Cambrian

The plainer direction of travel is more clearly shown around day 8. Now that’s a great winter setup. 0z EPS for 11th February at day 8 - low heights through the UK and Ireland, 531 dam the highest through the far southwest of Ireland. An elongated low pressure running north-south from Scandinavia to northern Italy, cyclonic northerly flow for the UK and Ireland. Thicknesses would be obligingly low. Hints of scope for the development of features around Iceland to run down in the flow. T850’s of -4 to -7 throughout the UK and Ireland on the ensemble mean, an exceptional mean. Atlantic jet stream fragmented and tracking well to the south, on mean, control and op (the mean shown here). The setup looks to have around 3 days in it in its purest form before the Atlantic looks like it might want to have a go, which again could get very interesting. Cyclonic, unstable northerly flow, and cold. It might have its detractors for this and for that (uppers too marginal, only back-edge in the south etc.) but if we get anything close to what is being represented here in the mean, that’s one of the best setups we’re going to see for general snow chances any time between now and next December, so we should feel entitled to thoroughly enjoy its manifestation (or not!) over the next week. Have a great day. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5028580

The plainer direction of travel is more clearly shown around day 8. Now that’s a great winter setup. 0z EPS for 11th February at day 8 - low heights through the UK and Ireland, 531 dam the highest through the far southwest of Ireland. An elongated low pressure running north-south from Scandinavia to northern Italy, cyclonic northerly flow for the UK and Ireland. Thicknesses would be obligingly low. Hints of scope for the development of features around Iceland to run down in the flow. T850’s of -4 to -7 throughout the UK and Ireland on the ensemble mean, an exceptional mean. Atlantic jet stream fragmented and tracking well to the south, on mean, control and op (the mean shown here). The setup looks to have around 3 days in it in its purest form before the Atlantic looks like it might want to have a go, which again could get very interesting. Cyclonic, unstable northerly flow, and cold. It might have its detractors for this and for that (uppers too marginal, only back-edge in the south etc.) but if we get anything close to what is being represented here in the mean, that’s one of the best setups we’re going to see for general snow chances any time between now and next December, so we should feel entitled to thoroughly enjoy its manifestation (or not!) over the next week. Have a great day.

Following on from @Cloud 10, the 12z GEPS with a long fetch northerly flow on the MSLP chart, sourced from the Siberian Arctic.. …is not alone at day 16. The 12z GFS control ends with an extraordinary setup, with a remarkably similar stamp to it, bringing snow through the UK and Ireland, France, down into northern Spain and Portugal - indeed, a “bank” of snow from Svalbard to Spain. What a delicious irony that would be after all that discussion of Iberian heights.

Ah, if only we could get the EPS on board within the 10 day timeframe with this idea of a trough set up to the east of us, digging south into Europe and completely flushing out the heights from Iberia, a surface low pressure over Denmark, with cold air spilling south on a northerly flow into the UK and Ireland… …and the cold, cyclonic pattern solidly indicated for several days now in these ensemble means beginning to feed through to the ops from day 9… 0z ECM, GEM …and some helpful EC46 outputs for the next two weeks showing the establishment of a trough working south out of Scandinavia into Europe with heights rising to the northwest, not over Iberia… …and those pesky ECM temperature anomaly charts to actually show clear cold through the middle to end of February… …and a growing NAO- signal on the regimes forecast alternating with blocking and Atlantic ridge signals from around 1 weeks time through to the middle of March… …then it might be worth getting just a little bit interested. But until there’s a core trend like that, I’ll be more swayed by single run outputs like the 6z GFS op… Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5027347

