Model Output Discussion - Colder but how cold and for how long?

[Marting]

3 minutes ago, Nick2373 said:

Through this period, the greatest likelihood is that high pressure will remain the more dominant influence on the weather, most likely centred somewhere to the northwest of the UK, with winds from the north or north-east perhaps more frequent than usual, with generally reduced amounts of precipitation. There is an increased chance, compared to normal of cold conditions along with the associated impacts from low temperatures. Even within a predominantly more settled pattern there is a still a chance that frontal systems could move in from the west or southwest at times, which while they would likely bring an interlude of slightly milder, more unsettled weather, for a time, this would also introduce a risk of snow and ice where it meets the colder air in place across the UK.

Updated: 15:00 (UTC) on Wed 10 Jan 2024

Yes i posted it early

 

Bizarrely they updated it at 12:30 but they haven't updated next week yet?

Just to note that this is yesterday s update, just with date changed for some reason. So expect another update this PM

[TSNWK]

13 minutes ago, Met4Cast said:

EXETER KEEP THE FAITH! 

Extended update via app, they see the block & hold holding on into February! 

Interesting they have updated the extended but the mid range starting Monday 15th is still yesterday's.  Never seen this before 

Maybe they need to take more time with details after the overnights but for now continue with broadbrush on the long range 

[Met4Cast]

Unfortunately the GFS 06z det really goes off on one in the extended!

[Norrance]

Remember that there is a thread for Met and BBC forecasts etc. Plese use it or posts will go missing.

Ta.

[Ice Day]

The full set of GEFS are out and they're absolutely excellent.

Majority cold out to day 11

 

[northwestsnow]

Just now, Ice Day said:

The full set of GEFS are out and they're absolutely excellent.

Majority cold out to day 11

 

Looks fab just the small matter of do we trust GEFS  

[Ali1977]

2 minutes ago, Met4Cast said:

Unfortunately the GFS 06z det really goes off on one in the extended!

I’d be ignoring the op if it was heading warn, however as it’s heading cold I think it’ll be correct either way the ens look very cold from Sunday to Friday - which in itself would be great with any snow cover!! 

[Speedbird]

3 minutes ago, Met4Cast said:

Unfortunately the GFS 06z det really goes off on one in the extended!

a new trend

[MJB]

4 minutes ago, Marting said:

Just to note that this is yesterday s update, just with date changed for some reason. So expect another update this PM

No, not really, the wording in the extended extended can stay the same for at least a couple of days, I would imagine the trickier period is the mid term

[Ice Day]

Just now, northwestsnow said:

Looks fab just the small matter of do we trust GEFS  

Oh, definitely we do 

 

[Rain All Night]

I think I need some GIFs to get my head around this morning...

Deterministic runs (to day 7, Wed 17th)

Ensemble means (to day 10, Sat 20th)

850hPa temps for Dorset (to day 8, Thu 18th)

ECM 0z

UKMO 0z

GFS 6z

Wind roses for Dorset (to Tue 23rd)

ECM 0z

GFS 6z

GEM 0z

Edited January 10 by RainAllNight

[Jason M]

6 minutes ago, Met4Cast said:

Unfortunately the GFS 06z det really goes off on one in the extended!

Many of the GEFS raise heights over Iberia towards the back end. That's a death sentence for cold weather.

Way to far out to worry about though!!!

 

[Chrisover93]

16 minutes ago, Met4Cast said:

Unfortunately the GFS 06z det really goes off on one in the extended!

literally 

[Bricriu]

13 minutes ago, Jason M said:

Many of the GEFS raise heights over Iberia towards the back end. That's a death sentence for cold weather.

Way to far out to worry about though!!!

 

It looks like a lot of ensembles are trending the wrong way in fi contrary to the op runs. It's a long way out anyway to worry about it. Also there is a chance they could change to extending the cold. As long as the UKMO update remains bullish about the long range I am happy enough.

