

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here are the locales from asia east to west coast of n america

kamkatchka

aleutian

alaska

if we use these areas to talk about high level blocking in the far n pacific region we will all know what we mean.

fwiw, the presence of mean blocking in these regions is the major player in the NH as we head into winter. without it, we would be looking at a strong polar vortex and a mean westerly flow. we havent seen a sw wind for two weeks now.

The 18z GFS continues the same theme as previous runs which will do me for the moment...

http://www.wetterzentrale.de/pics/Rtavn2041.png 

http://www.wetterzentrale.de/pics/Rtavn2161.png 

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Ladies and Gentleman, just had a look at the 18z GFS and the Two Armed Jetstreams are facing each other.

We see a lot of Blocking High Pressure in GFS 18z, same scales- enhanced blocking W SW off Greenland and NE of Canada plus Newfoundland Arctic High block, and a fabulous Iceland to SE Arctic WSW Norwegian Sea areas of Cold bringing Low Pressure.

Tuesday 3rd, and Wednesday 4th December the UK gives away the High and gradually get some NW flow from N Atlantic and Iceland.

Deep Low P areas in Central mid Tropic Latitude Mid N Atlantic Circulation Low and Meditteranean Low spread West and SW.

Upto T138 GFS 12z looks good, and the High in NW Atlantic blocks a New Deep Low surely squared at NE of New York SW away from interior NE Newfounland as the High in there fends it away.

And seeing a large Norwegian Sea SE Arctic In Very Cold low Pressure that stands out lively.

I hope we get that Cold Plunge on Thursday and Friday N E X T W E E K.

Bet the ECMWF and UKMO throw in the right numbers and GFS as we draw this outlook dreams closer to T84 hrs.

Good night on here.

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18z continues the frigid trend and I think represents an upgrade.

We see the extent of the b***** high slightly increased across the central arctic, and some evidence of ridgeing towards greenland at least at the surface. The midatantic high seems to be doing a better job of joining with the greenland high aswell, so we might be getting a better general block stretching from the mid atlantic to alaska. The caveat is that nasty cold pool between the b***** high and the greenland one. While communication between the midatlantic and greenland seems to have improved, it seems to have got worse wrt canada. So there is evidence of some spoiler lows at more northern latitudes which could present a problem. However the news is generally good and improving, and if we get a decent block in place before anything can get far enough east, then we may be looking at reboots rather than breakthroughs. 

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http://www.wetterzentrale.de/pics/Rtavn2403.png 
Not bad for this time of year.
On another note, a sequence of high tides is around these stiff northerlies so the prone areas of the east coast should be on alert from some flooding if verified.

Although several days outside of my usual 'confidence' line of around 5 days, a northerly looks quite probable now mid to late next week.
The longwave pattern will be subject to further change but seems to be on line. The shortwave detail however is going to be interesting to say the least. Any energy squeezing through and zipping SE across the UK once the cold stream is established could well threaten a decent snowfall for some.
I like others feel the reset is still likely next weekend but one should remain open-minded.

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Agree entirely. Looking for continued improvement on the ensembles as we move closer to the potential event! 🙂

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Just remember, we understand that being excited about the 12z and 18z GFS runs has a very tantalisingly close resemblance to being wishing it happens we should still keep Ourselves on Top of It at all Times.

The next day in the Morning just remember THINK about how the Two Jetstreams have to draw the High Pressure in the right way around and keep on your Toes say that you see ECMWF and the UKMO just like we talk about them that some of us should encourage this knowledge and recommend being here is good when we get the Weather Forecast Right.

I am very pleased with the GFS 12z and 18z runs for 1st Week and Weekend of December 2013, I can accept those and their pretty Model Discussion's but balanced Opinion is required and with the correct Methodology and aiming to Guess the reality VS Opinion will win those to get applauds if they gain a good success rate.

We again are getting Teased by the GFS and so far so good.

Next 5 days I hope we get a lot of good posters experienced just like me, it also is recommended that those following the day to day Models e.g. ECMWF, UKMO and GFS, GEM and JMA plus NAVGEM and with the talk of Ensemble Peterbations good luck I just hope we get a proper change soon - we are not there nor can say with Confidence about what the weather will Offer us- come the 4th to the 8th December- it can change as it's natural the Weather is not Controlled by us, take it easy on others and share your encouraging predictions we need balanced view's and comments on Weather Forecast Discussions- Good luck and Good night.

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An impressive northerly plunge but it doesn't last long before the block is flattened. 

http://www.wetterzentrale.de/pics/Rtavn2881.png

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I'd rather we use the incorrect spelling of Bearing high rather than something people might misread as 'Bartlet' !!!

Nice post though.

Actually it was the "glancing blow of cold" that I was querying.  Maybe it's terminology but to me a glancing blow implies very little of the cold uppers and only for perhaps 24 hours or so - hence my highlighting it looks like 3 days and uppers with thickness values into the mid-/low-520s.

It's correct that, even if that evolution is correct, the rising pressure will kill off the shower activity quite readily.

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But it lasts four days, Rob - and the subsequent evolution doesn't show the Atlantic floodgates opening. What it does is develop a slider, with the residual energy running SE and the cold edging back (having only left the far SE corner for less than 24 hours).

Here's the 18z ensemble fo2 2m temperatures for London:

0http://176.31.229.228/modeles/gens/graphe_ens4.php?temp=1&x=310&y=142&ext=1&run=18&runpara=0 

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Quantum, try posting the link twice with a space between the two.  That's the way I solved the problem when I post.  Not very elegant but it works.

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Here is the ECM 12z ensemble chart for London

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

The Op and the mean are in tight agreement to Day 9 - the Op was at the colder end for Day 10 but not quite an outlier.  After Day 10 the mean continues to run along in the 'cold' category but trending to slightly less cold by the end.

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Today's game - "Spot the Outlier"!

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=306&y=141&ville=Londres 
http://www.meteociel.fr/cartes_obs/gens_display.php?x=306&y=141&run=0&ville=Londres&runpara=0&type=3&ext=1 

If the op were to verify then we'd have a pretty decent (and doubtless snowy) cold spell. That's a mighty big "if" though and I wouldn't exactly stake my life on it being correct.

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