Cold Winter Night

The EPS regime chart this morning clearly shows how we moved into the present Atlantic Ridge regime (-BLO/Neg. EOF-1) and how how the ensemble output moves from this Atlantic Ridge to moderate European blocking (+BLO/Pos. EOF-1) around Day 4/5 and then, with some spread, towards a Negative NAO regime (Neg. EOF-2) around Day 8 and 9. This is reflected in the De Bilt plume, with some cold this week under the trough, in a slack easterly flow and under the High, and then a jump to higher temperatures in an onshore flow off the North Sea as a result of those NE-Atlantic heights. In my opinion the plume shows remarkably little spread in the extended right now. Based on the EPS, further amplification and a possible extension of cold (in Holland at least) has a low probability before month’s end. It’s also too early for possible stratospheric warming effects to be noticed within this period yet.

Not yet unfortunately. 2m temperatures in the extended are not much colder than for the 0z set. Indeed you would expect part of the ensemble to make that connection up North that the Op failed to make, but so far the real cold stays away. There is a slight shift in wind direction, with more NW-lies in De Bilt. This would point towards either an Atlantic ridge, or a bigger High to the NW that is just too far NW for Holland. The clusters will probably shed light on that.

So now we have GFS, GEM and EC all with a different view on the Arctic, but agreeing on ridging West/Northwest of the UK, and the UKMO is probably going there as well. There is a move away from heights to the Northeast though, with a trough over the Barentsz Sea area instead of a High. That's different from previous days of model output, but something we saw in the ensembles.

Not so sure about that. Compared to last Thursday, there is an increase in probability of -NAO and the sudden increase in +NAO mid-February has been removed in favour of more blocking. The shift from Red (Scandi/Euro blocking) to Green (-NAO) and Red, passing Purple (Atlantic Ridge) and Red does suggest a retrogression signal. IMO it's not worse than the previous EC46, a bit different early on and a bit better later on. Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4791386

Not so sure about that. Compared to last Thursday, there is an increase in probability of -NAO and the sudden increase in +NAO mid-February has been removed in favour of more blocking. The shift from Red (Scandi/Euro blocking) to Green (-NAO) and Red, passing Purple (Atlantic Ridge) and Red does suggest a retrogression signal. IMO it's not worse than the previous EC46, a bit different early on and a bit better later on.

Certainly. This morning's cluster that looked most similar to tonight's cluster 1 had 16 members, tonight there's 31. De Bilt's EPS meteogram shows more chance of (10m) winds from NE/E/SE in the extended, and is slightly colder too.

No such thing as stupid questions here. Clusters are automated output. Read all about them here: Clustering - ENS Medium-Range - Forecast User Guide - ECMWF Confluence Wiki CONFLUENCE.ECMWF.INT

Regime probabilities chart does show a higher probability of blocking into early February though, compared to Monday. Today and Monday's:

That in itself should not be a problem with a Scandi High in place -and it's a big one with a 500hPa geopotential of 576 dam/1050 hPa at the surface. Compared to the 0z, the trough into Europe is a bit less deep, giving the Atlantic ridge opportunity to quickly connect with the Ural/Kazakhstan High, blocking off the potential NE-SW flow of cold. Unfortunate on this run. However, another run, another shape to the High, and uppers could easily be low again. One to watch for sure, especially since it's only at day 9/10, far in FI.

EC 240h. Again NE heights, this time centered over West Russia. No access to deep cold though, and the UK is just too far West to profit. Here in Holland at least 6 consecutive frost nights and snow chances. With 11c and 27mm of rain (and counting) today, that's something to look forward to.

