Model Output Discussion - Deeper into Autumn

[Eagle Eye]

1 hour ago, joggs said:

Oh yes. Agree. Just trying to keep a little balance on here for newbies.

Short-term is definitely looking interesting but like you I'm holding back for now.

My recent posts have focused on the long-term signals because I'm very much a teleconnection person but I've had a go at breaking down the models anyway. There's going to be a lot of scepticism in this post and I've tried to balance my bias but let's see what we've got.

My main bit of interest, how the first low splits (or doesn't split)

06Z

vs 0Z

vs 18Z yesterday

Why is that of interest?

Well, let's have a look at the different developments down the line...

06Z

vs 00Z

vs 18Z yesterday

I think it's pretty clear that the evolution of the high has a lot to do with that splitting of the low and that's not even taking the ECM into account.

Dynamically, this essentially has a lot to do with an area of divergence forming and splits part of the low...

Here's a NOAA explanation of how it works.

Now, as we can see on the streamlines, it's quite strong in terms of wind strength at 500hPa and there's some fairly strong troughing but that's just based off the latest run.

The last 3 runs (a little further on)

18Z yesterday

vs 00Z

vs 06Z

Trend seems to be towards tighter troughing but it's difficult to tell.

I'll leave you all to discuss this and the future impacts just my few notes...

[Mark Smithy]

1 hour ago, Eagle Eye said:

Welcome to Netweather.

I think there should be a sign on this thread every Winter saying "Please do not take every GFS run as gospel"

An even better sign would be "Please take everything past T168 with a pinch of salt"

 

I don't know how many times it happens but people still don't learn. 19 times out of 20 cold set ups in F.I. don't come to pass in the UK. 

It behoves seasoned model watchers, of whatever weather tastes, to show restraint until charts come inside a 5 day timeframe (T120). Then by all means get excited.

[bluearmy]

The bifurcation of the jet to our west will dictate a lot as we move forwards

we know that this is tough for the models to resolve, especially given the strength of the blocking to our east and how strong the jet off the eastern seaboard will be 

so I’m afraid it remains a watching brief  - we have decent sized stub of raffle tickets though 

[geordiekev]

Really is something seeing charts almost mirror image of depths of Jan 63. Feet to remain firmly on ground as end of Jan & beginning of Dec are different beasts and the latter is still a forecast. Exciting times ahead

[Methuselah]

Not a bad GEFS 06Z temp ensembles; things inexorably headed in the desired direction:

      

[CoventryWeather]

Happy to say I'm learning quite a bit from people on here. I don't know all the scientific evidence into weather, but hopefully get some knowledge before university in a year or so.

Always love these times when runs go from one extreme to the other in a few hours. Makes weather much more enjoyable to watch.

[Jackski4]

Anyone else just sat waiting for the 12z runs

[Tamara]

Looking from some distance away from the UK and purely objectively about the seasonal pattern and not through the lens of a desired pattern:

There seems to be some belief, not sure what it is based on (beyond hope?) that the tropics are inextricably set to repeat a further active Pacific orbit later in December- both assumedly as means to keep (or reload) an anticipated cold pattern for NW Europe and as means to initiate a festive season SSW to set the path for winter 22/23 on an ice-age of yesteryear.

Personally, at this time, I would very much question this based on empirical knowledge of tropical convection/MJO periodicity timelines. Active cycles, particularly seen during transitional ENSO phases (in this case a weakening Nina base state) follow an upwards of 60 to 90 days timeline recurrence for intraseasonal active progressions of the 'mini ENSO cycle'. The autumn has seen prolonged active cycling within the tropics focussed on West Pacific convergence, propagating +AAM anomalies to the extra tropics and carving out the very amplified downstream hemispheric patterns that are being seen.

However, cycling of tropical forcing phasing, irrespective of long-term base state trends, both waxes...and wanes.