[Mcconnor8]

2 minutes ago, Bricriu said:

It looks like a lot of ensembles are trending the wrong way in fi contrary to the op runs. It's a long way out anyway to worry about it. Also there is a chance they could change to extending the cold. As long as the UKMO update remains bullish about the long range I am happy enough.

Short-Mid range ensembles are WAY better though which are far more important than what is going on in hours 300+, also subtle changes in the ECM 06z compared to the 0z towards the GFS 06z output, brings the Northerly in earlier on the 14th and weaker Azores low aiding amplification.

Edited January 10 by Mcconnor8

[Andy8472]

Not like we already didn't know but it's a bit wet over the uk until the summer drought hits 

[Battleground Snow]

Looks like it's trending back to a more robust block in the earlier timeframe after a little wobble overnight, results in the cold air getting further south faster.

06z ecm 

[A.J]

The GFS is crap

The GFS is great

It's a terrible model

Its the best model

It cant handle background signals

it's got a real handle on the background signals

 

Holy smokes, if I were the GFS watching this thread, I have to book in for a full frontal lobotomy as I've gone stark staring mad with all the bi-polar comments ! 

 

either ways, all models are firming up on cold & snow for some in the UK, bring it on !

[Bricriu]

6 minutes ago, Mcconnor8 said:

Short-Mid range ensembles are WAY better though which are far more important than what is going on in hours 300+, also subtle changes in the ECM 06z compared to the 0z towards the GFS 06z output, brings the Northerly in earlier on the 14th and weaker Azores low aiding amplification.

So it would seem the GFS has led the way on this as lrd said. You are right about the ensembles longer term,if the op runs remain consistent it could be the ensembles change. I know it's usually the other way around though.

[TSNWK]

4 minutes ago, Battleground Snow said:

Looks like it's trending back to a more robust block in the earlier timeframe after a little wobble overnight, results in the cold air getting further south faster.

06z ecm 

Every little helps.. the 06z control at 144 when it comes out about 2 will share a little more as well

[Tamara]

Bom dia e todos

I make no apologies for yet again re-pasting this sequence originally posted just prior to New Year, because it has become an even more focused roadmap. Not just for the upcoming 10 day period, but indeed confidence increasing as a blue-print for well into the second half of the winter:

....................................................................................................................................................................................

With the Nino attractor phases fully engaged, the amount of westerlies propagated into the atmospheric circulation between tropics & extra tropics do, as you suggest, indicate a higher floor to the angular momentum budget in the 'lull' ahead of the next upswing as the MJO traverses the tropics during January. GWO Phase 4 is a good medium base floor level I would think.

If we were to take a diagnostic template of GWO Phase 4 (and account for a likely return shallow orbit through phases 0,8 & back to 4) during an intermediate 'lull', then that very intermediate lull phase you describe will likely feature the return of a flat upper flow extending towards Europe.

The difference to recently though with the Atlantic forcing will be the jet suppressed further south - and with a cold pool established then attritional forcing of lows against the blocking likely to be a feature. (This accounts for some of the thinking as expressed within my previous posts in respect of the sub tropical jet)

With a cold pool established, any erosion from the south/west into NW Europe is likely to be attritional and not likely to displace cold pooling totally.

Taking into account we are still now in the lag period for the effect of +ve momentum from FT/MT mechanisms c/o the recent tropical>extra tropical cycle, we are seeing the new convective signal come into the Indian Ocean. Sea temp anomalies are supportive of deep thunderstorm convection. This, allied to convection in the western Pacific, will generate further mean zonal west wind anomalies to propagate across the tropics into the sub-tropics. With the westerly wind additions generated in December still in the atmospheric circulation, total and relative angular momentum will increase sending the GWO back into a (potential high amplitude) phase 5 orbit.

This progression & evolution suggests a strong -ve NAO with positive height anomalies shuffling between Greenland > Iceland and Scandinavia. Meantime southern Europe wet & mild under the sub tropical jetstream.

