Model Output Discussion - Deeper into Autumn

[Cheshire Freeze]

1 minute ago, sheikhy said:

So my man what we expecting later?!!a move towards ecm from gfs?!that ukmo was very weird in how it removed the scandi heights so quickly i must say!!

The direction of travel has looked very clear to me for a couple of weeks now. Eventually the Atlantic troughing will become penned right back. Even if this Scandi HP attempt fails we will see another amplification attempt soon after. 

[northwestsnow]

Regardless EC is better than the rest.

[sheikhy]

2 minutes ago, northwestsnow said:

Regardless EC is better than the rest.

Mate you know it!!!theres no comparison ecm is miles better!!!!

[northwestsnow]

Not sure if I'm looking forward to EC46 or not!!

Clearly its fine margins,really don't fancy more rain.

( sorry to reservoir huggers).

Edited November 10, 2022 by northwestsnow

[sheikhy]

1 minute ago, northwestsnow said:

Not sure if I'm looking forward to EC46 or nor!!

Clearly its fine margins,really don't fancy more rain.

( sorry to reservoir huggers).

Agree totally!!no more rain!!

[Frosty.]

On the cusp of the meteorological winter, P3 would do for me…hey, it even rhymes!  

[Kirkcaldy Weather]

38 minutes ago, johncam said:

As everyone suggested Scandi blown away very easily ,

ECM lovely run again 

[I remember Atlantic 252]

10 minutes ago, northwestsnow said:

Regardless EC is better than the rest.

240 very ugly, no cold air for system to edge in to, opposite to this in '96, one of my snowiest days

 

[phil nw.]

The Atlantic struggling to win against the block next week.The battleground looks like creating some wet conditions as the trough disrupts nearby.

The skirmish could continue for a while as those heights to our east look persistent.

Temperatures set to fall as the mild flow gets cut off in the coming days so a different and more seasonal feel to things.

Certainly a different and more interesting pattern than normal for late Autumn that's for sure.

[BLAST FROM THE PAST]

Both ECM and GFS have a potentially damaging storm to hit us around 19/20 Nov.  Will this materialise or will the block keep it at bay?  Interesting watching this

 

BFTP 

[bluearmy]

The 46 builds a scandi surface ridge in week 3 but that apart, there is little guidance beyond the two weeks of the eps with weak anoms to follow. 

[sheikhy]

1 minute ago, bluearmy said:

The 46 builds a scandi surface ridge in week 3 but that apart, there is little guidance beyond the two weeks of the eps with weak anoms to follow. 

Somethings brewing blue !!!!

[Polar Maritime]

Absolutely BA.. With ex tropical storms crossing the Atlantic towards us and ther position/track it's all very much 'what happens next' 

Very interesting model watching coming up one way or the other..

[northwestsnow]

7 minutes ago, bluearmy said:

The 46 builds a scandi surface ridge in week 3 but that apart, there is little guidance beyond the two weeks of the eps with weak anoms to follow. 

Very non committal.. 

Temps neutral too..

[Eagle Eye]

Here's my interpretation of some parts of Angular Momentum. Note that I'm 15, this is my first time looking at it and I'm not exceptionally quick at learning. So, I'll probably get some things wrong but hopefully I've also got a few things right. I imagine a few things will change in translation from Meteorology language to English. 

I've shortened a few words because this is the second time writing this after I accidentally deleted the tab first time around. 

AMB - Angular Momentum Budget  

AAM - Atmospheric Angular Momentum 

CI flow (Cross-Isobar flow) 

LP(High pressure) 

HP(High pressure) 

MT(mountain torque) 

GWT(gravity wave torque) 

FT(frictional torque) 

BL(boundary-layer) 

PGF(pressure gradient force) 

If AMB increases in the atmosphere it must have been transferred from another source since AMB is always conserved. The sources for AMB are from the Earth, the Oceans and the Atmosphere. 

One major aspect in affecting AAM are torques. A torque is the rotational force in the atmosphere.  

 

The 3 main torques affecting the atmosphere are: 

Mountain torque (MT) - The turning force applied with the effect of pressure systems on mountains. 