Ah, if only we could get the EPS on board within the 10 day timeframe with this idea of a trough set up to the east of us, digging south into Europe and completely flushing out the heights from Iberia, a surface low pressure over Denmark, with cold air spilling south on a northerly flow into the UK and Ireland… …and the cold, cyclonic pattern solidly indicated for several days now in these ensemble means beginning to feed through to the ops from day 9… 0z ECM, GEM …and some helpful EC46 outputs for the next two weeks showing the establishment of a trough working south out of Scandinavia into Europe with heights rising to the northwest, not over Iberia… …and those pesky ECM temperature anomaly charts to actually show clear cold through the middle to end of February… …and a growing NAO- signal on the regimes forecast alternating with blocking and Atlantic ridge signals from around 1 weeks time through to the middle of March… …then it might be worth getting just a little bit interested. But until there’s a core trend like that, I’ll be more swayed by single run outputs like the 6z GFS op…

I can see the temptation to look at today’s 0z EPS at day 9 as introducing the risk of a cut-off low setting up in the Atlantic, especially when we compare it with yesterday’s 0z for day 10, the trough is further west, and noticeably deeper. Same trend that the GEFS and EPS have been picking up on over the last few days with the trough dropping more out of Greenland in the first instance, before it moves east into Europe. But the low is also further south on today’s run, and look at those heights building north through Greenland. Today’s vs yesterday Moving on to today’s 0z EPS at day 10 - the Atlantic trough obligingly moving steadily east, the low heights merging with the PV trough over western Russia, so the broad west to east transfer is the same, except when comparing with yesterday’s day 11, some good low heights are getting into Iberia and the heights building up into Greenland are again much more impressive. Today’s vs yesterday There might be a slight delay being incurred by the development of the low over the Atlantic, but its more southerly track into the heart of Europe and the much cleaner sealing off of the pattern with the heights over Greenland serve to very much consolidate the cold pattern thereafter. It is once more jam tomorrow, but in this case, it could very well be a lot more jam tomorrow.

It’s the extent and starkness of the change on the 12z GEFS between day 8 and day 11 that is the eye-catching signal of the switch to come, fringe anticyclonic with a southwesterly flow exchanged for a cyclonic northwesterly… …with a drop in T850s that continues through to day 13, some properly cold air might well be in prospect if that’s the mean at this kind of range. The models firming up on the stretching of the PV east being followed by the leaking back west of the Eurasian lobe of the PV to the Greenland side. A closer look at the heights contours, comparing yesterday’s day 12 with today’s day 11 shows the emphasis on a Scandinavian trough being subtly modified to more of an emphasis on a Greenland trough (deeper too) pointing sharply southeast through Iceland to the UK and Ireland, holding the trough back further west as a result. This could well serve in the event to prolong the cold spell as it takes its time to grind east, the trough a long way south through Europe into the Mediterranean all the way through to day 14, its western flank looking to provide the route for disturbances to head sharply southeast through Iceland down into Western Europe. The UK and Ireland as is often the case is close to the cold boundary, but plenty of scope for wintry opportunities developing here in what could be a notable cyclonic setup for being combined with generous feeds of Arctic-sourced air that are “just cold enough”. This is an increasingly interesting outlook.

One of those times when it’s of particular benefit to have modest expectations of the models in the nearer ranges, not be swayed too much by individual operational runs and focus on the core evolution of what is actually being shown. 6z GEFS staying true to form with the modelling of recent days. Stage 1 : day 1, getting some fresher air in behind the cold front passing through tonight. Might see the sun tomorrow! Note the low to the east of Greenland. Stage 2 : day 3-5, the low moves through the Norwegian Sea to northern Scandinavia. This is the first (unsuccessful) attempt at setting up a Scandinavian trough. A strong build in heights to our west over the Atlantic is squeezed flat by day 5 as the next low exits Greenland. However, this one’s the boy for Scandinavia. Stage 3 : day 7-9, the low pressure sets up over Scandinavia, while there is another northwestward build of heights up through the mid Atlantic, an important phase as it pushes more directly north through Iceland, ridging north to Greenland. This build in heights keeps a substantial separation between the Scandinavian / NW Russia and eastern seaboard troughs, and pulls the flow through northwest Europe around more to the north. Stage 4 : day 10-12, the trough extends back west through Western Europe, clearing the heights out of Iberia, a decent cold signal developing by then, and at this range, not to be sniffed at. It’s a very well repeated core evolution of the models of the last few days. I’m looking forward to seeing if and how exactly something like it might transpire! Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5026060

