Zakos

. I'm not sure if Im reading this correctly, but I think the mean at +384 is very impressive, very weak vortex over Canadian arctic/ Greenland, all of the deep cold is pooling over Siberia. . . Fantastic jet profile in FI. . . Mean Anomaly from ECM and GFS at +240 screams blocked and southerly tracking jet , one thing I'm very confident if is no return to Atlantic conditions. ECM perhaps less keen to build heights over Greenland at this stage.

AO firmly set to dive negative now. Also, for the first time (to my knowledge) this season, we have a significant cluster of runs sending the NAO deeply negative. I dont believe Ive seen such a significant cluster heading below -2 at all this autumn, its been hovering around neutral for many month now.

Ah right I see now, thankyou!

I thought this was the case Just seemed odd to me how quickly the siberian high seemingly vanishes. . .

. Does anyone know if this very large block is a result of the Atlantic and Siberian high "merging" together ?

. Stunning anomalys again from the GFS. . . Lack of cold air initially is irrelevant IMO, when you consider the run ends with air being imported from central Siberia! Models definitely firming up on a very blocked end to November, and possibly a very blocked and cold start to winter.

. Better still on the 12z, Atlantic jet starting to look very weak now.

Wow, quite a shift in the output over the last 4 days! Significant upgrade for the ridging in the atlantic next week. Excellent mean height anomaly at day 10 from the GFS As many have noted, no sign of a notably cold airflow yet However, an even more impressive mean anomaly at 384 - December 1st. Strong signal for heights to our NW, plus low heights deeping over europe, possibly hinting towards a cold airflow from the NE as we enter December, perhaps as a result of a PV lobe dropping over Scandinavia. Certainly very little sign of the PV forming over Greenland/Canadian Arctic, with a strong signal that its core will remain within siberia. ] Lovely to see any attempt at PV formation over Greenland being swiftly swept aside and replaced with ridging. A far cry from the horror show that unfolded this time last year!

Its not without support either. It may be 2 weeks out, but the GFS has definitely been hinting at a major blocking event here for a while now. The runs show the atlantic high and the siberian high converging. I believe these highs merge and form a very large block in the atlantic/Greenland area. Same from the ECM. Once that area of low heights drops south towards Spain, it looks likely to me that the UK is going to experience fairly blocked conditions, hopefully we'll end up in a cold airflow too!

Wow, probably the best anomaly chart ive seen all season!

It has to be said the models are reluctant to bring in cold air at any fast pace, theyre certainly showing it to be a slow evolution if it occurs. Im not too phased by the apparent lack of cold 850's showing in the output. The difference between the 00z and 06z today shows how small tweaks in the flow can drastically alter the potency of the air heading our way. This was only at 120 hours out. As we are heading into December, I would have thought that aslong as a cold pattern manages to sustain itself, we would eventually receive cold air. The bigger picture looks very good in my opinion as we head into winter proper, a very timid vortex at day 10 from the GFS IMO, for the time of year

I think in regards to the jet stream you may well be right. However, there is still a trend for the jet stream to wane in strength throughout the duration of the runs. The height anomaly mean certainly indicates northern blocking may well begin to take hold again.

Technically you are right, but the amplified pattern over the atlantic indicates a ridging in the atlantic is likely, with low heights more likely over europe. The deep blue/purple colours are centred over eastern siberia, indicating this is where most of the ensembles show the Core of the PV to be placed. Yes, they do not show actual weather conditions, but I believe they indicate a definitive signal for blocking to our North West and a very slack jet stream.

Much the same from the 06z ensembles. going...going...Gone!

