[Model discussion highlights]

This has been the feature of the winter for me - the recurring Scandinavian trough. It hasn’t delivered wintry weather for all parts of the UK and Ireland equally, far from it, but it alone has been conspicuous in consistently delivering the right kind of air mass to our shores.

It’s been a winter where the modelling of heights into Scandinavia / easterly tease, though not transpiring, has proven to be a frequent prelude to the reassertion of the trough from the PV as it shuffles each time over from Canada to settle for lengthy periods on the Siberian side of the Arctic. 

If we look at the NH profile, we can see that it’s at it again! The signs were there last night on the GEFS, but now indeed, its arrival is being smartly expedited in the 0z ECM models. Yesterday’s 12z mean at 252h versus today’s 0z at 240h. 

 

All hail the arty rabbit looking thing - may your front legs grow long and maintain that southwestward orientation trend. 

Atlantic ridging and western Atlantic trough also a good deal further west, that push of heights into Greenland is outstanding for a day 10 mean, driving amplification for the trough but also serving to push the southwesterly flow well away and opening us up to the north. This is reflected in the mean T850’s too.

 

A big change in the models over just 12 hours.

There’s evidently still plenty of time for a meaningful cold spell. 

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5034848

[Model Output Discussion - Spring Has Sprung]

This has been the feature of the winter for me - the recurring Scandinavian trough. It hasn’t delivered wintry weather for all parts of the UK and Ireland equally, far from it, but it alone has been conspicuous in consistently delivering the right kind of air mass to our shores.

It’s been a winter where the modelling of heights into Scandinavia / easterly tease, though not transpiring, has proven to be a frequent prelude to the reassertion of the trough from the PV as it shuffles each time over from Canada to settle for lengthy periods on the Siberian side of the Arctic. 

If we look at the NH profile, we can see that it’s at it again! The signs were there last night on the GEFS, but now indeed, its arrival is being smartly expedited in the 0z ECM models. Yesterday’s 12z mean at 252h versus today’s 0z at 240h. 

 

All hail the arty rabbit looking thing - may your front legs grow long and maintain that southwestward orientation trend. 

Atlantic ridging and western Atlantic trough also a good deal further west, that push of heights into Greenland is outstanding for a day 10 mean, driving amplification for the trough but also serving to push the southwesterly flow well away and opening us up to the north. This is reflected in the mean T850’s too.

 

A big change in the models over just 12 hours.

There’s evidently still plenty of time for a meaningful cold spell. 

[Model Output Discussion - Spring Has Sprung]

If the 12z ECM’s nod towards a split PV at day 7/8 is taken at face value, the evolution from around that time shown in the 12z GEFS could well be of interest.

It’s much more definite in bringing the main PV action back to the Eurasian side from around mid month, here at days 8-14, developing a fresh Scandinavian trough that quite speedily reintroduces cold air, feeding steadily southwestwards through Northern Europe. 

 

That’s a very decent signal for a mean, even better if taken on the back of a prospective split. Looking forward to seeing the EPS later.

The models are definitely picking up on new signals today. Mid to late February still more than early enough to pack a punch in terms of winter interest, and for a good few weeks, before we properly turn the corner toward spring.

[Model discussion highlights]

Day 4 / 5 looking a bit chilly on the 0z ECM ensemble but otherwise above average temperatures for the foreseeable.

However, the very definite southerly track of the jet stream on the 0z ECM op - often heading into Iberia - would suggest that the mild outlook is a fairly precarious one. 

 

The day 10 mean anomaly gives the impression of being very blocked through the eastern Atlantic, good heights to the north and south but the heights through Western Europe are only marginally positive. The Atlantic trough will eventually try to head for the gap, but ironically looks that it will be blocked by the heights to the south.

   

0z EPS shows that the low is no longer being directed from Greenland, rather from a centre over Newfoundland, where the heights are lowest, all the while pumping heights north into Greenland and Iceland.