Frictional torque (FT) - Boundary layer dynamics. 

Gravity wave torque (GWT) - Subgrid (local) torque, upward movement and downward movement to do with the buoyancy. 

 

Now, onto the FT and BL dynamics: 

BL friction allows the lower atmosphere to flow across the isobars and for air masses to modify their vorticity/ The friction at the BL is what allows the exchange of AAM with FT. This friction allows the atmosphere to, in part, counteract the rotational force and allow the flow of air to be along the isobars. The CI flow brings in its own Coriolis and friction force parameters. The flow across the isobars is left of the geostrophic flow therefore there is a frictional force on the Coriolis force and so surface drag on the wind and so the PGF becomes the dominant force. 

LP dynamics: 

Air spirals inwards, creating convergence and so moisture creates clouds and rain. 

HP dynamics: 

Air moves away, creating divergence and so moisture 'moves away' and so the typical blue skies occur. 

Of course, that is an idealised version and because of mini and subgrid level differences, this is rarely the case, instead there is a general pattern of these dynamics. 

 

The mathematics (thanks to Olivia for verifying the mathematics made sense although I'm not sure why the Reading University mathematics department would get it wrong  ) : 

P = MV 

Linear momentum = mass x velocity vector 

 

m = r x MV 

Angular momentum = distance from origin x mass x velocity vector 

 

F = MA 

Force = Mass x Acceleration  

 

t = r X F 

Torque = distance from origin x force 

 

Differentiation of torque and angular momentum 

dm/dt = r x F 

 

To quote the document... 

"therefore we may see that the rate of change of Angular Momentum of a body is equal to the cross product of its distance from the origin about which it rotates and the total force applied to the body. This cross product r × F is called the ‘Total Torque’ applied to the body" 

 

Continuing on with the mathematics 

Uabs = Urel + Ω x r 

Absolute velocity of an air parcel = velocity relative to a viewer on Earth + rotation rate x distance of mass to point of which the Earth rotates. 

 

"The Angular Momentum of an air parcel of unit mass, defined L, in the Earth’s Atmosphere" 

L = r × (Urel + Ω × r) 

 

"and the Angular Momentum of an air parcel of unit volume, m" 

m = ρr × (Urel + Ω × r) 

 

where ρ is the density of the air parcel. 

 

Total Angular Momentum of the Earth’s Atmosphere against a vector: 

V is the volume of the atmosphere. 

the stretched f like symbols are integrals, here's a good website on them that hopefully works. 

Introduction to Integration

WWW.MATHSISFUN.COM

---

Math explained in easy language, plus puzzles, games, quizzes, worksheets and a forum. For K-12 kids, teachers and parents.

If you just saw that equation you would probably scream but breaking it down does make it a lot easier. 

Away from the mathematics:

If there is a net westerly surface wind, the atmosphere speeds up the Earth's rotation and transfers angular momentum to the earth and so there is a net decrease in AAM. The reverse happens with a net easterly wind.

Further mountain torque:

Fluctuation of pressure and orography and the force exerted due to the difference in pressure across the raised surfaces. High pressure on the west and side and low pressure on the east side imparts angular momentum into the Earth from the atmosphere. The opposite happening with the opposite case.

In the NH Winter:

Global MT anomalies are constructed by sypnotic waves that scatter energy across Asia and North America. These sypnotic waves trap the SLP anomaly and push them towards the south. Driven south and east of mountains. Sypnotic wave centres amplify aloft. MT associated with anomaly air parcel transportation in terms of momentum into latitudes its next to. More angular momentum is therefore moves to the 20-20N band. This is where the AAM anomaly appears significant. The anomaly quickly becoming equally uniform leading to a global FT that weakens the AAM anomalies. An anomalous distribution of mass accompanying the MT acting to balance the zonal winds in the 20-30N region. In the mid latitude, Eddy's the physical link between those two torques.

 The two main torques can be shown in a lag correlation and FT "leads" MT. The relationship related as previously mentioned in the last paragraph. SLP anomalies are related to FT and the coupling with MT.