ECM and GFS +192, still agreeing on an area of low heights over Greenland being displaced and moving southwards across the UK. Both models at day 10 show a resurgence of blocking in the atlantic, and I believe both models are showing high pressure starting to build, centred just to the North/North West of the UK. The GFS is certainly showing this in its later frames and has been for a while now. Its been showing a large positive anomaly over the most of the atlantic. The 00z Would be far better the UK, hugh anomaly over Greenland and the block is far west enough to bring some true arctic air to the UK. The GFS 00z ensemble mean show a clear trend towards a weakening jet stream. Cold is by no means guaranteed for the UK. but I'm seeing very little sign of atlantic weather taking hold towards the end of November. The mean certainly indicates the core of the Polar vortex will stay within siberia, with a solid signal for blocking to our North West. The AO and NAO are both set to dive negative, but just how negative will they go? Interesting model watching period coming up I think.

Im finding it quite difficult to spot any trends in the output recently. Although blocking in the atlantic is set to weaken, there is a signal that it will start to reassert itself at day 8. It looks like we are going to see a week or so of atlantic weather, before blocking in the atlantic may well take over again. In the later frames of the GFS, there is a tendency for the low heights over Greenland to drop into southern central europe, and the siberian and atlantic blocks are set to merge, creating significantly blocked conditions for the UK. The 00z an yesterday's 12z also showed this. However the 18z had the block form too far east, leaving us in a very mild and wet pattern. It looks like the AO is going to dive negative after a short uptick, hopefully the block will setup in a favourable position for the UK

GFS definitively firming up on the Atlantic ridge/Siberian high link up over Greenland on the last 3 runs.

The Russian high will certainly be our friend if it merges with the atlantic block over Greenland as many runs have shown to happen After a few days of atlantic weather, the low heights over Greenland are set to sink over Europe. This is why I remain confident that we are not going to see the atlantic suddenly fire up in the near future. The models never really show blocking in the atlantic fading completely. It only ever seems to temporarily weaken and then reasserts itself relatively quickly Both ECM and GFS show this at day 10. In the later frames, the GFS (on many runs) wants to push the core of the low heights in a south easterly direction, putting the UK into a very cold airflow By the end of the run, the atlantic is effectively dead, and Europe is locked into a cold pattern Perhaps in winters with a strong jet stream ,the russian high may be our foe.But it appears these next few weeks it may well be our friend. I personally have quite high hopes for cold weather over the Uk during the next few weeks.

The building blocks for cold are there in the reliable though The atlantic block as we speak has joined forces with the siberian block, but the ridge is too weak and the atlantic breaks through. throughout the GFS run, the atlantic block is constantly trying to merge with the siberian block Eventually, the blocks merge over Greenland, producing the above charts... the best case scenario in my opinion. Its not chasing cold, its looking at plausible evolutions of the pattern. This merging of the blocks has been mentioned by more knowledgeable members on the forum, and I personally am seeing this pattern change to be more likely each day. If the pattern was as it was last year.. then it would be classed as blindly chasing cold IMO. This pattern change is a very real possibility.

Its clear we are going to see some atlantic influence However, looking at the last 4 runs, the jet stream forecast for +120 hours is weaker, more disorganised and has made less progress eastwards into Europe on each run. I think the GFS is putting to much energy into the atlantic, and is certainly too progressive with removing the cold air from europe.

yes most definitely The waters to our east are anomalously warm aswell, this is probably partially to blame. These should however cool fairly quickly if this blocked pattern continues.

Yes, I think so too. A shame it has occurred just too early in the season, as i believe large swaths of the UK would have seen snowfall in this setup. Lets hope for more of the same in the coming weeks!

Very tempted to catch a bus to the peak district this afternoon, looks like the showers are falling as snow over there. Does anyone know if this pattern would have seen snow fall to low levels if it occurred during December?

I see, thankyou for your expert input, most appreciated! I am an avid model watcher, but my meteorological knowledge is basic at best. Im very keen to start learning now that I have the time on my hands.

00Z06z PV lobe over Greenland has virtually dissapeared on the 06z In my opinion, the GFS doesn't have a clue and is "defaulting" to the seasonal norm I wouldnt look beyond +120 in terms of UK weather conditions.