Zakos

Agreed very interesting ... the block is extensive and essentially in the same position right out to +384 hours on the 00z... The block holding firm throughout... tentative signs perhaps of an easterly flow eventually over the U.K... This is quite unusual for November... I haven't seen charts like these since Nov-2010... not to imply we will necessarily see a similar epic cold spell but the potential certainly is there....

An interesting period of cold and unsettled weather ahead, giving an opportunity for significant snowfall in the south, aswell as country wide snow showers. Not a snow-fest by any means but a welcome relief from this rather drab winter we have had so far I'd say. Thereafter, tentative signs of some notable cold encroaching from the east. The 06z is a drastic improvement... with high pressure centred over Scandinavia. This is what we want to see in the output IMO. A potently cold and snowy spell of weather could soon be upon us... The 06z unfortunately fires up the PV over Greenland, scuppering the cold spell just as the cold air gets to our shores... The CFS output for the month however would have us locked into a cold pattern for weeks on end.I personally feel this is the more likely scenario, it has been hinting at this for several days now and the blocking signal grows ever stronger.

Are the models programmed to factor in the effects of a sudden stratospheric warming? I don't believe they are, and this could explain the model volatility at present. The jet stream definitely trending more southerly on the majority of runs as they come out.The low imo does not pose an imminent threat to my untrained eye. looking at the satellite images, a lot of energy going eastwards. I think with luck the cold may hold on for sometime.. SVID_20180227_0827.mp4

excellent, a significant increase in pressure over Scandinavia at 93 hours, forcing the jet stream to take a more southerly track. This is far from over!

Me too. I'm not clued up on the science behind it, but I have heard that this is the case before on this forum. I believe the density of this brutally cold air should make it harder to shift. I believe "thickness" charts indicate air density Even without a block holding cold air in situ, logically it should be more difficult to shift than a less cold air mass. 2 days for a large swath of Europe seems awfully quick. The GFS has already backed down from its rapid breakdown, and it appears the 18z may be following the same trend...

I agree, such deep cold air is unlikely to displaced this quickly imo thats an incredibly hasty warm up from the gfs for western Europe in just over 48 hours... I dont buy it...

what a beautiful chart from the ECM. I believe the cold will already be too deep and entrenched over Europe for the Atlantic to spoil the fun as quickly as some models suggest.

Yes I believe so

Agree. Always far too quick with the Atlantic. I'll eat my hat if that cold pool is virtually removed from Europe within 4 days as the 18z shows

Unbelievable model viewing. I'm lost for words, and teeming with excitement. The block in question is monumental, and any supposed breakdown is very unlikely to be modelled with any real accuracy. Agree with other posters, GFS loosing the plot and "defaulting"to norm, there is no way imo such deep cold would be removed so quickly from Europe. The trend imo had been to increase the strength of the block and the severity of the cold that hits the uk. Are we in for a direct hit ? I unfortunately took a break from model watching, and almost jumped out of my chair when I saw the charts. I think we are in for a memorable event folks

] Good to see the cold pool over North America removed, with the jet becoming drastically weaker. This should help to keep the atlantic at bay. Without a raging stream perhaps the next time around we could have more luck and see an easterly flow develop?

Just to highlight as others have mentioned, the sea temperatures are below average to the North West, which will aid the snowfall potential. I believe the sea temperature has been above average in this area in recent years. Im personally looking forward to this event, even though I am unlikely to see any significant accumulations. It looks like the most potent North West incursion I can remember seeing in recent years

Wow Thats some incredibly cold air heading our way on the 06z, looks like the huge cold pool that has built over siberia may have the UK in its sights! The run ends with what has to be the most beautiful anomaly chart i have ever seen. Definitely a strong signal now from the models for heights to build out the NE, and to have low heights to our East/South East. with a bit of luck we could be in for a memorable cold spell IMO.

. I'm not certain, but given the potency of this cold shot, and the warm seas at this time of year, the temperature contrast could create disturbances in the airflow,leading to heavier and more widespread snow showers. And these possibly wouldn't be picked up by the models until nearer the event. Some GFS runs I believe have shown widespread snow showers across the UK, however the 18z appears to have a "wishbone effect " to flow, with many inland areas staying dry. Does anyone know what factors can cause a northerly to produce widespread snow showers inland?