Muito obrigada. Melhores Cumprimentos

......................................................................................

To update the template of this analysis:

A very starkly high octane angular momentum budget is emerging and prolific within the global-wind-flow budgets. This translates to stockpile ammunition supply levels for deeply sustained poleward amplification eddies taking on veritable tanker sized reserves.

Based on how much tropospheric led influence there has been on the NH pattern in recent weeks since the starting pistol was fired to destabilise the polar profile, these further poleward swathes of +ve momentum transport take on especially egregiously gargantuan proportions for future wholesale instability and implosion across the polar field. In this respect it is not hard to comprehend the latest sentiments of Amy Butler and how she sees the synoptic pattern imprinted

The copied post referred to a baseline phase landing place for the Global Wind Oscillation. This baseline, ahead of the strongest wind-additions yet c/o eastward progressing high amplitude MJO wave back to the Pacific has remained higher than intermediate phase 4 (as discussed in the copied post)

The latest GWO phasing, even under present lull stopgap at very low amplitude 5/6, reflects the remaining considerably high levels of +AAM anomalies within the atmospheric circulation as aggregate total AAM. (Phase 4 GWO would be more suggestive of flatter return of the jet and greater attrition from the Atlantic against blocking. (Though even this sharpens somewhat against late Jan/early Feb wavelengths)

This GSDM wind flow budget situation is significant. More on this shortly.

The GWO is a phase plot depiction of aggregate wind-flow within both the tropics (MJO related) and the extra tropics as a measure of how efficiently propagation of wind-flow is proceeding between the tropics & extra tropics. This matters, because it is a barometer for synoptic pattern (poleward) amplification potential and provides a diagnostic towards directional flux of wind-flow eddies.

Poleward flux has now become quite supercharged

What of the significance of this?

As the intraseasonally driven MJO crosses the Maritimes at high amplitude, then very strong +ve torque mechanisms will be re-engaged to over top a system already awash with +AAM anomalies. The GWO likely to drill upwards into very high amplitude Phase 5/6. Taking into account maximum winter wavelengths, then this teleconnects ever more strongly to entrenched -ve NAO (under chaotic stratospheric diminution to spotweld a deeply -ve Annular Mode).

How can this be visualised?

The upcoming next cascade of westerly wind burst propagation into the extra tropics creates white water rafting within the sub tropical jet from the Equatorial Pacific downstream to the Atlantic -at the same time as the polar profile becomes riven with -ve mean zonal -ve wind anomalies. Defining solid roadblocks for southward directive of a deeply unstable thermal boundary.

How can this in turn be visualised?

With deeper upper cold air ensconced north of the polar boundary, this leads to feedbacks of entrenched surface cold with time to feed an ever starker thermal boundary, This encourages and emboldens larger progressions of numbers of kayaks slipstreaming below it. This translates to trains of low pressure undercuts - and it is not difficult to envisage the potential for high impact weather events to unfold in such a scenario. 

The kayak posse delivers an "atmospheric river" of saturated sub tropical air and a large jump of temperature into the upper teens for my part of the world well below the thermal boundary at the same time as in contrast...

.... that is better left to the mercurial imaginations of any members who might be looking in from NW Europe.

Putting all this diagnostic analysis together, it is hard to see anything other than a tanked -ve Annular Mode relationship dominating much of the rest of the winter. However, and as ever, further analysis is wholly prudent to document how proceedings unfold.

Muito obrigada. Feliz quarta-feira

 

 

 

[sheikhy]

Ecm 06z looking juicy at just 90 hours!better block and colder air further south!!!

[Mcconnor8]

6 minutes ago, Tamara said:

Bom dia e todos

I make no apologies for yet again re-pasting this sequence originally posted just prior to New Year, because it has become an even more focused roadmap. Not just for the upcoming 10 day period, but indeed confidence increasing as a blue-print for well into the second half of the winter:

....................................................................................................................................................................................

