Model output discussion 9th April onwards

[Tamara]

 

17 hours ago, Singularity said:

There has been an enormous negative spike to the global sum of mountain torques, which is why AAM has dropped so much. This is the extratropical influence on AAM - but it's not what leads the overall direction of travel. For that, we have to look at the tropics and frictional torques. Those have also been negative but are now heading back toward neutral, a sign that the tropical cycle is ready to move on an start to shift AAM upward.

Despite this, such a big -MT does ease the door open for the scenario that ECM keeps jumping onto and off from, as an Atlantic trough briefly gets shunted in the direction of the UK.

If the cut-off low is still hanging around close enough to our shores, then that low has a shot at moving close enough to interact with it and keep the polar jet across the UK, in which case we'll be having to wait for AAM recovery to lift that trough out and allow the Scandinavian high regime to set up shop (most likely via an Azores high extension then breakaway), some 5-7 days later than was being advertised at longer lead times.

On the other hand, if the cut-off low is far enough east, the door will be shut and the trough is unlikely to make it to us before it stalls out (as the knock-on effects of the huge -MT subside). Without much to move that trough on, a good run of fine, warm weather could result, before the likely destabilisation, possibly via a substantial heat spike akin to what the ECM 12z of yesterday explored.

 

If you'd like a reason to be hopeful, consider what the ECM runs of a few days ago were predicting the cut-off low to get up to this week: Loitering in the Channel until Friday, even into the weekend. Now, that low is set to be clear of us by Wednesday afternoon!

A repeat performance would leave plenty of room for a GFS 06z style 'wall of high pressure' outcome.

A poorer read in here in general than NWP (allegedly) is, but this is another good post from @Singularityand more accurately and specifically pinpoints short term diagnostic departures in momentum tendency c/o extra tropical scrubbing of westerly inertia (based on a natural lull phase in the mini ENSO cycle) - vs the longer term outlook which will continue to be guided by limited sustained mechanisms to perpetuate a low angular momentum regime - such as I have tried to describe in two previous posts. The latter is obscured by overstating and over extrapolation of the former.

RMM high frequency tropical convection plots are equally poor at depicting amplitude of forward momentum beyond about 4/5 days, but during the first 10 days of July the next wave is due to progress eastwards from the Indian Ocean through to the Maritime continent - and then onwards into the Pacific.  There is natural means based on SST arrangements for tropical convergence and deep thunderstorm development to interact with trade winds and reverse momentum tendency in the extra tropics 

This is likely to further spook the numerical modelling as the pendulum of momentum snaps back. Therefore, NWP is heading down a potential cul de sac if it is overly scrambled by short term negative torque impacts in the extra tropics which have a periodicity of a number of days before evolution in the tropics cuts through the noise and forward momentum returns to jolt the pattern. Its worth re-stating once more in this respect that GSDM diagnostic is over simplified by x+y = *insert singular outcome* limited character soundbites via twitter - and which may be overly influenced by bias confirmation processes. Its true purpose is to give an insight into probabilistic ranges of outcomes -  also to give guidance to wavelength (timespans) of these changes and to see where NWP might become overly blindsided by a strong, but time limited signal. Like shoals of fish in midstream they are so often caused to change direction and why it is so bemusing to see so many observers the other other side of the ocean glass slavishly mirror this fickle midstream mentality.

 I am ambivalent of the UK outcome based on my new location, but for what little it is worth despite a natural scepticism towards all numerical model products it is still well worth looking closely at individual members in the GEM suite which rarely gets any attention - as there is a smorgasbord of solutions including quite a few that echo the theme of the ECM operational of today and which have much greater importance of possibilities to the UK than here in the Iberian continent where the outlook is much more assured..  

The lemming mentality to each and every operational output will no doubt continue, but I would continue to believe that the present -ve inertia is a means to re-set the trough in the Atlantic and then as high frequency tropical signal heads eastwards once more, the signal will increase to re-build (or simply just to re-intensify) a downstream ridge with potential for the heat advection processes spoken of previously interplaying with less progressive troughing in the Atlantic. Such heat intensifying processes continuing in earnest down here over the coming week.