Strong indication from the GFS and ECM in the long range for europe to be locked in a significant cold spell. The jet stream at present is astonishingly weak for the time of year, I see little evidence in the output for a return mild weather conditions once the cold air becomes entrenched I think a lot of coldies on here were left bitterly dissapointed from the last 2 seasons. But Im now personally convinced that we are in for noteable spell of cold weather, possibly a prolonged one if heights rise to our North East as some posters have hinted at. It's already been fantastic model watching so far this season, which seems to be getting more exciting and promising for cold prospects as times goes on.

Miles apart at just 120- the output is a dogs dinner. Very uncertain as we head into next week. My money is on a second cold shot, though it may be a long and drawn out process. Interesting to see the met office mention battleground scenarios during december, this has been hinted at several times by the GFS... At +144 the difference between the ECM and GFS is ridiculous, can't recall the last time i saw such a difference in the output.The models are clearly struggling with this setup.

Crewe how can a single model run indicate a trend ? There is little cause for concern in my opinion, especially when you consider the run still ends with a significant cold spell for the UK

I agree with you mostly. I think paul is right in a sense though that many posters are overreacting to each and every model run. Just because a run shows mild weather, that has no effect on the weather itself, and there is nothing to say that it will not swing back to showing cold weather on the next run. Ive seen cold spells appear out of nowhere at 96 hours, sometimes less. i personally feel that you really shouldn't pin too much hope on any output beyond 144, as you will suffer in the long run..the models love to tease! plus, the end result on the ECM is still a significant cold shot. all to play for IMO.

very encouraging from the ECM It shows that even with a potential delay in the second cold shot caused by the sinking high, the cold still makes inroads. Those pesky heights over europe are swiftly brushed aside. With such bullish blocking in the atlantic, and with such a timid jet stream, I would wager that cold weather in some form is almost inevitable.

Cold shot, cold reload, then a battleground scenario as the atlantic tries to make inroads. A recurring theme in the output, and the most likely scenario IMO What more could you want! fantastic model watching. Little evidence for a return to atlantic conditions. I for one am ecstatic that cold is on its way, and we are not constantly looking for glimmers of hope in charts 10 days out. What we would have given for a chart like this last season.it's only 54 hours away! and it's not even winter yet. very exciting times ahead I feel

The jet stream in the short range output is looking very weak for the time of year, I dont see much evidence for it to come crashing in once the cold air becomes established over Europe. Fingers crossed!

Excellent mean anomalies today from the GFS ECM and GFS at just 168 hours away Given the persistence of low heights over europe and the weakness of the jet stream at present, I personally think we are odds on for cold weather. The 18z is very reminiscent of December 2010! Are we potentially looking at a prolonged and memorable spell of cold weather? the block is looking very formidable IMO, exciting prospects.

Thats a pretty big shift in the space of 96 hours. I think the models can be excellent at predicting incoming atlantic depressions for example, but I have great difficulty taking any output beyond 96 hours seriously in a situation like this, there is simply no way that the models will be able to accurately predict such a drastic change. Once the block sets up, we should have a clearer idea of what will occur. Until then, I personally wouldnt get disheartened by any output, expect wild swings in the coming days.

Despite a ghastly 12z run for the UK, the bigger picture remains very good, and there is still plenty of scope for us to see cold weather. The polar vortex looks like it's taking a good pummeling on this run, a lot of warm air advection into the canadian arctic aswell, which can only be good news as winter approaches Even right out to the very end of the run, the vortex and jet stream appear to be in disarray. I think there is every chance we could see a notable cold spell before the months end, and there seems to be little to indicate that atlantic will take hold of our weather anytime soon

We are about to see a major pattern change,I wouldn't expect the models to perform very well until the block sets up. Despite a very negative AO, the 18z laughably has the UK in a warm southerly flow. However, the jet stream is weak and in disarray, aslong as a weak and disorganised polar vortex, a continuing trend in the output I believe. Exciting times ahead