With the Nino attractor phases fully engaged, the amount of westerlies propagated into the atmospheric circulation between tropics & extra tropics do, as you suggest, indicate a higher floor to the angular momentum budget in the 'lull' ahead of the next upswing as the MJO traverses the tropics during January. GWO Phase 4 is a good medium base floor level I would think.

If we were to take a diagnostic template of GWO Phase 4 (and account for a likely return shallow orbit through phases 0,8 & back to 4) during an intermediate 'lull', then that very intermediate lull phase you describe will likely feature the return of a flat upper flow extending towards Europe.

The difference to recently though with the Atlantic forcing will be the jet suppressed further south - and with a cold pool established then attritional forcing of lows against the blocking likely to be a feature. (This accounts for some of the thinking as expressed within my previous posts in respect of the sub tropical jet)

With a cold pool established, any erosion from the south/west into NW Europe is likely to be attritional and not likely to displace cold pooling totally.

Taking into account we are still now in the lag period for the effect of +ve momentum from FT/MT mechanisms c/o the recent tropical>extra tropical cycle, we are seeing the new convective signal come into the Indian Ocean. Sea temp anomalies are supportive of deep thunderstorm convection. This, allied to convection in the western Pacific, will generate further mean zonal west wind anomalies to propagate across the tropics into the sub-tropics. With the westerly wind additions generated in December still in the atmospheric circulation, total and relative angular momentum will increase sending the GWO back into a (potential high amplitude) phase 5 orbit.

This progression & evolution suggests a strong -ve NAO with positive height anomalies shuffling between Greenland > Iceland and Scandinavia. Meantime southern Europe wet & mild under the sub tropical jetstream.

Muito obrigada. Melhores Cumprimentos

......................................................................................

To update the template of this analysis:

A very starkly high octane angular momentum budget is emerging and prolific within the global-wind-flow budgets. This translates to stockpile ammunition supply levels for deeply sustained poleward amplification eddies taking on veritable tanker sized reserves.

Based on how much tropospheric led influence there has been on the NH pattern in recent weeks since the starting pistol was fired to destabilise the polar profile, these further poleward swathes of +ve momentum transport take on especially egregiously gargantuan proportions for future wholesale instability and implosion across the polar field. In this respect it is not hard to comprehend the latest sentiments of Amy Butler and how she sees the synoptic pattern imprinted

The copied post referred to a baseline phase landing place for the Global Wind Oscillation. This baseline, ahead of the strongest wind-additions yet c/o eastward progressing high amplitude MJO wave back to the Pacific has remained higher than intermediate phase 4 (as discussed in the copied post)

The latest GWO phasing, even under present lull stopgap at very low amplitude 5/6, reflects the remaining considerably high levels of +AAM anomalies within the atmospheric circulation as aggregate total AAM. (Phase 4 GWO would be more suggestive of flatter return of the jet and greater attrition from the Atlantic against blocking. (Though even this sharpens somewhat against late Jan/early Feb wavelengths)

This GSDM wind flow budget situation is significant. More on this shortly.

The GWO is a phase plot depiction of aggregate wind-flow within both the tropics (MJO related) and the extra tropics as a measure of how efficiently propagation of wind-flow is proceeding between the tropics & extra tropics. This matters, because it is a barometer for synoptic pattern (poleward) amplification potential and provides a diagnostic towards directional flux of wind-flow eddies.

Poleward flux has now become quite supercharged

What of the significance of this?

As the intraseasonally driven MJO crosses the Maritimes at high amplitude, then very strong +ve torque mechanisms will be re-engaged to over top a system already awash with +AAM anomalies. The GWO likely to drill upwards into very high amplitude Phase 5/6. Taking into account maximum winter wavelengths, then this teleconnects ever more strongly to entrenched -ve NAO (under chaotic stratospheric diminution to spotweld a deeply -ve Annular Mode).

How can this be visualised?