One of those times when it’s of particular benefit to have modest expectations of the models in the nearer ranges, not be swayed too much by individual operational runs and focus on the core evolution of what is actually being shown. 6z GEFS staying true to form with the modelling of recent days. Stage 1 : day 1, getting some fresher air in behind the cold front passing through tonight. Might see the sun tomorrow! Note the low to the east of Greenland. Stage 2 : day 3-5, the low moves through the Norwegian Sea to northern Scandinavia. This is the first (unsuccessful) attempt at setting up a Scandinavian trough. A strong build in heights to our west over the Atlantic is squeezed flat by day 5 as the next low exits Greenland. However, this one’s the boy for Scandinavia. Stage 3 : day 7-9, the low pressure sets up over Scandinavia, while there is another northwestward build of heights up through the mid Atlantic, an important phase as it pushes more directly north through Iceland, ridging north to Greenland. This build in heights keeps a substantial separation between the Scandinavian / NW Russia and eastern seaboard troughs, and pulls the flow through northwest Europe around more to the north. Stage 4 : day 10-12, the trough extends back west through Western Europe, clearing the heights out of Iberia, a decent cold signal developing by then, and at this range, not to be sniffed at. It’s a very well repeated core evolution of the models of the last few days. I’m looking forward to seeing if and how exactly something like it might transpire!

Exceptionally good agreement between the 12z ECM op and ensemble mean at day 10, even better with the day 9 mean as it happens! The heights anomaly chart for the day 10 op is interesting when put side by side with the T850s - due to the proximity of the low heights associated with the PV close to our northeast and generous pools of cold air to both our northwest and northeast, positive height anomalies even to the very north of Iberia do not prevent subzero T850s for all of the UK and Ireland and as cold as -4 to -8 away from the south. Even colder on the control, -4 to -8 for all of UK and Ireland off a similar heights profile… There is no doubt that heights to the south do impede the southward progress of Arctic air, and albeit that in this case the modelled incursion is relatively short-lived, these models (at least) suggest that it evidently might be a bit more nuanced than assuming that positive heights anomalies over Iberia prevent potentially wintry weather for much of the UK and Ireland.

There’s a clear trend in the 0z ECM ensemble mean towards a markedly colder week 2, a clearer trend than yesterday. Looking out for straight northerlies on the means is probably premature, but it’s good to see the surface westerlies and positive T850s at day 6… …being replaced by day 14 by surface northwesterlies with a fetch from Greenland, a cyclonic setup with a good deal of Arctic air in the mix, and subzero T850s throughout the UK and Ireland. It’s difficult to expect much more than this from the means if we’re looking for a credible movement in the models over the next couple of weeks away from a mild, zonal pattern to an increasingly colder one. A mean like that is probably blending out a good number of more direct solutions and occasional colder phases but looks to have a sensible core theme, as it does a believable job of tracking the steady movement of the trough from Newfoundland to Scandinavia between days 6 and 14, the animation sliced here in between the 0z EPS for those days - - all suggesting a gradual transition in air mass through the period from tropical maritime to polar maritime to what we’re increasingly seeing in the ops in the form of regular incursions that are more earnestly Arctic.

6z GEFS shows the Atlantic jet stream splitting around the sinking high pressure at day 10, as it dives southeast through the UK and Ireland into Europe to define the southern flank of the developing Scandinavian trough. The setup is an enduring one - the day 14 heights and anomalies shows a maintained northwest-southeast alignment of the heights contours through Western Europe, the area sandwiched between low heights to the northeast, part of a broad trough extending south into Central Europe, and positive heights to the northwest, extending up into southern Greenland. It’s looking like a mean northwesterly flow and fairly cold by that stage, with the 552 dam line running through the far southwest. This is a very sound basis from which to move forward to the 12z’s.