A 'waning' of the sustained Nino-esque interference with the ENSO state is becoming increasingly overdue based on the periodicity cycle and suggests that the autumn of strongly a-typical high angular momentum decoupling of the atmosphere cannot continue indefinitely for yet further weeks to come. Ergo a fall /correction in angular momentum must be viewed within a lens of time - which based on present long-term forcing may well further down the line spook NWP into something of an about-turn. Precise timing of this difficult to gauge at present, but becomes more and more likely heading further through December. The implication of this is some strength returning to the polar jet and pressure put on any mid-upper blocking pattern. 

With so much amplification inertia in the global atmospheric circulation, this may imply trough disruption rather than any wholesale downstream flatter zonal pattern, but clearly nothing should be taken for granted and a period of flatter Atlantic conditions is quite possible following the upcoming blocked pattern. If the tropics does witness a weaker cycle of tropical convection through later December into January, then this may imply that return to active cycling, (based on the 60 to 90 day periodicity timeline), results (possibly) in greater chance of renewed exertion on the tropospheric/stratospheric pathway being more likely around the mid-winter period - i.e mid to later January and even towards February. Such an SSW, not as automatic template to a classic arctic spell for the UK, but simply the means whereby a completely destabilised arctic profile might create the means for increased chance of cold air advection somewhere within the global mid latitudes

Putting all this together, no-one should be making assumptions already than whatever develops over the coming 10 to 15 days for the UK (different implications for down here in Portugal with potential for some very wet conditions) is somehow going to set the way forward for an even bigger top up around the festive to New Year period.   At some stage a collapse in AAM will be forthcoming, especially based on such an unstable disconnect, and if/when NWP latches onto this then modelling would undertake something of a volte face,

Just something to bear in mind as caution to making any assumptions and some considerable potential uncertainty maybe to come as times moves forward.

[Tim Bland]

55 minutes ago, Ed Stone said:

Not a bad GEFS 06Z temp ensembles; things inexorably headed in the desired direction:

      

Quite something to see every run between 0c and 5c in the south east at the end of the run…..

[Penrith Snow]

1 hour ago, geordiekev said:

Thought you'd posted the 62/63 pattern there for a moment

Notice the much lower heights (greens) in 1962 compared to this morning +240 ECM (Europe covered in yellow)

Any snowfall from that ECM chart would be very limited, we need lower heights to instil much greater instability to get proper snow from an easterly

The current high SSTs won’t help either.

Plenty of time for upgrades

Andy

[sheikhy]

Right as you can see in the images attached below!big difference at just 90 hours between the ecm and gfs!!gfs has big blue shortwave north east uk where as ecm no shortwave at all as its cleared way north ready for the scandi high to pounce......

 

[Valleyboy]

11 minutes ago, Penrith Snow said:

Notice the much lower heights (greens) in 1962 compared to this morning +240 ECM (Europe covered in yellow)

Any snowfall from that ECM chart would be very limited, we need lower heights to instil much greater instability to get proper snow from an easterly

The current high SSTs won’t help either.

Plenty of time for upgrades

Andy

Depends on the wind direction really.  Winds north of east will bring plenty of snow showers across the country.  The North Sea will be a big snow making machine this winter.

[Eagle Eye]

31 minutes ago, Tamara said:

 

Totally agree with you. Caution is most definitely the game right now. Most of the teleconnection signals are too weak for proper long term forecasting so anyone who's seen my long term forecasts should know that they are essentially the best case scenario with the teleconnection signals.

[TSNWK]

19 minutes ago, sheikhy said:

Right as you can see in the images attached below!big difference at just 90 hours between the ecm and gfs!!gfs has big blue shortwave north east uk where as ecm no shortwave at all as its cleared way north ready for the scandi high to pounce......

 

So ECM also does a 06z.  Jeeze it's relentless;) joking aside that would be a huge fail if our European model screws up at that range in our loca

[Skullzrulerz]

Still being quite cautious so far, it's exciting that we are getting some good sypnotics but at least in the short term is the lack of "Cold" air if your looking for widespread snowfall.