The upcoming next cascade of westerly wind burst propagation into the extra tropics creates white water rafting within the sub tropical jet from the Equatorial Pacific downstream to the Atlantic -at the same time as the polar profile becomes riven with -ve mean zonal -ve wind anomalies. Defining solid roadblocks for southward directive of a deeply unstable thermal boundary.

How can this in turn be visualised?

With deeper upper cold air ensconced north of the polar boundary, this leads to feedbacks of entrenched surface cold with time to feed an ever starker thermal boundary, This encourages and emboldens larger progressions of numbers of kayaks slipstreaming below it. This translates to trains of low pressure undercuts - and it is not difficult to envisage the potential for high impact weather events to unfold in such a scenario. 

The kayak posse delivers an "atmospheric river" of saturated sub tropical air and a large jump of temperature into the upper teens for my part of the world well below the thermal boundary at the same time as in contrast...

.... that is better left to the mercurial imaginations of any members who might be looking in from NW Europe.

Putting all this diagnostic analysis together, it is hard to see anything other than a tanked -ve Annular Mode relationship dominating much of the rest of the winter. However, and as ever, further analysis is wholly prudent to document how proceedings unfold.

Muito obrigada. Feliz quarta-feira

 

 

 

A proper Ramp  Thanks a lot for the detailed and clear explanations!

[nick sussex]

The GFS 06 hrs run increases the margin for error as it takes the shortwave to the nw se and away from the Atlantic low .

Be interesting to see what the latest 06 hrs ECM control run does when it comes out .

The JMA 06 hrs run removes the high over France and looks like a nice clean evolution at T132 hrs . 

Not a bad morning so much anticipation for this evenings outputs .

[Met4Cast]

11 minutes ago, Tamara said:

Bom dia e todos

I make no apologies for yet again re-pasting this sequence originally posted just prior to New Year, because it has become an even more focused roadmap. Not just for the upcoming 10 day period, but indeed confidence increasing as a blue-print for well into the second half of the winter:

....................................................................................................................................................................................

With the Nino attractor phases fully engaged, the amount of westerlies propagated into the atmospheric circulation between tropics & extra tropics do, as you suggest, indicate a higher floor to the angular momentum budget in the 'lull' ahead of the next upswing as the MJO traverses the tropics during January. GWO Phase 4 is a good medium base floor level I would think.

If we were to take a diagnostic template of GWO Phase 4 (and account for a likely return shallow orbit through phases 0,8 & back to 4) during an intermediate 'lull', then that very intermediate lull phase you describe will likely feature the return of a flat upper flow extending towards Europe.

The difference to recently though with the Atlantic forcing will be the jet suppressed further south - and with a cold pool established then attritional forcing of lows against the blocking likely to be a feature. (This accounts for some of the thinking as expressed within my previous posts in respect of the sub tropical jet)

With a cold pool established, any erosion from the south/west into NW Europe is likely to be attritional and not likely to displace cold pooling totally.

Taking into account we are still now in the lag period for the effect of +ve momentum from FT/MT mechanisms c/o the recent tropical>extra tropical cycle, we are seeing the new convective signal come into the Indian Ocean. Sea temp anomalies are supportive of deep thunderstorm convection. This, allied to convection in the western Pacific, will generate further mean zonal west wind anomalies to propagate across the tropics into the sub-tropics. With the westerly wind additions generated in December still in the atmospheric circulation, total and relative angular momentum will increase sending the GWO back into a (potential high amplitude) phase 5 orbit.

This progression & evolution suggests a strong -ve NAO with positive height anomalies shuffling between Greenland > Iceland and Scandinavia. Meantime southern Europe wet & mild under the sub tropical jetstream.

Muito obrigada. Melhores Cumprimentos

......................................................................................

To update the template of this analysis:

A very starkly high octane angular momentum budget is emerging and prolific within the global-wind-flow budgets. This translates to stockpile ammunition supply levels for deeply sustained poleward amplification eddies taking on veritable tanker sized reserves.