0z ECM nails it from my perspective, day 1-15 animations for the control (in effect the op past day 10) and mean. The main PV moving east out of Canada / Greenland to Scandinavia during the next week, before regathering and drawing a proportion of the Scandinavian lobe back west, on the op and reinforced by the mean. Chances for a northerly blast for a few days around day 10 before the pattern flattens again, except with the jet stream markedly further south, the flow is by then zonal but cold. The jet stream on the op and the mean T850s. It’s not deep cold but far from wall to wall mild either, the clear trend for colder air further and further south into week 2. It’s what the op is showing signs of doing at the end of the run is what is most eye-catching though. The regathering of the PV over Greenland is brief, the (by then) Siberian lobe is dominant, and successive systems are being passed from Greenland southeast to the base of the Siberian lobe. By the end of the run, the remnant limb of the PV over Greenland looks like it’s going to catch the same train, swing south east and reconsolidate the PV from Siberia through to Scandinavia, with very little PV left back out west. A system is working its way through Canada and the US and is looking to pump heights up into Greenland. Very interesting. A very long way off for now, but we’re getting close to the beginning of the initial very well telegraphed evolution with regard to the PV now, so for me, this is getting exciting - from a mild start, the models showing signs of being on the all go from here into a progressively colder February. Have a great day. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5025137

0z ECM nails it from my perspective, day 1-15 animations for the control (in effect the op past day 10) and mean. The main PV moving east out of Canada / Greenland to Scandinavia during the next week, before regathering and drawing a proportion of the Scandinavian lobe back west, on the op and reinforced by the mean. Chances for a northerly blast for a few days around day 10 before the pattern flattens again, except with the jet stream markedly further south, the flow is by then zonal but cold. The jet stream on the op and the mean T850s. It’s not deep cold but far from wall to wall mild either, the clear trend for colder air further and further south into week 2. It’s what the op is showing signs of doing at the end of the run is what is most eye-catching though. The regathering of the PV over Greenland is brief, the (by then) Siberian lobe is dominant, and successive systems are being passed from Greenland southeast to the base of the Siberian lobe. By the end of the run, the remnant limb of the PV over Greenland looks like it’s going to catch the same train, swing south east and reconsolidate the PV from Siberia through to Scandinavia, with very little PV left back out west. A system is working its way through Canada and the US and is looking to pump heights up into Greenland. Very interesting. A very long way off for now, but we’re getting close to the beginning of the initial very well telegraphed evolution with regard to the PV now, so for me, this is getting exciting - from a mild start, the models showing signs of being on the all go from here into a progressively colder February. Have a great day.

The EPS has been performing very well of late but it has tended to underestimate Atlantic heights past day 5, as well as the northward extent of the build of both Atlantic and European heights, while at the same time overestimating the relative heights over Iberia. First, the day 5 chart from the 21st 0z compared with the 0h chart from today’s 0z. Not much surprise, pretty much bang on. Happy days. Next, the day 10 chart from the 21st, compared with the day 5 chart from today, for the last day of January. Heights stronger than expected over the Atlantic and Eastern Europe. It didn’t pick up on such a firm development of that low pressure to the southwest of Portugal. Comparing the day 15 chart from the 21st with the day 10 chart from today, for the 5th of February. Again, an enhancement of the build of heights to the northwest in the more recent chart, as well as the adjustment of the Scandinavian trough a bit further east but markedly deeper. So looking at these charts, how they have been faring and adjusting, when we then look at today’s chart for day 15, taking on board the westward movement of the Scandinavian trough from day 10 and the possibility of a stronger northward build of heights through the Atlantic… …it’s evident that though there is little strongly indicative in the short term for those of us looking out for a bit more cold weather to round off the winter, there’s plenty to indicate that the next week or so of model-watching, looking forward to the week 2 period, may quite quickly become very interesting indeed.