 

[mb018538]

42 minutes ago, Tamara said:

 

A poorer read in here in general than NWP (allegedly) is, but this is another good post from @Singularityand more accurately and specifically pinpoints short term diagnostic departures in momentum tendency c/o extra tropical scrubbing of westerly inertia (based on a natural lull phase in the mini ENSO cycle) - vs the longer term outlook which will continue to be guided by limited sustained mechanisms to perpetuate a low angular momentum regime - such as I have tried to describe in two previous posts. The latter is obscured by overstating and over extrapolation of the former.

RMM high frequency tropical convection plots are equally poor at depicting amplitude of forward momentum beyond about 4/5 days, but during the first 10 days of July the next wave is due to progress eastwards from the Indian Ocean through to the Maritime continent - and then onwards into the Pacific.  There is natural means based on SST arrangements for tropical convergence and deep thunderstorm development to interact with trade winds and reverse momentum tendency in the extra tropics 

This is likely to further spook the numerical modelling as the pendulum of momentum snaps back. Therefore, NWP is heading down a potential cul de sac if it is overly scrambled by short term negative torque impacts in the extra tropics which have a periodicity of a number of days before evolution in the tropics cuts through the noise and forward momentum returns to jolt the pattern. Its worth re-stating once more in this respect that GSDM diagnostic is over simplified by x+y = *insert singular outcome* limited character soundbites via twitter - and which may be overly influenced by bias confirmation processes. Its true purpose is to give an insight into probabilistic ranges of outcomes -  also to give guidance to wavelength (timespans) of these changes and to see where NWP might become overly blindsided by a strong, but time limited signal. Like shoals of fish in midstream they are so often caused to change direction and why it is so bemusing to see so many observers the other other side of the ocean glass slavishly mirror this fickle midstream mentality.

 I am ambivalent of the UK outcome based on my new location, but for what little it is worth despite a natural scepticism towards all numerical model products it is still well worth looking closely at individual members in the GEM suite which rarely gets any attention - as there is a smorgasbord of solutions including quite a few that echo the theme of the ECM operational of today and which have much greater importance of possibilities to the UK than here in the Iberian continent where the outlook is much more assured..  

The lemming mentality to each and every operational output will no doubt continue, but I would continue to believe that the present -ve inertia is a means to re-set the trough in the Atlantic and then as high frequency tropical signal heads eastwards once more, the signal will increase to re-build (or simply just to re-intensify) a downstream ridge with potential for the heat advection processes spoken of previously interplaying with less progressive troughing in the Atlantic. Such heat intensifying processes continuing in earnest down here over the coming week.

 

Thanks @Tamara as ever for your detailed analysis.

At least in Portugal you know you'll get a decent summer 

For us here in Blighty, it hangs in the balance as you say. Perhaps the Met Office long ranger below hints slightly at what you've mentioned (highlighted) Re ECM/GEM ens, with a bit more ridging poking it's nose in than some of the washout runs we've seen. Time will tell.

 

Saturday 3 Jul - Monday 12 Jul

A chilly night in places leading into a warm Saturday, especially across the east. Unsettled conditions spreading from the southwest, signifying the change to more unsettled conditions. Sunshine and showers ahead of this band of cloud and rain, with the risk of sharp and thundery showers in southern and western areas later. Beyond the weekend, although confidence becomes lower, there is most likely to be a split between the southwest and northeast, with southern and western parts seeing some showers, and perhaps longer spells of rain, whilst the best of any dry weather remains across the north and east. Temperatures are likely to trend above normal, notably across some parts of the northeast. Winds remaining light to moderate for most, though possibly strong in the west at times.

[mushymanrob]

Well IF these charts are correct then the troughing is expected to remain to our near West, resulting in the conditions @Singularity mentioned above.

 

[MATTWOLVES 3]

3 hours ago, Ed Stone said:

Everything looks kind of 'normal', for July, to me . . . To early in the proceedings for hyperventilation, methinks? 

I keep telling Alderc and Co they need a good paper bag on hand everytime they view the daily operational output I think Tams recent post hits the nail on the head as well regarding knee jerk reactions to every op run, Singularity also putting out a very insightful post. I'm not  completely convinced about these recent model outputs either...far to much chopping and changing going on. In the shorter term it looks like an improvement over the next few days so that's a positive! Come the Weekend gradually more unsettled conditions spreading in from the SW! How long this will last im not so sure...perhaps towards the 2nd week of July a more thorough improvement will begin to take place. 