This is only the start of my learning and just a skin through the document that drove those last 2 paragraphs so I may include a part 2 but I'm not sure how long it may take me and what document Olivia will choose for me next week.

I'd like to thank @Tamara for linking me to multiple documents and threads that helped improve my understanding.

I'd also like to thank Olivia for the motivation and mathematical guidance. As well as Reading University for supplying my mainly used document when mathematically summarising momentum and torques.

Hopefully, this helps some people at least partly.

Also, the 10hPa zonal wind forecast. Looks to be going one of two ways towards the end.

Edited November 10, 2022 by Eagle Eye

[Don]

3 minutes ago, northwestsnow said:

Very non committal.. 

Temps neutral too..

Sounds like higher than normal uncertainty?!

[damianslaw]

I-Spy the first pocket of sub 528 dam air of the season, 18th Nov from the GFS 12z, albeit shortlived and reserved for the north, but its something I always look out for, indicative that a flow from between north and west is likely to be quite cold from now on.. 

1 hour ago, northwestsnow said:

There looks too much energy in the Atlantic sadly..

watch for the azoes high ridging into spain/france.

Hopefully not.

Think it's OK

Importantly the jet is sinking south which will keep the azores high at bay.

[damianslaw]

1 hour ago, phil nw. said:

The Atlantic struggling to win against the block next week.The battleground looks like creating some wet conditions as the trough disrupts nearby.

The skirmish could continue for a while as those heights to our east look persistent.

Temperatures set to fall as the mild flow gets cut off in the coming days so a different and more seasonal feel to things.

Certainly a different and more interesting pattern than normal for late Autumn that's for sure.

Hoping for the first snow of the season on the fells, certainly looks conducive.

[sheikhy]

Gfs 18z looks even worse in terms of scandi heights compared to 12z!over to the 00z!!

[ItNeverSnowsInWindsor]

Hopefully not the GFS op verifying for Norway!

[tight isobar]

8 minutes ago, sheikhy said:

Gfs 18z looks even worse in terms of scandi heights compared to 12z!over to the 00z!!

Ya need to take the overall concept of format block- not an exact eye on scandi height parameters!. It’s how fast the evolution of polar vortex resurgence relays- and noted warm air advection takes liberties on this!- take early / mid range prognosis atm.. and watch the momentum elaborate!... !- extended height shape/- and arming is the watch point...there is a hod load of possibilities evenfrom this point.. and there’s an array of mixed solutions that reprecate this @ at splits into the layers!!.. and reverberated in the lower outcomes..

Edited November 10, 2022 by tight isobar

[jules216]

"Suddenly" a lot of +NAO clusters appearing against those -NAO, its a far cry and typical turn around against from what its seasonal model showed in october update,even Nov for Dec. To the same "rubbish bag"belongs also UKMO with its 180° spin in wording of forecast 16-32d.

[Don]

6 minutes ago, jules216 said:

"Suddenly" a lot of +NAO clusters appearing against those -NAO, its a far cry and typical turn around against from what its seasonal model showed in october update,even Nov for Dec. To the same "rubbish bag"belongs also UKMO with its 180° spin in wording of forecast 16-32d.

As I said recently, these models need an upgrade of some kind!

[tight isobar]

8 minutes ago, jules216 said:

"Suddenly" a lot of +NAO clusters appearing against those -NAO, its a far cry and typical turn around against from what its seasonal model showed in october update,even Nov for Dec. To the same "rubbish bag"belongs also UKMO with its 180° spin in wording of forecast 16-32d.

But those positive oscillations-are “surely “ a bypass of syndrome!! Noted perfectly in raw - operational modelling!. It’s got switch/ and turn written all over it.. as angular season momentum exacts. And the overall pattern is at odds with probably outcome... already there is notable crisis with forward sync on vortex alignment.. due to so much circulation of waa!.. the formats “ Are far from deciphered atm”!! And watch the model raws swing like a pendulum in the nxt week!!!

Edited November 10, 2022 by tight isobar

[BelgianBlizzard]

We're back where we were a few days ago. Can somebody explain to me why every model suddenly showed some sort of a scandinavian high yesterday and today they all flip back?