I like the look of the 12z GEM op. It’s doing what we’re seeing a lot of the models do at the moment, in the splitting of the PV from Siberia through to Canada by day 3 or 4, the two lobes heading to the Bering Sea and Greenland, followed hot on its heels by the subsequent split of the Greenland lobe, with a chunk being imparted to the Barents Sea by day 5. It’s then it gets really interesting though, from day 5 to 10, the Greenland lobe becoming much depleted as it donates successive low pressure systems eastward through Iceland to the Norwegian Sea to phase with the spiralling eastern lobe now over Scandinavia, the path of each transferring low just a little bit further south, leaving the door open to a potential swipe to the UK and Ireland and an incursion from the north. The heights anomalies simplify the process beautifully, the European heights being drawn north through Scandinavia to the Arctic by day 6 or 7, followed by a brief attempt at establishing an Atlantic ridge edging into Iberia before those heights too are drawn north. While not bringing the prospect for now of a sustained cold spell, the machinations of the PV and the waves of northward transfer of these heights are producing a useful outcome in heralding the end of the period of high west to east mobility through the Atlantic and Europe. A really enjoyable run.

The devil will be in the detail as ever, but there is a consistent story emerging in the broad evolution in week 2, of a slow and steady fall in heights and pressure through Northern and Western Europe, the southwestward extent of which is important and to be firmed up over the coming days. From the 0z and 6z GFS mean (note the inter-run variability) and 0z ECM mean… 0z ECM ensembles for Birmingham and Madrid. The ECM can be hawkish with respect to letting go of heights, so a universal 12mb drop in pressure on the mean during the first few days of February is significant… …and particularly so in the context of those heights rises out west and the diminishing zonal flow - yesterday”s EC46 for 5-12 February, pressure and heights… Very clear in all these is the establishment of the trough in and around Scandinavia and northwest Russia, and in some runs this is setting up further west over Denmark like here on the 0z ECM control, with some cold air and good wintry potential entrained for the UK and Ireland… Though this doesn’t appear to have much scope for being deeply cold or long lasting, it is in keeping with the gaining trend by that stage for synoptics that are looking to actively entertain incursions from the northwest or north. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5024227

The devil will be in the detail as ever, but there is a consistent story emerging in the broad evolution in week 2, of a slow and steady fall in heights and pressure through Northern and Western Europe, the southwestward extent of which is important and to be firmed up over the coming days. From the 0z and 6z GFS mean (note the inter-run variability) and 0z ECM mean… 0z ECM ensembles for Birmingham and Madrid. The ECM can be hawkish with respect to letting go of heights, so a universal 12mb drop in pressure on the mean during the first few days of February is significant… …and particularly so in the context of those heights rises out west and the diminishing zonal flow - yesterday”s EC46 for 5-12 February, pressure and heights… Very clear in all these is the establishment of the trough in and around Scandinavia and northwest Russia, and in some runs this is setting up further west over Denmark like here on the 0z ECM control, with some cold air and good wintry potential entrained for the UK and Ireland… Though this doesn’t appear to have much scope for being deeply cold or long lasting, it is in keeping with the gaining trend by that stage for synoptics that are looking to actively entertain incursions from the northwest or north.