Still plenty of time for things to improve vastly,and I wouldn't rule out a backloaded Summer anyway...we are long overdue a decent August,surely to God...

Come on England

On the other hand the 0z has different ideas...you couldn't make it up..

Edited June 29, 2021 by MATTWOLVES

[Guest]

18 minutes ago, MATTWOLVES said:

I keep telling Alderc and Co they need a good paper bag on hand everytime they view the daily operational output I think Tams recent post hits the nail on the head as well regarding knee jerk reactions to every op run, Singularity also putting out a very insightful post. I'm not  completely convinced about these recent model outputs either...far to much chopping and changing going on. In the shorter term it looks like an improvement over the next few days so that's a positive! Come the Weekend gradually more unsettled conditions spreading in from the SW! How long this will last im not so sure...perhaps towards the 2nd week of July a more thorough improvement will begin to take place. 

Still plenty of time for things to improve vastly,and I wouldn't rule out a backloaded Summer anyway...we are long overdue a decent August,surely to God...

Come on England

On the other hand the 0z has different ideas...you couldn't make it up..

Hold on…..some of the output has been poor since the middle of the month (which many people kept saying it wasn’t and was the worst possible outcome so clearly couldn’t come off), now let’s compare to what we’ve actually seen down here in the last 12days…..

Rainfall, 84mm approx 160% of the June avg (in just 12days) 

Sun, just 42hrs, just 3.5hrs per day. (And 12hrs came in one day)

Temps, just three days reaching 21C. 

Those stats don’t lie, I don’t make this S+{t up…..

Now we have almost all the numerical models showing a potentially lengthy Atlantic incursion, think we’ve got the right to be concerned. 

[MATTWOLVES 3]

11 minutes ago, Alderc said:

Hold on…..some of the output has been poor since the middle of the month (which many people kept saying it wasn’t and was the worst possible outcome so clearly couldn’t come off), now let’s compare to what we’ve actually seen down here in the last 12days…..

Rainfall, 84mm approx 160% of the June avg (in just 12days) 

Sun, just 42hrs, just 3.5hrs per day. (And 12hrs came in one day)

Temps, just three days reaching 21C. 

Those stats don’t lie, I don’t make this S+{t up…..

Now we have almost all the numerical models showing a potentially lengthy Atlantic incursion, think we’ve got the right to be concerned. 

 Are you telling me you can make the call of a lengthy unsettled spell based on current NWP!  Just one look at the ECM 12z then this mornings 0Z suite tells you,it's struggling big time! Also worth noting the Noaa charts perhaps centre the trough further West. For sure conditions on the South Coast have been poor,your stats back that up,especially due the fact it should technically be one of the sunnier areas of the UK climate. But overall some places have been not that bad at all,and in all fairness some of our expectations are far too high of what conditions we expect in this country! Its a little like winter when some of us are expecting -20 uppers,yes there's a chance but it's a very unlikely chance! I said the other day it could be better for sure but it's still early and we have another 2 months of Summer remaining yet.

Edited June 29, 2021 by MATTWOLVES

[tight isobar]

3 hours ago, Singularity said:

On the other hand, the largest EPS cluster is only a little flatter with the ridge. So I think ECM is right to bring the Azores high into play, but takes it too far too fast.

Things are looking flatter than hoped for until at least a week into July, owing to AAM having to climb from a lower point than has been expected. Seems we’re not going to see this weeks low move quite far enough east to allow enough a ridge in between it and the Atlantic trough to entirely keep the latter at bay.

I’m still not seeing a UK trough setup as the favourite though - more of a changeable southwesterly or westerly regime via a trough to the west or northwest, most unsettled in the northwest. Not much cool air in the flow so it should tend to feel warm whenever the sun makes an appearance. 

Just popping in- to like this post/ assessment

[Britneyfan]

I don’t understand why people take unsettled weather so personal, who cares it’s the British weather, being an island it’s not surprising or shocking or a disaster if we endure 3 weeks of crap weather, models will chop and change and even under this low pressure I’ve reached 20, 21° each day even today it’s 19° and that’s with cloud cover, the models are still unsure on the outlook, it could change on the next run to hot and sunny who knows, that’s the excitement of British weather and model outlook, enjoy the model watching whatever the realistic outcome is 

[Fourty Point Three Degrees]

GFs 6z is another dreadful run, northern blocking looking like it wants to get comfy in its usual place

[northwestsnow]

7 minutes ago, 38.7°C said:

GFs 6z is another dreadful run, northern blocking looking like it wants to get comfy in its usual place

A horrible run.

