Winter Approaching: Forecast and Model Discussion Commentary

[swfc-ocs]

 blizzard81 it's also close to it's 12z run

[LRD]

Looks as though the GFS 18z op will turn out to be an outlier but it does show what might be possible. An outside horse at the moment but let's see what occurs

[blizzard81]

 swfc Even that run goes a bit off kilter. Models are going to struggle I think in the next few days. Personally I'm just looking at the trend for lowering heights over southern Europe to continue. If they do, we have the raffle ticket. 

[dain_bramaged]

So it's time we started seeing signs, just signs, of what may eventually occur and seeing some of these cold spells I had predicted for Nov 20th, December 19th and 4th of January hopefully come to fruition.

 

First image shows the jet stream position around the world. Possibly in relation to the mjo, you can see a very strong jet coming off starting near India, then moving across Korea and coming off China into the Pacific. Also note the bucking jet stream near the Atlantic, high pressure over Greenland and low pressure moving down over Scandinavia(helped in part by the possible position of the pv starting to buckle and orientate in favourably for us)  This is my previously mentioned massive push of energy from the west, normally a death knell, but for us, it essentially adds to much energy into the system( the bright colours indicate the jets its intense strength in this area). There is also plenty of heat being added into the system here as the oceans are very warm, so its way over spending its "budget" so the MJO may show some signs of resilience, with the pv not long ago, at or above, near record levels-it will with all this heat and energy want to do the dreaded COD(circle of death) and basically misses out phases 6,7,8 (blocking and the PV being more favourable for cold)and goes quickly back more traditional milder wetter phases 3,4,5 for us. Its this battle between the PV and the lower level influences which is fascinating. In footballing terms its a high score draw but with each side gaining an advantage at times. 

Some people have shown the mjo charts and its resilience to move into phase 6 and we have to hold out the possibility it may be the case, however as you see with the 2nd and 3rd image it still a distinct  possibility it will go into phase 6 and stay for a while so is not without support.

 

4th image is the Stratophere at 1hpa, its highest level, roughly 42km or 137,000ft. You can see a lot of heat now there and the pv at in the 5th image down at 30hpa, or 30km approx 98,000ft you can see some of it beginning to appear. Notice also the isobars and how they are tilted, they are normally more doughnut shaped...this should help us lowering heights in Scandinavia and driving a small wedge, punch or cut in the pv winds as indicated by the 6th and 7th images down. You can also see the pv winds easing(the purples aren't as deep). 

You can see in image 8 where this cold bottled up energy spills out of. So right now, you have this push from near the Pacific China into the Arctic, and this then wobbles and pushes some south ward colld unstable air near us, orientated in such a way(as indicated by the 30pa Stratophere image) and enhanced by my inclusion of image 9, showing the pressure anomaly chart as it seems to push the normally limpet Azores high pointed in the direction Greenland and linking up or heading in our general direction as indicated by image 10 and 11 also show this nicely.

The last and 12th image shows the heights, the SLP( Sea level pressure) and the arrows indicate where I think the kow pressure and high pressure will move and thus allow us a good snapshot of a cold spell and wintriness around the 19th of December.

 

 

 

 

 

 

 

Edited December 1, 2024 by dain_bramaged

[blizzard81]

I've just been comparing the ECM AI 00z run and the latest 12z run. It reminded me how much the tpv gets decimated in the latest suites generally.

[HarvSlugger]

 dain_bramaged cold doesn't smell!

[kumquat]

That double-up ridge at 180 on the 18z is something to behold 

[swfc-ocs]

 blizzard81  blizzard81 it's also close to it's 12z run .do the ai plots have any credibility 

[swfc-ocs]

 dain_bramaged thanks lot of work went into that.il bank it btw

[Lukesluckybunch]

Some lovley output this morning ,ICON looks outstanding and could lead to something prolonged.and the gefs mean at day 7

[Weather-history]

A 1050+mb Azores high is impressive

Similar to the end of January 2003

[carinthian]

Morning all. The Russian High this week starting to force its hand with a continued squeeze on the low pressure zones across The British Isles into Western Europe. Although the Omega shaped Mid - Atlantic block to develop by next week not a perfect orientation at this stage, I think we could all see some upgrades in the models for some early December snow potential as the week goes on. It is already starting to happen .

C

[Mcconnor8]

 Lukesluckybunch

ECM at Day 7 also very good!

Edited December 1, 2024 by Mcconnor8

[Lukesluckybunch]

No way ECM don’t do this to all of uswhat a chart!

1 minute ago, Mcconnor8 said:

Day 7 also very good!

Yes it is,plenty of cold building to the northeast,Russian high link up maybe,could produce a proper easterly here..let’s see

[Mcconnor8]

The entire GEFS suite goes for the colder air arriving on Saturday night with the mean for London now down to -5c for the 850s.

Edited December 1, 2024 by Mcconnor8

[thickness line]

Don't no if eney 1 has noticed we seem to have had a fair few northerly shots this year from September onwards some of the best winter evey have  started with frequent northerly shots sep oct Nov.could it be a precursor this year who nos

[Lukesluckybunch]

Brilliant run from the ECM progressively colder from the northeast,cold to very cold day 7 onwards

[Lukesluckybunch]

Day 10 ECM you can see the forcing of the PV transfering east to scandi,a relaxation could be possible but with sufficient pressure probably just about strong enough over scandi,any milder sector from the northwest would be brief I think,retrogression looks likely here I think

[northwestsnow]

144 - 168 seems to be the key timeframe..

EC looks better than GFS -

but by day 10 the high is beginning to come under too much pressure from the Northern arm ..

ive seen post day 10 and the Atlantic is coming ...

Maybe I'm greedy and its cold day 7 to 11 of course ..

Of course this is just the det ,hopefully there will be better ens..

Edited December 1, 2024 by northwestsnow

[DavidS]

 northwestsnow It is, but with a NW/SE jet, it isn’t mild mush.

[northwestsnow]

 DavidS

But it isn't cold enough for snow ..

Which is what most of us want ..

anyway ,its cold prior to FI so lets see where the det sits in the suite

Edited December 1, 2024 by northwestsnow

[northwestsnow]

Having looked at EC det surface temps there isn't even a frost south of the Midlands up to day 10..

We have to be careful not to get carried away by what looks at face value good synoptics ..

Up Scotland it's a v cold run though...

 

[Legend.Ice]

 dain_bramaged

We continue to see interesting developments in models, Mjo index is a data that normally changes very hard for a period of 5-10 days, and the models agree on it, but it has started to become unreliable data in the last few years, there is disagreement between Ecm Gfs and Cfs even for phase 6, Mjo cycle data is very important for model data input ( It interacts with many indexes and has a triggering role)  , however, this unpredictability can cause us to see sudden changes (+ 168 h) in the outputs

[johncam]

 northwestsnow in central belt not much frost either , highlands do well out of this run but no doubt it will change for better or worse

 

Ps currently in Dubai and talking about how cold it is here, 26C today so all about perspectives.

[Dennis]

good sunday all 

much better signs this 1 december day for coldies freaks over the coming days

( i start today in Norway with a hot 14 degrees here- )