The ensemble means have been an outstandingly useful indicator this winter. As noted by @bluearmy last night, only in the run-up to Christmas, when they toyed with the northerly, that got put back and back and then didn’t happen, have they erred. They’re great, but not faultless. For example, they also have the characteristic of often not being able to extend a more decisive trend to days 12-15 due to the averaging out that is incident upon them by their nature. All in all though, I do find them consistently very informative up to date 12. So here are the 0z ECM ensemble means to day 12 for heights and pressure, and the T850s. Again, as with the GEFS yesterday, we see the PV getting torpedoed, but here we also see the subsequent setting up of the main lobe over northern Scandinavia and northwest Russia. Notice the Iberian heights steadily on the wane from day 9. Ideally, for a proper cold shot it would be good to see the trough settle in a tad further west, hanging south into Denmark, but no bones about it, this is a much better prospect now developing in week 2 than we’ve been looking at of late. The T850s past around day 7/8 are never that numerically informative but are useful for observing trend. The milder / colder zonal pattern that removes the cold air from Scandinavia through the coming week is itself replaced, over Scandinavia at least, by a good push back of the cold air from the northeast from around day 9 through to day 12. It looks to me that it’s from around there that it begins to get more interesting again in terms of potential wintry weather for northwest Europe. Cold air reinstalled to our northeast, along with a relaxation of the Iberian heights. It still looks changeable but incoming systems are going to have to negotiate interaction with the cold air. And the day to day adjustments are getting interesting too. The 0z EPS for day 12 from yesterday, compared with the 0z from today for day 11. Not only is the trough deeper and the low heights further south and west closer to the Finnish border, but the heights up through Greenland and to the west of Iceland are markedly better too. The cold to the northeast is gaining a foothold. It’s attritional, but bit by bit, the outlook is getting steadily more and more interesting. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5023690

The ensemble means have been an outstandingly useful indicator this winter. As noted by @bluearmy last night, only in the run-up to Christmas, when they toyed with the northerly, that got put back and back and then didn’t happen, have they erred. They’re great, but not faultless. For example, they also have the characteristic of often not being able to extend a more decisive trend to days 12-15 due to the averaging out that is incident upon them by their nature. All in all though, I do find them consistently very informative up to date 12. So here are the 0z ECM ensemble means to day 12 for heights and pressure, and the T850s. Again, as with the GEFS yesterday, we see the PV getting torpedoed, but here we also see the subsequent setting up of the main lobe over northern Scandinavia and northwest Russia. Notice the Iberian heights steadily on the wane from day 9. Ideally, for a proper cold shot it would be good to see the trough settle in a tad further west, hanging south into Denmark, but no bones about it, this is a much better prospect now developing in week 2 than we’ve been looking at of late. The T850s past around day 7/8 are never that numerically informative but are useful for observing trend. The milder / colder zonal pattern that removes the cold air from Scandinavia through the coming week is itself replaced, over Scandinavia at least, by a good push back of the cold air from the northeast from around day 9 through to day 12. It looks to me that it’s from around there that it begins to get more interesting again in terms of potential wintry weather for northwest Europe. Cold air reinstalled to our northeast, along with a relaxation of the Iberian heights. It still looks changeable but incoming systems are going to have to negotiate interaction with the cold air. And the day to day adjustments are getting interesting too. The 0z EPS for day 12 from yesterday, compared with the 0z from today for day 11. Not only is the trough deeper and the low heights further south and west closer to the Finnish border, but the heights up through Greenland and to the west of Iceland are markedly better too. The cold to the northeast is gaining a foothold. It’s attritional, but bit by bit, the outlook is getting steadily more and more interesting.

12z GEFS showing the main action going on over the pole, with an Arctic high currently forming through the Barents / Kara Seas slicing through the PV by day 6. The torpedoing of the vortex is captured nicely in the day 1-8 animation. I sit here in admiration, adding my own sound effects. Of potential importance to us down the line as it frees at least part of the Greenland lobe of the PV to wander eastward towards Scandinavia by day 10, pulling the flow around to north of west and giving the Iberian heights a bit of a nudge west. The first rudimentary signs perhaps of the pattern returning to one that might accommodate some colder options for the UK and Ireland.

That’s the clock tower at Garvey’s in Eyre Square, Galway… A bustling part of a lovely city - very fortunate to have avoided serious casualties there.