This morning’s runs are have been a very welcome step in the right direction. Especially the EC producing a promising Scandi High at Day 10 is encouraging. I saw some this morning expressing concerns about those Low heights near Greenland. However, those are actually what got me most excited about the 240h chart. It’s true, we usually don’t want to see that at all, but with a proper Scandi High and lower heights over S-Europe in place, a firm tPV is exactly what we need, a combination that has been lacking so far this winter, both in the output and in reality. But what about “energy riding over the top”? Aren’t those Greenland purples an blues a very bad thing we want to avoid at all cost? No, not in a Scandi High situation. To sustain the High, it must be fed with Warm Air Advection (WAA), and the tPV near Greenland provides just that. The Low heights over Italy will help set up Cold Air Advection (CAA). The one thing most legendary cold spells (1917, 1942, 1947, 1963, 1987 to name a few) have in common, is that very Scandi High/W-Greenland Low setup in their beginning stages. January 1917 is an example of this and that year is not unlike this year. Also La Niña. In De Bilt, the first 3 days of January were even milder in 1917 than this year. (Disclaimer: I use 1917 as an illustration, it’s not a forecast for next week). The EPS regime chart shows the ensemble moving into the central circle as I yesterday suspected it would do. Extended output suggests it will move more toward +BLO, the upper half/upper left quarter of the chart. We must remain cautious though, as the ensemble majority still has heights more over us, or to our East, than to our Northeast (still +BLO), but the wind chart for De Bilt shows more E/SE winds later on. IMO, other models lately supporting something similar the EC Op, developing Scandi Highs on several runs give more weight to the direction of the high resolution run. It might be on to something. Now, let's hope for the best (ensemble swing to Scandi High) and prepare for the worst (EC dropping this solution altogether) on the 12z. Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4787775

This morning’s runs are have been a very welcome step in the right direction. Especially the EC producing a promising Scandi High at Day 10 is encouraging. I saw some this morning expressing concerns about those Low heights near Greenland. However, those are actually what got me most excited about the 240h chart. It’s true, we usually don’t want to see that at all, but with a proper Scandi High and lower heights over S-Europe in place, a firm tPV is exactly what we need, a combination that has been lacking so far this winter, both in the output and in reality. But what about “energy riding over the top”? Aren’t those Greenland purples an blues a very bad thing we want to avoid at all cost? No, not in a Scandi High situation. To sustain the High, it must be fed with Warm Air Advection (WAA), and the tPV near Greenland provides just that. The Low heights over Italy will help set up Cold Air Advection (CAA). The one thing most legendary cold spells (1917, 1942, 1947, 1963, 1987 to name a few) have in common, is that very Scandi High/W-Greenland Low setup in their beginning stages. January 1917 is an example of this and that year is not unlike this year. Also La Niña. In De Bilt, the first 3 days of January were even milder in 1917 than this year. (Disclaimer: I use 1917 as an illustration, it’s not a forecast for next week). The EPS regime chart shows the ensemble moving into the central circle as I yesterday suspected it would do. Extended output suggests it will move more toward +BLO, the upper half/upper left quarter of the chart. We must remain cautious though, as the ensemble majority still has heights more over us, or to our East, than to our Northeast (still +BLO), but the wind chart for De Bilt shows more E/SE winds later on. IMO, other models lately supporting something similar the EC Op, developing Scandi Highs on several runs give more weight to the direction of the high resolution run. It might be on to something. Now, let's hope for the best (ensemble swing to Scandi High) and prepare for the worst (EC dropping this solution altogether) on the 12z.

It looks like we can be fairly confident of the Atlantic Ridge building next week, with the trough plunging into Europe, bringing a N/NW flow to us around the North Sea. The EPS regime chart moves the ensemble firmly into Negative BLO for days 5-7. If this will result in snow on our own doorstep remains to be seen, that will have to be monitored in the small scale short term models, but at least there are decent snow chances for many next week, and seasonal temperatures. The regime chart also shows a general return towards the central circle (no regime), and based on the clusters there is a tendency to move the Atlantic High East, over the UK, and, in the extended period, towards the Southern Scandinavia/Baltic region. Not the coldest kind of Scandi High, and the futher NW in the UK you would be in a worse position, although the opportunity for a better setup remains, which would make those milder Westerlies a temporary thing. The alternative seems to be another NW-SE aligned lazy attempt at cold Pm flow (cluster 2). Going through the individual members at the very end (360h), most actually have a quite meridional look with blocking near Europe. There is certainly potential (yes, I hate that word as much as you do…), and there are not many members that show a classic Pos. NAO. Real cold is not found within the 15 day ensemble unfortunately: But because of the hemispheric view on the ensemble members at Day 15, interest remains for the last part of January. Meteociel - Panel ECMWF/CEP WWW.METEOCIEL.FR Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4786972