0z GEPS sends a ridge up through Iceland into Greenland at day 12, with a surface high over the Greenland plateau and a notable polar high.

Along with low pressure over the Barents Sea, this is feeding a cold northerly flow down into the Norwegian Sea. That is how we can get cold air back into Europe. The 0z ECM control is at something similar. Don’t worry about modelled uppers at this range, a path to insanity.

  

The Atlantic low can’t go north and is being blocked from disrupting southeast into Spain, so just stalls over the Atlantic, leaving the UK and Ireland at the southern edge of an Arctic block with easterlies or northerlies an option from there. 

The resilience of the southerly running jet stream and looking out for the Atlantic low to eventually pump enough heights north are the main aspects to watch here.

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5033825

[Model Output Discussion - Spring Has Sprung]

Day 4 / 5 looking a bit chilly on the 0z ECM ensemble but otherwise above average temperatures for the foreseeable.

However, the very definite southerly track of the jet stream on the 0z ECM op - often heading into Iberia - would suggest that the mild outlook is a fairly precarious one. 

 

The day 10 mean anomaly gives the impression of being very blocked through the eastern Atlantic, good heights to the north and south but the heights through Western Europe are only marginally positive. The Atlantic trough will eventually try to head for the gap, but ironically looks that it will be blocked by the heights to the south.

   

0z EPS shows that the low is no longer being directed from Greenland, rather from a centre over Newfoundland, where the heights are lowest, all the while pumping heights north into Greenland and Iceland.

0z GEPS sends a ridge up through Iceland into Greenland at day 12, with a surface high over the Greenland plateau and a notable polar high.

Along with low pressure over the Barents Sea, this is feeding a cold northerly flow down into the Norwegian Sea. That is how we can get cold air back into Europe. The 0z ECM control is at something similar. Don’t worry about modelled uppers at this range, a path to insanity.

  

The Atlantic low can’t go north and is being blocked from disrupting southeast into Spain, so just stalls over the Atlantic, leaving the UK and Ireland at the southern edge of an Arctic block with easterlies or northerlies an option from there. 

The resilience of the southerly running jet stream and looking out for the Atlantic low to eventually pump enough heights north are the main aspects to watch here.

[Model Output Discussion - Spring Has Sprung]

If not so much the charts themselves, I’ve been enjoying the discussion about the heights being too far north.

However, looking at the EPS charts for a week ago for day 9, and comparing with today’s 0z for day 2, particularly focusing on western Greenland, it’s more of a case of a complete reversal of predicted positive height anomalies to negative ones in that part of the world that is critical to the prospects for northwest Europe, contours of 520’s dam incrementally replaced during the last week by lower and lower heights, now 492 dam. 

 

It’s the unexpected depth of those low heights in that position around Greenland that has allowed the low to the south to be recruited and orientated north by the Greenland low - it’s not the heights anomaly that matters here, it’s the heights themselves.

A few days ago, I wrote that it looked like around 3 days in the cold air before the Atlantic had another go. That was based in part on having seen a succession of charts showing 501 dam heights up around Greenland, low heights and a trough through the UK and Ireland, like here from a week ago at day 12. Interestingly, when compared with today’s 0z chart for day 5, it’s still only around 501 dam, but is further east so has been able to link up with the UK / Ireland low. Notice as well though that the heights to our north, over the Norwegian Sea, are being underestimated. 

 

Looking ahead to day 8, there is ridging north through the UK and Ireland up into that region, the jet stream is strong only over the western Atlantic, and is on a southern track before splitting mid-ocean. No Atlantic onslaught in the offing and there is notable spread at day 8 over the Norwegian Sea so the build in heights there might be even more substantial.

   

The pressure anomalies show it nicely - it’s only going to take a bit more of a build into that zone to our north, the northwest Russia high drifts west and that Atlantic low is likely going under, with the low pressure over the eastern Mediterranean to help pull it through. 

Writing off the rest of a month in any particular direction before we’re out of the first week of it is not sensible when the balance is so fine and the scope so plausible. I’m actually looking forward to the next few weeks.