0z ECM ensemble mean at day 10. I wonder if there’s anyone out there on the Aleutian archipelago looking at that and saying “wow, day 10, a cross-polar flow all the way from the UK and Ireland”. The op showing a seriously lumpy PV, 4 separate lobes, with a Greenland wedge and Arctic high on the Siberian side. The wide ensemble spread throughout the Arctic superseded only by that over the UK and Ireland. The models are clearly struggling much more than usual with the PV. Contrast the current day 10 spread (left) with the equivalent day 10 spread chart from 10 days ago, when there was a pretty clear idea of the Greenland / Barents-Kara lumps being there or thereabouts for today and for the zonal setup through the North Atlantic into Northern Europe. This baseline of model uncertainty is what we’re seeing playing out in the inter-run variability of ops for week 2, like here with the 0z and 6z GFS ops. The modelling of the extent of Atlantic amplification very variable in what is by then the soft underbelly of the PV with the main action of the vortex being consistently removed to the Asian side. With the models struggling to pin the Arctic down, let alone the North Atlantic - Northern Europe sector, the pattern could become very different very quickly for any time from early week 2.

0z UKMO for the next 36 hours has the storm tracking slightly further south than yesterday’s runs. Gusts of 75mph or more possible pretty much anywhere up the western sides of the UK and Ireland late on Sunday into the early hours of Monday. A pocket of more violent winds, with gusts in excess of 90mph pushing across Ireland during this evening, up the Irish Sea into Cardigan Bay and northwest Wales before midnight, on to northwest England by the early hours of tomorrow, transferring to central Scotland in the hours leading up to dawn. Southsouthwesterly winds peaking as they veer more westerly, the strongest winds on the back edge of the front as it clears through. An exceptional storm because of the strength and duration of the winds across so many inland areas, could be very disruptive indeed. All accompanied by heavy, lashing rain, 3-4 inches of rain in for the high ground, parts of northwest Wales, northwest England, southern Scotland, but around 2 inches widely. Isha looks like it’s going to be one nasty Atlantic winter storm and well worth all the warnings. Batten down the hatches everyone, and be safe.

A confounding feature of this winter so far has been the extent of the tropospheric forcing and the spiritless stratosphere. It’s also been a winter of quite violent bursts of mobility followed by profound periods of stasis, typically signalled by an initial phase of retrogression. For the former, we have storm Isha and its followers for the coming week, and for the latter, it’s a waiting game. Out in week 2 with the 12z GEM ensemble mean what we’re really looking at is a splitting of the southern European heights, one pulse north into Scandinavia, but it’s all very longitudinal and has little traction for an easterly due to the lack of a proper clear out from the south, and ultimately little staying power over Scandinavia. The other slightly later pulse of heights is west from the Mediterranean into the Atlantic, its passage assisting in scuppering any potential easterly flow through Western Europe, but ultimately this retrogression leads to the prospect of an Atlantic ridge. Notice that the heights in Europe are slowly falling away. Looking north, I like the look of the way the PV is being handled, drawn first north away from eastern Canada, then east along the north of Greenland to north of Svalbard. The jet stream responds by its exit from the eastern seaboard being pulled a long way south between day 8 and day 16 beginning to split around the forming Atlantic high, here on the 12z GEPS. Most of all I like this evolution as it’s the most reasonable roadmap that I’ve seen so far with good potential to lead to the destination mapped out by the CanSIPS and CFS monthly anomalies (run dates Dec 31st and Jan 15th respectively) for February… …both with the European low anomaly, and strong heights to the west or northwest, and much scope to deliver a highly seasonal month. Despite the wait, plenty of opportunity for interesting developments to emerge along these lines (and potentially no doubt many others too!) in the next couple of weeks, as we move towards what could be a fascinating February. Original post: https://community.netweather.tv/topic/99793-model-output-discussion-cold-spell-ending-what-next/?do=findComment&comment=5019294