Nick F

Good confidence that the high over us will eventually sink south, though GFS is more progressive in doing this, with a band of rain and milder air spreading across all parts next Wednesday, whilst 00z EC doesn't have frontal rain pushing east across all parts until next Friday. The only glimmer of hope that the return of milder and unsettled SWly flow will be brief is from the 00z EC det. which days 9-10 has trough disruption in the N Atlantic and split trop PV with +ve 500mb heights over the north pole - which suggests potential for height rises to our north. But that far out we can't be confident on evolving like that.

Indeed, the broadscale state of the atmosphere which, let's face it, is on a completely different playing field to this time last year, will over longer-term have an imprint, NOT the direction that operationals take us in from the medium range. The ops are a good tool for the short-range for the finer detail, but there comes a point where ENS are more use, particularly past day 7. This is not purely because those who see better in the ENS don't see what they want to see in the ops ... but is fundamental to longer range pointers on how the atmospheric state will lead us.

Looking at the 06z GEFS updating on meteociel, plenty of perturbations looking more blocked (up to a half) at day 8 (T+192) with the ridge further north than the operational, which has sunk the high S/ SW by then. So 00z ECM deter may have some support.- which is also supported by EPS mean/anomaly.

As Knocker mentioned, 850-1000mb (partial) thickness charts are a good guide too to show where a colder/drier source of air is coming from, that may lower temps. For example, loop below of partial thickness this weekend shows colder/drier continental air feeding in from the near continent, bringing sunnier skies but also a return of frosts after a milder, cloudier and frost free end to this week:

Sorry for trending on GPs toes, but worth pointing out that any movement to phase 1 is shown as a weak signal on model forecasts - hence little impetus to change much in the model outputs. Need a more coherent movement of MJO in P1, i.e. orbiting further out. Lets hope GP is right re: more amplification later across the Atlantic, as the models are indeed meh for snow lovers for now!

Dew point forecasts normally good indicator that temps will get cold at the surface under clear skies

I don't think developing a deep trop Polar Vortex over E Canada is necessarily a bad thing, shifting the low heights away from our north into Canada may open up the Norwegian and Barents Seas to allow high pressure to be drawn north and northeast. Our stubborn block ain't going nowhere fast and if we get a PV lobe over NE Canada it may strengthen WAA northeastwards to our north to draw the block north - so long as some jet energy goes under towards SW Europe too. There seems little impetus to shift the pattern over the N Atlantic for a while, particularly the block. MJO signal is weak, so no atmospheric waves to work through to drastically change the pattern for now. Though the Aleutian high may push on the poles enough to affect the mslp over the arctic region.

Nice to see the London temp not get above 8C for 10 days and the 12z GFS op looks a mild outlier from the 8th to 12th

18z has Euro ridge and Aleutian ridge squeeze which goes for a full on bulldoze of low 500mb heights to our north

As you were this time next week, high pressure centred over N Sea, day maxima struggling with the flow off the near continent

Think we'll start to see plenty more teasers now from GFS FI over the coming days ... which will have Sidney running for Knocker's Woodshed. Just a question of waiting for the ridges and troughs to position favourably to bring the deep cold in.

Looking toward the end of the 11-15 day EC ensemble to the 13th - there's certainly a good squeeze on the pole by ridging from the Aleutian omega high and also ridge north from NE Atlantic/Iceland/UK area. The deep cold still out reach to our east but if we can retrograde the ridge over the UK, then we maybe in for chance to tap in ... pattern could be a lot worse!

Only in the troposphere, the stratospheric PV isn't splitting anytime soon, just displaced from the pole for now

One thing that interests my eye on the 18z, not so much the surface synoptics - which change most with every run, but at the 500mb level a vortex of deep cold air (purples) drifts SW toward Scandi towards day 10-11. 12z ECM det. showed similar too. Could be a result of the Aleutian omega ridge pushing poleward and displacing cold air equatorward the other side of the pole. Worth keeping eyes to the N over the pole as well as to the west and east!

Rare to have a PV split this side of the New Year, particularly during a westerly QBO, though obviously we've seen the displacement - which is not that common either in a +QBO. Perhaps the strengthening and migration back to the pole is why the AO and NAO forecasts are trending away from the negative values to more positive values as low heights develop over Arctic as per current/recent EPS and GEFS. Be interesting to see if the forecast Aleutian High development will push poleward enough, as a synoptic feature of wave number 1, to have an effect on the PV if does indeed move back to the North Pole.

Well, at least it will remain dry and chilly in the south with overnight frosts through next week, some cloud and rain in the north mid-week as Atlantic fronts return and winds turn westerly for a time here, before high pressure builds back in for all to end the week. The 500mb vortex gathering strength over Greenland toward the end of the run not such a nice sight though.

Is a rather lacklustre 00z GFS op for cold and snow lovers, the jet just won't amplify enough and is tracking a little too far north. Still, swings in the model output over recent days may mean there's still some hope ...

18z is a generally sad story with a kind of a happy ending ... until you one checks out the temperature profiles. Oh well, the daily grind to find snow continues, though appreciate winter's come early in the north.

perhaps a white Tuesday 6th Dec for some up north on 18z, finally it gets a token northerly in as the flow amplifies upstream

A strong and zonal jet across the far North Atlantic between New Foundland and UK/EIRE through next week and beyond into following weekend on the 18z kind of scuppering chances to get enough amplification to pull proper cold arctic air south across the UK. Hopefully Black Friday model output will offer some better festive promotions that coldies can't refuse to snap up!

Lots of footage of bad floods in NW Italy and Corsica coming out on media now, have talked about the risk of flooding over NW Italy, SE France and Corsica in my latest blog here: http://www.netweather.tv/index.cgi?action=news;storyid=7799;sess=

SW and NW England saw flooding and disruption to start the week. Now it's turn for NW Italy and far SE of France for a risk of flooding View the full blog here

Wow ... stark differences between EC and GFS operationals this morning in the 8-10 day range across the Atlantic. EC has a southerly tracking jet across the Atlantic which pushes a trough east towards Iberia - which looks unlikely given there's a ridge extending NE from the Azores days 6-7. And it would pump warm N across Europe too. GFS sticking to its guns with the amplifying ridge across NW Atlantic into Greenland while a 500mb cold pool drops south from the arctic further east across N Europe - but doesn't quite manage a clean northerly. Some volatility from EC over recent runs at the 500mb level while GFS seems more stable though with surface differences.

While the 18z trickles out ... the 12z GFS, unusually, more amplified with the upper flow looking at the northern hemisphere view than ECM on the 12z. Usually the other way round. ECM flat as a pancake days 9 and 10 compared to GFS. A lot more amplification upstream over U.S. on GFS ... wondering whether the GFS or ECM are handling properly the strong Pacific jet crashing into western U.S, with regards to mountain torque that amplifies a trough over central/west U.S. of which there are a few at least over coming days. GFS too amplified? Or ECM not amplified enough? Either way, has ramifications for the flow downstream toward Europe 216 240

Also ... worth taking note when the GFS consistently hints at northerlies, as historically I've found the model has been good at picking them up in later medium range compared to other models. It tends to have a good grip on the far north Atlantic sector and N America.