Fingers crossed its wrong , everything looks finely balanced mid term.

A brief Atlantic incursion is hardly unprecented , just don't want troughing getting stuck in our vicinity as 6z shows.

[Singularity]

Thanks for another detailed update @Tamara. Good to know we're still thinking along similar lines, in the fact of the usual modelling shenanigans.

The 00z ECM has more support than some have perceived on here. I do see it as being at the optimistic end in terms of the pace of developments, but it's a good fit to the typical broad-scale response to tropical events driving AAM back upward from a negative starting anomaly.

The 00z UKMO was in a middle ground of sorts, as of +168. The Azores High is trying to cross southern UK but the low over Scotland complicates matters. If that low adjusts west, something akin to the ECM 00z becomes plausible, as it more likely phases with the new low coming in from the southwest, while to the west of the UK.

[Frosty.]

There’s some good signs in the longer term GEFS 6z regarding the Azores high / ridge? I said the same yesterday about the 12z!..there’s a chance that July could eventually turn into a good month?

 

[Methuselah]

And again, a wee look at the miscreant GFS 06Z run reveals that it's nowhere near as bad as the doom-mongers are predicting:

    

    

    

And, as these ensembles show, the mean is better than the operational -- which is, in itself, not all that bad:

   

I guess The Buddha had something right: hankering after what isn't there can only end-up in misery!

[sheikhy]

A move towards ecm on both gfs and ukmo 12zs!!!

[mb018538]

9 minutes ago, sheikhy said:

A move towards ecm on both gfs and ukmo 12zs!!!

Really? GFS is terrible:

[sheikhy]

16 minutes ago, mb018538 said:

Really? GFS is terrible:

It looked like it between 120 and 144 hours with more of a ridge to the east but then went default again lol!!!

[Methuselah]

GFS 12Z doesn't look all that bad, to me; 22-25C, a fresh WSW breeze, sunshine and showers; perhaps even some longer spells of rain . . . Is that really so terrible, for Blighty? 

     

[mb018538]

 

Looks like we might even get a big Greenland high building too. Wonderful stuff  

[mushymanrob]

itll be interesting to see what tonights noaa charts show at around 8.15pm ... will they hold ground or shift to allow the low across the country like the gfs currently is predicting..

[Climate Man]

8 minutes ago, mb018538 said:

 

Looks like we might even get a big Greenland high building too. Wonderful stuff  

Yes, just been looking through the output and was going to comment on the Greenland heights- Yuk. Don't worry they will disappear in around 4 months - guaranteed 

Edited June 29, 2021 by Climate Man

[damianslaw]

The trend in the medium range isn't great for those who want sunshine and warmth.. short term very good for the NW. Change comes about at the weekend. Next week based on todays charts looks poor for early July with the trough trapped over the UK. Poor is the right word..

[Methuselah]

Thank goodness the weather is the archetypal Type 1 chaotic system!  

[winterfreak]

31 minutes ago, Ed Stone said:

GFS 12Z doesn't look all that bad, to me; 22-25C, a fresh WSW breeze, sunshine and showers; perhaps even some longer spells of rain . . . Is that really so terrible, for Blighty? 

     

I’d say that was nigh on perfect  

[JayAlmeida]

29 minutes ago, mushymanrob said:

itll be interesting to see what tonights noaa charts show at around 8.15pm ... will they hold ground or shift to allow the low across the country like the gfs currently is predicting..

I think we all know the answer to this looking at the recent model output.

[Guest]

45 minutes ago, Ed Stone said:

GFS 12Z doesn't look all that bad, to me; 22-25C, a fresh WSW breeze, sunshine and showers; perhaps even some longer spells of rain . . . Is that really so terrible, for Blighty? 

     

Ed, youre just talking out your backside now, it’s another terrible chart for the pinnacle of summer!

Heavy showers, mid to high teens, maybe somewhere in the east might sneak 20C . Can you please look at the underlying surface conditions…

Edited June 29, 2021 by Alderc