It will be chilly and actually quite seasonal for the time of year which makes a change considering how mild the year has been.

[sheikhy]

4 minutes ago, TSNWK said:

So ECM also does a 06z.  Jeeze it's relentless;) joking aside that would be a huge fail if our European model screws up at that range in our loca

Im gona try being positive here and say ecm is the correct one at 90 hours!!!!but yeh would be a big fail for my king model!!

[bluearmy]

52 minutes ago, Penrith Snow said:

Notice the much lower heights (greens) in 1962 compared to this morning +240 ECM (Europe covered in yellow)

Any snowfall from that ECM chart would be very limited, we need lower heights to instil much greater instability to get proper snow from an easterly

The current high SSTs won’t help either.

Plenty of time for upgrades

Andy

Indeed Andy - lots of pattern matching which takes no account of the thickness/heights 

Edited November 25, 2022 by bluearmy

[chris55]

Nice to see the forum getting busier with a more blocked pattern upcoming.

Looking forward to following all the dramas in the weeks and months ahead

Hopefully some snowfalls and ice days incoming. Sales of heated blankets will be through the roof! I’ve got mine ready .

 

Edited November 25, 2022 by chris55

[Notty]

22 minutes ago, TSNWK said:

So ECM also does a 06z.  Jeeze it's relentless;) joking aside that would be a huge fail if our European model screws up at that range in our loca

again …

[Ice Day]

I posted the GEFS 0z table from yesterday mornings run so thought I'd post todays equivalent to see which way we're trending (yesterdays on the left).

  

So whilst they are not the most reliable tool (they can flip at the drop of a hat), nevertheless the ensembles have undoubtedly trended colder over the last day.  Let's see what the 12z's have to say.

[sheikhy]

25 minutes ago, TSNWK said:

So ECM also does a 06z.  Jeeze it's relentless;) joking aside that would be a huge fail if our European model screws up at that range in our loca

Does an 18z aswell my friend!!!

[Notty]

5 minutes ago, Ice Day said:

I posted the GEFS 0z table from yesterday mornings run so thought I'd post todays equivalent to see which way we're trending (yesterdays on the left).

  

So whilst they are not the most reliable tool (they can flip at the drop of a hat), nevertheless the ensembles have undoubtedly trended colder over the last day.  Let's see what the 12z's have to say.

Colder and cold earlier 

[Eagle Eye]

Despite the constant downward trend forecasts for the AAM on the GWO it's stayed in quite a steady state.

So that still makes me a little wary of the latest CFS but there's no real reason not to believe it.

I've also noticed the GWO's chop and change a lot from run to run and aren't amazingly accurate considering that a small change in phases has quite a wide impact on future events.

14th November

Says by now we'd be on the border between phase 7 and the weak GWO.

18th November

Says by now we'd be firmly into the weak GWO (+7 etc is the amount of days)

vs where we are now (green dot)

So, not focusing on the forecast yet and a bit of realism, there is a lot that's at stake here and truthfully, there is no set-in stone answer for this December onwards.

The MJO pattern doesn't really have a solution to it

The ECM looks fairly good for moving back to phases 6 and 7 

However, the CFS and GFS extended both show it curving down towards phases 1,2 and 3. Note that the GFS especially has a large spread though and so MJO wise, there's too much spread to be definite of anything yet...

Going to be interesting to see what happens with this much spread, makes forecasting long-term very difficult

 

[Kirkcaldy Weather]

4 hours ago, Kirkcaldy Weather said:

I'll be keeping the frame from the latter stage of it saved as when I say that's signs of a classic snowy setup like the beauts of 2010, 2009 etc I'm not trying to hype 

 

GEFS makes that two means I'll be saving... 

 

[northwestsnow]

Really an uninspiring Exeter update..

Not even a mention of sleet !!

Let's see what the 12zs come up with..