[Model Output Discussion - Spring Has Sprung]

Here’s the ECM Thursday snow chance demise in all its gory detail, for all to see.

Yesterday’s 12z ensemble mean at 96h vs. today’s at 72h, heights / pressure 

 

and T850s.

 

Exactly, neither can I - unless it’s that version of the demise where the colder T850s are now modelled further south in what is turning into one heck of a battle zone, with much of the detail far from being resolved. 

[Model discussion highlights]

What a great Sunday morning to be up early looking at the charts! Especially when there’s such interesting ones on show, even now for the end of the same week.

0z EPS day 6 is a cracker of a surprise with the low pressure tracking to the south of Ireland through Wales and southern England, many of us kept on the cold side, or quickly brought back into it in the wrap. Just a point about how low the heights are - this is a mean, probably the best mean we have, showing 525 dam heights    to the southwest and through southeast England at day 6. There could well be a lot of surprises in store with this one.

 

Thereafter, by day 8, we have the centre of the low heading into Europe but with a meaty bit of troughing hanging back through the southern UK, with some properly cold air entrained in the northeasterly flow of the departing low. 

 

The icing on the breakfast cake for me this morning though is how quickly and solidly the high pressure builds in from the west by day 10, a surface high extending from the UK and Ireland northeast to Scandinavia. 

 

This puts one of the best types of prospect on the table - some snow on the ground, with a high pressure quickly established to trap in the surface cold over the snow. Potential for a good winter spell.

At this stage, we’re still very much defining and re-measuring the envelope. But it’s actually now surprisingly a bigger envelope than yesterday, with many more of our addresses being considered for being written on the front. Mornings like this are what makes this hobby so enjoyable. 

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5029260

[Model Output Discussion - Spring Has Sprung]

What a great Sunday morning to be up early looking at the charts! Especially when there’s such interesting ones on show, even now for the end of the same week.

0z EPS day 6 is a cracker of a surprise with the low pressure tracking to the south of Ireland through Wales and southern England, many of us kept on the cold side, or quickly brought back into it in the wrap. Just a point about how low the heights are - this is a mean, probably the best mean we have, showing 525 dam heights    to the southwest and through southeast England at day 6. There could well be a lot of surprises in store with this one.

 

Thereafter, by day 8, we have the centre of the low heading into Europe but with a meaty bit of troughing hanging back through the southern UK, with some properly cold air entrained in the northeasterly flow of the departing low. 

 

The icing on the breakfast cake for me this morning though is how quickly and solidly the high pressure builds in from the west by day 10, a surface high extending from the UK and Ireland northeast to Scandinavia. 

 

This puts one of the best types of prospect on the table - some snow on the ground, with a high pressure quickly established to trap in the surface cold over the snow. Potential for a good winter spell.

At this stage, we’re still very much defining and re-measuring the envelope. But it’s actually now surprisingly a bigger envelope than yesterday, with many more of our addresses being considered for being written on the front. Mornings like this are what makes this hobby so enjoyable. 

[Model discussion highlights]

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

[Model Output Discussion - Spring Has Sprung]

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. 

[Model Output Discussion - Spring Has Sprung]

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.

[Model discussion highlights]

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

[Model Output Discussion - Spring Has Sprung]

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…

[Model Output Discussion - Spring Has Sprung]

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.

[Model Output Discussion - Spring Has Sprung]

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. 

[Model discussion highlights]

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

[Model Output Discussion - Spring Has Sprung]

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!

[Model Output Discussion - Spring Has Sprung]

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. 

[Model Output Discussion - Spring Has Sprung]

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. 

[Model Output Discussion - Spring Has Sprung]

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. 

[Model discussion highlights]

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

[Model Output Discussion - Spring Has Sprung]

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.

[Model Output Discussion - Spring Has Sprung]

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. 

[Model Output Discussion - Spring Has Sprung]

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.