Based on how much tropospheric led influence there has been on the NH pattern in recent weeks since the starting pistol was fired to destabilise the polar profile, these further poleward swathes of +ve momentum transport take on especially egregiously gargantuan proportions for future wholesale instability and implosion across the polar field. In this respect it is not hard to comprehend the latest sentiments of Amy Butler and how she sees the synoptic pattern imprinted

The copied post referred to a baseline phase landing place for the Global Wind Oscillation. This baseline, ahead of the strongest wind-additions yet c/o eastward progressing high amplitude MJO wave back to the Pacific has remained higher than intermediate phase 4 (as discussed in the copied post)

The latest GWO phasing, even under present lull stopgap at very low amplitude 5/6, reflects the remaining considerably high levels of +AAM anomalies within the atmospheric circulation as aggregate total AAM. (Phase 4 GWO would be more suggestive of flatter return of the jet and greater attrition from the Atlantic against blocking. (Though even this sharpens somewhat against late Jan/early Feb wavelengths)

This GSDM wind flow budget situation is significant. More on this shortly.

The GWO is a phase plot depiction of aggregate wind-flow within both the tropics (MJO related) and the extra tropics as a measure of how efficiently propagation of wind-flow is proceeding between the tropics & extra tropics. This matters, because it is a barometer for synoptic pattern (poleward) amplification potential and provides a diagnostic towards directional flux of wind-flow eddies.

Poleward flux has now become quite supercharged

What of the significance of this?

As the intraseasonally driven MJO crosses the Maritimes at high amplitude, then very strong +ve torque mechanisms will be re-engaged to over top a system already awash with +AAM anomalies. The GWO likely to drill upwards into very high amplitude Phase 5/6. Taking into account maximum winter wavelengths, then this teleconnects ever more strongly to entrenched -ve NAO (under chaotic stratospheric diminution to spotweld a deeply -ve Annular Mode).

How can this be visualised?

The upcoming next cascade of westerly wind burst propagation into the extra tropics creates white water rafting within the sub tropical jet from the Equatorial Pacific downstream to the Atlantic -at the same time as the polar profile becomes riven with -ve mean zonal -ve wind anomalies. Defining solid roadblocks for southward directive of a deeply unstable thermal boundary.

How can this in turn be visualised?

With deeper upper cold air ensconced north of the polar boundary, this leads to feedbacks of entrenched surface cold with time to feed an ever starker thermal boundary, This encourages and emboldens larger progressions of numbers of kayaks slipstreaming below it. This translates to trains of low pressure undercuts - and it is not difficult to envisage the potential for high impact weather events to unfold in such a scenario. 

The kayak posse delivers an "atmospheric river" of saturated sub tropical air and a large jump of temperature into the upper teens for my part of the world well below the thermal boundary at the same time as in contrast...

.... that is better left to the mercurial imaginations of any members who might be looking in from NW Europe.

Putting all this diagnostic analysis together, it is hard to see anything other than a tanked -ve Annular Mode relationship dominating much of the rest of the winter. However, and as ever, further analysis is wholly prudent to document how proceedings unfold.

Muito obrigada. Feliz quarta-feira

 

 

 

Well.. 

Bloody hell. This is probably the strongest wording I've seen you use in terms of cold & significant winter weather impact potential for NW Europe. In essence, teleconnections remain solid for -NAO and -AO throughout the rest of winter with likely repeated periods of high latitude blocking. The next MJO cycle progresses eastwards will see a return to strong +FT & +MT driving total AAM tendency upwards once again from an already high established Nino (+AAM) base state. 

Myself and @Catacolhad noted that AAM tendency had bottomed out & returned to more neutral/positive values faster than anticipated, reading your post it seems you had expected a greater fall than observed too (GWO remaining above phase 4).

Thanks Tamara. As someone who is a lover of cold/snowy weather but also tries to remain balanced & unbiased in the context of the GSDM, for me, this is a very exciting update!!

Though of course, more regional (UK) based milage may vary, macro vs micro.

Edited January 10 by Met4Cast