It looks like we can be fairly confident of the Atlantic Ridge building next week, with the trough plunging into Europe, bringing a N/NW flow to us around the North Sea. The EPS regime chart moves the ensemble firmly into Negative BLO for days 5-7. If this will result in snow on our own doorstep remains to be seen, that will have to be monitored in the small scale short term models, but at least there are decent snow chances for many next week, and seasonal temperatures. The regime chart also shows a general return towards the central circle (no regime), and based on the clusters there is a tendency to move the Atlantic High East, over the UK, and, in the extended period, towards the Southern Scandinavia/Baltic region. Not the coldest kind of Scandi High, and the futher NW in the UK you would be in a worse position, although the opportunity for a better setup remains, which would make those milder Westerlies a temporary thing. The alternative seems to be another NW-SE aligned lazy attempt at cold Pm flow (cluster 2). Going through the individual members at the very end (360h), most actually have a quite meridional look with blocking near Europe. There is certainly potential (yes, I hate that word as much as you do…), and there are not many members that show a classic Pos. NAO. Real cold is not found within the 15 day ensemble unfortunately: But because of the hemispheric view on the ensemble members at Day 15, interest remains for the last part of January. Meteociel - Panel ECMWF/CEP WWW.METEOCIEL.FR

EC is really trying to copy your piece of art at 192h.

Well, if something like GEM/UKMO were to verify, there would certainly be room for all sorts of surprises. GEM shows several shortwaves dropping snow all over the UK and Europe 168-240h. Fingers crossed!

UKMO 168h, indeed like ICON, going for another trough dropping SE, with possible Atlantic ridging in its back, similar to GEM. However, both lack decent Hudson Bay/Labrador Low heights that could provide WAA and make it spectacular.

Then it might surprise you even more that the present EPS already has 137 vertical levels like the HRES Operational Since Cycle 47r2 in May 2021 actually. Implementation of IFS Cycle 47r2 - Forecast User - ECMWF Confluence Wiki CONFLUENCE.ECMWF.INT The update will give the EPS the same horizontal resolution as the Op, so like @RainAllNight, I too wonder if the Control will be left out as a redundant double of the HRES. There is no information yet about an Op upgrade anytime soon.

The big difference between GEM and EC is the combination of the Low at the American Eastern Seaboard and the Labrador High. GEM holds back the Low, lets the Labrador High and the Atlantic Ridge connect, and then that Low provides some WAA to strengthen the ridge. EC pushes the Low through, so that it connects with the trough near Iceland, effectively flattening the ridge. It cold be that it needs more repeats though. It would be better if there was no Labrador High at all though. I'd like to see Lower heights West of Greenland, to provide a much needed push of WAA for an Atlantic ridge to extend NE behind the trough moving into Europe, but alas.

Pretty powerful swing towards Atlantic amplification and trough dropping into Europe on GEM and GFS. UKMO is even more amplified at 144h than those two. UKMO 168h, interesting.

EC is slightly slower than GEM, but amplifies too at 216h, lowering heights over Europe. Don't let a seemingly flat look at 192h deceive you.

EC 12z is not interested in the GFS shenanigans and sides with GEM and UKMO at 168h Now watch that ridge and trough...

Getting interesting on GEM at 240h, too bad there is no extended to see. Trough moving into Europe, surrounded by heights. The trough moving deeper in to Europe, and the Atlantic and Arctic Highs meeting behind it? If it moves slowly, it could throw up heights into C-Europe, but if it moves faster, that risk would be reduced.

GEFS and GFS are separate products. GEFS had its last update (v12) in October 2020. However, according to their documentation, the next update they will be merged: "GEFS v12 is the final upgrade of a global ensemble system separate from the deterministic GFS at NCEP. The next GEFS upgrade will be merged with the version 17 upgrade of the GFS upgrade planned for 2023-2024." GEFS WWW.EMC.NCEP.NOAA.GOV Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4784223

GEFS and GFS are separate products. GEFS had its last update (v12) in October 2020. However, according to their documentation, the next update they will be merged: "GEFS v12 is the final upgrade of a global ensemble system separate from the deterministic GFS at NCEP. The next GEFS upgrade will be merged with the version 17 upgrade of the GFS upgrade planned for 2023-2024." GEFS WWW.EMC.NCEP.NOAA.GOV